Cardiac output and blood pressure during active and passive standing

Abstract

The present study compared the haemodynamic pattern of active and passive standing. We used non-invasive techniques with beat-to-beat evaluation of blood pressure, heart rate and stroke volume. Seven healthy subjects, aged 24-41 (mean 30) years were examined. Finger blood pressure was continuously recorded by volume clamp technique (Finapres), and simultaneous beat-to-beat beat stroke volume was obtained, using an ultrasound Doppler technique, from the product of the valvular area and the aortic flow velocity time integral in the ascending aorta from the suprasternal notch. Measurements were performed at rest, during active standing and following passive tilt (60 degrees). Active standing caused a transient but greater reduction of blood pressure and a higher increase of heart rate than passive tilt during the first 30s (delta mean blood pressure: -39 +/- 10 vs. -16 +/- 7 mmHg, delta heart rate: 35 +/- 8 vs. 12 +/- 7 beats m-1 (active standing vs. passive tilt; P < 0.01). There was a significantly larger increase in cardiac output during active standing (37 +/- 24 vs. 0 +/- 15%, P < 0.01) and a more marked decrease in total peripheral resistance (-58 +/- 11 vs. -16 +/- 17%, P < 0.01). A precipitous rise in intra-abdominal pressure (43 +/- 22 mmHg) could be observed upon rising only in active standing. This was interpreted as an indication of translocation of blood to the thorax. There was no significant difference in haemodynamic changes during the later stage of standing (1-7 min) between both manoeuvres. These results suggest that active standing causes a marked blood pressure reduction in the initial phase which seems to reflect systemic vasodilatation caused by activation of cardiopulmonary baroreflexes, probably due to a rapid shift of blood from the splanchnic vessels in addition to the shift from muscular vessels associated with abdominal and calf muscle contraction. Moreover, the ultrasound Doppler technique was found to be a more adequate method for rapid beat-to-beat evaluation of cardiac output during orthostatic manoeuvres.

Hemodynamics and brain blood flow during posture change in younger women and postmenopausal women compared with age-matched men

“…Tanaka et al (62) and Sprangers et al (59) also observed a decrease of total peripheral RI and MAP during postural transitions due to vasodilation and movement of blood to the lower body. The decrease of total peripheral RI was greater in men and could be due to greater leg muscle mass (55) and/or a greater number of dilated vessels.…”

Squatting test: a dynamic postural manoeuvre to study baroreflex sensitivity

“…This was interpreted as an indication of translocation of blood to the thorax. The greater BP reduction in the initial phase of active standing may reflect systemic vasodilatation caused by activation of cardiopulmonary baroreflexes; this is probably due to a rapid shift of blood from the splanchnic vessels in addition to the shift from muscular vessels associated with abdominal and calf muscle contraction [24]. At least similar, and probably even amplified, changes may be expected during the shift from squatting to standing.…”

“…Therefore, the homoeostatic mechanisms are the same, but with different quantity of the same time-dependent quality. A carefully performed study compared haemodynamic changes during active standing and following passive 60° tilt in young healthy subjects [24]. BP and HR were continuously recorded by a Finapres ® , and simultaneous beat-to-beat stroke volume was obtained using an ultrasound Doppler technique.…”

Squatting maneuver - an easy and efficient method to evaluate postural effect on human arterial blood pressure regulation

“…Further by Rossberg and Penaz and Krediet and Wieling added that on standing and loss of compression of the legs, there would be an immediate reduction in leg vascular resistance due to already existing locally mediated vasodilatation. [26][27][28][29] Moreover, also supported by studies by Tschakovsky and Sheriff as the muscular effort involved in standing up from a squat position is considerable, it has been demonstrated that rapid vasodilatory mechanisms act in proportion to contraction intensity. [30] This would be expected to cause further vasodilatation.…”