Haemodynamic responses to nonhypotensive central hypovolaemia induced by lower body negative pressure in men and women

1991 ◽  
Vol 63 (2) ◽  
pp. 151-155 ◽  
Author(s):  
M. A. Rahman ◽  
K. Goodhead ◽  
J. F. Medcalf ◽  
M. O'Connor ◽  
T. Bennett
Keyword(s):  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Lower Body ◽  
Men And Women ◽  
Central Hypovolaemia

scholarly journals Differentiating compensatory mechanisms associated with low tolerance to central hypovolemia in women

2019 ◽  
Vol 316 (3) ◽  
pp. H609-H616 ◽  
Author(s):  
Taylor Elyse Schlotman ◽  
Kevin S. Akers ◽  
Shawn C. Nessen ◽  
Victor A. Convertino
Keyword(s):  
Blood Volume ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Reduction Rate ◽  
Lower Body ◽  
Men And Women ◽  
Compensatory Responses ◽  
Arterial Blood ◽  
Compensatory Reserve ◽  
Lower Tolerance

Women generally display lower tolerance to acute central hypovolemia than men. The measurement of compensatory reserve (CRM) is a novel metric that provides information about the sum total of all mechanisms that together work to compensate for the relative blood volume deficit. Hemodynamic decompensation occurs with depletion of the CRM (i.e., 0% CRM). In the present study, we hypothesized that the lower tolerance to progressive central hypovolemia reported in women can be explained by a faster reduction rate in CRM compared with men rather than sex differences in absolute integrated compensatory responses. Continuous, noninvasive measures of CRM were collected from 208 healthy volunteers (107 men and 85 women) who underwent progressive stepwise central hypovolemia induced by lower body negative pressure to the point of presyncope. Comparisons revealed shorter ( P < 0.01) times in female participants compared with male participants to reach 30% and 0% CRM. Similarly, the lower body negative pressure level, represented by the cumulative stress index, was less at 30% and 0% CRM in women compared with men ( P < 0.01). Changes in hemodynamic responses and frequency-domain data (oscillations in cerebral blood flow velocity and mean arterial blood pressure) were similar between men and women at 0% CRM ( P > 0.05). We conclude that compensatory responses to central hypovolemia in women were similar to men but were depleted at a faster rate compared with men. The earlier depletion of the compensatory reserve in women appears to be influenced by failure to maintain adequate cerebral oxygen delivery. NEW & NOTEWORTHY We compared hemodynamic and metabolic responses in men and women to experimentally controlled reductions in central blood volume at physiologically equivalent levels of compensatory reserve. We corroborated previous findings that females have lower tolerance to central hypovolemia than males but demonstrated for the first time that compensatory responses are similar. Our findings suggest lower tolerance to central hypovolemia in women results from reaching critical cerebral delivery of oxygen faster than men.

scholarly journals The influence of combined lower body negative pressure and mental stress on cerebral blood flow in men and women

2013 ◽  
Vol 27 (S1) ◽  
Author(s):  
Angelea H. Young ◽  
Chelsea R. Strong ◽  
William H. Cooke ◽  
Jason R. Carter ◽  
John J. Durocher
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Negative Pressure ◽  
Mental Stress ◽  
Lower Body Negative Pressure ◽  
Lower Body ◽  
Men And Women

Age- and fitness-related differences in limb venous compliance do not affect tolerance to maximal lower body negative pressure in men and women

2004 ◽  
Vol 97 (3) ◽  
pp. 925-929 ◽  
Author(s):  
J. P. Hernandez ◽  
W. D. Franke
Keyword(s):  
Exercise Training ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Cuff Pressure ◽  
The Elderly ◽  
Venous Occlusion ◽  
Lower Body ◽  
Chronic Exercise ◽  
Venous Compliance ◽  
Men And Women

Aging and chronic exercise training influence leg venous compliance. Venous compliance affects responses to an orthostatic stress; its effect on tolerance to maximal lower body negative pressure (LBNP) in the elderly is unknown. The purpose of this study was to determine the influence of age and fitness, a surrogate measure of exercise training, on calf venous compliance and tolerance to maximal LBNP in men and women. Forty participants, 10 young fit (YF; age = 22.6 ± 0.5 yr, peak oxygen uptake = 57.1 ± 2.0 ml·kg−1·min−1), 10 young unfit (YU; 23.1 ± 1.0 yr, 41.1 ± 2.0 ml·kg−1·min−1), 10 older fit (OF; 73.9 ± 2.0 yr, 39.0 ± 2.0 ml·kg−1·min−1), and 10 older unfit (OU; 70.9 ± 1.6 yr, 27.1 ± 2.0 ml·kg−1·min−1), underwent graded LBNP to presyncope or 4 min at −100 mmHg. By utilizing venous occlusion plethysmography, calf venous compliance was determined by using the first derivative of the pressure-volume relation during cuff pressure reduction. We found that the more fit groups had greater venous compliance than their unfit peers ( P < 0.05) as did the young groups compared with their older peers ( P < 0.05) such that OU < YU = OF < YF. LBNP tolerance did not differ between groups. In conclusion, these data suggest that aging reduces, and chronic exercise increases, venous compliance. However, these data do not support a significant influence of venous compliance on LBNP tolerance.

Leg mass and lower body negative pressure tolerance in men and women

1998 ◽  
Vol 85 (4) ◽  
pp. 1471-1475 ◽  
Author(s):  
Lori A. Lawler ◽  
John R. Halliwill ◽  
Jolene M. Summer ◽  
Michael J. Joyner ◽  
Sharon L. Mulvagh
Keyword(s):  
Muscle Mass ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Lower Body ◽  
Critical Determinant ◽  
Men And Women ◽  
Men 2 ◽  
Intravenous Hydration ◽  
Leg Muscle ◽  
Forearm Vascular Resistance

To explore the hypothesis that lower body muscle mass correlates with orthostatic tolerance, 18 healthy volunteers (age 18–48 yr; 10 men, 8 women) underwent a graded lower body negative pressure (LBNP) protocol consisting of six, 5-min stages of suction up to 60 mmHg in 10-mmHg increments. Forearm blood flow, heart rate, and blood pressure were measured, and forearm vascular resistance was calculated. Leg muscle mass was assessed by dual-energy X-ray absorptiometry. All subjects received standard intravenous hydration for at least 8 h before the study. Six men and four women completed all stages of LBNP. Four men and four women developed presyncopal symptoms, including marked bradycardia and/or hypotension, at LBNP levels of 30 mmHg ( n = 2; 1 man, 1 woman), 40 mmHg ( n = 2; 1 man, 1 woman), and 50 mmHg ( n = 4; 2 men, 2 women). The presyncopal subjects had leg muscle masses ranging from 19.5 to 25.2 kg in men and from 11.7 to 16.6 kg in women. In subjects who completed all stages of LBNP, leg muscle mass ranged from 17.5 to 24.1 kg in men and from 10.4 to 18.0 kg in women. Leg muscle mass did not differ between presyncopal subjects and those who completed the protocol. Furthermore, there were no differences in the hemodynamic responses to LBNP between subjects with low vs. high leg mass. These data suggest that leg muscle mass is not a critical determinant of LBNP tolerance in otherwise healthy men and women.

Women have lower tolerance to lower body negative pressure than men

1996 ◽  
Vol 80 (4) ◽  
pp. 1138-1143 ◽  
Author(s):  
D. D. White ◽  
R. W. Gotshall ◽  
A. Tucker
Keyword(s):  
Negative Pressure ◽  
Heart Rate Response ◽  
Lower Body Negative Pressure ◽  
Cardiovascular Response ◽  
Stress Index ◽  
Lower Body ◽  
Men And Women ◽  
Cumulative Stress ◽  
Cardiovascular Variables ◽  
Lower Tolerance

Studies of the cardiovascular response to lower body negative pressure (LBNP) in men and women have suggested that women may have less tolerance to LBNP than men, although tolerance per se was not determined. To investigate the effect of gender on tolerance to LBNP, 10 men 10 women were subjected to increasing levels of LBNP until presyncopal symptoms developed. The cumulative stress index (CSI) score was determined, as were cardiovascular variables. Women had 62% less tolerance to LBNP with a CSI of 412 +/- 43 mmHg/min compared with a CSI of 1,070 +/- 149 mmHg/min for men. Cardiovascular changes associated with LBNP were similar for men and women when expressed relative to the occurrence of presyncope, but women had a higher heart rate response when the data were expressed at absolute levels of LBNP (-30 and -50 mmHg LBNP). Thus men and women had similar cardiovascular adjustments to the LBNP, with the changes in women occurring lower levels of LBNP. These data are important in a consideration of the development of antigravitational countermeasures for women. These data raise questions as to the manner in which blood pools within the lower body in men and women under LBNP.

Cardiovascular responses to lower body negative pressure before and after 4 h of head-down bed rest and seated control in men and women

2012 ◽  
Vol 113 (10) ◽  
pp. 1604-1612 ◽  
Author(s):  
H. Edgell ◽  
A. Grinberg ◽  
N. Gagné ◽  
K. R. Beavers ◽  
R. L. Hughson
Keyword(s):  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Venous Pressure ◽  
Bed Rest ◽  
Time Of Day ◽  
Lower Body ◽  
Central Venous ◽  
Men And Women ◽  
Cardiovascular Deconditioning ◽  
Before And After

Cardiovascular deconditioning after a 4-h head-down bed rest (HDBR) might be a consequence of the time of day relative to pre-HDBR testing, or simply 4 h of confinement and inactivity rather than the posture change. Ten men and 11 women were studied during lower body negative pressure (LBNP) before and after 4-h HDBR and 4-h seated posture (SEAT) as a control for time of day and physical inactivity effects to test the hypotheses that cardiovascular deconditioning was a consequence of the HDBR posture, and that women would have a greater deconditioning response. Following HDBR, men and women had lower blood volume, higher heart rate with a greater increase during LBNP, a greater decrease of stroke volume during LBNP, lower central venous pressure, smaller inferior vena cava diameter, higher portal vein resistance index with a greater increase during LBNP, but lower forearm vascular resistance, lower norepinephrine, and lower renin. Women had lower vasopressin and men had higher vasopressin after HDBR, and women had lower pelvic impedance and men higher pelvic impedance. Following SEAT, brachial vascular resistance was reduced, thoracic impedance was elevated, the reduction of central venous pressure during LBNP was changed, women had higher angiotensin II whereas men had lower levels, and pelvic impedance increased in women and decreased in men. Cardiovascular deconditioning was greater after 4-h HDBR than after SEAT. Women and men had similar responses for most cardiovascular variables in the present study that tested the responses to LBNP after short-duration HDBR compared with a control condition.

Neurohormonal responses to oscillatory lower body negative pressure in healthy subjects

2021 ◽  
Author(s):  
Akanksha Singh ◽  
Shival Srivastav ◽  
Kavita Yadav ◽  
Dinu S. Chandran ◽  
Ashok Kumar Jaryal ◽  
...  
Keyword(s):  
Negative Pressure ◽  
Healthy Subjects ◽  
Lower Body Negative Pressure ◽  
Lower Body
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