Journal of Applied Physiology, Vol 57, Issue 2 419-423, Copyright © 1984 by American Physiological Society
Interaction of sulfur dioxide and dry cold air in causing bronchoconstriction in asthmatic subjects
R. A. Bethel, D. Sheppard, J. Epstein, E. Tam, J. A. Nadel and H. A. Boushey
To determine whether sulfur dioxide and airway cooling and drying interact
in causing bronchoconstriction in persons who have asthma, we measured
specific airway resistance in seven asthmatic subjects before and after
they performed voluntary eucapnic hyperpnea for 3 min breathing four
different gas mixtures. The mixtures, which the subjects breathed through a
mouthpiece in random order on 4 different days, were 1) humidified
room-temperature air, 2) humidified room-temperature air containing 0.5 ppm
SO2, 3) cold dry air, and 4) cold dry air containing 0.5 ppm SO2. Each
subject breathed at a rate and depth known from preliminary studies to
cause little or no bronchoconstriction when that subject inhaled 0.5 ppm
SO2 in humidified room-temperature air or cold dry air. When given
independently in the blinded study, 0.5 ppm SO2 or cold dry air again
caused insignificant bronchoconstriction, but when given together the two
stimuli caused significant bronchoconstriction, as indicated by an increase
in specific airway resistance from 6.94 +/- 2.85 to 22.35 +/- 10.28 l X
cmH2O X l-1 X s (mean +/- SD) (P less than 0.001). thus airway cooling
and/or drying increases the bronchoconstriction induced by inhaled SO2 in
persons who have asthma. This increase suggests that persons who have
asthma may be more sensitive to the bronchoconstrictor effects of ambient
SO2 in cold dry environments than in warm moist environments.
