FACIAL COOLING, BUT NOT NASAL BREATHING OF COLD-AIR, INDUCES BRONCHOCONSTRICTION - A STUDY IN ASTHMATIC AND HEALTHY-SUBJECTS

Reflex-mediated bronchoconstriction in cold climates may be more impor tant than it has previously been thought. This issue has seldom been s tudied using physiological methods. We wanted to investigate, using ph ysiological methods, what triggers the bronchoconstriction occurring a t cold ambient temperature during resting nasal ventilation: cooling o f the skin of the face or cooling of the nasal cavity. Three experimen ts were carried out in 15 stable asthmatics and 10 healthy volunteers: 1) a whole-body exposure to subfreezing temperature in an environment al chamber, during which the subjects breathed cold air through the no se; 2) a similar exposure to subfreezing temperature except that the s ubjects now breathed warm air through the mouth from outside the chamb er; and 3) nasal breathing of subfreezing air from a heat exchanger wh ilst the subjects sat at room temperature. Spirometric values and faci al skin temperature were measured both during and after the exposures. Maximal decrements (means +/- standard errors) of forced expiratory v olume in one second (FEV(1)) in experiments 1, 2 and 3 were: 5.8 +/- 0 .8, 5.1 +/- 0.7 and 2.1 +/- 0.5%, respectively (p<0.001). Only the two experiments in the environmental chamber induced significant bronchoc onstriction. All responses were of similar magnitude in the asthmatic and the healthy subjects. The cooling of the skin of the face seems to be the trigger for the bronchoconstriction during resting nasal venti lation at cold ambient temperature both in asthmatic and nonasthmatic subjects.