Effect of cold air on exercise capacity in COPD: increase or decrease?

STUDY OBJECTIVE To clarify the effect of cold air on exercise capacity in COPD. DESIGN Cycle ergometer tests under different environmental conditions. SETTING Pulmonary function laboratory and an environmental chamber at a university hospital. PARTICIPANTS Eighteen patients with stable COPD; 14 completed the study. INTERVENTIONS A preliminary cycle ergometer test followed by two incremental, symptom-limited cycle ergometer tests, one at 24 degrees C and the other at -20 degrees C. MEASUREMENTS On the first study day: arterial blood gas analysis, 12 to 15 s maximal voluntary ventilation, maximal expiratory flow-volume curves before and 1 h after inhalation of 80 microg of ipratropium bromide, and diffusion capacity of the lung. During the exercise challenges: spirometric indices, minute ventilation (VE), oxygen consumption (VO2), carbon dioxide production (VCO2), facial skin temperature, and heart rate. The feeling of dyspnea was assessed with a visual analogue scale. RESULTS The maximal work load was 87.5+/-7.3 W at -20 degrees C compared with 96.4+/-6.9 W at 24 degrees C (p<0.05). Accordingly, the exercise duration was shorter in the cold. Exercise dyspnea was more severe in the cold at equal work loads. The shortening of exercise duration induced by cold air correlated with the enhancement of exercise dyspnea. Furthermore, cold air cooled the facial skin and induced immediate bronchoconstriction. VE, VO2, VCO2, and heart rate did not differ between the warm and cold challenges. CONCLUSIONS Cold air decreases exercise capacity in COPD, probably by increasing exercise dyspnea.