Denis Pauze
Respiratory distress represents a compensatory response to impaired oxygen delivery to tissues, with or without decreased carbon dioxide elimination. The respiratory tract can be divided into two anatomic categories: (1) the lungs, or gas-exchange portion; and (2) the “respiratory pump,” consisting of the thoracic cage, respiratory muscles, and neural pathways governing the system, Pathology involving any of these areas can present with signs and symptoms of respiratory distress. Other factors, outside the respiratory system, can also lead to shortness of breath, including myocarditis, supraventricular tachycardia (SVT), sepsis, and metabolic abnormalities such as diabetic ketoacidosis (DKA). Depending on the etiology of the respiratory compromise and the time until presentation to the emergency department (ED), these signs and symptoms may be obvious or subtle.
There are a number of differences between the pediatric and the adult patient that place children at greater risk for respiratory compromise. Infants and young children have a subglottic airway that is smaller and has less cartilaginous support, making it easier for obstruction to occur secondary to edema, secretions, constriction, or compression. Dynamic collapse of a partially obstructed airway, as seen in croup during inspiration, is an example of the consequences of a high-compliance airway (1). Children younger than 1 to 2 years of age may not have the anatomic pathways or “collateral ventilation” that allows aeration distal to an obstruction, thereby increasing the risk of atelectasis and ventilation–perfusion mismatching.
Because of the increased chest-wall compliance of the pediatric patient, compensatory diaphragmatic breathing may result only in distorting the rib cage as opposed to creating the necessary negative pressure to expand the lungs. The younger the child, the greater the pliability of the chest wall. This places the neonate at greatest risk for fatigue and respiratory failure.
In addition to anatomic differences, there are important physiologic differences. Hypoxemia and acidosis occur more rapidly in children with respiratory compromise because of their higher metabolic rate, which causes an increase in oxygen demand (1). Furthermore, tachypneic infants experience increased insensible losses in the form of exhaled water vapor. These losses become clinically significant as patients experience feeding difficulties in the face of progressive respiratory compromise.
CLINICAL PRESENTATION
The presentation of a child in respiratory distress varies, depending on the specific etiology, duration of illness, age, underlying medical conditions, and interventions prior to arrival in the ED.
Signs of respiratory distress can be separated into those that are visible and those that are audible (Table 232.1). Initially, simply observing a child and listening from afar (avoiding prolonged eye contact or use of a stethoscope) can provide critical information without creating anxiety or agitation, which may serve to worsen the patient’s condition.
TABLE 232.1
Indicators of Actual or Possible Respiratory Compromise
Visual inspection begins with the child’s subjective behavior. Normal behavior does not rule out pathology, but does indicate that the child is comfortable and needs no urgent intervention. When possible, children should be allowed to find their “position of comfort” to optimize oxygenation and ventilation; the demeanor and position assumed can be diagnostic. For example a quiet, serious child who prefers sitting upright in a sniffing position is a cause for concern and requires immediate assessment. Restlessness and irritability can be subtle clues to hypoxemia. Drooling or changes in phonation should also be considered an emergency until proven otherwise. Altered mental status can represent either generalized central nervous system (CNS) disease or hypercarbia, with or without hypoxemia.
The presence of either tachypnea or bradypnea is taken as evidence of respiratory compromise. It is important for clinicians to be familiar with the range of normal pediatric respiratory rates and to appreciate the wide range of “normal.” In addition, fever, pain, and anxiety may result in an increased respiratory rate in the absence of primary pulmonary disease. Patients younger than 1 year of age have a median respiratory rate of 37–43, with a range from 22–66. Patients 2 to 3 years of age have a median range of 28, with ranges from 18–38. Respiratory rates in children 8 and above start falling in the adult range (2).
The best markers of respiratory distress are changes in the respiratory rate, character, and depth, rather than the number of breaths per minute measured at a fixed point in time. Shallow respirations are often seen in lower airway obstruction, and deep respirations often represent central compensatory mechanisms in response to metabolic acidosis. Retractions may be seen in the supraclavicular, subcostal, and intercostal areas. Chest retractions begin subcostally with mild disease and progress upward as patient’s condition becomes worse. Nasal flaring is sometimes a subtle sign that is more commonly present in infants and younger children and is associated with lower tract disease. Head bobbing with each breath and “see-saw” or “rocky” respirations, where the chest pulls in as the abdomen thrusts out, are signs of severe distress; the latter is an inefficient means of ventilation that can quickly lead to respiratory failure (1). Cyanosis usually correlates with a PO2 <40 and an arterial oxyhemoglobin saturation of ≤85%. Anemic patients can be acyanotic and profoundly hypoxic, making cyanosis an unreliable indicator of hypoxemia (1).
Certain indicators of respiratory distress can be heard without the use of a stethoscope. Persistent, forceful, nonproductive coughing may indicate a foreign body lodged in the upper airway, with the potential for complete obstruction. Stridor is a harsh, crowing sound occurring during inspiration (3) and commonly seen in the pediatric population. Stridor, produced by rapid, turbulent air flow through a narrowed area, signifies upper airway pathology. Wheezing represents expiratory obstruction of the lower airways. If heard without chest auscultation, wheezing indicates serious disease and the need for urgent intervention. Grunting, an end-expiratory sound, is produced by glottic closure during exhalation in an attempt to provide physiologic positive end-expiratory pressure (PEEP). Grunting indicates a disease process causing increased alveolar and/or interstitial fluid. An abnormal voice or cry, particularly if muffled in quality, should alert the clinician to possible upper airway disease and the need for prompt, nonthreatening evaluation. In the absence of visual and audible signs of respiratory distress, the likelihood of an infant or child having serious respiratory pathology requiring emergent intervention is small.
Neonates deserve special mention. Normally, neonates have respiratory rates of approximately 40 to 50 breaths/min. A respiratory rate of 60 or more should usually be considered abnormal. Neonates with tachypnea may also exhibit grunting, stridor, accessory muscle use, and central cyanosis. On the other hand, neonates may present with irregular, but nonetheless normal, breathing patterns because of immature respiratory centers. Additionally, the neonate with shortness of breath may also have intermittent episodes of apnea, as seen with advanced RSV.
DIFFERENTIAL DIAGNOSIS
Determining the precise etiology of respiratory distress in the pediatric patient can be challenging; the differential diagnosis is substantial (Table 232.2). Clinicians must recognize the signs and symptoms of respiratory distress in a child and must be able to judge the degree of severity. In moderate to severe degrees of distress, a rapid assessment of the likely etiology is necessary so that appropriate therapy can be initiated. The most common etiologies include asthma, bronchiolitis, croup, and pneumonia, which are described in other chapters.
TABLE 232.2
Etiologies of Respiratory Distress
Age is an important factor in differentiating etiologies of dyspnea. Neonates are more prone to congenital diaphragmatic hernia, congenital lobar emphysema, bronchogenic cysts, and tracheomalacia, which may present within the first days or weeks of life. Other congenital anomalies, such as vascular rings or laryngeal webs, though uncommon, are additional potential etiologies of dyspnea in the neonatal period.
Stridor indicates some form of upper airway obstruction, and when it is associated with fever, one should suspect an infectious etiology. Croup classically presents between 6 months and 3 years of age with a history of a low-grade fever and upper respiratory infection (URI) symptoms for a few days, followed by the gradual onset of a barking cough, hoarseness, and stridor, with or without chest retractions (4).
In any child thought to have croup, the diagnosis of epiglottitis must also be considered. Epiglottitis may also be a life threatening cause of stridor, and can occur at any age. While epiglottitis was once common in the 3–8 year age range, the post vaccination era has shifted epiglottitis towards older patients. Today viruses, other bacteria and different Hib serotypes make up the etiologic factors behind acute epiglottitis (5). On physical examination, the most common signs of epiglottitis have been reported to be stridor (88%), retractions (81%), and temperature ≥38°C (85%); drooling (66%) and a preference for sitting (58%) are less common. The time course from the first clinical sign of epiglottitis to respiratory failure can be short, often less than 12 hours (6). Other early signs and symptoms of epiglottitis include “pain out of proportion to examination” and a child that is “not getting better with antibiotics.” In distinguishing between epiglottitis and croup in a child presenting with fever, stridor, and retractions, the importance of the history cannot be overemphasized. Drooling in the absence of spontaneous cough is the most specific indicator of acute epiglottitis.
Recurrent croup should be noted as a red flag. Approximately one-third of these children may have some type of anatomical airway abnormality and should be referred to a specialist for evaluation of the airway anatomy (7).
Other etiologies to consider in a child with fever and stridor include bacterial tracheitis and peritonsillar or retropharyngeal abscesses (RPAs). Patients with bacterial tracheitis typically have initial symptoms suggestive of croup but with progressive development of high fever, toxicity, and purulent tracheal secretions, resulting in airway compromise (8). Peritonsillar abscesses are most common in older adolescents and young adults (9). There is sudden elevation of temperature, ill appearance, and unilateral throat pain following a preceding tonsillitis. The patient complains of trismus, drooling, and a muffled voice (10). Examination may reveal bilateral tonsillar hypertrophy or unilateral tonsillar enlargement with uvular deviation contralaterally (11). Unlike peritonsillar abscesses, RPAs usually present in young children, from infancy to 3 years of age (12). The clinical picture may be similar to epiglottitis but with a less sudden onset (12). Children with RPA present with limitation of neck movement, especially when looking upward. Patients with RPA rarely present with respiratory distress or stridor but do tend to be febrile and ill-appearing. Computed tomography (CT) scan is useful to distinguish RPA from retropharyngeal cellulitis. Most patients with retropharyngeal cellulitis and a few with RPA can be treated without surgery.
Not infrequently, a URI alone can cause signs of mild-to-moderate respiratory distress in the very young infant. Suctioning the nares with a bulb syringe after placing a few drops of saline can be very useful and may be all that is required in these patients. This is an opportune moment to educate parents on proper suctioning technique so as to optimize home care after discharge from the ED.
Infectious etiologies of the lower respiratory tract that may cause respiratory distress include bronchiolitis and pneumonia. Bronchiolitis presents as any wheezing-associated illness in the first year of life that is preceded by a URI (13). Differentiation from acute attacks of asthma, often triggered by viral infections, may be difficult. As a general rule, patients presenting with wheezing in the first year of life are assumed to have bronchiolitis and not asthma, which therefore precludes treatment with steroids.
In patients presenting in respiratory distress that is not clearly associated with infection, the history and physical examination should quickly provide an answer. Most commonly, a diagnosis of reactive airway disease will be made. An important etiology to include in the differential diagnosis is anaphylaxis, a multisystem syndrome involving the cutaneous, respiratory, cardiovascular, and gastrointestinal systems; involvement of at least two systems is required to make the diagnosis (8). Both the upper and lower airways can be involved, leading to hoarseness, stridor, wheezing, and cough. Early diagnosis and differentiation of anaphylaxis from more benign conditions is essential, as these patients can progress rapidly to anaphylactic shock (8).
Foreign-body aspiration (FBA) can be difficult to diagnose and is a leading cause of death in children under the age of four. Commonly aspirated food products include nuts, seeds, grapes, corn, and beans; peanuts account for nearly 25% of food-based aspirations. Aspiration of hot dogs, candy, and grapes causes the highest mortality. Marbles, coins, toys, and pills are also responsible for many cases (14). The presenting signs and symptoms depend upon the location of the foreign body in the respiratory tract. A partially obstructing foreign body in the upper airway may cause stridor and shortness of breath and requires immediate intervention to prevent progression to complete obstructions. Children with prolonged cough, unilateral wheezing, or recurrent pneumonias should also be evaluated for FBA. Stridor or wheezing that is not responsive to therapy requires further evaluation, beginning with lateral and anteroposterior radiographs of the neck and chest, preferably during both inspiration and expiration (15).
Not all shortness of breath has an airway, lung, or respiratory cause. Children with myocarditis or cardiomyopathy may present with wheezing and dyspnea. Unfortunately, these entities may easily be confused with RSV, bronchiolitis, bronchitis, or pneumonia. Arrhythmias such as SVT are also common, and may lead to dyspnea and heart failure. Other important causes of respiratory compromise in the child include seizures, cystic fibrosis, and metabolic acidosis caused by sepsis, DKA, renal disease, and certain ingestions (e.g., salicylate, methanol, ethylene glycol).
Neuromuscular diseases, including Guillain–Barré, botulism, and myasthenia gravis, also should be considered. Vocal cord dysfunction, believed to represent a conversion disorder, results in either inspiratory or expiratory stridor that may be confused with wheezing. Congenital anomalies should be considered in infants younger than 6 months who present with stridor; such anomalies include vascular rings, laryngeal webs, vocal cord paralysis, and laryngomalacia. Hypocalcemia, in addition to having neurologic, cardiovascular, and psychiatric manifestations, can also result in apnea, laryngeal spasm, bronchospasm, or biphasic respiratory noises and should be included in the differential diagnosis of any patient with respiratory distress (16).
ED EVALUATION
The pediatric assessment triangle (PAT), comprised of work of breathing, general appearance, and circulatory status, is a widely used evaluation tool for the assessment of the pediatric patient. It is simple and allows for a rapid global assessment of the potentially ill child. The initial evaluation begins when the physician enters the room, noting any visual and audible indicators of actual or possible respiratory compromise. The child in respiratory distress must be approached in a gentle, reassuring manner and allowed to find the most comfortable position, whether it be on the examining table or on a parent’s lap. Initial priorities (concurrent with the PAT triangle) include assessing the relationship between work of breathing and hydration status. Clinicians must establish baselines in these two areas from which clinical changes can be measured. Patients with increased work of breathing, especially infants, are likely to have had greater difficulties feeding and greater insensible water losses from exhaled water vapor. Bringing these two factors together in pediatric patients is vital and goes beyond merely quantifying the respiratory rate. The hydration status is a foundational component of disposition decisions in young infants and children with respiratory illnesses and should not be overlooked. Patients with moderate degrees of tachypnea who otherwise look well must prove that they can maintain their hydration status as outpatients before being discharged.
In the child who is alert and attentive, the evaluation can proceed with the history and physical examination. However, any child with altered mental status, irritability, or restless with other evidence of distress must have an immediate assessment of the ABCs of resuscitation – airway, breathing, and circulatory status.
Important historic points include underlying medical problems (e.g., asthma, cystic fibrosis, or seizure disorder), the onset and type of current symptoms, and the possibility of FBA or ingestion. If epiglottitis is suspected, forced visualization of the pharynx should be avoided in the ED. Forced visualization may result in a vasovagal response, causing cardiopulmonary collapse, respiratory obstruction, and death (17). We recommend the traditional approach where the child with suspected epiglottitis goes to the operating room for direct visualization of the airway under optimal conditions and in the presence of personnel skilled in establishing the airway.
Following the history and physical examination, the etiology of the respiratory distress is usually clear. Noninvasive monitoring can be used to help with clinical assessment. Pulse oximetry provides a continuous and generally valid measure of the arterial hemoglobin oxygenation saturation and arterial pulse. Blood gas measurements stress an already distressed child, add little or no useful information to the evaluation, and should be avoided.
In situations in which FBA is suspected, lateral and anteroposterior neck and/or chest radiographs should be obtained; if normal, either an assisted expiratory film, bilateral decubitus radiographs, or fluoroscopy should be done (18). One should have a low threshold for specialty consultation despite negative imaging results, if FBA is seriously suspected. Direct visualization with bronchoscopy is the test of choice when clinical suspicion is high but the initial evaluation is negative. If the distinction between croup and epiglottitis is not obvious, and the child is stable and only mildly ill, a lateral neck radiograph has been traditionally viewed as appropriate. However, Ragosta et al. (19) found lateral neck films to be of limited value in the initial evaluation of suspected epiglottitis and recommend against their use.
Repeated evaluations at regular intervals, as well as noninvasive monitoring, are essential in any child presenting in respiratory distress. Once appropriate therapy is instituted, the child’s response to treatment must be periodically assessed. Often, the best way to determine whether an adult or older child is improving is simply to ask, “Are you feeling better?” In the nonverbal or frightened child, changes in clinical parameters that have been observed early in the evaluation (e.g., activity level, eye contact, and ability to take fluids) are appropriate to gauge improvement.
The plain chest X-ray (CXR) remains the diagnostic tool of choice for the evaluation of dyspnea in pediatric patients. The CXR may reveal pneumothorax, pneumonia, foreign body, pleural effusion, or cardiomegaly, and offers the advantage of being fast and readily accessible.
Ultrasound may gain favor as a diagnostic tool for assessing pulmonary pathology. Ultrasound can be fast and informative, minimizes radiation exposure, and can be performed at the bedside. Ultrasound also offers the opportunity to repeat examinations serially to monitor for progression of illness or response to treatment. For the diagnosis of pneumonia, ultrasound has been compared to conventional chest radiography and has been judged to be as reliable as CXR in experienced hands (20). However, the use of ultrasound for this indication is still somewhat preliminary; and as with all ultrasound studies the utility of the test is operator dependent.
KEY TESTING
• Pulse oximetry
• Chest radiographs as indicated depending on differential diagnosis
• Thorough history and physical examination
ED MANAGEMENT
The importance of a gentle, nonthreatening approach cannot be overemphasized. Interventions of any sort are usually poorly tolerated by young children and, at least temporarily, may result in a worsening of their condition. The benefit of any intervention must always be weighed against its potential for adversely affecting the child.
Management of the child in respiratory distress generally involves two goals: Keeping the patient calm and comfortable and providing appropriate therapy. Treatment typically begins with humidified oxygen. Infants and some children often do not tolerate masks well and, depending on their oxygen requirement, may best be served with blow-by oxygen administered by the parent. In addition to the physical examination, pulse oximetry is useful in determining oxygenation status. Normal pulse oximetry readings have been reported as 91.5% to 100% in infants 6 months and younger who are awake, and 96% to 100% (median, 99.5%) in children 2 to 16 years of age who are asleep. If the anxiety produced by the administration of oxygen to children in mild distress worsens their condition, the oxygen is clearly doing more harm than good and should be avoided. However, the anxiety elicited by the administration of oxygen is usually transient. For severely distressed or cyanotic patients, 100% humidified oxygen must be provided quickly, irrespective of their acceptance.
Common diagnoses that respond to specific medical therapy include croup, asthma, and bronchiolitis. Steroids, given orally, parenterally, or via nebulizer, have been shown to be effective in the management of croup, however (10,21–23). For severe croup, nebulized epinephrine can rapidly relieve distress, but its effect lasts only 1 to 3 hours (24). Although nebulized epinephrine’s activity is short lived, studies indicate that when it is used with steroids (e.g., dexamethasone, 0.15 to 0.6 mg/kg, intramuscularly or orally), patients can be safely discharged home after 2 to 4 hours if clinically well (e.g., without retractions and stridor at rest) (24–26). Caution should be used when employing nebulized epinephrine if epiglottitis is suspected, as it may precipitate airway obstruction.
CRITICAL INTERVENTIONS
• Keep patients in their position of comfort for as long as possible.
• Consider a foreign body in the patient who presents with paroxysmal cough or new-onset wheezing.
• Give steroids when administering epinephrine for croup.
• Assessing hydration status in conjunction with respiratory status.
DISPOSITION
For the stable child in moderate distress, admission to an inpatient pediatric floor is appropriate. When there is a concern that the patient may deteriorate because of the particular disease process (e.g., anaphylaxis) or medical history (e.g., an asthmatic previously requiring intubation), admission to a PICU should be considered. If necessary, transfer to the nearest hospital having a PICU should be arranged, in accordance with federal guidelines. The transfer should be done by personnel skilled in airway management (i.e., an advanced cardiac life-support unit or the pediatric transfer team of the receiving hospital). Ground transport is adequate for the stable child in only moderate distress.
Children in severe distress should be admitted to a PICU. If transfer is necessary, consideration should be given to intubating and stabilizing the airway before departure, rather than risking deterioration and the need for a potentially difficult intubation en route. Transfer by ground units with personnel skilled in airway management is adequate for most patients in severe distress. However, the need for ground versus air transport must always be individualized.
Common Pitfalls
• Starting an intravenous line that is not needed for initial therapy (24).
• Forcing oxygen on the child in mild distress who will not tolerate it.
• Obtaining blood for blood gas analysis in a severely distressed patient before providing therapy.
• Doing a detailed history and physical examination before intervening in the severely distressed child.
• Misinterpreting decompensation for improvement.
• During pulse oximetry monitoring, determining a sleeping infant to be hypoxic without further evaluating him or her in an awake state.
• Failing to consider the addition of intravenous fluid therapy in a child with increased insensible losses and decreased oral intake due to tachypnea.
ACKNOWLEDGMENTS
The author gratefully acknowledges the contributions of Richard Cantor to the content of this chapter.
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