Loren G. Yamamoto
HIGH-YIELD FACTS
• The relatively large tongue in an unconscious infant is the most common cause of airway obstruction. An oral or nasopharyngeal airway can resolve the problem.
• Overinflation with bag-mask ventilation (BMV) can result in gastric distention and restrict lung expansion. This can be resolved by placing a nasogastric tube.
• A self-inflating bag does not deliver blow-by oxygen when it is not being compressed.
• Before using sedatives and paralytics for tracheal intubation, be sure to assess for conditions that may be associated with a “difficult airway.”
• Selection of a sedating agent for tracheal intubation is based on recognition of three specific clinical conditions: head trauma (increased intracranial pressure [ICP]), asthma, and hypotension.
• Confirmation of tracheal intubation should always include use of an end-tidal CO2 (ETCO2) device.
AIRWAY ANATOMY
Appreciation of pediatric airway conditions is based on the anatomy of the airway. Figure 17-1(A and B) shows lateral neck x-rays of a child with croup. The patient’s nose (anterior) is on the right and the occiput (posterior) is on the left. Note the lordotic (extended) cervical spine vertebral bodies.
FIGURE 17-1. A. Lateral neck x-ray of a child with croup. B. Labeled version of Figure 17-1A. Identify the following structures. To: Tongue (posterior portion). The laryngoscope blade slides over this portion to visualize the airway. V: Valleculla, also called the preepiglottic space. The tip of the laryngoscope blade can be directed into this space to lift the epiglottis anteriorly. E: Epiglottis. This structure is a curved paddle (an elongated spoon). Understanding this structure in three dimensions helps to understand its radiographic appearance depending on the angle of the x-ray beam. Note that the hinge of the epiglottis is anterior. Gravity causes the epiglottis to fall posteriorly and inferiorly (downward) to cover the opening to the airway. Tr: Trachea. The Tr label is in the superior aspect of the trachea. The portion of the airway between the upper trachea and the epiglottis is the larynx which contains the vocal chords. In this particular x-ray, the trachea narrows inferiorly due to subglottic edema (croup). PV: Prevertebral soft tissue, also called the retropharyngeal soft tissue because it is behind the pharynx. This tissue should be approximately the width of half a vertebral body. C2 and C3: Cervical spine vertebral bodies C2 and C3. (Reproduced with permission from Boychuk RB. Drooling, stridor, and a barking cough: croup?? In: Yamamoto LG, Inaba AS, DiMauro R, eds. Radiology Cases in Pediatric Emergency Medicine. 1994:1(10). www.hawaii.edu/medicine/pediatrics/pemxray/v1c10.html. Accessed January 2, 2008.)
PEDIATRIC AIRWAY DIFFERENCES
Physical factors that differ between adults and children account for the airway differences that are clinically important. The most important of these is a smaller airway diameter. Smaller airways with the same degree of airway edema result in proportionately greater obstruction (Fig. 17-2). Some textbooks have quoted Poiseuille’s equation describing airflow resistance is proportional to the fourth power of the radius. This is not quite correct under conditions of respiratory distress since Poiseuille’s law describes laminar flow, and during respiratory distress, nonlaminar flow dominates; however, airway resistance is proportionately greater and coupled with a weaker patient, the degree of ventilation compromise is greater.
FIGURE 17-2. Similar degrees of edema result in proportionately greater degrees of narrowing in smaller airways compared with larger airways.
The tongue of children is relatively larger.1 The posterior portion of the tongue can easily fall backward in the supine position, compromising the upper airway. Some patients have a particularly large tongue, amplifying this factor. The narrowest point of the child’s upper airway is the cricoid ring (which is below the vocal cords), whereas the narrowest portion of the adult airway is the vocal cords.1 This is important because occasionally an endotracheal tube (ETT) will pass through the cords, but it cannot be advanced further because the cricoid region is too narrow for this tube, in which case a smaller tube should be used. The larynx in children is more cephalad, the epiglottis is softer and more curved, and the airways are less rigid.1 This is especially noticeable in patients with tracheomalacia and laryngomalacia.
RECOGNIZING CONDITIONS ASSOCIATED WITH A DIFFICULT AIRWAY
An airway emergency will present with an acute process that adversely affects a normal airway, or an exacerbation of a chronic airway condition. Some children have airway conditions that place them at higher risk of airway obstruction, other children have airway conditions that make intubation and visualization of the airway more difficult, and some children have both. Children with chronic airway conditions include those with Down syndrome, Pierre Robin syndrome, and other congenital conditions and malformations that affect the tongue, mandible, and neck. Tumors, masses, swelling, and edema (e.g., burns, chemical inhalations, and allergic reactions) in this area can also lead to airway compromise and difficult intubation.1 Laryngomalacia and tracheomalacia place patients at higher risk for airway obstruction. Head trauma, neck trauma, and multiple trauma require cervical spine immobilization making visualization of the larynx potentially more difficult. Trauma of the face, mouth, neck, and airway structures can directly injure the airway resulting in airway compromise. Infections such as croup, epiglottitis, bacterial tracheitis, and retropharyngeal abscess can narrow the airway, with epiglottitis and bacterial tracheitis presenting with the most serious degree of airway obstruction. Patients with an altered sensorium and patients who are pharmacologically sedated are at higher risk for airway compromise as the oral structures relax and fall posteriorly over the airway when the patient is in a supine position.
CLINICAL ASSESSMENT
Air exchange and the degree of airway obstruction can be assessed by observation, auscultation, and technology, but preferably by all three.
A patient with an airway obstruction might have visibly abnormal chest movements with retractions and exaggerated respiratory efforts. A gentle rise and fall of the chest suggests good air exchange. If the patient is wearing an oxygen mask, you might be able to see condensation on the mask with each breath, which suggests significant exhaling (a good sign).
A patient with an airway obstruction might have noisy breathing. More severe obstruction might have no noise if all air movement has ceased. Auscultation of the chest can usually assess the degree of air exchange. Noisy environments and obese or muscular individuals can make auscultation difficult.
End-tidal CO2 (ETCO2) monitoring is useful to confirm the degree of air exchange. While monitors are often used inline on a ventilator for intubated patients, they can also be used near the patient’s mouth or nose to partially assess air exchange. Colorimetric ETCO2 detectors are less sensitive for this purpose. Pulse oximetry does not measure air exchange directly, but the presence of hypoxia suggests that air exchange might be poor.
AIRWAY MANAGEMENT
The ability to rescue a patient from an airway emergency in order to maintain oxygenation is a vital skill that emergency physicians must possess.
MANUAL MANIPULATION OF THE AIRWAY
Most airway repositioning maneuvers work by moving the posterior portion of the tongue to a more anterior location so that it does not block the airway. Figure 17-3A and B demonstrates how the jaw thrust maneuver opens the airway. Note that this maneuver should not move the cervical spine if immobilization is required. While placing your thumbs on the patient’s zygoma or maxilla, grasp the mandibular angle with your fingers and pull it anteriorly (Fig. 17-4). The chin-lift maneuver is similar but if the head is tilted, this could move the cervical spine. If cervical spine movement is not a concern, then other maneuvers that can be attempted with varying degrees of success include the following:
FIGURE 17-3. A. This is the same lateral neck x-ray in Figure 17-1A, except that the image is now rotated to the supine position. The nose is pointing upward, and the occiput is down below. B. Labeled version of Figure 17-3A. Note that gravity will move the tongue (To) downward (white arrow) to narrow the airway opening. The dotted line is the angle of the mandible (M). By pushing the angle of the mandible anteriorly (upward in this position, black arrow), this will move the tongue (To) anteriorly (upward) to open the airway. (Reproduced with permission from Boychuk RB. Drooling, stridor, and a barking cough: croup?? In: Yamamoto LG, Inaba AS, DiMauro R, eds. Radiology Cases in Pediatric Emergency Medicine. 1994;1(10). www.hawaii.edu/medicine/pediatrics/pemxray/v1c10.html.)
FIGURE 17-4. Jaw thrust maneuver. By placing your thumbs on the patient’s maxilla or zygoma, grasp the mandibular angle with your fingers and pull the mandible forward (black arrow) to open the airway. This can be done without cervical spine movement.
1. Raising the patient’s occiput (putting a thick towel underneath it) into the sniffing position. This brings the tongue more anterior, opening the airway and improving the angle of view for laryngoscopy and intubation.
2. Placing a towel roll under the patient’s scapulae and upper thoracic spine while permitting the head to tilt backward. This essentially does the opposite of raising the occiput, but the backward tilt of the head can often raise the posterior portion of the tongue. An excessive head tilt can stretch and compress the airway.
3. Placing the patient on his/her side with the face slightly downward. This permits gravity to move the tongue forward.
4. Placing the patient prone. While this position permits gravity to move the tongue forward and secretions drain out of the mouth, it does not permit easy access to the airway for other manipulations such as laryngoscopy. However, bag-mask ventilation (BMV) can be done in this position. This position might be especially optimal for a patient with epiglottitis in respiratory failure. The large inflamed epiglottis in the prone position falls backward obstructing the airway. The patient prefers to be in the “tripoding” position (erect, leaning forward) to keep the epiglottis off the airway. As the patient tires and succumbs to respiratory failure, placing the patient in the prone position utilizes gravity such that the epiglottis falls anteriorly, opening the airway and permitting BMV, which should optimally be performed using the two-rescuer method.
PHARMACOLOGIC TREATMENT OF THE AIRWAY
Aerosolized epinephrine can improve air exchange in croup and other conditions resulting from upper airway edema. Note that the standard dose of 0.5 mL of 2.25% racemic epinephrine is equal to 5.5 mg (5.5 mL of 1:1000) epinephrine. Aerosolized and systemic corticosteroids can also reduce airway swelling caused by inflammation. Anticholinergics (atropine, ipratropium) and albuterol can reduce airway resistance in some instances.
OXYGEN ADMINISTRATION
For spontaneously breathing patients, supplemental oxygen can be delivered via nasal cannula, blow-by oxygen mask, nonrebreather oxygen mask, or Rusch bag and mask (Fig. 17-5). Nasal cannula and blow-by oxygen enrich the oxygen concentration in the oral–nasal area to improve the inspired fraction of oxygen depending on the flow rate. Even at high-flow rates, this enrichment is modest. Conventional oxygen masks leak and entrain substantial amounts of room air. Nonrebreather oxygen masks have a reservoir bag that should be inflated with pure oxygen such that when the patient inhales, pure oxygen from the reservoir bag is inhaled. A Rusch bag and mask is a closed circuit so that with a tight mask seal, close to 100% FIO2 can be delivered. In addition, continuous positive airway pressure (CPAP) and positive-pressure ventilation can be administered with a Rusch bag and mask.
FIGURE 17-5. Different types of oxygen delivery devices. Nasal cannula, standard oxygen mask, nonrebreather mask, Rusch bag and mask.
RESCUE BREATHING AND BAG-MASK VENTILATION
BMV is a vital skill that must be practiced for proficiency. Airway repositioning is generally required simultaneously. The two-rescuer technique is easier (Fig. 17-6). One rescuer uses both hands to apply a properly fitting mask seal covering the patient’s mouth and nose, while simultaneously optimizing the patient’s airway position. The second rescuer squeezes the bag to provide positive pressure, while ideally checking the chest rise. A third rescuer, if available, can auscultate the chest to confirm air exchange and/or assist with airway repositioning to optimize ventilation.
FIGURE 17-6. Two-rescuer method of BMV. Note that one rescuer uses both hands to secure a mask seal, whereas a second rescuer squeezes the bag.
The single-rescuer technique is more difficult to perform optimally (Fig. 17-7). With one hand, the rescuer holds the mask with the thumb and index finger, while using the other three fingers to grasp the patient’s mandible. This is called the E-C (or CE) method because the thumb and index finger form the letter C, whereas the other three fingers form the letter E. This hand must also position the airway properly to optimize ventilation. The other hand must be used to squeeze the bag. Rescuers with large hands can squeeze the bag directly, whereas those with smaller hands can squeeze the bag against their thigh.
FIGURE 17-7. Single-rescuer method of BMV. Note the E-C method of holding the mask against the child’s face. The thumb and index finger apply pressure on the mask whereas the other three fingers are used to “hook” the patient’s mandible. The bag can either be squeezed with a large hand, or it can be squeezed against the rescuer’s thigh as shown in this photo.
Overinflation by BMV can result in gastric distention, which can restrict lung expansion and place the patient at risk for gastric regurgitation. Applying cricoid pressure (the Sellick maneuver) can reduce gastric inflation to some degree. Excessive ventilation volumes and pressures can also increase intrathoracic pressure impeding venous return.2
VENTILATION BAG TYPES
There are basically two different bag types. The self-inflating bag is stiffer (Fig. 17-8). The Rusch bag (also called anesthesia bag) is more floppy and it normally collapses (Figs. 17-5 and 17-9). The term “ambu” bag can refer to both types of bags. The self-inflating bag (Fig. 17-8) does not require a positive-pressure gas source. Since it inflates spontaneously, it can entrain room air and ventilate the patient with room air without an oxygen tank. If the tail of the bag is attached to a high-flow oxygen source, the patient will be ventilated with an oxygen-rich mixture that can approach 100% FIO2. This type of bag should not be used in conjunction with a mask to deliver blow-by or mask oxygen to a spontaneously breathing patient because oxygen does not flow through the bag unless the bag is squeezed, regardless of how much oxygen is flowing into the tail of the bag.
FIGURE 17-8. Self-inflating bag. The tail is on the left. High-flow oxygen entering the tail increases the FIO2 entering the bag. This particular model has an opening for an optional PEEP valve.
FIGURE 17-9. Rusch bag and mask. Note the built-in manometer.
The Rusch bag (Fig. 17-9) is a closed circuit system. Oxygen flows into the bag inflating it, and it is squeezed out the ventilation connection port. No outside air is entrained if a proper mask seal is maintained, so 100% oxygen can be easily delivered if 100% oxygen enters the bag. If the patient is spontaneously breathing, this differs from the self-inflating bag in that the Rusch bag mask setup functions as an oxygen-flow mask because oxygen flows into the mask even if the bag is not squeezed. Another useful application of the Rusch bag and mask is that it can be used to visibly monitor ventilation. If the gas flow is adjusted optimally with a proper mask seal, the bag will collapse partially as the patient inhales, and the bag will fill as the patient exhales. This visible bag movement is an indicator of air exchange.
Both bag types can deliver positive end-expiratory pressure (PEEP), which is useful and sometimes essential for pulmonary edema and some other respiratory failure conditions. The Rusch bag delivers PEEP more routinely by simply increasing the gas flow, so that during exhalation, the bag is still full (exerting some positive pressure even during the exhalation phase). Most Rusch bags have a controlled leak valve and a visible pressure gauge or a pressure gauge connector to measure inspiratory and expiratory pressures. This also permits CPAP for spontaneously breathing patients. The self-inflating bag normally does not provide positive pressure during exhalation (PEEP); however, the addition of a PEEP valve attached to the exhalation port (Fig. 17-8) provides resistance during exhalation so that PEEP is provided. Both bag types have advantages and disadvantages. Know how to use both types properly. Table 17-1 summarizes the differences.
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TABLE 17-1 |
Advantages and Disadvantages of Self-Inflating Bag Versus Rusch Bag |
The laryngeal mask airway is an alternative to endotracheal intubation. As with any airway device, training and practice is required for proficient use. When endotracheal intubation is not possible, the laryngeal mask airway is an acceptable adjunct, but it is associated with a higher incidence of complications in young children.2
TRACHEAL INTUBATION
Tracheal intubation is best accomplished via the rapid sequence intubation (RSI) method with direct visualization using a laryngoscope. Other techniques that have been described are blind nasal tracheal intubation, blind oral intubation via palpation, intubation via fiberoptic or video laryngoscopy visualization and guidance. These techniques have been less well described and hence the experience level among practitioners is not as extensive. Under the stress of an airway emergency, the likelihood of success is greatest with the technique that the practitioner has the greatest skill, expertise, and experience with. In teaching centers, another factor is the requirement that the procedure is supervisable and confirmable by the teaching physician.
RSI is described in a series of the following steps (a sequence):
1. Patient assessment, preparation, resuscitation
2. Premedications
3. Hyperoxygenation
4. Cricoid pressure (Sellick maneuver)
5. Paralyzing agent
6. Sedation agent
7. Intubation
8. Confirmation of intubation
Step 1. Assess the patient and perform immediate resuscitation measures such as mask ventilation, if necessary. Patient assessment includes determining the need and priority for intubation. Decompressing the stomach with a nasogastric tube can be helpful to improve ventilation; however, it makes the maintenance of a mask seal more difficult if BMV is necessary, it can be noxious triggering movement, which would be adverse to patients with cervical spine injuries, and it can interfere with gastroesophageal sphincter function increasing the risk of gastric regurgitation. In most instances, it is better to pass a nasogastric tube after intubation.2 Clinical assessment includes the determination of whether a nasogastric tube should be inserted prior to intubation or after intubation is confirmed. Preparation includes procuring the supplies necessary for the procedure (suction, laryngoscope, ventilation devices, ETT, tracheal intubation confirmation devices, etc.) as well as the practice sessions and creating an environment conducive to optimally performing RSI. The latter of which must be in place prior to the presentation of the emergency case requiring RSI. Posting Table 17-2 would be part of basic preparation.3
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TABLE 17-2 |
RSI Drugs, Doses (mg/kg), Sizes, Distances |
Step 2. Premedications depend on the clinical circumstances and practitioner preference. An abbreviated list of these includes atropine and lidocaine. Atropine potentially reduces oral secretions and the risk for laryngoscopy-induced bradycardia. Lidocaine potentially blunts the rise in intracranial pressure (ICP) during laryngoscopy, which is more important for patients with elevated ICP.
Step 3. RSI includes a brief period of apnea during intubation, which is best tolerated if the patient can maintain oxygenation during this period. This is best accomplished with hyperoxygenation prior to intubation. For patients who are breathing spontaneously, applying 100% FIO2 by high-flow nonrebreathing mask or Rusch bag and mask maximizes oxygen hemoglobin saturation which is measurable via pulse oximetry, and additionally, it saturates the nonhemoglobin (plasma) oxygen content which is not measurable via pulse oximetry but can increase oxygen content by approximately 20%. Hypoxic patients and patients who are not spontaneously breathing sufficiently should be mask ventilated via BMV (PEEP may be necessary in many of these patients) to maximally oxygenate the patient prior to intubation. Patients who are still hypoxic despite rescue measures are at high risk for worsening hypoxia and deterioration during intubation. However, such scenarios are commonly encountered in the emergency department, and they must still be intubated to take resuscitation to the next step.
Step 4. Cricoid pressure occludes the esophagus. This optional step is known as the Sellick maneuver and it potentially reduces the risk of passive regurgitation. It can also push the larynx more posteriorly to facilitate visualization during laryngoscopy. While cricoid pressure potentially reduces the risk of passive gastric regurgitation, it does not prevent vomiting if the patient is actively retching.
Step 5. Selecting a paralyzing agent is controversial. The two common choices are succinylcholine and rocuronium. A detailed discussion of the differences between these two is beyond the scope of this chapter. The basic differences are that succinylcholine has a shorter duration, but a higher risk of adverse reactions that include malignant hyperthermia, and hyperkalemia, whereas rocuronium has a longer duration of paralysis but a lower risk of adverse reactions. The onset of paralysis by using agents such as vecuronium and pancuronium is slower than the onset of succinylcholine. The onset time of rocuronium is similar to the onset time of succinylcholine.
Further reading about RSI will reveal principles known as priming and defasciculation. Many experts recommend these; however, this practice prolongs the time to intubation. While these principles fit best with anesthesia practices for stable patients, the typical emergency department patient requires emergent intubation. “Priming” is the principle of giving a small dose of rocuronium 1 to 2 minutes prior to the full dose of rocuronium. Priming reduces the paralysis onset time of the full dose of rocuronium by a few seconds, but it prolongs the RSI procedure by 1 to 2 minutes. “Defasciculation” is the practice of administering a small dose of rocuronium 1 to 2 minutes before administering succinylcholine. Succinylcholine typically results in brief muscle contractions prior to the onset of paralysis known as fasciculations, which are sometimes associated with muscle pain (in muscular patients), movement, and hyperkalemia. Defasciculation prevents these fasciculations. Both priming and defasciculation have minimal benefit or no benefit while delaying the intubation itself.
Step 6. Selection of a sedation agent is similarly controversial. A detailed discussion of this is beyond the scope of this chapter. Table 17-2 describes a basic method of selecting a sedation agent.3 Selection criteria may be separated into patients with head trauma (or increased ICP), hypotension, and respiratory failure due to asthma. Considering these three factors permits the selection of a sedative. Thiopental has cerebroprotective properties, but it is a myocardial depressant, can lower blood pressure, and it is no longer available. Ketamine increases blood pressure and bronchodilation, but it also increases ICP. Etomidate is a more intermediate agent, and is purported to be a universal RSI sedative because of less adverse effects and it has some cerebroprotective properties. Benzodiazepines are moderate sedatives, require titration (not feasible in RSI), and most often do not result in sedation deep enough for intubation. However, they have few adverse side effects and are used by some practitioners for RSI. Propofol has also been added to the list of possible sedatives with RSI; however, it does not have substantial advantages over the agents listed in Table 17-2. Another option is to use no sedative at all. This is a serious consideration in hypotensive patients or those at risk for septic shock. Any agent administered to patients under significant cardiovascular stress (including benzodiazepines, ketamine, and etomidate) could result in acute deterioration such as cardiac arrest, and thus the benefit of a sedative must be considered against this risk for severe patients.
Another issue of controversy is whether to give the sedative before the paralyzing agent or vice versa. Giving the paralyzing agent first reduces the time to intubation. Since the paralyzing agent takes 60 to 90 seconds to achieve sufficient paralysis, the sedation agent can be given during this waiting time. Giving the sedation agent first (as listed in Table 17-2) permits the patient to avoid the sensation of becoming paralyzed. These differences have different priorities in various clinical circumstances. Giving the paralyzing agent first makes more sense in severe patients in need of immediate intubation. Giving the sedation agent first makes more sense if the patient is conscious and the patient is less seriously in need of immediate intubation. Regardless of which is given first, the paralyzing agent and the sedation agent should be given in “rapid sequence.”
Step 7. ETT size selection is critical in children. The common formula cited is 4 + (age/4). Thus, a 6-year-old would need a 5.5 ETT. Newborns should be intubated with a 3.0 or 3.5 ETT (smaller for premature infants). However, memorizing a formula may risk error. Using a length-based resuscitation system or posting Table 17-2 in the resuscitation room would be more reliable. Posting Table 17-2 has the added advantage of including drug doses, drug selection criteria, and the depth of the ETT. Selection of a laryngoscope blade type is a matter of personal preference. The classic teaching is that straight blades are better for young children, and curved blades are better for older children; however, both blade types are available in all sizes and are really a matter of personal preference. Visualization of the larynx can be facilitated by adjusting the degree of cricoid pressure. Repeating the fact that the narrowest point of the airway is the cricoid (below the cords) is useful because advancing the ETT through the cords will sometimes stop at the cricoid. ETTs can be cuffed or uncuffed. A cuffed ETT provides better airway protection and a tighter seal, which is beneficial when higher ventilation pressure is required. However, with small ETTs, the deflated cuff significantly increases the size of the ETT making it more difficult to advance. A commonly cited cutoff in the past was age 9 (size 6 ETT), below which uncuffed ETTs were recommended. However, current recommendations permit the option of cuffed ETTs to infants and children,2 but not neonates. Cuff inflation pressures should be measured and kept below 20 cm H2O.2
Step 8. Confirmation of tracheal intubation should be confirmed with more than one method and one of these methods should be a carbon dioxide detection device. Colorimetric ETCO2 indicators that visibly change color during ventilation (Fig. 17-10) reliably confirm that the trachea is intubated in most instances. These colorimetric ETCO2 indicators come in different sizes. Using an adult sized unit for a newborn will not work since the volume of CO2produced by the newborn will be insufficient to change its color. In addition, many colorimetric ETCO2 indicators will eventually become disabled due to water vapor saturation. An ETCO2 monitor quantifies the ETCO2 (which can be correlated to the patient’s venous or arterial PCO2), displays the actual waveform of ETCO2 production, and it can be used continuously and indefinitely. A typical square waveform reliably confirms tracheal intubation, whereas a nonsquare waveform raises concerns that the trachea is not intubated (Fig. 17-11).
FIGURE 17-10. ETCO2 colorimetric detector. This particular model is small, made for neonates. Color changes from purple to yellow if CO2 is detected. (Reproduced with permission from Fuchs S, Yamamoto L, eds. APLS: the Pediatric Emergency Medicine Resource. 5th ed. Sudbury, MA: Jones and Bartlett Publishers; 2012.)
FIGURE 17-11. ETCO2 monitor wave forms. This tracing shows a pulse oximeter waveform on the top. The upper pair of tracings shows an irregular peaked ETCO2 waveform (red arrow), which does not confirm tracheal intubation. The lower tracing (yellow arrow) shows a regular square wave ETCO2 waveform that confirms tracheal intubation. (Reproduced with permission from Fuchs S, Yamamoto L, eds: APLS: the Pediatric Emergency Medicine Resource. 5th ed. Sudbury, MA: Jones and Bartlett Publishers; 2012.)
ETCO2 is not produced in the absence of pulmonary perfusion. Inadequate CPR will result in no ETCO2. CPR is a known false-negative (i.e., the trachea is intubated, but ETCO2 is negative). The presence of an ETCO2 square waveform during CPR confirms tracheal intubation and pulmonary perfusion, confirming effective chest compressions.
Auscultation can confirm equal chest aeration, and the absence of gastric breath sounds. Visualization can confirm chest rise and fall with ventilation, and condensation visible in the ETT. Improvements in oxygenation and resuscitation parameters are consistent with tracheal intubation. None of these definitively confirm tracheal intubation; however, collectively, the presence of all of these highly support successful tracheal intubation. The esophageal detector bulb (also known as the “turkey baster”) method utilizes a rubber bulb attached to an ETT connector (Fig. 17-12). Squeeze the bulb, then apply it to the ETT. If the bulb inflates rapidly, this suggests that the tube is in the trachea or the pharynx. If the bulb inflates slowly or it does not inflate, this suggests that the tube is in a collapsible tube such as the esophagus.
FIGURE 17-12. Esophageal detector device (turkey baster). This bulb attaches to the ETT. By squeezing the bulb, it should rapidly inflate if the trachea is intubated. Slow inflation indicates that the esophagus is intubated.
If tracheal intubation is in doubt, direct visual confirmation with the laryngoscope should be attempted. Once tracheal intubation is confirmed, the ETT depth needs to be optimized based on the clinician’s visual intubation depth (during laryngoscopy) and the ETT depth guidelines in Table 17-2. The ETT should be secured. There are several ways to do this using tape, and there are commercial products designed for securing the ETT. A chest x-ray is useful to confirm the placement of the tip of the ETT, which should be within the trachea, above the tracheal bifurcation. The ETT position can be readjusted if needed, being careful not to extubate the patient.
CAN’T VENTILATE, CAN’T INTUBATE SCENARIO
Preparing for this difficult scenario requires preparation to initiate airway access through the anterior neck. Cricothyrotomy (also known as cricothyroidotomy and transtracheal ventilation) is one of these options. The cricothyroid membrane is punctured with a large IV catheter or an airway quick catheter. Most large bore IV catheters are placed by puncturing the cricothyroid membrane aiming in an inferior (caudal) direction. The catheter is advanced and the catheter hub is attached to a 3.0 ETT connector. Holding the catheter hub in place is critical since the catheter can be easily kinked, which would narrow it substantially. If a bag is used, substantial effort is required to squeeze the bag to deliver a sufficient tidal volume (a self-inflating bag accomplishes this better than a Rusch bag). A jet ventilation setup (Fig. 17-13) can deliver greater tidal volumes through an IV catheter.
FIGURE 17-13. This jet ventilation setup can be used for transtracheal ventilation via an IV catheter. By occluding the open end or the thumbhole, high-pressure oxygen is forced through the transtracheal catheter. Releasing this results in passive exhalation. This diagram shows connection to the IV catheter using a 3 mL syringe and an 8.0 ETT connector. Instead, a 3.0 ETT connector can connect directly into the hub of the IV catheters. However, the connector has no Luer lock onto the catheter hub, and under high inflation pressures, this could pop off. (Adapted with permission from Yamamoto LG: Rapid sequence anesthesia induction and advanced airway management in pediatric patients, Emerg Med Clin North Am. 1991;9(3):611–638.)
Having a commercially configured quick airway kit in the resuscitation room is better since the airway diameter provided is larger. Many airway kits puncture the cricothyroid membrane and utilize a dilator and a wire similar to the Seldinger vascular access technique. The specifics of each kit should be reviewed prior to the presentation of an airway emergency in which it is needed. In smaller children, the cricothyroid membrane cannot be easily identified. Estimating its location is essential to these interventions.
An emergency surgical airway such as a tracheostomy or surgical cricothyrotomy is complication prone, but in the “can’t intubate, can’t ventilate” scenario, this might be the only option to oxygenate the patient.3 The actual procedure is beyond the scope of this chapter. If this is to be attempted, a surgical airway kit should be available at all times and the procedure should be reviewed ahead of time.
A complication to avoid is explosive combustion. The patient is likely being ventilated with high-flow oxygen during this procedure. The use of electrocautery or heat cautery must be avoided since this can trigger explosive combustion.
REFERENCES
1. Hendry PL. Chapter 2. The pediatric airway in health and disease. In: Fuchs S, Yamamoto L, eds. APLS: The Pediatric Emergency Medicine Resource. 5th ed. Sudbury, MA: Jones and Bartlett Publishers; 2012:38–95.
2. Kleinman ME, Chameides L, Schexnayder SM, et al. Part 14: Pediatric advanced life support: 2010 American Heart Association Guidelines for cardiopulmonary resuscitation and emergency cardiovascular care. Circulation. 2010;122:S876–S908.
3. King BR, King C, Coates WC. Chapter 26. Critical procedures. In: Fuchs S, Yamamoto L, eds. APLS: The Pediatric Emergency Medicine Resource. 5th ed. Sudbury, MA: Jones and Bartlett Publishers; online component supplement to text; www.aplsonline.com.