Abstract
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.
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