THE ACUTE EFFECTS OF 0.2 PPM OZONE IN PATIENTS WITH CHRONIC OBSTRUCTIVE PULMONARY-DISEASE

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Abstract
Epidemiologic data suggest that patients with chronic obstructive pulmonary disease (COPD) might be more sensitive than normal persons to the respiratory effects of oxidant pollutant exposure. To determine the response of patients with COPD to ozone, 13 white men with nonreversible airways obstruction (mean FEV1/FVC [1-s forced expiratory volume/forced vital capacity], 58%), of whom 8 were current smokers, were randomly exposed for 2 h to air and to 0.2 ppm ozone on 2 consecutive days in a single-blind crossover design. During either exposure, subjects exercised for 7.5 min every 30 min. Measures of respiratory mechanics obtained preexposure and postexposure were not significantly affected by either exposure. Ventilation and gas exchange measured during exercise showed no differences between exercise periods or exposure days. Arterial O2 saturation (SaO2), measured by ear oximetry during the final exercise period each day, was lower (94.8%) at the end of O3 exposure than SaO2 obtained at the end of air exposure (95.3%); the difference (0.48%) was significant (P = 0.008). Because normal subjects undergoing comparable exposures show a threshold for respiratory mechanical effects at .apprx. 0.3 ppm ozone, mild to moderate COPD apparently is not associated with increased sensitivity to low ozone concentrations. The response of such subjects might be exaggerated at higher ozone concentrations. The consistent (in 11 of 13 subjects) though small decrease in SaO2 may indicate that indexes of ventilation/perfusion distribution might be more sensitive measures of O3 effect in this compromised patient group than are conventional respiratory mechanics measures.