Pre-exposure to ozone does not enhance or produce exercise-induced asthma.
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)
Weymer
A R
AR
Department of Medicine, UCLA Medical Center.
Gong
H
H
Lyness
A
A
Linn
W S
WS
D000328:Adult; D001250:Asthma, Exercise-Induced / Q000139:chemically induced* / Q000175:diagnosis / Q000503:physiopathology; D001985:Bronchial Provocation Tests; D004305:Dose-Response Relationship, Drug; D005080:Exercise Test; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D008297:Male; D016210:Methacholine Chloride; D010126:Ozone / Q000009:adverse effects*; D012720:Severity of Illness Index; D016037:Single-Blind Method; D013997:Time Factors; D014797:Vital Capacity
D016210:Methacholine Chloride; D010126:Ozone