Pressure-flow studies in man during the Valsalva maneuver with observations on the mechanical properties of the ascending aorta.

SUMMARY The pressure-gradient technique was used to obtain continuous measurements of both blood pressure and flow in the ascending aorta of eight normal subjects who were performing a standardized Valsalva maneuver. From these recordings the beat-to-beat changes in stroke volume, peak blood flow, peripheral vascular resistance, duration of ejection, and an index of total systolic duration were calculated. Stroke volume and peak blood flow were not changed with the onset of straining (phase I), but were decreased to approximately 50% of control values immediately prior to release (phase II). During the overshoot period (phase IV) stroke volume and peak flow were increased above control levels. Both the duration of ejection and the duration of systole were shortened during straining (phase II). The concomitant changes in blood pressure in these subjects were similar to previously reported pressure recordings. An estimate of the pressure-radius relationships in the ascending aorta of these patients was obtained angiographically. The mean cross-sectional area of the ascending aorta changed by 17% during the Valsalva maneuver. Indicator-dilution technique Aortic comp Ejection period Systolic period T HE EFFECT of the Valsalva maneuver on the cardiovascular system has been of interest to circulatory physiologists for many years. In order to characterize these effects, one should know beat-to-beat values for both aortic pressure and flow. Continuous recordings of blood pressure during the Val-salva maneuver are well documented' 5; however , measurements of instantaneous flow have not previously been available because of the technical problems encountered in quantita-ting phasic aortic blood flow in the intact human subject. Consequently, alterations in blood flow during the Valsalva maneuver have either been inferred from pressure data or estimated with indicator-dilution techniques.6 d Since these methods require several seconds for completion, they cannot be used to estimate beat-to-beat changes in flow during an unsteady state. At present the pressure-gradient technique provides the only practical method for measuring instantaneous aortic blood flow in the intact human subject.8 This report presents blood pressure and flow data recorded continuously in the ascending aorta