Irwin J. Fox

Direct measurements of right and left heart outputs in a Valsalva-like maneuver in dogs.

Summary While changes in systemic flow produced by Valsalva-like maneuvers in dogs closely resembled those of Valsalva maneuvers performed by humans, systemic arterial pressure fell much more in the Valsalva-like maneuvers as the pulmonary prssure—flow ratio rose markedly (+ 1100%). Right and left heart outputs decreased to 20 and 30% of control, respectively, while pulmonary blood volume decreased by 140 ± 45 ml or by approximately 40% in the Valsalva-like maneuver. The course of the atrial pressures, rapid fall in right heart output and development of acute right heart insufficiency suggest a hitherto unreported site of obstruction to flow in the Valsalva and Valsalva-like maneuvers, namely, at the small pulmonary vessels. Ventricular function curves and a phase shift between ventricular filling (atrial) pressures suggest that the Frank—Starling mechanism plays a role in restoration of cardiac balance after this maneuver. The authors thank Professor M. B. Visscher, Mr. Michael R. Tripp, Dr. Claude Swayze of the Department of Physiology, and Professor E. H. Wood of the Mayo Graduate School, University of Minnesota, for their helpful advice in the preparation of the manuscript.

Effect of Protein and Electrolyte on the Spectral Stabilization of Concentrated Solutions of Indocyanine Green

Summary The presence of protein and electrolyte in the concentrated indocyanine green solution was shown to slow the rate of optical stabilization following dilution of the concentrated solution in plasma. This finding explains some of the reported discrepancies in flow measurement with the dye. When the concentrated dye was prepared in distilled water the spectral stabilization after dilution was rapid (<2 sec) and should not be a source of error in flow measurement. The authors thank Professors F. Wold and A. Moscowitz of the Departments of Biochemistry and Chemistry for illuminating discussions of detergent micelle stabilization by proteins and Drs. W. J. Runge of the Pathology Department and J. L. Holtzman of the Pharmacology Department for technical assistance.

Abnormal Indicator Dilution Patterns in Dogs Produced by Flowmeter Probes on the Pulmonary Artery

In acute experiments on open chested dogs, indicator dilution curves were recorded before and after placing electromagnetic flow probes on the pulmonary artery. The flow probes caused severe abnormalities in the dilution curves. The abnormalities resembled those seen in cases with left-to-right shunts. The following facts suggest that the abnormalities are caused by turbulence and eddy formation near the flowmeter probe: (a) Direct measurements with a fiberoptic densitometer showed that clearance of dye just proximal to the probe was delayed. (b) The abnormalities disappeared immediately after removal of the probe or when the dye was injected just downstream to the probe. (c) The areas under curves recorded from the pulmonary artery upstream from the probe were greater than the areas under curves recorded at this same site without the probe. Cardiac output and systemic arterial pressure were lower in animals with abnormal dilution curves than in those with normal femoral curves.