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 midexpiratory 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 significantly during the postexercise period. When compared to normal subjects, the 12 asthmatic patients demonstrated a significant reduction in FEV₁ an MMEFR (ΔFEV₁: 5 min, -300; 15 min, -304; 30 min, -208 ml; -18%, -17%, and -15%; ΔMMEFR: 5 min, -15; 15 min, -9; 30 min, -1L/M; -23%, -18%, and -6%) (p < 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.