Hemodynamic strategies in blood pressure regulation during orthostatic challenge in women.
Several studies indicate that carotid baroreflex responsiveness is a good predictor of orthostatic tolerance. Two groups of healthy women with high (HI) and low (LO) carotid baroreflex responsiveness were studied (a) to determine any differences in the level of orthostatic tolerance of the two groups, and (b) to study the hemodynamic strategies used by HI and LO responders to regulate arterial pressure during the orthostatic challenge of lower body negative pressure (LBNP). Orthostatic tolerance was similar between the two groups, whereas the hemodynamic strategies recruited to maintain blood pressure at -40 mmHg LBNP differed: HI responders exhibited greater LBNP-induced decreases in stroke volume and cardiac output, as well as a greater increase in peripheral resistance compared to LO responders (p < .05). In addition, a significant increase in plasma renin activity during LBNP was found in the HI responders only. No significant between-group differences were found in arterial and cardiopulmonary control of vascular resistance or arterial baroreflex control of heart rate during LBNP.
Culham
T L
TL
School of Physical and Health Education, Queen's University, Kingston, ON.
Savard
G K
GK
D000293:Adolescent; D000328:Adult; D017704:Baroreflex; D001794:Blood Pressure / Q000502:physiology*; D002302:Cardiac Output / Q000502:physiology; D002339:Carotid Arteries / Q000502:physiology*; D005260:Female; D006339:Heart Rate / Q000502:physiology; D006439:Hemodynamics; D006801:Humans; D007024:Hypotension, Orthostatic / Q000503:physiopathology; D008150:Lower Body Negative Pressure