Am. J. Respir. Crit. Care Med., Vol 149, No. 6, Jun 1994, 1413-1419.
Pre-exposure to ozone does not enhance or produce exercise-induced asthma
AR Weymer, H Gong Jr, A Lyness and WS Linn
Department of Medicine, UCLA Medical Center.
We evaluated whether acute exposure to ozone (O3) enhances or produces
exercise-induced asthma (EIA) in asthmatic subjects who have or do not have
EIA, according to standardized exercise challenge. Twenty-one otherwise
healthy asthmatic subjects, 19 to 40 yr of age, with forced expiratory
volume in one second (FEV1) greater than 70% of predicted and methacholine
hyperresponsiveness, underwent three 1-h exposures on separate days to 0.10
ppm ozone in filtered air (FA), 0.25 ppm ozone in FA, and FA alone
(randomized order, single-blinded, crossover design). Of these subjects, 12
underwent an additional exposure to 0.40 ppm ozone in FA. The subjects
performed intermittent light exercise (with mean ventilation of 27 L/min)
while in an environmentally controlled chamber (21 degrees C and 40%
relative humidity). After each exposure, the subjects rested 1 h in clean
air and performed serial postexposure spirometry. The subjects then
underwent a standardized exercise challenge in clean air, followed by
serial spirometry for 60 min. No significant changes in FEV1 or forced
vital capacity (FVC) were found following 1-h exposures to 0, 0.10, and
0.25 ppm ozone (regardless of EIA status). The 12 subjects who underwent
all four exposures showed a significant excess reduction in FEV1 (-0.35 +/-
0.37 L or -9.6%) after 1-h exposure to 0.40 ppm O3 (p = 0.017), regardless
of EIA status. Postexposure FEV1 returned to baseline levels within 1 h.
Postexposure changes in FVC showed similar magnitude and time course but
were not statistically significant across exposure conditions or EIA
status.(ABSTRACT TRUNCATED AT 250 WORDS)
