Pulmonary responses of asthmatic and normal subjects to different temperature and humidity conditions in an environmental chamber. Lung

Abstract

Abstract. Determining the possible adverse health effects of air pollutants can be complicated by differences inthe environmental conditions of temperature and humidity. To evaluate the potentially confounding effects of differences in temperature and humidity, we exposed 8normal male subjects and 8 male subjects with asthma to the extremes in temperature and humidity that could be maintained in an environmental chamber. We performed serial pulmonary function tests for these subjects before and during 6 hr exposure periods on 5 separate occasions: cold, dry (I0°C, 10 % relative humidity); cold, humid (10°C, 50 % relative humidity); normal ambient (22°C, 40 % relative humidity); hot, dry (37°C, 15 % relative humidity); and hot, humid (37°C, 60 % relative humidity). The exposure period included a i2 min exercise on a cycle ergome-ter. We found no significant change in spirometry, airways resistance, or diffusing capacity for either group of subjects at rest alone over the 6 hr period of exposure for any exposure condition. However, there were changes in spirometry and airways resistance as a result of the 12 min period of exercise. The subjects with asthma had significant decreases in forced expir-atory volume in 1 sec (FEV0 (20-21%) and increases in specific airways resistance when exercising in conditions of cold and dry, cold and humid, and hot and dry. The normal subjects had an average increase in FEVI of approximately 6 % when exercising in the hot and humid conditions. We found significant correlations for the changes in FEV1 with the water content of the exposure conditions for both groups of subjects. We also found that the work performance ( xpressed as the external work performed ivided by the oxygen consumed) was decreased for the subjects in both groups a