Exercise induced ventilation/perfusion inequality in the horse.
Exercise in normal human subjects causes deterioration of matching of ventilation to blood flow in the lungs, but only in about 50% of those examined. A previous study (Wagner et al. 1989) of 5 horses showed no significant worsening of ventilation/blood flow (VA/Q) relationships during heavy exercise as determined by multiple inert gas elimination technique (MIGET). Because of the small number of horses in that study and the 50% human incidence of exercise induced VA/Q mismatch, we studied an additional 6 Thoroughbreds, comparing VA/Q relationships at the walk (1.4 m/s, 0 degrees incline) and during galloping (9.6 +/- 0.3 m/s, 7% incline). Such data were collected under 4 different conditions wherein inspired gas was 1) air, 2) 21% O2 in helium, 3) 15% O2 in N2 and 4) 15% O2 in helium. Each horse exercised 4 times (morning and afternoon of 2 days, with inspired gas conditions randomised). There was a small but significant increase in VA/Q mismatch (similar under all 4 conditions). The second moment of the VA/Q distribution (determined by the MIGET) increased significantly (P < 0.01) from 0.31 +/- 0.01 at the walk to 0.38 +/- 0.02 during gallop. This increase however is small: 0.38 is well within the range of this parameter for normal human subjects (where the 95% upper confidence limit is 0.60). This study shows that a small amount of exercise induced VA/Q mismatch can occur in the horse as in man, but the mechanism remains to be elucidated and its clinical significance remains to be established.(ABSTRACT TRUNCATED AT 250 WORDS)
Seaman
J
J
Department of Medicine, University of California, San Diego, La Jolla 92093, USA.
Erickson
B K
BK
Kubo
K
K
Hiraga
A
A
Kai
M
M
Yamaya
Y
Y
Wagner
P D
PD
D000704:Analysis of Variance; D000818:Animals; D006736:Horses / Q000502:physiology*; D000860:Hypoxia / Q000662:veterinary; D008168:Lung / Q000098:blood supply / Q000502:physiology*; D005082:Physical Exertion / Q000502:physiology*; D011652:Pulmonary Circulation; D011659:Pulmonary Gas Exchange / Q000502:physiology; D014692:Ventilation-Perfusion Ratio / Q000502:physiology*