Journal of Applied Physiology, Vol 61, Issue 1 210-214, Copyright © 1986 by American Physiological Society
Reduced hyperpnea-induced bronchospasm following repeated cold air challenge
F. Haas, N. Levin, S. Pasierski, M. Bishop and K. Axen
This study assessed reduction in expiratory function in 12 asthmatic
subjects both after 5 min of cold air provocation (CAP) with dry air
conditioned to approximately 0 degrees C and after exercise (to 85% of
predicted maximum heart rate) while breathing ambient room air
(approximately 21 degrees C and 40% relative humidity). These assessments
were done both before and after the following training protocol. Three
5-min periods of isocapnic cold air hyperpnea separated by 5-min rest
periods were performed breathing 0 degrees to -10 degrees C air, for 36
sessions over 12 wk. As expected, pretraining expiratory function was
significantly reduced (P less than 0.001) after both CAP and exercise. The
posttraining reduction in expiratory function after CAP and exercise,
however, was significantly less pronounced (largest P less than 0.05).
These data support our hypothesis that repeated bouts of cold air challenge
result in airway acclimatization to cold air and consequent decrease in
exercise-induced bronchospasm. Acclimatization may result directly either
by habituation of the airways or by vasodilation leading to increased
bronchial blood flow and consequent reduced airway cooling. An
unanticipated finding, though, is that repeated cold air challenge may also
cause long-term inflammatory changes in the airways. A significant
percentage of subjects experienced reduced base-line pulmonary function and
overall exacerbation of asthma symptoms during the training period.
