Correlation of initial emergency department pulse oximetry values in asthma severity classes (steps) with the risk of hospitalization

Background The oxygen saturation (OSAT) of wheezing children presenting to an emergency department has been shown to be a predictor for hospitalization. The purpose of this study is to determine if hospitalization predictive power can be increased by further stratifying this by the step severity categories (based on chronic symptoms). Methods Data were collected prospectively at 6 centers over a 22-month period on 1219 pediatric patients. Asthma step severity categorization was determined by chronic symptom history. Presenting ED OSAT values, extensive clinical histories (obtained in the ED and during several telephone follow-up calls by study personnel), treatments, and disposition were recorded for each study subject. Results The overall hospitalization rate was 15%. Hospitalization rates in severity step categories 1, 2, 3, and 4 were 13%, 16%, 13%, and 22% (P = .008), respectively. Hospitalization rates by presenting OSATs were 98% or higher (6%), 95% to 97% (12%), 93% to 94% (28%), 90% to 92% (45%), 85% to 89% (65%), and 80% to 84% (100%). From 95% to 100% OSAT values, hospitalization rates are similar between the severity groups. In the 93% to 94% OSAT group, the hospitalization rate is 43% in step category 4 patients, compared with 27%, 24%, and 13% for step categories 1, 2, and 3, respectively, but this difference was not statistically significant. At presenting OSAT values of 90% and below, the hospitalization rates are higher but did not differ significantly between the severity step groups. No recognizable trend was present to suggest that the hospitalization predictive value is increased by adding the step severity categories. Conclusions The presenting OSAT is the dominant initial predictor of hospitalization. The step severity categories do not appear to provide substantial additional predictive value for hospitalization.