CHAPTER 71

Stridor and Croup

David B. Burbulys, MD

Noisy breathing is a common symptom that often accompanies respiratory infections in children. The presence of stridor, a high-pitched crowing sound, often concerns children’s caregivers. Some parents and guardians try home remedies to alleviate the symptoms, whereas many others immediately seek help in the office or emergency department setting. Croup is an inflammation of the larynx, trachea, and upper bronchioles (ie, laryngotracheobronchitis) that causes noisy breathing and stridor. It is among the most common causes of a seal-like barking cough and stridor in children.

Epidemiology

Croup most commonly affects children between 6 months and 3 years of age, generally in the fall or early winter. Children younger than 1 year account for 26% of cases. Infants are frequently more severely affected than older children. The condition is more common in boys than girls; two-thirds of all hospitalized children with croup are boys.

Stridor, which may be indicative of croup, may also be a sign of epiglottitis. The incidence of epiglottitis in children has dramatically decreased since 1988 following the development and widespread use of the vaccine against Haemophilus influenzae type b. Many young children may be incompletely immunized, and other bacteria exist that may cause epiglottitis; thus, epiglottitis should still be considered in toxic-appearing children with rapid onset of symptoms of upper airway obstruction. Before Haemophilus influenzae type b immunization, the ratio of cases of epiglottitis to croup was 1:100. Currently, epiglottitis in children is exceedingly rare.

Clinical Presentation

Viral Croup

Viral croup commonly begins with 2 to 3 days of viral upper respiratory symptoms (eg, rhinorrhea, sore throat, cough) and a generally low-grade fever. Higher-grade fevers may occur depending on the causative agent. At day 3 or 4, the characteristic signs of a hoarse voice, barking cough, and inspiratory stridor manifest. This frequently occurs suddenly and often at night. Symptoms worsen in the next 1 to 2 days and then resolve over the next several days.

Spasmodic Croup

Spasmodic croup typically occurs in children 2 to 5 years of age and often presents suddenly, commonly at night, without the previous complaint of upper respiratory symptoms. As in viral croup, hoarseness, barking cough, and stridor occur; however, these symptoms generally are less severe in spasmodic croup. The condition frequently resolves completely when affected children are exposed to cool or humified air. It may be recurrent. Some children may have the prodrome of a viral upper respiratory syndrome. Fever is uncommon. The etiology is unknown but is likely a reaction to a viral infection or an allergic phenomenon. A family history of recurrent stridor in children with spasmodic croup may exist.

Bacterial Tracheitis

The classic presentation of bacterial tracheitis is of a school-age child presenting with a prodrome of an upper respiratory infection. After a few days, this is followed by the abrupt progression to toxic appearance. A high fever, productive cough, inspiratory stridor, and tachypnea with moderate to severe respiratory distress commonly occur. This generally occurs as the airway becomes secondarily infected with staphylococcal or streptococcal species. White blood cell counts are frequently significantly elevated. Abrupt decompensation may occur as pseudomembranes loosen and obstruct the airway.

Epiglottitis

Whereas acute bacterial epiglottitis was classically seen in young children, currently it is more common in adolescents and young adults. Historically, it presented with the abrupt onset of toxic appearance, high fever, sore throat, odynophagia, and muffled voice. Rapid progression followed with severe respiratory distress, drooling, stridor, tripod positioning, and frequent airway obstruction. Modern presentations are commonly less severe or progressive because of the change in pathogens. Sore throat, odynophagia, muffled voice, and significant tenderness to palpitation of the larynx frequently occur, but currently, toxic appearance and progression to airway obstruction are uncommon.

Foreign Body

Laryngotracheal foreign body aspiration may occur as a witnessed event. Choking, coughing, gasping, and stridor frequently occur, and the patient may present with these symptoms or they may have resolved by the time the patient is seen in the doctor’s office. Presenting symptoms of foreign bodies in the lower larynx include dysphagia, gagging, and throat discomfort. Presenting symptoms of foreign bodies in the trachea include coughing, wheezing, and, with time, pneumonia.

Pathophysiology

Stridor

Stridor is generally caused by partial obstruction of the airway between the nose and larger bronchi. Obstruction at the level of the nose or pharynx may produce snoring or gurgling sounds. Turbulent airflow in the laryngeal area or upper trachea causes the high-pitched crowing sound characteristic of stridor. Edema and inflammation at the vocal cords and subglottic areas result in inspiratory stridor, whereas obstruction below the cricoid cartilage may cause inspiratory and expiratory stridor. Some of the more common causes of stridor are listed in Box 71.1.

The sounds produced at various levels of obstruction can give the primary care physician clues about the etiology of the problem. The most common cause of stridor that begins shortly after birth is tracheomalacia, a condition secondary to the immaturity of the cartilage of the trachea. Laryngomalacia, which is caused by floppy supraglottic structures, resolves after several months.

The upper airway of infants and children is more susceptible to obstruction as the result of anatomic differences between children and adults. The tongues of children are relatively large, and the epiglottis is floppy and shaped somewhat like the Greek letter omega (Ω). The angle between the epiglottis and glottis is more acute in children, which makes direct visualization of the airway more difficult than in adults. Cartilaginous structures are less rigid in infants. During inspiration, negative intraluminal pressure is generated below the level of obstruction, which causes narrowing of the airway and turbulence of the airflow. This occurs more often in children than adults because the tracheal rings are not well formed. Additionally, the smaller size of the airway in children makes resistance to airflow greater when obstruction is present.

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