Journal of Applied Physiology, Vol 59, Issue 4 1313-1321, Copyright © 1985 by American Physiological Society
Increased cardiac output increases shunt: role of pulmonary edema and perfusion
P. H. Breen, P. T. Schumacker, J. Sandoval, I. Mayers, L. Oppenheimer and L. D. Wood
In low-pressure pulmonary edema increased cardiac output (QT) increases
shunt (Qs/QT); we tested whether the mechanism is an increase in
extravascular lung water in turn mediated by the accompanying increase in
microvascular pressure. In six pentobarbital sodium-anesthetized dogs
ventilated with O2 we administered oleic acid into the right atrium. From
base line to 2 h post-oleic acid we measured concurrent significant
increases in Qs/QT (6-29%, O2 technique) and extravascular thermal volume
(ETV, 2.6-7.1 ml/g dry intravascular blood-free lung wt, thermal-green dye
indicator technique) that were stable by 90 min. Then, bilateral femoral
arteriovenous fistulas were opened and closed in 30-min periods to cause
reversible increases in QT and associated Qs/QT. When fistulas were open
the time-averaged QT increased from 5.1 to 6.9 min (P less than 0.05), the
simultaneous Qs/QT rose from 30.7 to 38.4% (P less than 0.05), but ETV did
not increase. We conclude that increasing lung edema does not account for
our rise in Qs/QT when QT increased.
