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°C and the other at −20°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 µg 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°C compared with 96.4±6.9 W at 24°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.