Mild lower body suction (5-20 mmHg) in healthy men significantly decreased aortic pulse area, with 47% of the decline occurring by 5 mmHg, triggering efficient haemodynamic adjustments.
Does graded lower body suction alter arterial pressure, cardiac autonomic outflow, and thoracic aorta dimensions in healthy young men?
Small reductions in effective blood volume reduce aortic baroreceptive areas and trigger efficient hemodynamic adjustments, challenging the notion that 'non-hypotensive' hypovolemia does not alter arterial pressure or baroreceptor activity.
p-value: p=<0.05
The notion that small, 'non-hypotensive' reductions of effective blood volume alter neither arterial pressure nor arterial baroreceptor activity is pervasive in the experimental literature. We tested two hypotheses: (a) that minute arterial pressure and cardiac autonomic outflow changes during hypovolaemia induced by lower body suction in humans are masked by alterations in breathing, and (b) that evidence for arterial baroreflex engagement might be obtained from measurements of thoracic aorta dimensions. 2. In two studies, responses to graded lower body suction at 0 (control), 5, 10, 15, 20 and 40 mmHg were examined in twelve and ten healthy young men, respectively. In the first, arterial pressure (photoplethysmograph), R-R interval, and respiratory sinus arrhythmia amplitude (complex demodulation) were measured during uncontrolled and controlled breathing (constant breathing frequency and tidal volume). In the second, cross-sectional areas of the ascending thoracic aorta were calculated from nuclear magnetic resonance images. 3. Lower body suction with controlled breathing resulted in an increased arterial pulse pressure at mild levels (5-20 mmHg; ANOVA, P 0.92) or individual subjects (orthogonal polynomials, 12 of 12 subjects) were assessed. 4. Aortic pulse area decreased progressively and significantly during mild lower body suction, with 47% of the total decline occurring by 5 mmHg. 5. These results suggest that small reductions of effective blood volume reduce aortic baroreceptive areas and trigger haemodynamic adjustments which are so efficient that alterations in arterial pressure escape detection by conventional means.
Taylor et al. (Wed,) conducted a other in Healthy (n=22). Graded lower body suction vs. 0 mmHg (control) was evaluated on Arterial pulse pressure and aortic pulse area (p=<0.05). Mild lower body suction (5-20 mmHg) in healthy men significantly decreased aortic pulse area, with 47% of the decline occurring by 5 mmHg, triggering efficient haemodynamic adjustments.