Association of sex and age with responses to lower-body negative pressure

Frey, Mary; Hoffler, G. W.

doi:10.1152/jappl.1988.65.4.1752

Cited by 89 publications

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“…Moreover, women often demonstrate less effective BP regulation than men during acute challenges (eg, orthostatic stress) and in response to vasoactive drugs. 1,2,4,6,[11][12][13][14] The responsible mechanisms have not been identified, but the results of the present study indicate that a reduced ability for BRB of acute changes in BP may play a central role in the less effective short-term BP control observed in women.…”

Section: Discussionmentioning

confidence: 62%

“…The ability of baroreflexes to "buffer" acute changes in BP under such conditions (ie, baroreflex buffering [BRB]) is reduced in certain physiological 9 and disease 10 states associated with impaired short-term BP regulation and/or altered responsiveness to vasoactive medications. In light of previous reports of less effective short-term regulation of BP in women than in men, 1,2,6,[11][12][13][14] we also hypothesized that premenopausal women have lower BRB of BP than men of similar age.…”

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confidence: 92%

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Women Have Lower Tonic Autonomic Support of Arterial Blood Pressure and Less Effective Baroreflex Buffering Than Men

et al. 2005

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Section: Discussionmentioning

confidence: 62%

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confidence: 92%

Women Have Lower Tonic Autonomic Support of Arterial Blood Pressure and Less Effective Baroreflex Buffering Than Men

et al. 2005

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“…Small changes in intravenous pressure owing to changes in blood flow will have an effect on venous volume, and unstressed venous volume may thus decrease, as shown in the extremities using ischemic handgrip or LBNP (17,39). Basal arterial inflow to the lower limb seems to be similar in women and men (21,28), and a majority of studies have found no sex difference in arterial vasoconstriction (9,10,13,58), although men may respond with greater vasoconstriction during LBNP (7). A greater vasoconstriction in men, however, would have led to an underestimation of the differences in capacitance response in the present study.…”

Section: Discussionmentioning

confidence: 99%

“…with men, although this difference may be due to differences in body size (38). Other factors of importance for the susceptibility to orthostatic stress in women might be reduced cardiovagal baroreflex gain, peripheral resistance, muscle sympathetic nerve activity, and/or different adrenergic receptor sites, response time, and duration to orthostatic stress (3,7,30,51). Larger decrease in stroke volume has also been found in women compared with men (4,9).…”

Section: Discussionmentioning

confidence: 99%

Sex-related effects on venous compliance and capillary filtration in the lower limb

Lindenberger

Länne²

2007

American Journal of Physiology-Regulatory, Integrative and Comp

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Recent studies in humans have suggested sex differences in venous compliance of the lower limb, with lower compliance in women. Capillary fluid filtration could, however, be a confounder in the evaluation of venous compliance. The venous capacitance and capillary filtration response in the calves of 12 women (23.2 Ϯ 0.5 years) and 16 men (22.9 Ϯ 0.5 years) were studied during 8 min lower body negative pressure (LBNP) of 11, 22, and 44 mmHg. Calf venous compliance is dependent on pressure and was determined using the first derivative of a quadratic regression equation that described the capacitance-pressure relationship [compliance ϭ ␤ 1 ϩ (2 ⅐ ␤2 ⅐ transmural pressure)]. We found a lower venous compliance in women at low transmural pressures, and the venous capacitance in men was increased (P Ͻ 0.05). However, the difference in compliance between sexes was reduced and not seen at higher transmural pressures. Net capillary fluid filtration and capillary filtration coefficient (CFC) were greater in women than in men during LBNP (P Ͻ 0.05). Furthermore, calf volume increase (capacitance response ϩ total capillary filtration) during LBNP was equivalent in both sexes. When total capillary filtration was not subtracted from the calf capacitance response in the calculation of venous compliance, the sex differences disappeared, emphasizing that venous compliance measurement should be corrected for the contribution of CFC. lower body negative pressure; capillary filtration coefficient; venous capacitance THE VENOUS SECTION OF THE cardiovascular system can be looked upon as a voluminous blood reservoir (70% of total blood volume), designed to preserve a proper inflow of blood into the heart during various cardiovascular adjustments. Thus central venous pressure and filling of the heart may be maintained at a fairly stable level, despite variations in venous blood volume (49). During upright posture, however, the pooling of blood in the veins of the lower part of the body decreases central blood volume and venous return (4, 5, 16). The venous compartment in the legs, rather than the pelvic or abdominal region, seems to have a hemodynamic impact during lower body negative pressure (LBNP) (16), and in studies on men, a greater calf venous compliance has been linked to an increased venous capacitance response with a concomitant reduction in central blood volume (44,56). This, in turn, elicits an increased sympathetic response with higher peripheral resistance and increased heart rate (4, 5, 10, 16, 44, 58). Thus venous compliance of the lower limb may have an impact on cardiovascular responses to orthostatic stress and orthostatic tolerance, although there might be differences between sexes confounding such a link (4).Women are more susceptible to orthostatic stress than men (4,10,13,40,51,58), and in accordance with some findings in the arterial tree, it may be hypothesized that women have greater venous compliance in the lower limbs predisposing to orthostatic intolerance (52). This seems to be refuted however, by recent fi...

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“…However, evidence for this conclusion was not definitive, because the results were obtained from a very small number of subjects analyzed retrospectively. Frey et al (13,14) proposed that women might respond to orthostatic challenges with more prominent vagal withdrawal, whereas men might respond with greater sympathetic stimulation to the peripheral vasculature. This notion was supported by the observation that women demonstrated greater elevations in heart rate (HR) than men (7,35,51), but was not consistent with the finding that peripheral vascular resistance was similar for both genders at onset of presyncope (7).…”

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confidence: 99%

Hemodynamics of orthostatic intolerance: implications for gender differences

Arbab‐Zadeh

Perhonen

et al. 2004

American Journal of Physiology-Heart and Circulatory Physiology

171

163

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Women have a greater incidence of orthostatic intolerance than men. We hypothesized that this difference is related to hemodynamic effects on regulation of cardiac filling rather than to reduced responsiveness of vascular resistance during orthostatic stress. We constructed FrankStarling curves from pulmonary capillary wedge pressure (PCWP), stroke volume (SV), and stroke index (SI) during lower body negative pressure (LBNP) and saline infusion in 10 healthy young women and 13 men. Orthostatic tolerance was determined by progressive LBNP to presyncope. LBNP tolerance was significantly lower in women than in men (626.8 Ϯ 55.0 vs. 927.7 Ϯ 53.0 mmHg ϫ min, P Ͻ 0.01). Women had steeper maximal slopes of Starling curves than men whether expressed as SV (12.5 Ϯ 2.0 vs. 7.1 Ϯ 1.5 ml/mmHg, P Ͻ 0.05) or normalized as SI (6.31 Ϯ 0.8 vs. 4.29 Ϯ 0.6 ml⅐m Ϫ2 ⅐mmHg Ϫ1 , P Ͻ 0.05). During progressive LBNP, PCWP dropped quickly at low levels, and reached a plateau at high levels of LBNP near presyncope in all subjects. SV was 35% and SI was 29% lower in women at presyncope (both P Ͻ 0.05). Coincident with the smaller SV, women had higher heart rates but similar mean arterial pressures compared with men at presyncope. Vascular resistance and plasma norepinephrine concentration were similar between genders. We conclude that lower orthostatic tolerance in women is associated with decreased cardiac filling rather than reduced responsiveness of vascular resistance during orthostatic challenges. Thus cardiac mechanics and Frank-Starling relationship may be important mechanisms underlying the gender difference in orthostatic tolerance. orthostatic hypotension; stroke volume; vascular resistance; pulmonary capillary wedge pressure; lower body negative pressure IN HUMANS, TOLERANCE TO ORTHOSTATIC stress requires the successful integration of multiple elements of cardiovascular control. Syncope may occur when there is an abnormally large postural decrease in central blood volume, cardiac filling pressure, stroke volume (SV), and cardiac output (CO), or inadequate neurohumoral reflex responses to orthostasis, primarily tachycardia and vasoconstriction (2). It has been noted that women have lower orthostatic tolerance than men (7,15,23,35,50). Specific mechanisms underlying this difference have not been totally elucidated and are probably multifactorial.One recent study (50) on astronauts suggested that the incidence of orthostatic presyncope after spaceflight was greatest in women, and this was ascribed to a combination of inherently lower resistance and relative hypoadrenergic responses. However, evidence for this conclusion was not definitive, because the results were obtained from a very small number of subjects analyzed retrospectively. Frey et al. (13,14) proposed that women might respond to orthostatic challenges with more prominent vagal withdrawal, whereas men might respond with greater sympathetic stimulation to the peripheral vasculature. This notion was supported by the observation that women demonstrated greater elevations in ...

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Association of sex and age with responses to lower-body negative pressure

Cited by 89 publications

References 0 publications

Women Have Lower Tonic Autonomic Support of Arterial Blood Pressure and Less Effective Baroreflex Buffering Than Men

Women Have Lower Tonic Autonomic Support of Arterial Blood Pressure and Less Effective Baroreflex Buffering Than Men

Sex-related effects on venous compliance and capillary filtration in the lower limb

Hemodynamics of orthostatic intolerance: implications for gender differences

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