Pulmonary gas exchange response to exercise- and mannitol-induced bronchoconstriction in mild asthma.

Both exercise (EIB) and mannitol challenges were performed in asthmatic patients to assess and compare their pulmonary gas exchange responses for an equivalent degree of bronchoconstriction. In 11 subjects with EIB [27 +/- 4 (SD) yr; forced expiratory volume in 1 s (FEV(1)), 86 +/- 8% predicted], ventilation-perfusion (Va/Q) distributions (using multiple inert gas elimination technique) were measured 5, 15, and 45 min after cycling exercise (FEV(1) fall, 35 +/- 12%) and after mannitol (33 +/- 10%), 1 wk apart. Five minutes after EIB, minute ventilation (Ve; by 123 +/- 60%), cardiac output (Qt, by 48 +/- 29%), and oxygen uptake (Vo2; by 54 +/- 25%) increased, whereas arterial Po2 (Pa(O2); by 14 +/- 11 Torr) decreased due to moderate Va/Q imbalance, assessed by increases in dispersions of pulmonary blood flow (log SD(Q); by 0.