Measurement of cardiac output in man with a nonrecirculating indicator

Stephen M. Wittenberg; Francis J. Klocke; David G. Greene; Ivan L. Bunnell; Herman L. Falsetti; Joseph A. Zizzi

doi:10.1172/JCI106631

Measurement of cardiac output in man with a nonrecirculating indicator

Stephen M. Wittenberg, Francis J. Klocke, David G. Greene, Ivan L. Bunnell, Herman L. Falsetti, and Joseph A. Zizzi

Published July 1, 1971 - More info

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Abstract

The present investigation was undertaken to evaluate the utility of constant-rate injection of a nonrecirculating indicator (H₂) for the measurement of cardiac output in man. 42 patients were studied during cardiac catheterization and 8 during acute complications of arteriosclerotic heart disease, including acute myocardial infarction. Pulmonary (or systemic) arterial H₂ concentration was measured chromatographically from 2.0 ml blood samples drawn during constant-rate injection of dissolved H₂ into the systemic venous circulation (or left heart). The chromatograph was a thermal conductivity unit housed in a constant-temperature water bath to achieve an improved signal-to-noise ratio. Intrapulmonary H₂ elimination from mixed venous blood was measured directly in 14 patients and averaged 98 ±1.5% (SD). Reproducibility of output measurements was evaluated using triplicate determinations obtained over 45-60 sec in 25 consecutive patients. Coefficients of variation (SD/Mean × 100) averaged 3.4 ±2.0%, making it possible to evaluate relatively small changes in measured output with conventional statistical tests. Individual measurements could be repeated at 10-15 sec intervals. Comparisons of H₂ and direct Fick measurements were made in 14 patients; H₂ outputs averaged 106 ±4% (SEM) of Fick outputs (P > 0.1). Comparisons of H₂ and dye dilution measurements were performed in an additional 24 patients. Seven had angiographically-negligible valvular regurgitation and dye outputs averaged 106 ±3% of H₂ outputs (P > 0.1). 17 had moderate-to-severe regurigation and dye outputs averaged 91 ±4% of H₂ outputs (P < 0.05), suggesting a small but systematic error due to undetected recirculation of dye. The H₂ technique appears advantageous for rapidly repeated determinations of output, for quantitation of small changes in output, and for situations in which recirculation of conventional indicators is a potentially significant problem.