Grading asthma severity: using the APS component of the Apache II system.

OBJECTIVE

Measurement of severity is fundamental to the description and comparison of case series, treatment regimens and disease outcomes. This study examines the Acute Physiology Score (APS) as a severity measure of an acute "life-threatening" asthma attack.

DESIGN

The APS in the emergency department (ED) and ICU, demographic, treatment and outcome variables were prospectively studied. Relationships between severity, treatment and progress were investigated. In addition, patients were stratified according to ED APS and differences between the participating hospitals were examined.

SETTING

Emergency Departments and Intensive Care Units of two New Zealand hospitals.

PATIENTS

64 admissions to the ICUs following an acute episode of asthma.

INTERVENTIONS

Standard management of acute asthma as practised at the two participating hospitals.

MEASUREMENTS AND RESULTS

Both the treatment delivered (intravenous salbutamol, sodium bicarbonate and IPPV) and the rate of improvement as defined by change in APS between the ED and the ICU were found to be strongly related to ED APS. Similarly, the length of stay in the ICU correlated with the ICU APS. Stratification on the basis of ED APS allowed small but significant differences in patient physiologic derangement, dose of salbutamol, use of IPPV and incidence of complications to be detected between patients at the two hospitals.

CONCLUSION

This prospective study involving two hospitals validates the APS as a method for measuring the severity of an acute asthma attack. It demonstrates how correction for severity can be used to compare treatment and outcome variables in different case series.