title: Sulfur dioxide-induced bronchoconstriction in freely breathing, exercising, asthmatic subjects.
abstract: The purpose of this study was to determine whether 0.50 ppm sulfur dioxide (SO2) in filtered air causes bronchoconstriction in freely breathing asthmatic subjects exercising at a moderately heavy work rate. Ten volunteers who had mild asthma breathed air containing no SO2 or containing 0.50 ppm SO2 In an exposure chamber as they exercised for 5 min on a cycle ergometer at a work rate of 750 kilopond meters/min (about 125 watts). We determined their specific airway resistance by body plethysmography before and after exercise. Specific airway resistance increased by 13.55 +/- 9.18 cm H2O X s (mean +/- SD) when subjects exercised and breathed 0.50 ppm SO2 but only by 2.24 +/- 2.34 when they exercised and breathed air without SO2 (p less than 0.005). Thus, 0.50 ppm SO2 causes significant bronchoconstriction in freely breathing asthmatics during moderately heavy exercise.
mesh_terms: D000328:Adult; D000403:Airway Resistance / Q000187:drug effects*; D001249:Asthma / Q000503:physiopathology*; D001980:Bronchi / Q000187:drug effects / Q000503:physiopathology*; D005260:Female; D006801:Humans; D008297:Male; D005082:Physical Exertion; D012119:Respiration; D013458:Sulfur Dioxide / Q000009:adverse effects*
chemical_list: D013458:Sulfur Dioxide