EFFECT OF POSTURE ON ARTERIAL PRESSURES, TIMING OF THE ARTERIAL SOUNDS AND PULSE-WAVE VELOCITIES IN THE EXTREMITIES

We have recorded systolic and diastolic blood pressure, and the intervals between the QRS complex of the electrocardiogram and the Korotkoff arterial sound at systolic and diastolic pressure (QK(s) and QK(d), respectively), at the brachial and posterior malleolar arteries, for normal subjects in the supine, standing, or head-down positions on a tilt table. These data make it possible to calculate an apparent mean pulse wave velocity. Results indicate: when the subject is supine (O°), brachial and posterior malleolar artery blood pressures are virtually identical; upon standing (+90°), both systolic and diastolic pressures in the foot are elevated by a mean of approximately 70 mm Hg, whereas brachial artery systolic pressure is unaffected and brachial diastolic pressure is raised 7 mm of mercury; conversely, in the head-down (feet-up) position (-30°) the blood pressure in the foot was decreased approximately 20 mm of mercury, whereas the brachial arterial pressure is again unaffected; as one changes from the head-down to the supine to the standing positions, the mean QK(d) interval at the brachial artery was increased by 5 and 15 msec, respectively; conversely, the arrival of the pulse wave in the leg was hastened, with QK(d) decreasing by 7 and then 18 msec. The effects of QK(s) were slightly smaller in the brachial artery but considerably larger in the malleolar artery, with a decrease of 16 msec and then 49 msec; mean apparent pulse wave velocity increases from 9.1 to 10.9 to 17.6 m/sec, as one changes from -30° to 0° to + 90°.