Effect of prolonged heavy exercise on pulmonary gas exchange in horses (original) (raw)

Journal of Applied Physiology

Effect of prolonged, heavy exercise on pulmonary gas exchange in athletes. J. Appl. Physiol. 85(4): 1523-1532, 1998.-During maximal exercise, ventilation-perfusion inequality increases, especially in athletes. The mechanism remains speculative. We hypothesized that, if interstitial pulmonary edema is involved, prolonged exercise would result in increasing ventilation-perfusion inequality over time by exposing the pulmonary vascular bed to high pressures for a long duration. The response to shortterm exercise was first characterized in six male athletes [maximal O 2 uptake (V O 2 max ) ϭ 63 ml · kg Ϫ1 · min Ϫ1 ] by using 5 min of cycling exercise at 30, 65, and 90% V O 2 max . Multiple inert-gas, blood-gas, hemodynamic, metabolic rate, and ventilatory data were obtained. Resting log SD of the perfusion distribution (log SD Q ) was normal [0.50 Ϯ 0.03 (SE)] and increased with exercise (log SD Q ϭ 0.65 Ϯ 0.04, P Ͻ 0.005), alveolar-arterial O 2 difference increased (to 24 Ϯ 3 Torr), and end-capillary pulmonary diffusion limitation occurred at 90% V O 2 max . The subjects recovered for 30 min, then, after resting measurements were taken, exercised for 60 min at ϳ65% V O 2 max . O 2 uptake, ventilation, cardiac output, and alveolararterial O 2 difference were unchanged after the first 5 min of this test, but log SD Q increased from 0.59 Ϯ 0.03 at 5 min to 0.66 Ϯ 0.05 at 60 min (P Ͻ 0.05), without pulmonary diffusion limitation. Log SD Q was negatively related to total lung capacity normalized for body surface area (r ϭ Ϫ0.97, P Ͻ 0.005 at 60 min). These data are compatible with interstitial edema as a mechanism and suggest that lung size is an important determinant of the efficiency of gas exchange during exercise. multiple inert-gas elimination technique; interstitial pulmonary edema