Journal of Applied Physiology, Vol 39, Issue 1 159-165, Copyright © 1975 by American Physiological Society
Estimation of cardiac output by analysis of respiratory gas exchange
L. D. Homer and B. Denysyk
Cardiac output is estimated by least squares fitting of a model of
pulmonary gas exchange to measurements of respiratory gas composition
obtained with a mass spectrometer during a rebreathing maneuver. This new
technique estimates cardiac output on spontaneously breathing subjects at
rest and requires neither central venous nor arterial blood samples.
Principal features of the technique are the use of multiple gases
simultaneously in the analysis, the use of a mathematical model for
breath-to-breath evaluation of gas exchange, and simultaneous estimation of
gas exchange and alveolar gas tensions with the same instrumentation. The
technique is compared with thermal dilution estimates in dogs before and
during hemorrhagic shock. Two-thirds of these estimates were within 20% of
one another. The standard deviation of replication was 15%. Shortcomings,
possibilities for improvement, and possible applications are discussed.
