Chapter 377 Acute Inflammatory Upper Airway Obstruction (Croup, Epiglottitis, Laryngitis, and Bacterial Tracheitis)
The lumen of an infant’s or child’s airway is narrow; because airway resistance is inversely proportional to the 4th power of the radius (Chapter 365), minor reductions in cross-sectional area due to mucosal edema or other inflammatory processes cause an exponential increase in airway resistance and a significant increase in the work of breathing. The larynx is composed of 4 major cartilages (epiglottic, arytenoid, thyroid, and cricoid cartilages, ordered from superior to inferior) and the soft tissues that surround them. The cricoid cartilage encircles the airway just below the vocal cords and defines the narrowest portion of the upper airway in children <10 yr of age.
Inflammation involving the vocal cords and structures inferior to the cords is called laryngitis, laryngotracheitis, or laryngotracheobronchitis, and inflammation of the structures superior to the cords (i.e., arytenoids, aryepiglottic folds [“false cords”], epiglottis) is called supraglottitis. The term croup refers to a heterogeneous group of mainly acute and infectious processes that are characterized by a bark-like or brassy cough and may be associated with hoarseness, inspiratory stridor, and respiratory distress. Stridor is a harsh, high-pitched respiratory sound, which is usually inspiratory but can be biphasic and is produced by turbulent airflow; it is not a diagnosis but a sign of upper airway obstruction (Chapter 366). Croup typically affects the larynx, trachea, and bronchi. When the involvement of the larynx is sufficient to produce symptoms, they dominate the clinical picture over the tracheal and bronchial signs. Traditionally, a distinction has been made between spasmodic or recurrent croup and laryngotracheobronchitis. Some clinicians believe that spasmodic croup might have an allergic component and improves rapidly without treatment, whereas laryngotracheobronchitis is always associated with a viral infection of the respiratory tract. Others believe that the signs and symptoms are similar enough to consider them within the spectrum of a single disease, in part because studies have documented viral etiologies in both acute and recurrent croup.
377.1 Infectious Upper Airway Obstruction
Etiology and Epidemiology
With the exceptions of diphtheria, bacterial tracheitis, and epiglottitis, most acute infections of the upper airway are caused by viruses. The parainfluenza viruses (types 1, 2, and 3; Chapter 251) account for ∼75% of cases; other viruses associated with croup include influenza A and B, adenovirus, respiratory syncytial virus (RSV), and measles. Influenza A has been associated with severe laryngotracheobronchitis. Mycoplasma pneumoniae has rarely been isolated from children with croup and causes mild disease (Chapter 215). Most patients with croup are between the ages of 3 mo and 5 yr, with the peak in the 2nd yr of life. The incidence of croup is higher in boys; it occurs most commonly in the late fall and winter but can occur throughout the year. Recurrences are frequent from 3-6 yr of age and decrease with growth of the airway. Approximately 15% of patients have a strong family history of croup.
In the past, Haemophilus influenzae type b was the most commonly identified etiology of acute epiglottitis. Since the widespread use of the HiB vaccine, invasive disease due to H. influenzae type b in pediatric patients has been reduced by 80-90% (Chapter 186). Therefore, other agents, such as Streptococcus pyogenes, Streptococcus pneumoniae, and Staphylococcus aureus, now represent a larger portion of pediatric cases of epiglottitis in vaccinated children. In the prevaccine era, the typical patient with epiglottitis due to H. influenza type b was 2-4 yr of age, although cases were seen in the 1st year of life and in patients as old as 7 yr of age. The typical patient with epiglottitis is an adult with a sore throat, although cases still do occur in underimmunized children; vaccine failures have been reported.
Clinical Manifestations
Croup (Laryngotracheobronchitis)
Croup is a clinical diagnosis and does not require a radiograph of the neck. Radiographs of the neck can show the typical subglottic narrowing, or steeple sign, of croup on the posteroanterior view (Fig. 377-1). However, the steeple sign may be absent in patients with croup, may be present in patients without croup as a normal variant, and may rarely be present in patients with epiglottitis. The radiographs do not correlate well with disease severity. Radiographs should be considered only after airway stabilization in children who have an atypical presentation or clinical course. Radiographs may be helpful in distinguishing between severe laryngotracheobronchitis and epiglottitis, but airway management should always take priority.
Acute Epiglottitis (Supraglottitis)
The diagnosis requires visualization of a large, cherry red, swollen epiglottis by laryngoscopy. Occasionally, the other supraglottic structures, especially the aryepiglottic folds, are more involved than the epiglottis itself. In a patient in whom the diagnosis is certain or probable based on clinical grounds, laryngoscopy should be performed expeditiously in a controlled environment such as an operating room or intensive care unit. Anxiety-provoking interventions such as phlebotomy, intravenous line placement, placing the child supine, or direct inspection of the oral cavity should be avoided until the airway is secure. If epiglottitis is thought to be possible but not certain in a patient with acute upper airway obstruction, the patient can undergo lateral radiographs of the upper airway first. Classic radiographs of a child who has epiglottitis show the thumb sign (Fig. 377-2). Proper positioning of the patient for the lateral neck radiograph is crucial in order to avoid some of the pitfalls associated with interpretation of the film. Adequate hyperextension of the head and neck is necessary. In addition, the epiglottis can appear to be round if the lateral neck is taken at an oblique angle. If the concern for epiglottitis still exists after the radiographs, direct visualization should be performed. A physician skilled in airway management and use of intubation equipment should accompany patients with suspected epiglottitis at all times. An older cooperative child might voluntarily open the mouth wide enough for a direct view of the inflamed epiglottis.
