The respiratory status of children with croup

In a prospective investigation of 35 children with croup, an attempt was made to correlate arterial blood gas measurements with clinical and radiologic findings. In the 29 who were hypoxemic, the respiratory rate was the best indicator of the lowered arterial oxygen tension, which could last for several days. Hypercapnea, present in 19 patients, was not reflected by any of the clinical criteria. The degree of hypoxemia was greater than the degree of hypercapnea and is probably due to the development of alveolar-arterial oxygen differences secondary to abnormal distribution of ventilation/perfusion ratios. Croup may, therefore, be associated with pulmonary disease as well as with upper airway obstruction; the resultant hypoxemia can be assessed accurately only by determination of arterial blood gases.