Lawrence P. Cahalin
INTRODUCTION
Examination of the pulmonary system requires optimal use of auditory, observational, tactile, auscultatory, and medical information. A significant part of this chapter will focus on the actual physical therapy examination process. Perturbation of initial examination findings with auditory, positional, or tactile maneuvers may yield information that could (1) direct further examination techniques, (2) direct treatment techniques, and (3) provide important prognostic information. The following section will review each of the examination techniques and the application of specific maneuvers that may help to direct and predict the effects of these techniques. A review of medical information and the specific tests and measures providing the most clinically useful information will also be presented.1–5 Much of this information and the approach used to examine a patient with pulmonary disease are outlined in Box 9-1. This information can be documented in the initial patient note presented in Appendix 1 of this chapter.
Box 9-1
A Suggested Examination Approach to the Patient Designed to Determine the Disablement of Pulmonary Disorders and Direct and Predict Physical Therapy: a Patient Case Example
1.Why are you here today?*
2.Have you been diagnosed with a pulmonary disorder in the past?
3.Have you had any special tests to examine your lungs like pulmonary function tests?
4.Do you experience shortness of breath at rest, only with activity/exercise, or both at rest and with activity/exercise?
5.If you become short of breath during activity or exercise, could you please describe the type of activity or exercise that produces your shortness of breath?
6.Can you describe your shortness of breath? Can you help me understand your shortness of breath by pointing to your level of shortness of breath using this 10-point scale or by marking this Visual Analog Scale?
7.Can I place this finger probe on your index finger to obtain an oxygen saturation measurement?
8.Can I listen to your lungs with my stethoscope?
9.Could I place one of my hands on your stomach and one hand on your upper chest to determine how you breathe?
10.Could I place my hands on the lowermost ribs on each side of your chest to determine how you breathe?
11.Could I place my hands on your back to determine how you breathe?
12.Could I wrap my tape measure around your chest at several different sites to determine how you breathe?
13.Now that I understand some very basic information about the manner in which you breathe, could you please breathe in the manner I instruct you via sounds I make, pressure from my hands, methods I show to you, or different body positions? I will occasionally place my hands on your chest and wrap my tape measure around your chest to determine how you breathe during these simple tests, and I will ask you to identify your level of shortness of breath using the 10-point scale or Visual Analog Scale—Is this OK with you?
14.Could I measure the strength of your breathing muscles by having you place this mouthpiece in your mouth and breathe in and out as deeply and as forcefully as you are able to do?
15.I would like you to now perform the activity or exercise that produces your shortness of breath—Could you please do this now?
16.Thank you for giving me the chance to examine you today. I will call your physician to get some more information about you such as the pulmonary function tests that you said were performed last week as well as the arterial blood gas results, chest X-ray, and exercise test results. In the meantime, I would like you to practice breathing in the manner that we discovered that helped you feel less short of breath and produced the best chest wall motion that I felt with my hands and measured with the tape measure. I will see you next week for further examinations and treatments.
*The information given in bold identifies important examination procedures for patients with pulmonary disorders.
PHYSICAL THERAPY EXAMINATIONS
Medical Information and Risk Factor Analysis
The past medical history is an important part of the systems review of all patients. This is particularly true of patients with known or suspected pulmonary disease. A number of previous medical problems may predispose a person to pulmonary disorders. Examples of such previous medical problems are shown in Box 9-2 and include recurrent pulmonary infections, cardiac disease (eg, heart failure), and neuromuscular disorders.6–8
Box 9-2
Risk Factors for Pulmonary Disorders
Previous medical problems predisposing a person to pulmonary disorders
1.Recurrent pulmonary infections
2.Heart failure
3.Neuromuscular disorders (eg, cerebrovascular accident (CVA), Guillain–Barré syndrome, muscular dystrophy)
4.Musculoskeletal disorders (eg, scoliosis, ankylosing spondylitis, pectus excavatum)
5.Integumentary disorders (eg, marked burns to thorax, scleroderma)
6.Past oncologic disorder treated with chemotherapy or radiation therapy
7.Obesity
8.Premature birth
Primary and secondary risk factors for pulmonary diseases Obstructive lung disease
1.Smoking
2.Occupational exposure to irritants or allergens (eg, asbestos, chemicals)
3.Residing in locations with high levels of air pollution
4.Premature birth—bronchopulmonary dysplasia
5.Emphysema
6.α1-Antitrypsin deficiency
7.Asthma
8.Bronchitis
9.Bronchiectasis
10.Cystic fibrosis
Restrictive lung disease
1.Occupational exposure to irritants or allergens (eg, asbestos, chemicals)
2.Cardiovascular disorders (eg, pulmonary edema from heart failure, pulmonary emboli)
3.Neuromuscular disorders (eg, spinal cord injury [SCI], CVA, Guillain–Barré syndrome, muscular dystrophy)
4.Musculoskeletal disorders (eg, scoliosis, ankylosing spondylitis, pectus excavatum)
5.Integumentary disorders (eg, marked burns to thorax, scleroderma)
6.Immunologic disorders (eg, Wegener granulomatosis, Goodpasture syndrome)
7.Past oncologic disorder treated with chemotherapy or radiation therapy
8.Trauma (eg, crush injuries)
9.Surgical pain or scarring
10.Obesity
11.Pregnancy
12.Premature birth—hyaline membrane disease
Pulmonary hypertension
Primary pulmonary hypertension
1.Autoimmune dysfunction
2.Vascular dysfunction
Secondary pulmonary hypertension
1.Severe obstructive or restrictive lung disease
2.Severe heart failure
The primary and secondary risk factors for pulmonary diseases are also listed in Box 9-2 and include environmental and self-imposed risks. Of all risks, a history of smoking is the greatest key to unlocking the likelihood and severity of pulmonary disease. A smoking history is typically reported in pack years (the number of packs of cigarettes per day multiplied by the number of years smoked). A smoking history of greater than 70 pack years appears to be associated with a greater likelihood of developing emphysema.9 Smoking less than 70 pack years is associated with less of a risk of developing lung disease, but not smoking at all is associated with far less risk of developing lung disease. Secondhand smoke is also associated with a greater risk of emphysema and other pulmonary disorders.10–12
Listening to a patient’s past history and primary complaints is critical in the examination process. In fact, a good history can provide important information that can be very useful in diagnosing a variety of pulmonary disorders. Badgett et al. found that a previous diagnosis of chronic obstructive pulmonary disease (COPD) and smoking for 70 or more pack years yielded a diagnosis of COPD with a sensitivity of 40% and a specificity of 100%.9 The only physical examination findings that significantly improved the sensitivity were diminished breath sounds and peak flow. Adding these two variables increased the sensitivity of diagnosing COPD to 77% and slightly decreased the specificity to 95%.9 Overall, diminished breath sounds were the best sign of moderate COPD. The importance of good listening as the beginning part of the auditory examination cannot be overstated. Listening to a patient’s past history, habits, and complaints (and attempting to quantify these variables) are instrumental in understanding the absence or presence of disease, severity of disease, treatment choice, treatment effects, and quality of life. A patient’s appearance can also provide information about the presence and severity of pulmonary disease.
Patient Appearance
The appearance of a patient can suggest the presence and severity of several pulmonary disorders such as emphysema, chronic bronchitis, or restrictive lung disease such as spinal cord injury. In fact, appearance, historically, has been a method to categorize patients with COPD. Patients with spinal cord injury often lack adequate abdominal muscle support, which results in a characteristic posture described as a “pot-belly” appearance. These examples are just a few of the many characteristics that can be observed in a patient’s appearance (Table 9-1). Other signs of pulmonary disease are also presented in Table 9-1.
TABLE 9-1 Particular Patient Characteristics Suggestive of a Pulmonary Disorder
Dyspnea—Methods to Evaluate Shortness of Breath
One of the major complaints of patients with pulmonary disorders is shortness of breath. The purpose of this section is to present the different methods that may be used to evaluate shortness of breath. A variety of different methods to evaluate dyspnea are available and are shown in Table 9-2.13–15 The strengths and weaknesses of each of the methods to measure dyspnea are also presented in Table 9-2. The most common method to evaluate dyspnea is likely the Borg-modified dyspnea scale of 0 to 10, which is anchored with descriptive terms that describe the sensation and amount of dyspnea a patient is experiencing. The original Borg rating of perceived exertion is occasionally used to evaluate dyspnea and overall systemic exertion at rest or during exercise. Both the original and the modified dyspnea scales and their descriptive terms are provided in Table 9-3. Other scales such as the Mahler dyspnea scale are available, but often their clinical utility is diminished because of the time and effort needed to administer them to patients.16 Other important aspects of the auditory examination will be presented in the following section.
TABLE 9-2 Different Methods to Evaluate Dyspnea
TABLE 9-3 Original and Modified Borg Dyspnea Scales
Auditory Examination
Listening to the Breathing Cycle
Listening to the breathing cycle of a patient, one can provide very important information about other needed patient examinations and treatments. Listening to the baseline inspiratory and expiratory cycles of breathing can provide information about the respiratory rate, type of primary lung disease, and the effects of specific maneuvers on the baseline breathing pattern, which may be helpful to direct specific therapeutic interventions.17
For example, a rapid respiratory rate with short and shallow inspiratory and expiratory periods heard at rest may indicate a primary lung abnormality. Likewise, a prolonged expiratory portion of the inspiratory–expiratory duty cycle may be suggestive of a primary obstructive lung disease. A rapid respiratory rate with a prolonged expiratory phase may be indicative of a patient with isolated obstructive lung disease or combined obstructive and restrictive lung disease.17, 18 These auditory patterns are described in Table 9-4.
TABLE 9-4 Listening to the Breathing Cycle at Rest and During Perturbations
Simple perturbations of the baseline breathing cycle via body position changes, pursed-lip breathing, or therapist-simulated breathing (breathing out loud with the patient in a desired pattern of breathing) can direct further examination techniques or suggest potential treatment techniques.19,20 Several possible perturbations to the baseline breathing cycle are listed in Table 9-4. Auscultation of the lungs follows the auditory examination and will be presented in the next section.
Auscultation of the Lungs
Proper Use of the Stethoscope
Proper use of the stethoscope is crucial in the examination of patients with cardiopulmonary diseases.21,22 The stethoscope is a medical tool that is often taken for granted. It was developed in 1816 by Rene Laennec after he observed children with their ears pressed against the end of a long, hollow log, while other children were tapping with stones at the other end of the log. Laennec shortly thereafter used tightly wound newspapers and large wooden tubes to examine the sounds heard in the thorax. He later refined the wooden tubes and while doing so developed a new clinical tool and terminology that is still in use today. The stethoscope has since undergone significant modifications and has enabled health care professionals throughout the past two centuries to enhance physical examinations and determine the effects of medical treatment. Although the clinical utility of auscultation has been questioned and the reliability of auscultation has been observed to be modest to poor, it remains a useful adjunct in the examination of patients with cardiovascular and pulmonary disorders.21–24 Furthermore, the recent introduction of electronic stethoscopes now provides superior acoustic recognition, digital signal processing, and recording of breath and heart sounds that can be downloaded to personal computers. Auscultation of the heart and lungs with an electronic stethoscope appears to address many of the limitations previously identified with traditional auscultation.
The stethoscope usually consists of a diaphragm and bell as shown in Fig. 9-1. Stethoscopes without the bell exist but are frequently lower-quality stethoscopes with limited auscultatory ability. The stethoscope should be of acceptable quality to enable accurate auscultation of the heart and lungs and should have most of the characteristics that are listed in Box 9-3. The presence of a diaphragm and bell, tubing size of at least 50 cm, and a comfortable earpiece fit are possibly the most important qualities of a good stethoscope. The presence of a diaphragm and bell on the stethoscope ensure that the stethoscope is of a moderate to high quality, and a comfortable and correct earpiece fit will enable longer periods of auscultation.
FIGURE 9-1 The stethoscope and sites for optimal auscultation with underlying lung segments.
Box 9-3
Important Characteristics and Use of the Stethoscope
1.Optimal auscultation can be performed with a stethoscope that has both a bell and a diaphragm (see Fig. 9-1).
2.Use the diaphragm of the stethoscope to auscultate for high-frequency sounds.
3.Use the bell of the stethoscope to auscultate for low-frequency sounds.
4.Optimal tubing length (long enough to allow for adequate distance between patient and therapist, but not too long to cause excessive movement of the tubing, which may interfere with auscultation; approximately 20–26 cm).
5.Comfortable and well-fitting earpieces.
6.Position the earpieces in the ears with both of the earpieces pointing toward the patient or client to be examined (see Fig. 9-1).
7.Ensure correct position of the head of the stethoscope when auscultating with the bell and diaphragm (see Fig. 9-1).*
8.Auscultate directly over the skin with firm pressure on the diaphragm—never auscultate over clothing. Auscultation with the bell should be performed with light pressure on the bell, which will enhance the detection of low-frequency sounds (see Chapter 10 for more information on auscultation with the bell of the stethoscope).
9.Minimize hand movement on the stethoscope and movement of the stethoscope on the skin when auscultating in the areas shown in Fig. 9-1.
10.Encourage patients or clients to take one to two deep breaths at each of the above sites and compare auscultatory findings to the opposite side as shown in Fig. 9-1.
11.Provide patients a rest period after several deep breaths to prevent fatigue, dizziness, or other complaints.
12.Auscultate in a quite environment.
*The head of the stethoscope with both a bell and a diaphragm can rotate so that sound is heard from either the bell or the diaphragm, but never from both at the same time. When the head of the stethoscope is rotated to the bell or diaphragm, a small hole at the base of the metal stethoscope will line up with either the bell or the diaphragm (see Fig. 9-1) and allow sounds to be transmitted through from the head of the stethoscope to the tubing and upward to the ears. Figure 9-1 shows the open hole for use of the bell and the closed hole for use of the diaphragm when auscultating.
The earpieces are inserted into the ears with the earpieces facing (pointing toward) the patient. This aligns the earpieces with the auditory canal. Placing the earpieces into the ears backward (with the earpieces pointing to the therapist) reduces heart and lung sounds and is a common error of students and new clinicians. Optimal auscultation of the lungs can be accomplished by using the helpful hints listed in Box 9-3.21,22
Method of Auscultating the Lungs
The method of auscultating the lungs requires proper use of the stethoscope as well as the correct placement of the diaphragm of the stethoscope on the chest. A systematic approach to lung auscultation is important and is always performed in such a manner that allows one side of the chest to be compared to the other side at the same level.21,22 The traditional sites used for auscultation of the lungs are shown in Fig. 9-1. This figure shows that there are six to eight auscultatory sites on the posterior chest and four to six sites on the anterior chest. Two sites are also present in the left and right axillary areas. Placement of the diaphragm of the stethoscope in these areas in a systematic manner and comparing both sides of the chest will improve lung auscultation efforts.
It is not uncommon for patients to become dizzy and fatigued during continuous auscultation of the chest because of repeated deep breathing. Patients should be instructed to stop and rest during a complete lung auscultatory examination. It is recommended that the patient take two complete deep breaths while the diaphragm of the stethoscope is applied at each site followed by a short rest.21,22 Figure 9-1 may be helpful in understanding what lobes of the lungs are being auscultated when the diaphragm is placed at each of the sites on the chest. The second and third laboratory exercises mentioned at the end of this chapter may also be helpful.
Sounds Heard During Auscultation of the Lungs—Breath Sounds
The sounds heard during auscultation of the lungs can be summarized as tracheal, bronchial, bronchovesicular, or vesicular.23 Other extra (adventitious) sounds also may be heard during auscultation of the lungs. The different types of breath sounds and the different qualities of the traditional breath sounds are listed in Table 9-5. It is important to note that the four traditional breath sounds are normally heard in the locations listed in Table 9-5. Breath sounds heard in areas where they are not supposed to be suggest that a pathological problem likely exists.23 Subtle, yet specific, characteristics may accompany the presence of a breath sound in an area where it should not exist. Identifying the presence of a breath sound in an area where it should not be, combined with other specific characteristics, enables the clinician to better understand the pathological process and direct further examination and subsequent treatment. A summary of different breath sounds heard when auscultating the lungs and their pathological implications is listed in Table 9-6.24
TABLE 9-5 Distinguishing Characteristics of Breath Soundsa
TABLE 9-6 Breath Sounds and Other Examination Findings Commonly Associated with Specific Pathologies
Chest Wall Excursion and Breathing Patterns
Examination of the baseline breathing pattern is possibly one of the most important and useful examination techniques of patients with pulmonary disease. The absence or presence of an abnormal breathing pattern may better direct other examinations and may be useful to direct specific management efforts (see Chapter 20). Several major types of breathing patterns include normal breathing, abdominal paradoxical breathing, upper-chest paradoxical breathing, and excessive accessory muscle breathing without abdominal paradoxical breathing.25 The characteristics and examination techniques of these breathing patterns are listed in Table 9-7.
TABLE 9-7 Characteristics and Examination Techniques of Different Breathing Patterns
Identifying an abnormal breathing pattern in a patient with known pulmonary disease may help to direct therapeutic interventions. For example, a patient demonstrating a paradoxical breathing pattern may obtain relief by a change in body position (see Chapter 20).26,27 Normal and abnormal breathing patterns can be appreciated only after review of the (1) muscles of ventilation, (2) biomechanics of breathing, and (3) tests used to measure breathing patterns. A more detailed review of the ventilatory muscles and the biomechanics of breathing are provided in Chapters 4 and 5, respectively.
Examining the Muscles of Breathing
Inspiratory muscles—The muscles of inspiration consist of primary and secondary (or accessory) muscles. The diaphragm is the primary muscle of inspiration accounting for approximately 75% of the work of inspiration. The secondary or accessory muscles of inspiration include the external intercostals, internal intercostals (the parasternal portion), scalenes, and sternocleidomastoid muscles, which account for approximately 25% of the work of inspiration.28 Figure 9-2 shows the muscles of inspiration, which should facilitate the examination of these muscles. Observation, palpation, and perturbation of these inspiratory muscles can provide important information about other examination techniques and primary areas of treatment. For example, a patient with obstructive lung disease observed and palpated to have excessive use of the scalene and sternocleidomastoid muscles with adequate perturbated diaphragmatic descent would likely benefit from inhibitory breathing techniques to the scalene and sternocleidomastoid muscles while facilitating diaphragmatic breathing.29 Information such as that obtained during the initial examination of a patient can facilitate specific therapeutic interventions. Methods to measure and determine the degree of accessory muscle use and diaphragmatic activity and movement (or potential for movement) will be discussed in the latter part of this chapter.
FIGURE 9-2 The muscles of inspiration and expiration. Anterior view of the chest wall depicting the bony cavity formed by the ribs, vertebrae, and sternum. Muscles of expiration (left) and inspiration (right) are shown.
Expiratory muscles—Expiration is normally a passive activity, and the muscles of expiration are rarely active except during increased levels of exercise and in several pulmonary diseases. The muscles of expiration consist of the abdominal muscles (rectus abdominis, oblique externus abdominis, oblique internus abdominis, and transversus abdominis) and internal intercostals (except for the parasternal portion). Figure 9-2 also shows the muscles of expiration, which should facilitate the examination of these muscles. Observation, palpation, and perturbation of these expiratory muscles can provide important information about other examination techniques and primary areas of treatment. For example, a patient with obstructive lung disease observed and palpated to have excessive use of his abdominal muscles, internal intercostals, and paravertebral muscles would likely benefit from inhibitory breathing techniques to the abdominal, internal intercostals, and paravertebral muscles while facilitating different body positions (eg, forward leaning) and breathing techniques (eg, pursed-lip breathing) to assist exhalation. As in the previous example, with excessive use of the inspiratory muscles, information such as that obtained during the initial examination of a patient can direct and facilitate specific therapeutic interventions.
Biomechanics of Breathing
The biomechanics of breathing are critical in understanding the results of all examination techniques of patients with pulmonary disorders. A schematic of the biomechanics of breathing is provided in Box 9-4.30–32 A quick glance at this schematic reveals the simplicity, yet complexity, of breathing.
Box 9-4
In normal breathing, it is necessary for the diaphragm to contract against the abdominal contents. As the diaphragm contracts and descends against the abdominal contents, it causes an increase in intra-abdominal pressure. The increase in intra-abdominal pressure produces three distinct motions. One motion is to separate the lower ribs, which essentially expand the lower rib cage. The increased intra-abdominal pressure transmits pressure laterally to the lower ribs, which separate them minimally (yet importantly) at end inspiration.29
A second motion is the upward and outward motion of the lower ribs, which is often referred to as the bucket handle motion. The bucket handle motion occurs as the diaphragm contracts and descends against the increased intra-abdominal pressure, which produces a fulcrum effect and causes the lower ribs to move upward and outward. This upward and outward motion is the result of the (1) diaphragm’s descent on the abdominal contents (increasing the intra-abdominal pressure), producing a fulcrum from which the diaphragm’s muscle fibers can pull the lower ribs upward and outward and (2) the orientation that the diaphragm’s muscle fibers are attached to the ribs in such a way that when they pull downward they actually cause the ribs to rotate medially and lift laterally in an upward/outward direction.29
The best way to picture the diaphragm’s descent on the abdominal contents and pull on the lower ribs is to place your hands in front of your body at chest level about 6 in. apart with elbows at your side; then bring you hands together and move them downward, allowing the elbows to move upward and outward away from your body. The outward motion of both arms (with elbows rising upward) represents the upward and outward motion of the lower ribs (bucket handle motion). Combining the inward motion of the clenched hands with upward rising elbows demonstrates how the diaphragm’s descent on the abdominal contents produces the bucket handle motion of the lower ribs.
Another way to visualize the bucket handle motion is to use a bucket with two handles: one handle representing the diaphragm and the other handle representing the lower ribs. Position one handle at the top of the bucket (top dead center) and the second handle at the bottom against the side of the bucket. Movement of the top handle downward represents diaphragmatic descent, whereas movement of the bottom handle (the one against the side of the bucket) upward represents bucket handle motion during inspiration. During expiration, these movements are reversed and yield the so-called bucket handle motion of the lower ribs. Observing the amount of diaphragmatic descent as well as the amount of bucket handle motion is critically important in managing patients with cardiopulmonary disorders.
A third motion is the anteroposterior motion of the upper ribs, which is often referred to as pump handle motion. Pump handle motion is less related than bucket handle motion to the increase in intra-abdominal pressure. It is more related to the contraction of the accessory muscles of breathing that, upon contraction (shortening), pull the upper ribs in an anterior and outward manner, which move posterior or inward upon relaxation of the accessory muscles. Pump handle motion can be best appreciated by visualizing an old-fashioned water pump (similar to the type used at a campsite). Pushing down on a pump handle is synonymous to the relaxation of the accessory muscles, which produce the posterior or inward motion of the upper ribs. The upward motion of the pump handle is synonymous with the contraction of the accessory muscles of breathing, which moves the upper ribs anterior and outward.29
Methods to Measure Breathing Patterns
A variety of methods to measure breathing patterns exist, many of which are listed in Boxes 9-5 and 9-6 and also shown in Fig. 9-3. These methods will be described in the following section.
Box 9-5
Methods to Directly and Indirectly Evaluate Chest Wall Motion and Diaphragmatic Excursion
1.Fluoroscopy
2.Distribution of ventilation via nitrogen washout and xenon distribution (133Xe)
3.Chest wall motion via respiratory inductive plethysmography tape measure or ultrasound
4.Pulmonary function test results
5.Maximal inspiratory and expiratory mouth pressures
6.Transdiaphragmatic, abdominal, and intrathoracic pressures
7.Palpation—placing the fingertips above and under the anterior lower ribs bilaterally, approximately 6–8 cm lateral from the xiphoid process during a sniff; palpation of abdominal and upper chest wall motion (hand placement on the abdomen and upper chest, respectively); palpation of the anterior chest wall with the thumbs over the costal margins and thumb tips meeting at the xiphoid process (with movement of the hands laterally and slightly upward at least 5–8 cm); see Fig. 9-3A
8.Percussion in the anterior and posterior aspects of the thorax between the lowermost ribs and the 12th thoracic vertebrae; see Fig. 9-3B
9.Auscultation of breath sounds
10.Visual observation
Box 9-6
FIGURE 9-3 Methods to measure breathing patterns and diaphragmatic descent. (Modified with permission from Cherniack RM, Cherniack L. Respiration in Health and Disease. 2nd ed. Philadelphia, PA: WB Saunders; 1972.)
Observation—Observation of the breathing pattern can be made by focusing on the upper chest wall movement (from the xiphoid process upward) and the lower chest wall movement (abdominal area around the umbilicus). The normal breathing pattern consists of an outward upper and lower chest wall motion during inspiration and inward upper and lower chest wall motion during expiration. The outward lower chest wall motion during inspiration is due to the downward descent of the diaphragm on the abdominal contents, which increases the intra-abdominal pressure and causes the abdominal contents to move forward, or actually, outward. The outward upper chest wall motion during inspiration is due to increased intra-abdominal pressure (from diaphragmatic contraction) and contraction of the accessory muscles of inspiration.30–32
While seated, place one hand on your lower chest (abdominal area) and one hand on your upper chest (midsternal area) and observe and palpate the chest motion during inspiration and expiration.
Palpation—Placement of the hands on the upper and lower chest of a patient while breathing will yield valuable examination information about the principal breathing pattern. Palpation in the abdominal area (for lower chest wall motion) and in the midsternal area (for upper chest wall motion) should direct the examiner to areas of hypermobility or hypomobility of the thorax.
Palpation of the chest wall can also be performed with the hands placed in a manner different from the method mentioned previously. The hands can be placed posteriorly or anteriorly in several different areas of the chest to evaluate the primary breathing pattern. The posterior hand placement locations include the base of the lungs bilaterally, between the scapulae bilaterally, and on the shoulders (on the superior and posterior aspects of the trapezius) bilaterally. The anterior hand placement locations include the base of the lungs bilaterally (immediately below the breasts), just above the breasts bilaterally, and on the shoulders bilaterally (on the superior and anterior aspect of the trapezius). An example of such hand placement is shown in Fig. 9-3.
Such gross examinations are helpful to determine the severity of chest wall motion abnormalities, but more objective measurement techniques exist, which increase the likelihood for correct and accurate examination and management techniques. The remaining sections will present other objective techniques to measure chest wall excursion in patients with pulmonary and even cardiac disorders.
Chest wall excursion via tape measure—Simple measurements of chest wall excursion using a tape measure can quantify motion in different areas of the thorax. We have found the measurement of chest wall excursion at three anatomical sites to be beneficial in better understanding the chest wall excursion of a variety of subjects with and without disease.33–35 The three anatomical sites include the sternal angle of Louis on the sternum (at the second rib), the xiphoid process, and a midpoint between the xiphoid process and the umbilicus (see Fig. 9-3A). Chest wall excursion measurements made at the sternal angle may best represent upper chest wall motion, whereas measurements made at the xiphoid process site represent middle chest wall motion. Chest wall excursion measurements made at the midpoint between the xiphoid process site and the umbilicus represent lower chest wall motion. In fact, the midpoint between the xiphoid process and the umbilicus appears to be the site at which much of the bucket handle motion can be measured. The sternal angle site as well as the xiphoid process site likely measures much of the pump handle motion. Therefore, using these three anatomical locations to measure chest wall excursion can provide an objective measure of upper and lower chest wall motion (or the amount of pump handle and bucket handle motion, respectively).
The technique to measure chest wall excursion at the aforementioned anatomical sites involves using a standard tape measure that is pulled taut, but not so tight that it prevents inspiration at the site being measured. Adding a spring-loaded metal phalange to the end of the tape can improve the measurement technique and decrease measurement error. Spring-loaded metal phalanges are quite inexpensive and can be purchased from a variety of medical suppliers.
The tape should be wrapped around the thorax at the level of the anatomical landmark, which can be identified with a marker to ensure similar measurement sites (especially the site for lower chest wall excursion measurements—midpoint between the xiphoid and the umbilicus). After the tape is checked for levelness, the subject is asked to inspire normally (not maximally). The tape measure should move horizontally as the subject inspires and the distance from preinspiration to end of normal inspiration is measured. The method of measuring from the end of expiration to the end of normal inspiration is shown in Fig. 9-3 and further described in Box 9-6.33–35 A data input sheet for measurements of chest wall excursion is also included in Box 9-6.
The amount (distance) of chest wall motion during normal breathing (which can be referred to as tidal volume [VT] breathing) should be recorded in centimeters or inches on the data input sheet of Box 9-6 under VT breathing. This table can be used during the laboratory session during normal conditions or when students are submerged in water as referred to in Box 9-6.
Chest wall motion during a maximal inspiration should be measured in the manner described previously, and the amount of motion should be recorded in centimeters or inches under vital capacity (VC) breathing in Box 9-6. It may be difficult to measure chest wall excursion at all three anatomical sites, but measurements at the sternal angle and midpoint between the xiphoid process and umbilicus will yield important information related to pump handle and bucket handle motion. This information can be used to direct therapeutic interventions and to evaluate the effectiveness of interventions.
Chest Wall Excursion via Respiratory Inductive Plethysmography
Respiratory inductive plethysmography is considered by some to be the “gold standard” technique to evaluate chest wall excursion and the relationship between upper and lower chest wall excursion.36 Inductive plethysmography is a technique that requires two elastic bands to be placed around the thorax at two anatomical sites (see Figs. 9-4A and 9-4B). One strap is wound around the thorax at the level of the nipples and the other strap is wound around the thorax at the level of the umbilicus. The straps have electrical wires sewn into the elastic, which enables chest wall motion to be identified as a change in the electrical potential. The change in electrical potentials is relayed to an analog-to-digital converter, which provides accurate analysis and recording of the chest wall motion at the two sites as well as the relationship between the chest wall excursion at the upper and lower chest straps. The chest straps and the resultant data from them (Fig. 9-4C) are also shown in Fig. 9-4B.
FIGURE 9-4 Respiratory inductive plethysmography unit and ultrasound measurement of chest wall motion. (A) Plethysmography unit with elastic bands. (B) Placement of the bands around the thorax. (C) Resultant graph of measures obtained from the plethysmography unit. (D, E) Ultrasound unit used to measure chest wall motion.
Other Novel Techniques to Measure Chest Wall Excursion
Several other novel techniques to measure chest wall excursion are presently being developed. The use of ultrasound rays emitted from a transducer, which has the capacity to measure motion of the chest and digitize the motion at each site of a transducer (or a series of transducers), can provide information about chest wall motion in a manner that has not been possible before now. The placement of six transducers over the thorax can analyze the motion occurring in all areas of the thorax or individually in the upper, lower, or right/left sides of the thorax. For example, the upper and lower chest wall excursions can be evaluated by combining the data from the two transducers in the upper right and left quadrant (upper chest wall) and comparing it to the data from the two transducers in the lower right and left quadrant (lower chest wall). However, the chest wall motion of the left upper quadrant can also be compared to the motion in the upper right quadrant as well as to one or both of the transducers over the lower quadrants. The device to measure chest wall motion in this manner is shown in Figs. 9-4D and 9-4E.
Electromyography (EMG) does not measure actual chest wall motion, but it provides important information that is directly related to chest wall motion. The EMG activity of the respiratory muscles can be observed visually and can be analyzed to determine whether the muscle activity is normal, hyperactive, or hypoactive. The EMG can also be used as a biofeedback tool to help patients understand different ways in which to breathe and use the respiratory muscles.37,38 Such methods have proven to be beneficial for a variety of patient populations.
Important Considerations When Examining Breathing Patterns
Diaphragmatic Movement
The ability of the diaphragm to move is critically important when attempting to understand particular breathing patterns. It is also an important examination technique when utilized to determine the correct intervention for subjects with cardiopulmonary disease (see the hypothesis-oriented algorithm in Chapter 19). The lack of diaphragmatic movement or limited amount of diaphragmatic motion may be responsible for specific abnormal breathing patterns.29For example, if the diaphragm is unable to contract as in spinal cord injury or if it contracts poorly because of moderate-to-severe flattening from obstructive lung disease, particular abnormal breathing patterns are likely to be observed. Likewise, specific interventions can be more confidently provided when diaphragmatic motion, or lack of it, can be determined.
In patients with complete spinal cord injuries above the third cervical level, the diaphragm is unlikely to receive nervous system signals to contract, and as a result, they will require immediate mechanical ventilation to enable them to breathe. A person with a spinal cord injury below the fifth cervical level will very likely receive nervous system signals for the diaphragm to contract, but will not have abdominal or other accessory muscle function, which will likely result in an upper chest paradoxical breathing pattern. This breathing pattern is characterized by a prominent outward motion of the abdominal area (as the diaphragm contracts and descends and pushes the abdominal contents forward and outward) and a prominent inward motion of the upper chest (due to the lack of structural support from paralyzed thoracic musculature) during inspiration (see Fig. 9-5A).39,40
FIGURE 9-5 Paradoxical breathing: (A) Upper chest paradoxical breathing, (B) abdominal paradoxical breathing. (Modified, with permission, from Massery M. The patient with neuromuscular or musculoskeletal dysfunction. In: Principles and Practice of Cardiopulmonary Physical Therapy. 3rd ed. Mosby Yearbook; 1996.)
In patients with severe emphysema and hyperinflated chests, the diaphragm is frequently pushed downward (from severe air trapping in emphysematous lungs) and is often referred to as flattened. The flattening of the diaphragm places the skeletal muscle fibers of the diaphragm in a shortened position, which makes it difficult for the muscle fibers to optimally contract. In addition, the flattened position of the diaphragm leaves very little room for the diaphragm to descend. Both the shortened muscle fibers and the flattened position of the diaphragm will prevent the generation of necessary negative pressure to ventilate the lungs. As a result, the accessory muscles of breathing frequently become more active and perform much of the work needed to breathe. In fact, the generation of negative pressure needed to ventilate the lungs becomes prominent in the pump handle area of the chest (upper chest), whereas the diaphragm produces very little negative pressure to ventilate and breathe. Under such a condition, the lack of adequate diaphragmatic contraction and descent produces very little generation of negative pressure in the bucket handle area (lower chest), and the negative pressure generated in the upper chest area sucks the abdominal area inward while the upper chest moves outward during inspiration (see Fig. 9-5B). This breathing pattern is termed as the abdominal paradoxical breathing pattern and is associated with ventilatory failure.41–43 Both the previously cited breathing patterns are shown in Fig. 9-5.
Of utmost importance is the examination of diaphragmatic movement or the potential for movement. The following section will review a variety of examination techniques (listed in Box 9-5) to determine the amount of diaphragmatic motion and the potential for improvement in motion.
Methods to Directly and Indirectly Measure Diaphragmatic Motion
A number of methods are available to directly and indirectly measure diaphragmatic motion and include fluoroscopy, magnetic resonance imaging (MRI), differences between abdominal and transdiaphragmatic pressures, chest wall excursion measurements, palpation, mediate percussion, and several other methods. A list of all methods to directly and indirectly measure diaphragmatic motion is provided in Box 9-5.29
Palpation—In view of the previous discussion, it should be apparent how important it is to evaluate the ability of the diaphragm to move. Palpation of the movement of the diaphragm during breathing can be performed indirectly by placing the hands upon the thorax (one hand on the abdomen and one hand on the upper chest to evaluate abdominal and upper chest wall motion, respectively). However, a more specific indirect method of palpating diaphragmatic motion is to place the fingertips of both hands under the lower ribs anteriorly, placing the fingertips above and under the anterior lower ribs bilaterally, approximately 6 to 8 cm lateral from the xiphoid process (see Fig. 9-3). As the person inspires, the downward descent of the diaphragm can be appreciated as the fingertips of both hands are pushed away from the lower ribs. Patients with no or very little diaphragmatic descent will not push the fingertips away from the lower ribs. If it is difficult to feel the push of the fingertips away from the lower ribs, it is helpful to complete the palpation examination for diaphragmatic movement by asking the patient to sniff forcefully. Sniffing is likely to enhance diaphragmatic contraction, which is necessary to completely understand the amount and potential of diaphragmatic movement.29
Examining the descent of the diaphragm in the aforementioned manner can also be helpful in understanding whether both hemidiaphragms are contracting and descending downward. Patients with cerebrovascular accidents may have only one hemidiaphragm functioning and may demonstrate a “pushing away” of the fingertips only on the side that is actively contracting downward.
Another potentially useful method to clinically evaluate diaphragmatic excursion is palpation of the anterior chest wall with the thumbs over the costal margins and thumb tips meeting at the xiphoid process, with normal movement of the hands laterally and slightly upward at least 5 to 8 cm during a deep inspiration (see Fig. 9-3).29 Patients with severe COPD and hyperinflated lungs may demonstrate very little palpable motion due to very little diaphragmatic excursion.
Mediate percussion and auscultation— Mediate percussion and auscultation are two additional methods to indirectly measure diaphragmatic excursion. Mediate percussion is a technique which physicians often use to understand the status of structures inside the body by listening for the quality of sound produced by a fingertip tapped on the middle finger of the opposite hand placed flat against the body. The dullness or lack of dullness identifies the presence or absence of an underlying organ or foreign body. The descent of the diaphragm during inspiration and the ascent of the diaphragm during expiration can be appreciated by performing mediate percussion during the breathing cycle on the posterior aspect of the thorax at the lower ribs.29
Mediate percussion in the posterior thorax at the level of the lowermost ribs may yield important differences in sound quality associated with diaphragmatic movement. Movement of resonance (loud or high amplitude, low-pitched, and long-duration sounds heard over air-filled organs such as the lungs) during inspiration and expiration provides an indirect measure of diaphragmatic excursion. Mediate percussion at maximal end inspiration can identify the lowest level of diaphragmatic descent by identifying a resonant tone. Mediate percussion at end exhalation should normally reveal a higher level on the thorax at which the resonant tone is heard. The difference between the levels of higher and lower resonance on the thorax is an indirect measure of diaphragmatic excursion and is normally 3 to 5 cm (see Fig. 9-3B). The change in levels of resonance during the respiratory cycle provides an indirect measure of the caudal and cranial movement of the diaphragm.29
Less than 3 cm of audible movement is suggestive of limited diaphragmatic movement. No change in the quality of sound during mediate percussion throughout the respiratory cycle is strongly suggestive of a diaphragm that is not moving. Resonance that is unchanged throughout the respiratory cycle is likely to be associated with minimal diaphragmatic excursion and is often found in severe COPD with hyperinflation of the lungs. It is important to note that the quality of sound will be affected by adipose tissue and other space-occupying structures such as tumors, enlarged organs, or diffuse pulmonary disease.29
Finally, auscultation of breath sounds may provide some indirect information regarding diaphragmatic excursion during diaphragmatic breathing (DB) with greater breath sounds in the basilar segments of the lungs occurring with greater diaphragmatic excursion. However, the clinical utility of both of these techniques (auscultation and mediate percussion) requires further investigation.29
Another very important adjunct when examining breathing patterns and understanding the reasons for particular patterns of breathing is the strength and endurance of the respiratory muscles. The following sections will address the available methods to measure the strength and endurance of the breathing muscles but will be preceded by an overview of the significance of the strength and endurance of the breathing muscles upon the pressure changes during the breathing cycle.
Pressure Changes During the Breathing Cycle
The importance of pressure changes during the breathing cycle is evident in Box 9-4. During normal breathing, it is necessary for intrathoracic pressure to become more negative during inspiration and more positive (yet still negative) during expiration. These changes in the intrathoracic pressure allow for atmospheric air to move into the lungs during inspiration and for the air to leave the lungs during expiration. Pressure changes within the thorax and lungs also reflect the changes occurring within the intrathoracic area. These pressure changes are shown in Fig. 9-6A.44
FIGURE 9-6 Changes in volume, pressure, flow, and ventilation.
During inspiration, the intrathoracic pressure decreases, which is also accompanied by a decrease in the intrapleural pressure and alveolar pressure as shown in Fig. 9-6A. As a result of the changes in pressure in each of the aforementioned areas, the volume of air increases and inward flow increases during mid-to-late inspiration. During expiration, the intrathoracic pressure, which is also accompanied by an increase in intrapleural pressure and alveolar pressure, increases. These increases in pressure during expiration cause the volume of air to decrease and outward flow to increase.44
The effects of these changes in pressure during the respiratory cycle (preinspiration, inspiration, end inspiration, and forced expiration) are shown in Fig. 9-6B. Intrapleural pressure decreases to a maximal level of –8cmH2O at end inspiration, but can quickly rise to +30cmH2O during a forced expiration. Alveolar pressure decreases to a maximal level of –2cmH2O at midexpiration, but increases to 0 cm H2O at end inspiration. Alveolar pressure increases much more during a forced expiration. Other very important pressure changes seen in Fig. 9-6 include the airway pressures and the opposing pressures, which significantly affect volume and flow during both inspiration and expiration. During inspiration and expiration, it is important for the airway pressure to match as closely as possible the opposing pleural pressure. However, during expiration it may be difficult to maintain similar pressures due to the force of expiration or the presence of pulmonary disease. If the difference between the airway pressure and the opposing pleural pressure is great, it is possible that the airway will collapse as shown in Fig. 9-6.44 Such a collapse during expiration will significantly decrease the volume and flow of air leaving the lungs.
Figure 9-6C also shows the typical volume and flow of a single normal alveoli. Note that the flow is characterized by a certain unit of time, which is typically measured in minutes. Normal alveolar ventilation is approximately 5,250 mL/min, whereas normal total ventilation is approximately 7,500 mL/min. The normal volume of alveolar gas is approximately 3,000 mL and the normal VT is approximately 500 mL.44 Pulmonary disease will markedly change these volumes and flows and will significantly alter the biomechanics of breathing. The altered biomechanics of breathing associated with pulmonary disease are frequently due to abnormal pressures throughout the breathing cycle and throughout the lung.
Pressure Differences Within the Lung
The abnormal pressure differences throughout the breathing cycle of a person with pulmonary disease are often due to abnormal pressure differences throughout the lung. This can be better understood by viewing Fig. 9-7, in which a more normal presentation of the pressure differences within the lung are shown. Because of the weight of the lungs on the abdominal contents, the intrapleural pressure at the base of the lungs is greater than that at the apex. The intrapleural pressure at the base is still negative (–2.5cmH2O), but it is less negative than that at the apex of the lung (–10 cmH2O).44
FIGURE 9-7 Pressure differences in the top of the lungs compared to those at the bottom in (A) health and (B) disease.
Under conditions like emphysema, or even in aging, the intrapleural pressures at both the base and the apex are less negative than those in the normal person. In fact, at very low lung volumes such as in advanced emphysema, the intrapleural pressure at the base of the lung can actually be positive (see Fig. 9-7B). Therefore, the pressure at the base of the lung exceeds the pressure within the airways, which is likely to collapse the airways at the base of the lungs.44
Noninvasive Measurement of Inspiratory and Expiratory Pressures
In view of the preceding discussion, breathing muscle strength is an important examination technique that is critical in understanding abnormal breathing patterns and in directing optimal interventions for persons with cardiopulmonary disease. A number of different techniques exist to measure breathing muscle strength that include manual muscle testing, measurements of maximal inspiratory pressure and maximal expiratory pressure (MIP and MEP, respectively), and tests of breathing muscle strength via weighted breathing (ie, weights are added to the abdominal area of a supine patient).45 Only MIP and MEP measurements provide the specificity and quantification of breathing muscle strength necessary to establish the primary problem and mode of intervention for patients with cardiopulmonary disorders. However, a brief discussion of the other noninvasive techniques will be provided in an attempt to strengthen the clinical utility of MIP and MEP measurements.
Manual muscle testing—Manual muscle testing of the respiratory muscles is difficult, because it is virtually impossible to perform a manual muscle test of the diaphragm, and it is very difficult to quantify the combined strengths of the accessory muscles of breathing and their contribution to the breathing process. However, several of the methods to examine diaphragmatic motion, previously described and listed in Box 9-5, can be adapted in such a way that manual resistance applied during inspiration may provide an indirect measure of inspiratory muscle strength. Attempting to resist the (1) pushing away of the fingertips from under the lower ribs bilaterally, (2) bucket handle motion of the lower ribs bilaterally, or (3) outward movement of the abdomen during inspiration may all provide an indirect manual measurement of diaphragmatic muscle strength.
Maximal inspiratory and expiratory pressure measurements—Measurement of MIP and MEP has increased in popularity in recent years.46,47 Several different devices are available, which allow for MIP and MEP to be measured. An example of one such device, the Magnehelic, is shown in Fig. 9-8. Each device works essentially the same way and measures the amount of negative pressure developed during a maximal inspiration and the amount of positive pressure developed during a maximal expiration. The unit of measure to record the strength of the breathing muscles for MIP and MEP is frequently in centimeters of water (cm H2O). These electronic devices measure with greater accuracy and reliability than do the other devices. However, accurate and reliable measurements can also be achieved when using these less costly devices by carefully observing the magnitude of needle deflection during inspiratory and expiratory measurements of ventilatory muscle strength.
FIGURE 9-8 Left, the Magnehelic, a device used to measure maximal inspiratory and expiratory pressure. Right, a Threshold inspiratory muscle loading device to measure ventilatory muscle endurance.
The methods of measuring MIP and MEP are presented in Box 9-7, which also contains a data input sheet. It is very important that measurement of MIP be performed after a maximal expiration (near residual volume [RV]) and that measurement of MEP be performed after a maximal inspiration (total lung capacity [TLC]). It is also important to standardize the testing procedures and to test the patients while seated in a chair with their hips perpendicular to the back.46,47 The patient should be encouraged during the measurement of both MIP and MEP but should not be allowed to flex forward or to extend backward during testing. An adequate seal at the mouthpiece is also important to obtain accurate and reliable MIP and MEP measurements.
Box 9-7
In addition to the measurement of MIP and MEP, spirometric measurement of VC at the patient’s bedside can yield additional and important information about the patient’s ability to move air into and out of the lungs. Figure 9-9shows two commonly used spirometer devices for the bedside measurement of PFTs.
FIGURE 9-9 Examples of two portable spirometers used for pulmonary function testing.
Weighted breathing as a test of breathing strength—Placing weights upon the abdominal area of a patient with cardiopulmonary disease has previously been described as a method to test and train the ventilatory muscles.48 It has been advocated as a method to increase the strength and endurance of the respiratory muscles and has been used extensively for persons with spinal cord injury.48 Although placing progressively greater weight on the abdominal area during breathing can identify a particular level of strength and point at which a patient may no longer be able to breathe, it actually measures the breathing endurance of a patient. Therefore, weighted breathing is less specific for breathing strength and more specific for breathing endurance. The following section will present other methods to test breathing muscle endurance.
Noninvasive Measurement of Ventilatory Muscle Endurance
A number of different methods to measure breathing muscle endurance exist.49 The most widely used methods and their strengths and weaknesses are listed in Table 9-8. The primary methods to measure ventilatory muscle endurance include (1) the ability to sustain breathing loads (frequently 70%–85% of maximum voluntary ventilation [MVV]) for a particular duration, (2) breathing with an externally applied mechanical load (eg, threshold loading), (3) measurement of sustainable pressure loads in which a subject begins breathing at a load of 90% MIP that is gradually decreased in 5% decrements until the load can be sustained for greater than 10 minutes, or (4) progressive incremental breathing against resistance (beginning at approximately 20%–30% of MIP and increasing the load every 2 minutes by 10%–20% increments for as long as possible).50
TABLE 9-8 Strengths and Weaknesses of Various Methods to Measure Ventilatory Muscle Endurance
Perhaps the most clinically useful and applicable test of ventilatory muscle endurance is the progressive incremental breathing against resistance. Such inspiratory muscle endurance testing has been described by Martyn et al.51The measurement of inspiratory muscle endurance can be performed with a threshold loading device, which will provide a patient resistance during inspiration. An example of the threshold loading device is shown in Fig. 9-8. The test usually begins at 20% of MIP, and the patient is asked to breathe with the device for 2 minutes. If the patient tolerates breathing with resistance set at 20% of MIP, the resistance will be progressed by 20% increments (based on the initial MIP) until exhaustion. End-tidal carbon dioxide and oxygen saturation levels, inspiratory muscle use, and level of dyspnea are often monitored; and testing is terminated if abnormal carbon dioxide levels are observed, if a paradoxical breathing pattern occurs, or if a patient reports of severe dyspnea (Borg-modified dyspnea score of ≥7/10). The measurement of ventilatory muscle endurance using this method has been found to be safe, reproducible, and representative of other measurements, often accepted as a measure of ventilatory muscle endurance.52–54 The specific methodology of (progressive) incremental ventilatory muscle endurance testing and a data input sheet are provided in Box 9-8.
Box 9-8
The pressure changes inside and outside of the lung during breathing are what allow for adequate oxygenation of the blood and the removal of carbon dioxide from the blood. Therefore, it is now necessary to discuss the effects of the previously cited pressure changes during breathing on ventilation and oxygenation of the lungs. The methods to examine ventilation, perfusion, and oxygenation of the lungs are medical examinations that are rarely performed by physical therapists but are used extensively by physical therapists to diagnose, allocate specific interventions, and determine a likely prognosis for patients with cardiovascular and pulmonary disorders.
MEDICAL EXAMINATIONS USED BY PHYSICAL THERAPISTS
Ventilation and Perfusion of the Lungs
Ventilation of the lungs can be simply defined as the movement of air into and out of the lungs. Perfusion of the lungs can also be simply defined as the movement of blood into and out of the lungs. Ventilation of the lungs can be examined in several different ways including auscultation of the lungs, ventilation–perfusion scans, and arterial blood gases.55–57 Perfusion of the lung can be examined via the aforementioned ventilation–perfusion scan during which a radioisotope is administered by intravenous injection and another isotope is administered via inhalation. The uptake of the inhaled isotope by the lungs and the uptake of the injected isotope by the pulmonary circulation is examined with radiographic techniques (X-rays) that provide detailed information about the areas of the lung and the amount of lung tissue receiving air (ventilation) and circulation (perfusion).55–57 Deficit areas, or areas of mismatch, are indicative of particular diseases. This method is considered the “gold standard” to measure ventilation and perfusion of the lungs, but other less sophisticated and invasive methods can also provide some information related to the ventilation and perfusion of the lungs; however, they are often less sensitive and specific to certain diseases.55–57 The other less informative methods include auscultation of the lungs, use of a respirometer, respiratory inductive plethysmography, and arterial blood gases. The methods, strengths, and weaknesses of each of the measurement techniques of ventilation and perfusion of the lungs are presented in Table 9-9.
TABLE 9-9 Measurement Techniques of Ventilation and Perfusion of the Lungs: Methods, Strengths, and Weaknesses
It is important to note that if the pressure changes during the breathing cycle that were discussed previously are minimal, patients will often suffer from less ventilation, which will result in elevated carbon dioxide levels and poor oxygenation.55–57 Such abnormalities can be better understood by examining arterial blood gases.
Arterial Blood Gases
The pressure changes that occur during breathing, which were discussed in several of the preceding sections, allow for alveolar ventilation and oxygenation to occur.55–57 Arterial blood gases provide the opportunity to examine alveolar ventilation, oxygenation, and the acid–base relationship of the body. Box 9-9 provides an overview of the examination process of arterial blood gases. From Box 9-9 it is apparent that only two blood gas variables are needed to understand basic arterial blood gas status. The two blood gas variables are (1) the level of carbon dioxide in the arterial blood (PaCO2) and (2) the blood pH. The level of PaCO2 in arterial blood will provide an insight into the level of alveolar ventilation, and the pH level will yield information about the effect of PaCO2 on the body’s homeostatic environment (acid–base relationship).58 It is critical to understand that increased levels of PaCO2 decrease pH and decreased levels of PaCO2 increase the pH.58 This inverse relationship between PaCO2 and pH is the basis for much of arterial blood gas analyses because the carbon molecule is countered by the negative charges of two O2 molecules. This relationship can be better understood by referring to the Henderson–Hasselbalch equation.59
Box 9-9
Methods to Analyze Arterial Blood Gases
Two main pathways can be followed when interpreting arterial blood gas data. The direction of the pathway is determined by the pH. One pathway identifies an acidosis and the other pathway identifies an alkalosis. Identification of a primary respiratory problem versus a primary metabolic problem is accomplished by examining the pH and PaCO2 relationship on the second and fourth levels of this figure. The compensatory ability of the body to manage an acidic or alkalotic environment is reflected by the concentration of bicarbonate (HCO3 and PaCO2) on the sixth and seventh levels of this figure. A primary respiratory problem is associated with an inverse relationship (opposite directions) between PaCO2 and pH. A primary metabolic problem is associated with a direct relationship (in the same direction) between PaCO2 and pH. Abnormal bicarbonate levels can provide important information to better distinguish acute versus chronic respiratory and metabolic problems. If the relationship between pH and PaCO2 is direct, the problem is likely to be primarily metabolic while an indirect relationship between the two likely identifies a primary respiratory problem.
The Henderson–Hasselbalch equation examines the relationship between carbonic acid and bicarbonate ions, which in turn yield the pH:
pH = pK + Log [HCO3-]/H2CO3].
The specific relationship between carbonic acid and bicarbonate ions and calculation of pH using the previous equation is somewhat complex. It is clinically acceptable to replace carbonic acid (H2CO3) with PaCO2 to calculate pH.59However, the specific calculation of pH is rarely calculated by hand. Automated blood gas analysis systems that have been programmed with the Henderson–Hasselbalch and other equations rapidly calculate the pH and other blood gas measures. Perhaps one of the most important principles of the aforementioned relationships and equations is that the pH is the negative log of the hydrogen ion concentration.59 It is this fact that enables the inverse relationship between PaCO2 and pH, presented previously, to be applied clinically. An excellent source to learn more about the Henderson–Hasselbalch equation and its role in pH and blood gas analysis can be found at http://www.tmc.tulane.edu/departments/anesthesiology/acid/default.html.
Methods of Measuring Arterial Blood Gases
Obtaining a blood sample— A sample of arterial blood is taken from an indwelling arterial line or an arterial puncture is made that will provide access to arterial blood. Venous blood samples or mixed venous samples can be obtained from a peripheral vein puncture or from a pulmonary artery catheter. Usually one to two test tubes of blood are taken from a patient, and the sample is often immediately sent to the laboratory for analysis.60
Arterial blood gas analysis— When arterial blood gases are analyzed, blood samples are subjected to an automated pH–blood gas analyzer, which consists of an oxygen and carbon dioxide sensor. Standardized calibration of the analyzer is performed with reference gases before the sample obtained for study is subjected for analysis. Hemoximetry is usually performed in conjunction with blood gas–pH analysis; it utilizes a multiple wavelength spectrophotometer to examine total hemoglobin and its components because oxygenation is dependent on hemoglobin concentration.60
Making sense of arterial blood gas data—pH and PaCO2 interpretation (inverse or direct relationship)—Box 9-9 lists two main pathways that can be followed when interpreting arterial blood gas data. One pathway identifies a primary respiratory problem, whereas the other pathway identifies a primary metabolic problem. A primary respiratory problem can be easily differentiated from a primary metabolic problem because of the presence of an inverse relationship between PaCO2 and pH in a primary respiratory problem.58–60 For example, alveolar hypoventilation is a term that is frequently used in the analysis and interpretation of arterial blood gases. Alveolar hypoventilation is characterized by elevated levels of carbon dioxide in the blood because of poor ventilation to the alveolar area. Therefore, poor ventilation to the alveolar area is a primary respiratory problem, rather than a primary metabolic problem, and produces an acidic environment. Similarly, alveolar hyperventilation is a term occasionally used in the analysis of arterial blood gases and is associated with an inverse relationship between PaCO2 and pH.
However, the inverse relationship is opposite from that which is seen with alveolar hypoventilation. Alveolar hyperventilation is characterized by increased alveolar ventilation and a subsequent decrease in carbon dioxide, which then increases the pH. This increase in pH because of excessive alveolar ventilation produces an alkalotic environment as shown in Box 9-9.58–60
A primary metabolic problem will often be determined by the presence of a direct relationship between PaCO2 and pH. A quick glance at Box 9-9 reveals that a primary metabolic acidosis or alkalosis is associated with direct relationships between pH and PaCO2.. The PaCO2 of a metabolic acidosis is less than the accepted low end of normal (35 mm Hg), and the pH is less than the accepted normal of 7.40; thus, both values are less than the accepted normal value in a similar direction, which produces the direct relationship between PaCO2 and pH. The PaCO2 of a metabolic alkalosis is greater than the accepted high end of normal (45 mm Hg), and the pH is also greater than the accepted normal of 7.40; thus, both values are greater than the accepted normal value in a similar direction, which produces the direct relationship between PaCO2 and pH.58–60
Bicarbonate HCO3- in terpretation—Abnormal bicarbonate levels can provide important information to better distinguish acute versus chronic respiratory and metabolic problems. Box 9-9 shows that acidosis can be associated with a HCO3- less than the accepted low end of normal (22 mEq) or an HCO3- greater than the accepted high end of normal (26 mEq). In the former situation of acidosis and below normal HCO3-, the patient is likely suffering from a primary metabolic acidosis, whereas in the latter situation of acidosis and above normal HCO3-, the patient is likely suffering from a primary respiratory acidosis with the kidneys attempting to compensate for the acidic environment by releasing more HCO3-. Of note is the relationship between the pH and HCO3-. If the relationship between pH and HCO3- is direct (in the same direction), the problem is likely primarily metabolic, whereas an indirect relationship (opposite directions) between the two likely identifies a primary respiratory problem.58–60
Box 9-9 also shows that alkalosis can be associated with a HCO3- greater than the accepted high end of normal (26 mEq) or an HCO3- less than the accepted low end of normal (22 mEq). In the former situation of alkalosis and above normal HCO3-, the patient is likely suffering from a primary metabolic alkalosis; whereas in the latter situation of alkalosis and below normal HCO3-, the patient is likely suffering from a primary respiratory alkalosis with the kidneys attempting to compensate for the alkalotic environment by releasing less HCO3-. Again, it is important to note the relationship between the pH and HCO3-. If the relationship between pH and HCO3- is direct (in the same direction), the problem is likely primarily metabolic, whereas an indirect relationship (opposite directions) between the two likely identifies a primary respiratory problem.58–60
Oxygen interpretation— The interpretation of oxygen is often the last variable examined in the analysis of arterial blood gases. Arterial blood gas analysis of oxygen is performed with an oxygen sensor in the automated pH–arterial blood gas analyzer, which measures the partial pressure of oxygen (PaO2) in the arterial blood as well as the amount of oxygen saturating the hemoglobin molecule via hemoximetry. A PaO2 above 75 mm Hg is normal, whereas levels lower than 75 mm Hg are abnormal. The degree of abnormality can be determined by the magnitude the PaO2 is from 75 mm Hg. Mild hypoxemia is defined as a PaO2 between 65 and 74 mm Hg, whereas moderate hypoxemia is defined as a PaO2 between 50 and 65 mm Hg. Severe hypoxemia is defined as a PaO2 less than 45 to 50 mm Hg.
Oxygen status is also evaluated via the amount of oxygen saturating the hemoglobin molecule. Normal oxygen saturation is accepted as 95% or greater, whereas mild hypoxemia is defined as oxygen saturation between 90% and 95%. Moderate and severe hypoxemia are defined as oxygen saturation levels between 80% and 90% and less than 75% to 80%, respectively.58–60 Oxygen saturation is related to PaO2 via the oxyhemoglobin saturation curve as discussed in Chapter 5. A simple way to remember the relationship between oxygen saturation and PaO2 is to construct a table with the numbers 40, 50, and 60 on the top row and the numbers 70, 80, and 90 on the bottom row as shown in Table 9-10. The top row represents the PaO2, and the bottom row represents oxygen saturation (Table 9-10). A quick glance at Table 9-10 provides an estimate of the oxygen saturation when the PaO2 is a certain value or vice versa. For example, if the PaO2 is 60 mm Hg, then the oxygen saturation is approximately 90%; and if the oxygen saturation is 80%, the PaO2 is approximately 50 mm Hg.
TABLE 9-10 Relationship Between PaO2 and Oxygen Saturation
Pulse oximetry provides a very similar measure to the direct measurement of oxygen saturation, discussed previously. The infrared sensor of a pulse oximeter worn on the finger, earlobe, or any other body part senses the amount of oxygen saturating hemoglobin by interpreting the density of the blood flow through the particular body part with the probe (see Fig. 9-10). The oxygen saturation is then calculated automatically via regression equations within the pulse oximeter. Although the values for normal and specific degrees of hypoxemia are identical to those previously cited, the accuracy of pulse oximetry is less than the direct measurement of oxygen saturation via arterial blood gases. The degree of error associated with pulse oximetry has been established to be approximately ±3%. Potential causes of less accurate pulse oximetry measurements include darker skin color, poor circulation, Raynaud phenomenon, presence of nail polish, and poor placement of the finger probe, among others.
FIGURE 9-10 On the left, a combination pulse oximeter-ECG unit. Note the finger sensor in the lower left portion of the photo.
“Other” related issues— From the previous discussion, it is apparent that arterial blood gas values are frequently influenced by the ability or inability of the breathing muscles to properly ventilate the lungs. Although the arterial blood gas information is extremely helpful and important in the management of patients with cardiopulmonary disease, identification of a blood gas abnormality is occasionally too late to adequately intervene with physical therapy interventions. Many of the specific interventions to improve abnormal arterial blood gas findings involve improving the (1) biomechanics of breathing, (2) airway diameter, or (3) alveolar ventilation and oxygenation by removing retained pulmonary secretions or providing mechanical ventilation. Besides arterial blood gas analysis, observation of the patient’s appearance (color, degree of distress, and breathing pattern) and auscultation of the lungs can provide important information about the biomechanics of breathing, airway diameter, and alveolar ventilation and oxygenation, which may direct therapeutic interventions to rapidly improve a patient’s status before arterial blood gases deteriorate. In addition, the methods of perturbating the breathing of a patient with a pulmonary disorder can provide information that may be useful in the implementation of therapeutic interventions (Table 9-4). However, there does appear to be limited data suggesting that particular patients with markedly abnormal pulmonary function may be unable to improve their biomechanics of breathing.29
Pulmonary function testing can provide important information about both the patient and the lung function.
Pulmonary Function Tests
Pulmonary function tests measure the volume and flow of air during inspiration and expiration. A flow–volume loop provides a graphic display of both inspiratory and expiratory flows and volumes (see Fig. 9-11).61–63 The flow–volume loop is a standard measure of pulmonary function, and it is useful in interpreting not only inspiratory flow and volumes but also patient effort and somewhat of an accurate graphic depiction of many types of pulmonary disorders including obstructive, restrictive, and interstitial lung diseases. Many pulmonary disorders have a characteristic flow–volume loop (see Fig. 9-11B–E) due to abnormal airway function, lung tissue, biomechanics of breathing, or some combination of these abnormalities.
FIGURE 9-11 Graph of flow–volume loops. (A) Normal flow–volume loop. (B) COPD flow–volume loop. (C) Interstitial lung disease flow–volume loop. (D) Restrictive lung disease flow–volume loop. (E) Ventilatory muscle weakness flow–volume loop.
Many measurements of pulmonary function exist (Table 9-11), but perhaps the two most frequently used and clinically important measurements of pulmonary function are the forced vital capacity (FVC) and the forced expiratory volume in 1 second (FEV1). The FVC is the amount of air expelled during a forceful exhalation from the end of inspiration to the end of expiration. The FEV1 is the amount of air expelled during the first second of a forceful exhalation. Examining just these two values can provide a wealth of information about the presence or absence of pulmonary disease as well as the severity of pulmonary dysfunction (Tables 9-11 and 9-12).61–63 The values presented in Table 9-12 are values that have been predicted from the actual volume of air that a person can exhale, which can be used to diagnose the severity of lung disease. This information and measurement of pulmonary function will be discussed in the following sections.
TABLE 9-11 Typical Pulmonary Function Test Results in a Patient with Severe Emphysema
TABLE 9-12 American Thoracic Society Classification of Lung Disease
Standard Measurements of Pulmonary Function
Perhaps the best methods to describe the measurement of pulmonary function are to explain how two antiquated measurement devices (a water-sealed spirometer and the Vitalograph) measure pulmonary function (see Fig. 9-12). Although these antiquated systems are seldom used today because of newer automated systems, their mechanism of operation clearly reveals the origin of the measurements obtained during a pulmonary function test. The water-sealed spirometer records a patient’s breathing efforts with a pen attached to the spirometer that moves upward or downward as air is blown into or out of the spirometer (see Fig. 9-12A). Actually, as a person inspires and draws air from the spirometer into their lungs, a large metal cylinder that moves within the water-sealed chamber is pulled downward, which causes the attached pen to deflect upward. (A counterweight pulley system seen at the top of the large metal cylinder in Fig. 9-12A produces this inverse relationship.) As a person exhales into the water-filled spirometer, the air has no place to go so the cylinder moves upward causing a downward deflection of a pen that marks the revolving chart paper (allowing each upward and downward excursion of the pen to be recorded). The marks drawn on the chart paper during the upward and downward excursions of the pen can be measured and a specific volume and flow of air during the inspiratory and expiratory maneuvers can be calculated. These volumes and flows are shown in Fig. 9-12A.
FIGURE 9-12 (A) A water-sealed spirometer and the resultant static lung volume curve. (B) Recording of an expiratory flow–volume curve on specialized Vitalograph chart paper.
Several measurements of pulmonary function can be viewed moving from right to left (the actual direction that the pen records on the revolving chart paper) of Fig. 9-12A. The first measurement is the VT, which is the amount of air moving in and out of the lungs during normal, relaxed breathing (the small cyclical sine wave in the center of the figure displays the VT; the amount of air moved normally is regular and similar during inspiration and expiration). However, the first large upward deflection above the VT is the inspiratory reserve volume (IRV). It is the result of a maximal inspiration and reflects the volume of air that can be moved, which is on reserve above the VT (to be used during maximal exercise or functional tasks). Adding the VT to the IRV provides a measure of inspiratory capacity (IC), which is also shown in Fig. 9-12A.61–63
The next major deflection below the VT moving from right to left is the expiratory reserve volume (ERV). It is the result of a maximal exhalation and reflects the volume of air that can be moved, which is on reserve below the VT(to also be used during maximal tasks). Adding the sum of the VT and the IRV (the IC, as presented above) to the ERV yields the VC. Two additional measurements displayed in Fig. 9-12A, but not measured with the water-sealed spirometer, are the RV and the functional residual capacity (FRC). The FRC and RV can be measured via body plethysmography, helium dilution, or nitrogen washout methods. Each of these tests and the methods by which they measure FRC and RV are described in Table 9-13. The RV measures the volume of air left in the lungs at the end of a maximal expiration. The RV provides information about air trapped within the lungs. The RV and other measurements shown in Table 9-11 under the heading “Lung Volumes” also provide information that can help to diagnose the severity of lung disease and to predict treatment outcomes.61–63 This is particularly true for patients with lung disease who may need breathing retraining such as diaphragmatic breathing.
TABLE 9-13 Methods to Measure Functional Residual Capacity and Residual Volume
CLINICAL CORRELATE
Patients with marked hyperinflation of the lungs with very large RV and TLC who have very little diaphragmatic motion (because of diaphragmatic flattening from the marked hyperinflation of the lungs that produces the very large RV and TLC) are likely to do poorly with diaphragmatic breathing and have been found to benefit from non-invasive positive pressure ventilation (NPPV).29
The FRC is the sum of the ERV and the RV, and represents the amount of air remaining in the lungs at the end of VT breathing (see Fig. 9-12A). The FRC also represents the point in the respiratory cycle where the forces expanding the chest wall equal the forces that have the potential to collapse the lungs. Finally, the TLC is the sum of the RV and the VC.61–63 Patients with severe COPD typically have a very large TLC that greatly exceeds the expected values for age, height, and gender (the percentage of predicted TLC is often greater than 100% of predicted values; see Table 9-11). Measurement of the FEV1 and several of the other pulmonary function test results shown in Table 9-11 are unable to be measured with the water-sealed spirometer but can be measured with the Vitalograph.
The Vitalograph works in a manner that is similar to the water-sealed spirometer, but without the water medium. The Vitalograph is constructed with a calibrated flow–volume pen that moves when a person exhales into a mouthpiece. The deflection of the pen records the expiratory flow and volume, which can be calculated from the axes of the special Vitalograph recording paper. A recording of expiratory flow and volume on the Vitalograph paper is shown in Fig. 9-12B. The FVC and FEV1 can be easily calculated from the specialized chart paper and the recorded data.
Once the measurements of pulmonary function have been made, they can be compared to the pulmonary function results of other people of similar age, height, and gender (Tables 9-11 and 9-14). The actual measured values of a patient can then be evaluated as a percentage of what others have been observed to have in one or more of the pulmonary function test measurements.61–63
TABLE 9-14 Prediction Equations and Charts to Estimate Pulmonary Function Test Results
For example, a 51-year-old female patient who was 163.5 cm in height was measured to have a FVC of 1.11 L (Table 9-11). Many research studies have been performed, which have determined that the average FVC of a 51-year-old female who is 163.5 cm in height is 3.32 L. Therefore, either by using a regression equation or by looking at a chart of normal values from these research studies, we can determine the percentage that the FVC of our subject is to that of the FVC of other 51-year-olds who are 163.5 cm tall. Table 9-13 provides the regression equations and tables to determine the percentage of predicted FVC of this subject and of others with a known age, height, and gender. Knowing the actual measurement of FVC as well as the percentage of the predicted value can help to categorize the severity of a patient’s pulmonary disease as well as the prognosis. This is evident by examining Table 9-12. In fact, using the FVC regression equation in Table 9-13 to determine the predicted FVC for a 51-year-old woman who is 163.5 cm tall, it is clear that the patient’s predicted FVC should be 3.32 L. The patient’s measured FVC was 1.11 L, which is 33% of the predicted value (1.11/3.32 = 33%). When viewing Table 9-12, it is evident that this patient suffers from severe pulmonary disease based on the percentage of predicted FVC of 33% (an FVC <50% is associated with severe lung disease).61–64
Evaluating Chest Radiographs
Evaluation of chest radiographs is frequently performed by physical therapists involved in the direct care of patients in the intensive care unit. A quick overview of the methods to evaluate chest radiographs is presented in the following section and is summarized in Box 9-10. The methods of examining chest radiographs are dependent on identifying the presence of the white and dark areas on radiographs. The white areas are referred to as opacities and the dark areas are referred to as lucencies. Identifying the correct amount of both opacities and lucencies in the correct location of the chest is the basis for chest radiograph interpretation.65,66
Box 9-10
Methods to Examine Chest Radiographs
1.Begin examining the chest radiograph from the center of the film and examine it outward.
2.Identify the bones, soft tissues, and organs of the body.
a.Mediastinum from the larynx to the abdomen
b.Heart, lungs, and vascular tree
c.Hila
d.Diaphragm/hemidiaphragm
3.Specific lung field examination: Compare observed chest radiograph images to expected images.
a.Mediastinum should be a vertical translucent shadow overlying the cervical vertebrae.
b.Heart and great vessels should occupy the lower two-thirds of the mediastinum with two distinct visible curves on the right side and four distinct curves on the left side of the cardiovascular tree. On the right side, the first curve is formed by the right atrium that begins at the right cardiophrenic angle and proceeds superiorly as well as the inferior vena cava entering the right atrium inferiorly. The second curve on the right side is the ascending aorta and the superior vena cava. The four distinct curves on the left side include the transverse arch and descending aorta, main pulmonary artery, left atrial appendage (which may or may not be visible), and the border of the left ventricle.
c.Hila should be poorly defined areas of variable density in the medial part of the central portion of the lung fields.
d.Diaphragm/hemidiaphragm should be visible and the dome of the right hemidiaphragm is normally 1 to 2 cm higher than the left (diaphragm is elevated if during inspiration < 9 ribs are visible above the level of the domes and depressed if > 10 ribs are visible).
e.Lung fields should be examined in view of the different lobes of the lungs and the various bronchopulmonary segments of the different lobes. Lesions in the lungs can be localized by a silhouette sign (normal lines of demarcation between different structures are partially or completely obscured) or changed vascular markings (increased vascular markings are associated with venous dilation and decreased markings are often associated with hyperinflation of the lungs).
1.Search for abnormal density within all lung fields that would be identified by radiopacity (white image) in areas where there should be radiolucency (dark image).
2.Examine the position of the diaphragms.
3.Examine the angle of the ribs (normally oriented obliquely; may be oriented horizontally with severe hyperinflation of the lungs as in chronic COPD) and the intercostal spaces.
Methods to Evaluate Chest Radiographs
The methods used to examine chest radiographs include orienting oneself to the radiograph, identifying the right from the left side of the chest radiograph, looking for areas of increased or decreased opacity and lucency, identifying the inferior angles of the lungs and the height of the diaphragm, and identifying enlarged or irregular structures on the radiograph. Each of these examination techniques will be briefly reviewed in the following sections and is presented in Box 9-10.
Orienting oneself to the chest radiograph requires the reader of the radiograph to view it as if facing the patient. Examining a frontal chest film on a view box is viewed as if the patient’s right side were on your left side. Examining a left lateral chest film on a view box is viewed as if the patient’s left side were facing the examiner. The standard chest radiograph consists of a posteroanterior view and a left lateral view, and for patients hospitalized in the intensive care unit, an anteroposterior view is standard. The radiograph is typically performed while the patient is holding his or her breath after a deep inspiration.65,66
The left side of the chest radiograph can be appreciated by simply identifying the heart and the great vessels. Once found, the size, shape, and location of the heart and great vessels are examined. The inferior angles of the lungs and the height of the diaphragm can be found by counting the number of ribs that are visible during breath holding after a deep inspiration. If fewer than 9 ribs are visible above the level of the domes, the diaphragm is elevated; if more than 10 ribs are visible, the diaphragm is depressed.65,66
Increased or decreased opacity and enlarged or irregular structures can be found by careful evaluation of the chest radiograph, which usually requires mentoring and experience as well as a good understanding of the anatomy underlying specific bony landmarks.65,66 Participating in patient rounds at any hospital or clinic where chest radiographs are discussed, will likely provide the mentoring and experience that will enable a physical therapist to interpret and utilize chest radiographs.
“Other” Imaging and Investigational Studies
Other sophisticated methods of examining and evaluating pulmonary pathologies exist and are frequently employed when one or more of the previous tests demonstrate suspected pathologies in need of further investigation. The most common methods of further examination include computed tomography (CT), MRI, ultrafast scanning, lung biopsy, and sputum tests.
Computed Tomography
A CT test is simply digitized radiography, which allows numerous digital images (taken at many different angles) of a specific tissue to be mathematically manipulated based on the characteristics of the tissue being examined. The degrees of radiolucency and radiopacity are quantified, which then allows for the digitized radiograph to be computed and acquired.67,68
Magnetic Resonance Imaging
An MRI test is the result of hydrogen nuclei perturbations by a magnet combined with the computation of digitized images as described previously with CT. The magnet of an MRI scanner produces a magnetic field in the area of the body being imaged. The magnetic field makes the hydrogen nuclei resonate and align themselves with the magnetic field. A radio signal is then introduced to the magnetic field, which further stimulates the hydrogen nuclei and allows for a radio antenna in the MRI scanner to digitally record the resonating and realigned hydrogen nuclei. This quantifies and qualifies the tissue being scanned, which then allows for computation and acquisition of the MRI.
Ultrafast Scanning
Ultrafast three-dimensional contrast-enhanced MRI scanning tests are fast becoming an additional method of fully examining patients with suspected pathologies. It is the result of a very rapid MRI with more sophisticated application and computation abilities than the traditional MRI, yielding high-resolution three-dimensional examinations of the entire mediastinum in a single 10- to 30-second breath-hold. Ultrafast scanning can also be done with an angiogram to provide more specific information about arterial and venous disorders.69,70 A radioactive contrast administered during magnetic resonance angiography improves the delineation of vessel borders and enables three-dimensional reconstruction of the heart and great vessels as well as of the pulmonary vasculature.69,70
Bronchoscopy
Bronchoscopy is simply the visualization of the proximal airways of the lungs through a bronchoscope.71,72 The bronchoscope is a relatively large flexible scope that requires lubrication and some degree of anesthetic before insertion through the mouth into the trachea. The primary reasons for bronchoscopy include the visualization of the proximal airways and the removal of secretions in the proximal airways.71,72 Occasionally, a physical therapist may assist a physician who is performing a bronchoscopy by applying a variety of secretion clearance techniques in hope of removing more pulmonary secretions than those obtained via bronchoscopy alone.
Secretion/Sputum Tests
Secretions or sputum removed via bronchoscopy or by a physical therapist is often in need of analysis. Sputum obtained during chest physical therapy is typically collected in a small sputum specimen collection cup using sterile techniques. Sterile techniques include wearing gloves and collecting only the patient’s sputum in the collection cup. The time and date as well as the patient’s name are recorded on a label that is applied to the collection cup. The collection cup is frequently placed in a plastic bag and brought to the hospital laboratory. The physical therapist often notes the color, consistency, and smell of the sputum as presented in Box 9-11.73
Box 9-11
Laboratory analysis of the sputum sample includes many different tests for specific pathogens. Box 9-11 lists many of the possible results from the laboratory analysis of sputum. The results of sputum analyses provide physicians with important information about particular pathogens that may be treated with specific medications.73
Lung Biopsy
Lung biopsies are performed to examine lung tissue under a microscope. The procedure used for a lung biopsy includes a bronchoscopy followed by the insertion of a special catheter through the bronchoscope. Once the catheter reaches the desired area of lung, a small scissors-like device cuts or crimps away a very small specimen of lung tissue that is removed via the bronchoscope and prepared for microscopic examination.74
EXERCISE TESTING
Traditional Exercise Testing
Traditional exercise testing of patients with pulmonary disease appears to be less commonplace in many research and clinical settings. This is likely due to a variety of issues of which the major reasons are the limited exercise performance of persons with pulmonary disease; cumbersome and often uninformative exercise test results; limited measurements and analyses of respiratory gases in patients with pulmonary diseases requiring supplemental oxygen, which are often less clinically useful; and time/reimbursement constraints. Nonetheless, traditional exercise testing on a cycle ergometer or occasionally on a treadmill is performed in patients with pulmonary disease.75–77
The most common reasons traditional exercise testing is employed in patients with pulmonary disease are to (1) better understand the causes and severity of dyspnea, (2) better understand the oxygen and carbon dioxide relationships as well as oxygen saturation level at rest and during exercise, (3) determine the level of exercise tolerance, and (4) investigate the presence of heart disease.78–80 The methods of traditional exercise testing in patients with pulmonary disease will be discussed in the following section and will be followed by a discussion of other types of less traditional exercise tests (eg, walk tests, stair climbing tests), which may be more acceptable and clinically useful for patients with pulmonary disease.
Methods to Administer Traditional Exercise Testing in Pulmonary Disease
The methods employed during traditional exercise testing often include pretest pulmonary function testing; pre-, during, and posttest analysis of arterial blood gases and lactate levels; the evaluation of heart rate, heart rhythm, and signs of myocardial ischemia via electrocardiography before, during, and after exercise; and the measurement of blood pressure, oxygen saturation, respiratory gases, and rating of perceived exertion during exercise.78–80Occasionally, evaluation of heart function is also performed via echocardiography or other methods, which will be discussed in Chapter 10.
Preexercise Test Procedures
Before the exercise test, the patient is questioned about risk factors for heart and lung disease, recent and past complaints, recent and past medical history, and the primary problem that they perceive has brought them to seek medical attention. After questioning, a physical examination is performed, which includes the examination of blood pressure, heart sounds, breath sounds, the electrocardiogram, and pulmonary function test results. Comparisons will be made with any past questioning and tests are given with emphasis placed on recent and past complaints, blood pressure measurements, electrocardiogram, and pulmonary function tests. The variables that are very important to measure before exercise testing of patients with pulmonary disease include FEV1, MVV, oxygen saturation, resting dyspnea level, Borg rating of perceived exertion, and for some patients, measurements of arterial blood gases. Finally, an estimate of the patient’s exercise tolerance will be made, which will help to determine the exercise testing protocol and magnitude of workload increments. An estimate of the patient’s exercise tolerance is made based on the aforementioned baseline measurements, current levels of activity and exercise, and possibly previous exercise test results.78–80
During Exercise Test Procedures
During the exercise test, the patient is provided a short period to “warm up” or the initial workloads of the exercise testing protocol are minimal and are progressed slowly with modest workload increments. Many patients with pulmonary disease will undergo cycle ergometry exercise testing and will be provided a short period of time to warm up by cycling without resistance for 1 to 2 minutes.78–80
After warming up, the workload will be gradually increased to a level that will enable the patient to (1) reach several steady-state levels until exhaustion or more commonly, until a predetermined submaximal endpoint has been achieved or (2) progressively ramp up to workloads that allows for 8 to 12 minutes of exercise before exhaustion. These methods of exercise testing will enable modestly accurate predictions of exercise performance and peak oxygen consumption using steady-state levels of exercise or more accurate measurements of maximal exercise performance using ramping protocols.78–80
The same measurements performed before exercise testing are frequently repeated during the exercise test (often at one-minute intervals and at peak exercise). Many of these variables and a data input sheet are presented in Chapter 10. The measurements most important to critically examine patients with pulmonary disorders include symptoms (via a Visual Analog Scale or Borg rating of perceived exertion), accurate provision of workloads, oxygenation (via pulse oximetry or PaO2 from arterial blood gas analyses), ventilation (via CO2 levels or respiratory gas analyses), electrocardiography (to examine the heart rate, heart rhythm, and signs of myocardial ischemia), and respiratory gas analyses (ventilation [VE], dyspnea index [peak VE/MVV], ventilatory threshold, and oxygen consumption).78–80 Numerous other variables can also be considered during traditional exercise testing with respiratory gas analyses, but which have greater clinical utility for patients with heart disease and will, therefore, be discussed in Chapter 10.
Postexercise Test Procedures
Immediately after exercise testing, the patient will be asked to remain seated on the seat of the cycle ergometer or brought to a more comfortable seat. Laying the patient supine, as is done after exercise testing in patients with known or suspected heart disease, is often impossible in a patient with pulmonary disease. If respiratory gas analysis was performed, the mouthpiece or face mask used for the collection of respiratory gases can be removed immediately after the exercise test. This will likely make the patient more comfortable and allow them to breathe easier. The same previously cited measurements should also be frequently repeated (every 1–2 minutes) until the values return to baseline (or near baseline).78–80
Analysis of Exercise Test Results
The analysis of exercise test results in a patient with pulmonary disease involves determining the (1) primary reason(s) for terminating exercise (was the test submaximal and terminated because of attainment of a predetermined endpoint, or was the test maximal and terminated due to symptoms or adverse signs) and whether the peak workload was achieved (and at what percentage of the expected workload did the patient achieve); (2) oxygenation response via oxygen saturation or PaO2; (3) ventilation response via respiratory gas analysis, PaCO2, or dyspnea index (VE/MVV); (4) maximal achieved heart rate and what percentage it is of the age-predicted maximal heart rate (208 – 0.7 X age); (5) maximal blood pressure achieved; (6) “other” respiratory gas analysis measurements such as the ventilatory threshold and peak oxygen consumption; and (7) electrocardiogram for signs of rhythm abnormalities and myocardial ischemia.78–80 The methods of analyzing respiratory gases and the electrocardiogram as well as examining heart rate and blood pressure will be further discussed in Chapters 10 and 11. However, one respiratory gas analysis measurement that is necessary to discuss for patients with pulmonary disorders is the dyspnea index.
The dyspnea index is of value when analyzing the exercise test results of patients with known or suspected pulmonary disorders. Comparing the calculated MVV (FEV1 X 0.35) to the peak ventilation achieved during an exercise test can provide insight into the influence of a pulmonary limitation to exercise.
CLINICAL CORRELATE
When the exercise test peak ventilation equals or exceeds the calculated MVV, a patient is diagnosed with a pulmonary limitation to exercise80 Normally, peak ventilation is approximately 70% of the calculated MVV.
Walk Tests
The short exercise duration, limited amount of information, and difficulty of traditional exercise testing with respiratory gas analysis have resulted in greater research and clinical use of walk tests. The 12-, 6-, and 3-minute walk tests have been used in many clinical research trials and appear to be important tests capable of measuring improvement or deterioration in patients undergoing medical treatment and rehabilitation for pulmonary disorders.75–77,81–84
The first walk test was reported by McGavin et al., who evaluated the clinical utility of the 12-minute walk test.82 These investigators discovered moderate-to-good correlation between the 12-minute walk test distance ambulated and several measures of pulmonary function. Other investigators have demonstrated similar relationships between walk test distances ambulated during different timed tests and measures of pulmonary function, respiratory gases, and arterial blood gases. Therefore, the distance ambulated during 12, 6, or 3 minutes appears to be a good measure of functional performance and is much easier to administer than traditional exercise testing. The only equipment needed include a premeasured hallway in which to walk and a stopwatch to determine when to stop the walking test depending on the duration of the test.75–77,81–84
Methods to Administer Walking Tests
Information about the walking test to be administered to a patient can be very helpful for the patient and therapist and can be provided to the patient in writing or verbally a day prior or immediately before the walk test. The information and instructions for therapists and those given to patients before a walking test are provided in Box 9-12. The specific methods to perform a 6-minute walk test, record the walk test results, and analyze the walk test results are provided in Box 9-13. The data input sheet of Box 9-13 can be extremely helpful when administering a walk test.82–84
Box 9-12
Instructions for the 6-Minute Walk Test
Inform patients of the purpose of the test
The purpose of the 6-minute walk test is to understand how far you can walk in 6 minutes. It also gives us both an opportunity to see how you walk and something with which we can compare how you are doing in the future.
Instructions given to the patient
The purpose of the 6-minute walk test is to understand how far you can walk in 6 minutes, giving your best effort possible. The goal of the walking test is for you to walk at a pace that will allow you to walk as far as possible within 6 minutes. You can stop if you need to, but the clock will continue to run and you must stop walking when 6 minutes have elapsed. Remember, the time clock will continue to run if you stop walking for a rest, and the goal of this walking test is for you to walk as far as possible in 6 minutes. Do you understand? Do you have any questions?
We will ask you to walk down this hallway to the end, at which time we want you to turn around and walk back to this line. We want you to continue walking back and forth until 6 minutes have elapsed or until you believe you must stop. Do you have any questions?
We will walk slightly behind you with this monitor, and we will ask you how short of breath you are several times during the walking test. We do not want you to run during this test—the goal is for you to walk as far as possible in 6 minutes. A number of measurements will be made and documented before, during, and after the walk test and include the heart rate, blood pressure, respiratory rate, oxygen saturation, your rating of perceived exertion, possibly electrocardiogram, the number of stops you take if needed, and the total distance walked.
Responsibilities of the test administrator
Provide patients a 5-minute rest period before walking to establish baseline values.
Possibly monitor the electrocardiogram of patients with a history of heart disease, cardiac arrhythmias, palpated irregular pulse, or pulmonary hypertension.
Monitor and document the heart rate, blood pressure, respiratory rate, oxygen saturation, and rating of perceived exertion before and after the walk test as well as minutes 2, 4, and 6 of ambulation.
Repeat several times before and during the walk test that “the goal of the walk is to walk as far as possible in 6 minutes.”
Allow the patient to set the walking pace, which can often be accomplished by walking slightly behind the patient.
Document distance ambulated by recording the number of completed laps on a premeasured (premeasuring can be accomplished with a surveyor’s wheel, which can also be used to measure final ambulated distances that may be near a pre-measured marker) hallway.
Document the number of rest stops needed.
Document the use and amount of supplemental oxygen or walking assists if needed.
Standardize the use or lack of encouragement during the walk test.
Terminate the walk test if
a.the oxygen saturation decreases < 80% or if other signs/symptoms of significant desaturation are present (ie, confusion, stupor)
b.dizziness
c.level II/IV angina
d.marked dyspnea
e.marked fatigue
f.severe musculoskeletal pain or vascular insufficiency such as leg claudication
g.greater than moderate discomfort from any cause
h.ataxic gait
i.patients monitored with electrocardiography demonstrate
i.increasing multifocal premature ventricular contractions (PVCs), coupled PVCs, or ventricular tachycardia (three consecutive PVCs)
ii.rapid atrial arrhythmias
iii.signs of myocardial ischemia
Box 9-13
The shuttle walk test is another walking test that is administered in a manner slightly different from that of other walking tests. The shuttle walk test is different from other walking tests in that a metronome is used during the test to which the walking cadence is synchronized. The synchronization of walking to the increased cadence of a metronome is done to increase the walking velocity such that patient motivation can be more controlled. As the metronome increases, the walking velocity is expected to increase. However, no method of ensuring increased walking velocity similar to that used with the metronome is mentioned in the methods of performing the shuttle walk test.85Therefore, if the shuttle walk test is to be performed properly, it appears that frequent monitoring of the walking velocity is necessary to ensure that it is in keeping with the metronome. However, this is easier said than done. Likewise, patients with hearing difficulty and neurologic or orthopedic problems may find the shuttle walk test difficult due to the figure-of-eight pattern of walking that is needed to perform the shuttle walk test.
“Other” Types of Exercise Tests and Methods of Administration
Other types of exercise tests include step tests and stair climbing tests. The different types of step tests and stair climbing tests as well as the methods to administer them are provided in Table 9-15. Although traditional step tests have been used very little in patients with pulmonary disease, stair climbing tests have been used in several studies and have been helpful in identifying patients with pulmonary pathologies who are most appropriate for thoracic surgery and other medical interventions (Table 9-15).86–88 Figure 9-13 provides an illustration of these types of tests.
TABLE 9-15 Other Types of Exercise Testsa
FIGURE 9-13 One- and two-step stair climbing tests and a vertical climbing test.
EXAMINATION OF OUTCOMES AND QUALITY OF LIFE IN PULMONARY DISEASE
Table 9-16 provides an overview of many instruments that can be used to measure outcomes and quality of life in pulmonary disease. A summary of the general health status questionnaires and the disease-specific questionnaires commonly used with persons suffering from pulmonary disease is outlined. Likewise, the strengths and weaknesses of the different instruments are also presented in Table 9-16.89,90 The most frequently used instruments used to evaluate the quality of life of persons with pulmonary disease appear to be the Saint George’s Health Questionnaire, Chronic Respiratory Disease Questionnaire, Living with Asthma Questionnaire, and Pulmonary Functional Status Scale (PFSS). The Medical Outcomes Study Short Form, Health Survey, or MOSSF-36, and the pulmonary functional status scale both appear to be very useful tools for the physical therapist because they examine the general perceived health status (MOSSF-36) and true functional tasks as well as the manner in which they affect dyspnea and other outcome measures (PFSS). The MOSSF-36 is shown in Fig. 9-14.
TABLE 9-16 Quality of Life and Health-Related Instruments
FIGURE 9-14 The MOSSF-36. (Reprinted with permission of QualityMetric, Inc.)
SUMMARY
The majority of the methods of examination presented in this chapter have focused on those that can be allocated by a physical therapist. The traditional medical tests and measures for a patient with pulmonary disorders have also been presented, but the focus of these tests and measures has been on the clinical application for the patient being examined and treated by a physical therapist. A number of data sheets have been incorporated into the tables of this chapter and an initial patient note has been provided in the Appendix. The key tests and measures presented in this chapter include examining (1) the appearance of the patient, (2) the breathing pattern of the patient, (3) the potential for changing the breathing pattern and diaphragmatic motion, (4) the breath sounds via auscultation, (5) the ventilatory muscle strength and endurance, (6) the pulmonary function test results, (7) the exercise and functional abilities via exercise testing, and (8) the outcome measures and quality of life of patients with known or suspected pulmonary disorders. Of all these examinations, observing the breathing pattern and evaluating the potential for changing abnormal breathing patterns may be the most clinically useful for the physical therapist. The information gained from these examinations can then be used to allocate treatment interventions and determine appropriate outcome measures and effects on quality of life. In fact, a hypothesis-oriented algorithm has been developed for the treatment of patients with pulmonary disorders in which the observation of the breathing pattern is the primary point from which further examinations and treatments follow. This hypothesis-oriented algorithm is presented in Chapter 19 and incorporates many of the examinations presented in this chapter. The results of these examinations have been used to allocate further examinations and treatments based on previously published literature. Such an evidence-based examination is needed in physical therapy.
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APPENDIX 1
II. Suggested Laboratory Exercises
Laboratory Exercise 1: Evaluation of risk factors for pulmonary disease—Students role-play patients and physical therapists and simulate an initial interview session during which pertinent information is discussed and obtained between the physical therapists and the patients (half of the students role-play patients and the other half role-play therapists; if time permits, students should be paired and switch roles after interview is complete), using Tables 9-1through 9-6 as reference sources.
Laboratory Exercise 2: Anatomy of the thorax (identifying the bony landmarks of the chest to appreciate the lobes of the lungs)—Students draw bony landmarks and lung lobes with washable markers using specific landmarks described in the following. Drawing the figures by hand in the space provided at the end of this laboratory exercise may facilitate the completion of this lab: sternum—palpate and draw the manubrium, sternal angle of Louis, body of the sternum, and xiphoid process.
a.Manubrium: Superiorly begins at the suprasternal notch (horizontal to the level of T2)—outline the suprasternal notch with a washable marker and palpate the junction of the clavicle with the manubrium to locate and draw the lateral aspect of the manubrium. The inferior aspect of the manubrium can be located and drawn by identifying the sternal angle of Louis (horizontal to T4 and T5 and easily located by the raised ridge on the anterior of the sternum).
b.The sternal angle of Louis is found by locating the second rib. The second rib can be found by palpating the sternoclavicular joint (SCJ), moving slightly inferior to the first rib (which may be difficult to palpate because it lies underneath the clavicle), and the next rib inferior to the first is the second rib. Palpating medially toward the center of the sternum will reveal a raised ridge, which is the sternal angle of Louis. The sternal angle is the point where the trachea bifurcates into the right (wider and more vertical) and left mainstem bronchi (narrow and more horizontal). After the trachea bifurcates at the sternal angle of Louis:
i.The right mainstem bronchus divides into three lobar bronchi:
1.right upper lobar bronchus that divides into
a.three segmental bronchi to the right upper lobe
2.right middle lobar bronchus divides into
a.two segmental bronchi to the right-middle lobe
3.right lower lobar bronchus divides into
a.five segmental bronchi to the right lower lobe
ii.The left mainstem bronchus divides into two lobar bronchi:
1.left upper lobar bronchus that divides into
a.three segmental bronchi to the left upper lobe
2.left lower lobar bronchus that divides into
a.four segmental bronchi to the left lower lobe
The divisions of the lobar bronchi and segmental bronchi to the different lobes of the lung are relatively rapid and short and can be hypothetically visualized on the thorax (with the drawings described above and below) as occupying only a small area traveling laterally, superiorly, and inferiorly from the sternum. The rest of the sternum inferior to the sternal angle is the body of the sternum from which the underlying lobar and segmental bronchi travel outward to the different lobes of the lungs.
c.The body of the sternum should now be easily palpated and drawn as well as the attachments of the ribs 3 through 7.
d.The xiphoid process should also be easily palpated and drawn at the base of the sternum.
Ribs: Palpate and draw the ribs (12 ribs exist—7 true ribs, which are attached to the sternum anteriorly and vertebrae posteriorly, and 5 false ribs, which are attached to the vertebrae posteriorly but not attached directly to the sternum).
a.The seven true ribs can be palpated by moving inferiorly along the lateral aspects of the sternum until reaching the xiphoid process. Moving inferior from the xiphoid process will allow for palpation of the remaining false ribs.
b.The false ribs can be palpated by moving inferiorly from the xiphoid process. Ribs 8, 9, and 10 are attached to a cartilage sheet arising from the sternum anteriorly, while ribs 11 and 12 are free-floating ribs and are not attached anteriorly to the cartilage sheet.
Lungs: Locate the right and left lungs by
a.Drawing a line superior and laterally from the SCJ to a point that is approximately 2.5 cm above the medial one-third of the clavicle and continuing the line to a point that is on the clavicle at one-third the distance from the end of the clavicle at the acromioclavicular joint. This should be done bilaterally. These lines identify the superior borders of the lungs.
b.Drawing a line from the right SCJ to the center of the sternal angle down the sternum to the xiphoid process. This line identifies the anterior border of the right lung.
c.Drawing a line from the left SCJ to the center of the sternal angle down the sternum to the fourth rib, where the line should be continued laterally along the fourth rib to a point approximately 3 cm from the sternal border from which the line should be continued inferiorly and slightly medially to the sixth rib and then back medially to the sternum. This line identifies the anterior border of the left lung.
d.Drawing a line laterally from the inferior end of the above anterior borders of the right and left lungs crossing the midclavicular line (at the 6th rib), midaxillary line (at the 8th rib), midscapular line (at the 10th rib), and finally ending at the spinous process of T10. This should be done bilaterally. These lines identify the inferior borders of the lungs.
e.Drawing a line cranially (and approximately 2.0 cm lateral from the thoracic spinous processes) from the level of the T10 spinous process to the level of the C7 spinous process. This should be done bilaterally. These lines identify the posterior borders of the lungs.
f.Drawing a line caudally and laterally from the spinous process of T3 to the costochondral junction of the sixth rib. This should be done bilaterally. These lines identify the oblique fissure, which on the right separates the lower lobe from the upper and middle lobes and on the left separates the lower lobe from the upper lobe.
g.Drawing a horizontal line from the point where the oblique fissure line crosses the right midaxillary line along the fourth rib to the right anterior border of the lung. This line identifies the horizontal fissure that separates the right middle lobe from the right upper lobe.
Students should attempt to draw figures of each previous exercise to complete “Laboratory exercise 2” and to gain a better appreciation for the anatomy of the thorax:
Laboratory Exercise 3: Auscultation of the lungs—breath sounds using Tables 9-4 through 9-6 and Box 9-3.
Laboratory Exercise 4: Arterial blood gases; practice Boxes 9-5 and 9-6.
Laboratory Exercise 5: Examining the effects of body position change on breathing (using Table 9-8 to record respiratory rates and provide structure to the laboratory, but not measuring chest wall excursion with a tape measure until laboratory exercise 6) by
a.observing upper chest motion and the respiratory rate while supine, sitting, and standing
b.observing lower chest motion and the respiratory rate while supine, sitting, and standing
c.observing both upper and lower chest motion and the respiratory rate while supine, sitting, and standing
Laboratory Exercise 6: Chest wall excursion measurements—with a tape measure comparing supine to sitting to standing or chest wall excursion on land and in water using Table 9-8.
Laboratory Exercise 7: Performing measurements of ventilatory muscle strength and endurance using Tables 9-9 and 9-10.
Laboratory Exercise 8: Performing pulmonary function tests with the Vitalograph (use principles introduced in Table 9-9 and information shown in Table 9-11 through Table 9-13 as well as that shown in Fig. 9-10).
Laboratory Exercise 9: Examining chest radiographs—using Table 9-14 and Fig. 9-11.
Laboratory Exercise 10: Exercise testing in pulmonary disease—cycle ergometry exercise testing and walk tests (Boxes 9-11 through 9-13).
Laboratory Exercise 11: Quality of life examination—Practice administering several quality-of-life tools followed by a discussion of the pros and cons of each using Figure 9-14 and Table 9-16.