Viral Croup: A Current Perspective

Alexander K.C. Leung, MBBS, FRCPC, FRCP (UK & Irel), FRCPCH; James D. Kellner, MD, FRCPC; David W. Johnson, MD, FRCPC


J Pediatr Health Care. 2004;18(6) 

In This Article

Pathogenesis and Clinical Manifestations

Viral infection of the upper airway results in inflammation and edema of the larynx, trachea, and bronchi and production of mucus that further obstructs the airway. The subglottic trachea is the narrowest part of a child's upper airway, the narrowing of which results in audible inspiratory stridor (Malhotra & Krilov, 2001). Because of the subglottic trachea is outside the pleural cavity, the negative pressure generated on inspiration tends to narrow the airway further (Hall & Hall, 2001). As the disease progresses, the tracheal lumen becomes further obstructed by fibrous exudates. Swelling of the vocal cord, on the other hand, results in hoarseness of voice. The barking cough is engendered by the inflammation in the larynx and trachea.

The incubation period is 2 to 6 days (Cressman & Myer, 1994). Viral croup typically is preceded by a prodrome consisting of rhinorrhea, mild cough, and low-grade fever. The duration of the prodrome is usually 12 to 48 hours (Cherry, 2004). The child then develops the characteristic "barking" or "brassy" cough, hoarseness, and inspiratory stridor. Symptoms are characteristically worse at night and are aggravated by agitation and crying (Knutson & Aring, 2004). More than 80% of children have mild symptoms. In approximately 60% to 95% of children, the symptoms resolve within 2 and 5 days, respectively (Johnson & Williamson, 2001). More severe cases may have, in addition, tachycardia; tachypnea; nasal flaring; supraclavicular, infraclavicular, intercostal, and sternal retraction; continuous stridor; and cyanosis. A number of rating scales have been devised to assess the severity of croup; the most popular and commonly used is the Westley croup score ( Table 1 ) (Brown, 2002; Powell & Stokell, 2000). The rating scales are of limited value in clinical practice. They are used mainly in research studies to assess treatment outcomes.


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