The usefulness of pulse oximetry in evaluating acutely ill asthmatics.

To examine the usefulness of pulse oximetry in determining the severity of acute asthma, the arterial oxygen saturation (SaO2) of 196 acutely ill asthmatic children was measured while the children were being treated in the emergency department (ED). The measure of severity used was the disposition from the ED--discharge or hospitalization--after receiving standard ED care. The mean pretreatment SaO2 of the 172 children discharged was 96.4% (range, 84-100%), and that of the 24 children admitted was 94.4% (range, 85-100%). A Receiver Operating Characteristic curve indicated that the optimal cutoff point for identifying disposition was an SaO2 of 93%. The sensitivity of an SaO2 < or = 93% was 35%, and the specificity was 92%. We conclude that SaO2 lacks the sensitivity to differentiate the child who will respond to ED therapy from the child who will require further inpatient care.