Journal of Applied Physiology, Vol 54, Issue 4 943-949, Copyright © 1983 by American Physiological Society
Effect of air embolism on the measurement of extravascular lung thermal volume
R. C. Allison, J. C. Parker, C. E. Duncan and A. E. Taylor
To determine the accuracy of thermal-dye indicator-dilution measurements of
lung water during perfusion abnormalities, we embolized air into the lungs
of 10 dogs anesthetized with pentobarbital and mechanically ventilated. A
control period was followed by a period of air injection (10 ml) and
subsequent air infusion (E1), a second period of air injection and infusion
(E2), and a recovery period. Thermal and dye-dilution curves were obtained
during each period, and cardiac output (CO), total thermal volume,
intravascular volume, and extravascular thermal volume (ETV) were
calculated. Pulmonary arterial pressure (Ppa) increased from 16 +/- 2 cmH2O
during control to 29 +/- 3 cmH2O during E1 and to 40 +/- 3 cmH2O during E2
and decreased to 21 +/- 2 cmH2O during recovery. CO did not change, and
pulmonary vascular resistance changed in a pattern similar to Ppa. ETV fell
from 113 +/- 8 ml during control to 59 +/- 11 ml during E1 and to 29 +/- 9
ml during E2 and rose to 136 +/- 23 ml during recovery. There was no
increase in extravascular lung water or mass determined gravimetrically at
the end of the experiments. We conclude that the thermal-dye technique will
underestimate lung water in nonedematous lungs if emboli prevent complete
diffusion of the thermal indicator.
