Effects of breathing warm humidified air on bronchoconstriction induced by body cooling and by inhalation of methacholine.

The effect of breathing warm humidified air upon bronchoconstriction induced with body cooling or inhalation of methacholine was studied in two groups of eight asthmatic subjects. One group had the body cooled using one-minute exposures, first to a cold shower at 15 degrees C and then to a current of wind. The other group received methacholine by inhalation until a decrease of 20 percent or more occurred in the forced expiratory volume in one second. Both groups of asthmatic subjects were tested when breathing room air and warm humidified air. Pulmonary functions were assessed before and after cooling of the body and during inhalation of methacholine. Breathing warm humidified air substantially reduced bronchoconstriction induced by body cooling, but not that induced by inhalation of methacholine. Thus, bronchoconstriction induced by cooling of the body appears to be related to cooling of the airways, which may be compensated by breathing warm humidified air.