Effect of whole-body exposure to cold and wind on lung function in asthmatic patients.

To assess the effect of subfreezing temperature and wind on lung function in asthmatic patients, an exposure to subfreezing temperature at rest, a moderate exercise challenge at subfreezing temperature, and a similar exercise challenge at room temperature were performed in 19 stable asthmatic subjects in an environmental chamber with an artificial wind. The mean maximal falls in FEV1 were 5.3, 11.7, and 4.8 percent, respectively. The two challenges at subfreezing temperature caused statistically significant changes in FEV1, but the exercise challenge at room temperature had no effect. A large variation in the sensitivity to cold was found. The time courses of the responses varied between the challenges, suggesting at least partially different mechanisms. The results indicate that even moderate exercise can cause severe bronchoconstriction in certain stable asthmatic subjects at climatic conditions similar to the Scandinavian winter. The importance of reflex mechanisms causing bronchoconstriction in physiologic conditions is discussed.