EFFECTS OF ACUTE PASSIVE SMOKING ON EXERCISE-INDUCED BRONCHOCONSTRICTION IN ASTHMATIC-CHILDREN

This study was designed to investigate the acute effects of environmen tal tobacco smoke (ETS) in children with mild asthma during rest and e xercise. We studied 13 children [8 males, 5 females; mean age 10 (rang e 8-13) yr; mean forced expired volume in 1 s (FEV1) 93% (range 82-108 %) of predicted] with exercise-induced bronchoconstriction [46 +/- 4% (SE) fall in FEV1 after exercise during cold air breathing]. Children were exposed to ETS (20 ppm carbon monoxide) or ambient air (AA) for 1 h. During the first 54 min of exposure, children were at rest, and du ring the last 6 min they exercised on a bicycle ergometer (2 W/kg body wt). Spirometry was performed before and during exposure and after ex ercise. Respiratory symptoms were recorded before and after exposures. In seven children the experiments with AA and ETS were done in duplic ate. FEV1 between 5 and 54 min of exposure at rest decreased by 3.2 +/ - 0.8% (SE) during AA and by 7.2 +/- 2.3% during ETS exposure compared with preexposure values; the difference between AA and ETS was statis tically significant (P = 0.04). The drop in FEV1 was achieved within 5 min and did not change with ongoing exposure. Analysis of individual data revealed that the mean changes during ETS were mainly effected by three children with a significant fall and one child with a significa nt improvement in FEV1 (P < 0.05). Maximum postexercise fall of FEV1 w as 25 +/- 4% after AA and 24 +/- 3% after ETS, which did not differ si gnificantly. Upper and lower respiratory tract symptoms were not signi ficantly different between exposures. We conclude that, in children wi th mild asthma, short-term exposure to ETS can be associated with a tr ansient fall in FEV1 in sensitive subjects but does not increase exerc ise-induced bronchoconstriction. The acute airway response to exercise can be increased significantly by cold and clean air compared with ai r polluted by ETS.