Evaluation of exercise-induced bronchospasm in the adult asthmatic.

It has been shown that most asthmatics respond to exercise with bronchospasm. This study was undertaken to develop a safe and reliable method for quantifying exercise-induced bronchospasm in the asthmatic adult. Five normal adult volunteers and 12 stable asthmatics were exercised to 80% of their predicted maximal heart rate according to a multistage branching treadmill protocol. Their responses in terms of forced expiratory volume in 1 sec (FEV1) and maximum midexpriatory flow rate (MMEFR) at 5, 15, and 30 min after exercise were assessed, while standing, with a Jones Pulmonar II waterless spirometer. This submaximal stress test was chosen because 80% of predicted maximal heart rate could be obtained by all individuals and allowed the asthmatics to exercise long enough for inducible bronchospasm to occur. Audible wheezing was induced in 100% of the asthmatics and in none of the nonasthmatics. In the normal individuals, FEV1 and MMEFR increased signficantly during the postexercise period. When compared to normal subjects, the 12 asthmatic patients demonstrated a significant reduction in FEV1 an MMEFR (deltaFEV1 : 5 min, -300; 15 min, -304; o9 min, -208 ml; -18%, -17%, and -15%; deltaMMEFR: 5 min, -15; 15 min, -9; 30 min, -1L/M; -23%, -18%, and -6%) (p less than 0.01). The use of a rigidly controlled exercise stress with a cardiovascular endpoint in the measurement of FEV1 and MMEFR in the postexercise period appears to be a useful tool in assessing the presence and severity of exercise-induced bronchospasm in the adult asthmatic.