Exercise-induced VA/Q inequality in subjects with prior high-altitude pulmonary edema.
Ventilation-perfusion (VA/Q) mismatch has been shown to increase during exercise, especially in hypoxia. A possible explanation is subclinical interstitial edema due to high pulmonary capillary pressures. We hypothesized that this may be pathogenetically similar to high-altitude pulmonary edema (HAPE) so that HAPE-susceptible people with higher vascular pressures would develop more exercise-induced VA/Q mismatch. To examine this, seven healthy people with a history of HAPE and nine with similar altitude exposure but no HAPE history (control) were studied at rest and during exercise at 35, 65, and 85% of maximum 1) at sea level and then 2) after 2 days at altitude (3,810 m) breathing both normoxic (inspired Po2 = 148 Torr) and hypoxic (inspired Po2 = 91 Torr) gas at both locations. We measured cardiac output and respiratory and inert gas exchange. In both groups, VA/Q mismatch (assessed by log standard deviation of the perfusion distribution) increased with exercise. At sea level, log standard deviation of the perfusion distribution was slightly higher in the HAPE-susceptible group than in the control group during heavy exercise. At altitude, these differences disappeared. Because a history of HAPE was associated with greater exercise-induced VA/Q mismatch and higher pulmonary capillary pressures, our findings are consistent with the hypothesis that exercise-induced mismatch is due to a temporary extravascular fluid accumulation.
Podolsky
A
A
Department of Medicine, University of California, San Diego, La Jolla 92093-0623, USA.
Eldridge
M W
MW
Richardson
R S
RS
Knight
D R
DR
Johnson
E C
EC
Hopkins
S R
SR
Johnson
D H
DH
Michimata
H
H
Grassi
B
B
Feiner
J
J
Kurdak
S S
SS
Bickler
P E
PE
Severinghaus
J W
JW
Wagner
P D
PD
D000328:Adult; D000375:Aging / Q000502:physiology; D000531:Altitude; D000532:Altitude Sickness / Q000097:blood / Q000503:physiopathology*; D001784:Blood Gas Analysis; D002302:Cardiac Output / Q000502:physiology; D004734:Energy Metabolism / Q000502:physiology; D015444:Exercise / Q000502:physiology*; D005260:Female; D006439:Hemodynamics / Q000502:physiology; D006801:Humans; D019344:Lactic Acid / Q000097:blood; D008297:Male; D005741:Noble Gases; D011652:Pulmonary Circulation / Q000502:physiology; D011654:Pulmonary Edema / Q000097:blood / Q000503:physiopathology*; D011659:Pulmonary Gas Exchange / Q000502:physiology; D014692:Ventilation-Perfusion Ratio / Q000502:physiology*
D005741:Noble Gases; D019344:Lactic Acid