The value of pulmonary function tests in the management of acute asthma.

We examined the influence of the forced expiratory volume in 1 second (FEV1) on the decision to admit or discharge patients who present with acute bronchospasm due to asthma and the ability of the FEV1 to predict the need for admission or the likelihood of relapse after discharge. The FEV1 was recorded at presentation before treatment and immediately after a decision to admit or discharge had been made. Of the 96 patients 10.4% were admitted, 10.4% were discharged but suffered a relapse, and 79.2% were discharged and did not suffer a relapse. The FEV1 had a low positive predictive value (47%) for admission or relapse when it was 0.7 L/min or less at presentation and 2.1 L/min or less before discharge or admission. The FEV1 did not alter the decision to admit or discharge in 97% of the cases. We believe that the FEV1 fails to identify patients who should be admitted or those who will likely suffer a relapse; however, patients with a final FEV1 greater than 2.4 L/min may be discharged with confidence.