Journal of Applied Physiology, Vol 45, Issue 3 469-473, Copyright © 1978 by American Physiological Society
Cold-induced pulmonary hypertension in cattle
D. H. Will, I. F. McMurtry, J. T. Reeves and R. F. Grover
The frequency with which cattle develop right-heart failure during the
winter at high altitude suggested that cold might contribute to hypoxic
pulmonary hypertension. Indeed in a preliminary study conducted
out-of-doors during early Spring, two calves with known hyperreactive
pulmonary vessels showed elevated pulmonary arterial pressures attributed
to their prior exposure to nighttime cold (-5 degrees C). In a second study
five hyperreactive calves had increases in mean pulmonary arterial pressure
from 29 to 45 Torr (+ 55%) during 48 h of exposure to cold (0 to -5 degrees
C) in a climatic chamber. Three calves with less reactive lung vessels
increased their pressures from 25 to 36 Torr (+ 44%). In a more complete
study, six calves selected as potential hyperresponders showed increases in
pulmonary arterial pressure (+ 60%), blood flow (+ 18%), and vascular
resistance (+ 38%) during 48 h of cold exposure. Arterial PO2 decreased
(-10 Torr) and PCO2 rose (+6 Torr) suggesting hypoventilation. Oxygen
breathing returned pulmonary pressures and resistance to near control
values, suggesting that cold had induced a hypoxic pulmonary
vasoconstriction and an increased blood flow. Thus, a cold produced
pulmonary hypertension in cattle at the modest altitude of 1,524 m and the
pressor responses were greater in calves with more reactive lung vessels.
