Comparison of pulmonary responses of asthmatic and nonasthmatic subjects performing light exercise while exposed to a low level of ozone

To determine if asthmatic subjects (ASTH, n = 17) experience greater O-3-induced pulmonary decrements than nonasthmatic subjects (NONA, n = 13), both groups were exposed for 7.6 h to both clean air and 0.16 ppm O-3. Exposures consisted of seven 50-min periods of light exercise (V-E = 14.2 and 15.3 l/min/m(2) for ASTH and NONA, respectively), each followed by 10 min rest. A 35-min lunch period followed the third exercise. Following O-3 exposure, decrements in forced expiratory volume in one second (FEV(1)) and FEV(1) divided by forced viral capacity (FVC), corrected for air exposure, for ASTH (-19.4 +/- 3.1 % and 6.2 +/- 2%, respectively) were significantly greater (p = 0.04 and 0.02) than for NONA (-9.8 +/- 1.9% and -1 +/- 1%, respectively). There was no difference (p = 0.33) for decrements in FVC between ASTH (-11.8 +/- 1.9%) and NONA (-8.8 +/- 2.1%). Nine of 17 ASTH experienced wheezing with O-3, while only one experienced wheezing with air (p = 0.004); no NONA experienced wheezing. Six of 17 ASTH requested inhaled P-agonist bronchodilator prior to and/or during O-3 exposure and experienced some temporary alleviation of decrements. At end exposure, however, ASTH who were medicated had greater Os-induced decrements than those who were not medicated. ASTH who had the larger Os-induced decrements had lower baseline FEV(1)/FVC and lower baseline %predicted FEV(1). These data indicate that in ASTH, unlike NONA, some portion of O-3-induced pulmonary decrements experienced was related to bronchoconstriction, and that O-3-responsiveness for ASTH depended upon baseline airway status.