Journal of Applied Physiology, Vol 58, Issue 6 1767-1775, Copyright © 1985 by American Physiological Society
Effects of chronic right-to-left cardiac shunt on hypoxic sensitivity of mongrel dogs
J. H. Von Colditz, R. L. Coon, P. S. Clifford, F. O. Igler, S. B. Litwin and J. P. Kampine
Resting ventilation (VI), blood gases, hypoxic sensitivity, and the
ventilatory responses to intravenous sodium cyanide (NaCN, 100
micrograms/kg), doxapram (DOX, 500 micrograms/kg), and dopamine (DOPA, 20
micrograms/kg) were analyzed in four normal mongrel dogs (group I-N) and
seven mongrel dogs with chronic (5-11 yr) right-to-left cardiac shunt
(group II). The group I-N animals were also studied during steady-state
isocapnic hypoxia (group I-H). The shunt procedure used for these studies
produced a model for ventilatory studies during chronic shunt hypoxemia.
The increases in VI per percent decrease in O2 saturation, which occurred
during a four-breath N2 test, were 30, 43, and 13 ml X kg-1 X min-1 in
groups I-N, I-H, and II, respectively. The decrease in hypoxic sensitivity
of the group II animals, compared with groups I-N and I-H, occurred in the
presence of an increase in PaCO2 from 21.9 to 26.0 Torr during the
four-breath N2 test. A decrease in PaCO2 from 34.7 to 30.0 and from 33.6 to
30.4 Torr was observed in groups I-N and I-H. The response to DOX, a
general analeptic agent, was greatest in group II and least in group I-N.
However, the ventilatory responses to NaCN and DOPA were not sufficiently
different among the three groups to suggest a difference in carotid body
function as assessed by these drugs.
