The management of acute croup.

Croup is an inflammatory condition of the larynx or trachea accompanied by stridor, which is the harsh noise characterizing upper airway obstruction, as opposed to wheezing which characterizes lower airway obstruction. The sound may be of high or low pitch and is due to sound waves set up by the fast flow of air past a narrow point in the airway. This causes stridor of medium or high pitch, chiefly during inspiration. Stridor may however, be of low pitch and rattling in quality when surrounding tissue structures are set into oscillatory motion. This applies particularly to the epiglottis and aryepiglottic folds. Stridor arises primarily from the larynx but may be caused at any point between the pharynx and upper trachea (Fig. 1). The anatomy of this region is crucial to the position and nature of the obstruction, which varies according to the main site of impact of the inflammatory lesion. Anatomy is also important in that there may be underlying structural abnormality, which is discovered by superimposed inflammation and modifies the subsequent course of the disease and its management.