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Biomedical subjects

D G Greene

Publications and source records attributed to D G Greene.

At least 37 records · Page 2Linked to original sources
PubMed1972

Evaluation of venous bypass grafts from aorta to coronary artery by inert gas desaturation and direct flowmeter techniques.

Blood flow through aorta-to-coronary artery bypass grafts has been measured selectively in 16 patients at or within 6 wk after operation. Inert gas desaturation curves were obtained from coronary venous blood samples after a 7-15 min infusion of dissolved H(2) directly into the graft. Samples were analyzed chromatographically and curves resolved to 1-3% of initial H(2) concentrations. Average flow per unit volume (F/V) was 67+/-21 (sd) ml/min per 100 g. Semilogarithmic plots showed F/V to be distributed heterogeneously in every case. In nine studies at operation, H(2) measurements of average F/V were combined with electromagnetic measurements of total flow to estimate revascularized tissue mass. Electromagnetic flows ranged from 25 to 170 ml/min and averaged 69 ml/min. Tissue mass ranged from 46 to 155 g and averaged 88 g. We conclude that bypass grafts provide nutritive flow to significant amounts of myocardium at and shortly after operation. However, nutritive flow is not distributed evenly throughout the revascularized segment. The majority of the segment has a F/V within the accepted range of normal but there remain areas in which F/V is reduced significantly. The combination of inert gas and electromagnetic techniques allows a revascularized area to be characterized in terms of total flow, F/V, and tissue mass.

Adult↗
PubMed1971

Measurement of cardiac output in man with a nonrecirculating indicator.

The present investigation was undertaken to evaluate the utility of constant-rate injection of a nonrecirculating indicator (H(2)) 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 H(2) concentration was measured chromatographically from 2.0 ml blood samples drawn during constant-rate injection of dissolved H(2) 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 H(2) 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 x 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 H(2) and direct Fick measurements were made in 14 patients; H(2) outputs averaged 106 +/-4% (SEM) of Fick outputs (P > 0.1). Comparisons of H(2) and dye dilution measurements were performed in an additional 24 patients. Seven had angiographically-negligible valvular regurgitation and dye outputs averaged 106 +/-3% of H(2) outputs (P > 0.1). 17 had moderate-to-severe regurigation and dye outputs averaged 91 +/-4% of H(2) outputs (P < 0.05), suggesting a small but systematic error due to undetected recirculation of dye. The H(2) 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.

Arteriosclerosis↗