Effect of prolonged, heavy exercise on pulmonary gas exchange in athletes.
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 short-term exercise was first characterized in six male athletes [maximal O2 uptake (V(O2)max) = 63 ml x kg-1 x min-1] by using 5 min of cycling exercise at 30, 65, and 90% V(O2) max. Multiple inert-gas, blood-gas, hemodynamic, metabolic rate, and ventilatory data were obtained. Resting log SD of the perfusion distribution (log SDQ) was normal [0.50 +/- 0.03 (SE)] and increased with exercise (log SDQ = 0.65 +/- 0.04, P < 0.005), alveolar-arterial O2 difference increased (to 24 +/- 3 Torr), and end-capillary pulmonary diffusion limitation occurred at 90% V(O2)max. The subjects recovered for 30 min, then, after resting measurements were taken, exercised for 60 min at approximately 65% V(O2)max. O2 uptake, ventilation, cardiac output, and alveolar-arterial O2 difference were unchanged after the first 5 min of this test, but log SDQ increased from 0.59 +/- 0.03 at 5 min to 0. 66 +/- 0.05 at 60 min (P < 0.05), without pulmonary diffusion limitation. Log SDQ was negatively related to total lung capacity normalized for body surface area (r = -0.97, P < 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.
Division of Physiology, Department of Medicine, University of California, San Diego, La Jolla, California 92093, USA. shopkins@ucsd.edu
S R
SR
Hopkins
T P
TP
Gavin
N M
NM
Siafakas
L J
LJ
Haseler
I M
IM
Olfert
H
H
Wagner
P D
PD
Wagner
D000328:Adult; D001794:Blood Pressure; D002302:Cardiac Output; D015444:Exercise / Q000502:physiology*; D005540:Forced Expiratory Flow Rates; D005541:Forced Expiratory Volume; D006439:Hemodynamics; D006801:Humans; D008297:Male; D010100:Oxygen / Q000097:blood; D010101:Oxygen Consumption; D010807:Physical Endurance / Q000502:physiology; D012044:Regression Analysis; D012129:Respiratory Function Tests; D015656:Respiratory Mechanics / Q000502:physiology*; D013177:Sports / Q000502:physiology*; D014692:Ventilation-Perfusion Ratio; D014797:Vital Capacity
D010100:Oxygen