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

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.