CARDIOVASCULAR RESPONSE TO ACUTE LOWER BODY NEGATIVE PRESSURE IN OLDER MALES.

1995 ◽  
Vol 27 (Supplement) ◽  
pp. S234
Author(s):  
D. Johnston ◽  
Y. Nurhayati ◽  
Y. Cotton ◽  
P. McLaren ◽  
S. H. Boutcher
Keyword(s):  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Cardiovascular Response ◽  
Lower Body ◽  
Older Males

Simulation of cardiovascular response to lower body negative pressure from 0 to -40 mmHg

1994 ◽  
Vol 77 (2) ◽  
pp. 630-640 ◽  
Author(s):  
F. M. Melchior ◽  
R. S. Srinivasan ◽  
P. H. Thullier ◽  
J. M. Clere
Keyword(s):  
Heart Rate ◽  
Negative Pressure ◽  
Baroreflex Sensitivity ◽  
Lower Body Negative Pressure ◽  
Cardiovascular Response ◽  
Left Ventricular ◽  
Diastolic Filling ◽  
Lower Body ◽  
Arterial Baroreflex ◽  
Arterial Baroreflex Sensitivity

This paper presents a mathematical model for simulation of the human cardiovascular response to lower body negative pressure (LBNP) up to -40 mmHg both under normal conditions and when arterial baroreflex sensitivity or leg blood capacity (LBC) is altered. Development of the model assumes that the LBNP response could be explained solely on the bases of 1) blood volume redistribution, 2) left ventricular end-diastolic filling, 3) interaction between left ventricle and peripheral circulation, and 4) modulations of peripheral resistances and heart rate by arterial and cardiopulmonary baroreflexes. The model reproduced well experimental data obtained both under normal conditions and during complete autonomic blockade; thus it is validated for simulation of the cardiovascular response from 0 to -40 mmHg LBNP. We tested the ability of the model to simulate the changes in LBNP response due to a reduction in LBC. To assess these changes experimentally, six healthy men were subjected to LBNP of -15, -30, and -38 mmHg with and without wearing elastic compression stockings. Stockings significantly reduced LBC (from 3.9 +/- 0.3 to 1.8 +/- 0.4 ml/100 ml tissue at -38 mmHg LBNP; P < 0.01) and attenuated the change in heart rate (from 23 +/- 4 to 8 +/- 3% at -38 mmHg LBNP; P < 0.05). The model accurately reproduced this result. The model is useful for assessing the influence of LBC or other parameters such as arterial baroreflex sensitivity in diminishing the orthostatic tolerance of humans after spaceflight, bed rest, or endurance training.

Physical fitness and cardiovascular response to lower body negative pressure

1984 ◽  
Vol 56 (1) ◽  
pp. 138-144 ◽  
Author(s):  
P. B. Raven ◽  
D. Rohm-Young ◽  
C. G. Blomqvist
Keyword(s):  
Negative Pressure ◽  
Maximal Exercise ◽  
Lower Body Negative Pressure ◽  
Cardiovascular Response ◽  
Performance Testing ◽  
Young Male ◽  
Reflex Response ◽  
Lower Body ◽  
Maximal Aerobic Capacity ◽  
Endurance Exercise Training

Fourteen young male volunteers (mean age 28.1 yr) underwent maximal exercise performance testing and lower body negative pressure (LBNP) challenge to -50 Torr. Two distinct groups, fit (F, n = 8), mean maximal aerobic capacity (VO2max) = 70.2 +/- 2.6 (SE) ml O2 kg-1 X min-1, and average fit (AF, n = 6), mean VO2 max V 41.3 +/- 2.9 ml O2 kg-1 X min-1, P less than 0.001, were evaluated. Rebreathing CO2 cardiac outputs, heart rate (HR), blood pressure (BP), and leg circumference changes were monitored at each stage of progressive increases in LBNP to -50 Torr. The overall hemodynamic responses of both groups of subjects to LBNP were qualitatively similar to previous findings. There were no differences between F and AF in peripheral venous pooling as shown by a leg compliance (delta leg volume/delta LBNP) for the F of 12.6 +/- 1.1 and for the AF 11.6 +/- 2.0, P greater than 0.05. The F subjects had significantly less tachycardic response [delta HR/delta systolic BP of F = 0.7 beats/Torr] to LBNP to -50 Torr than the AF subjects [delta HR/delta systolic BP of unfit (UF) = 1.36 beats/Torr], P less than 0.05. In addition, overall calculated peripheral vascular resistance was significantly higher in the AF subjects (P less than 0.001), and there was a more marked decrease in systolic BP of the F subjects between the LBN pressures of -32 to -50 Torr. We concluded that the reflex response to central hypovolemia was altered by endurance exercise training.

Cardiovascular response to lower body negative pressure stimulation before, during, and after space flight

2000 ◽  
Vol 30 (12) ◽  
pp. 1055-1065 ◽  
Author(s):  
F. Baisch ◽  
L. Beck ◽  
G. Blomqvist ◽  
G. Wolfram ◽  
J. Drescher ◽  
...  
Keyword(s):  
Space Flight ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Cardiovascular Response ◽  
Lower Body

scholarly journals Mobile Lower Body Negative Pressure Suit as an Integrative Countermeasure for Spaceflight

2019 ◽  
Vol 90 (12) ◽  
pp. 993-999 ◽  
Author(s):  
Lonnie G. Petersen ◽  
Alan Hargens ◽  
Elizabeth M. Bird ◽  
Neeki Ashari ◽  
Jordan Saalfeld ◽  
...  
Keyword(s):  
Mechanical Loading ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Cardiovascular Response ◽  
Axial Loading ◽  
The Body ◽  
Lower Body ◽  
Fluid Shift ◽  
Cross Sectional

BACKGROUND: Persistent headward fluid shift and mechanical unloading cause neuro-ocular, cardiovascular, and musculoskeletal deconditioning during long-term spaceflight. Lower body negative pressure (LBNP) reintroduces footward fluid shift and mechanical loading.METHODS: We designed, built, and tested a wearable, mobile, and flexible LBNP device (GravitySuit) consisting of pressurized trousers with built-in shoes to support ground reaction forces (GRF) and a thoracic vest to distribute load to the entire axial length of the body. In eight healthy subjects we recorded GRF under the feet and over the shoulders (Tekscan) while assessing cardiovascular response (Nexfin) and footward fluid shift from internal jugular venous cross-sectional area (IJVa) using ultrasound (Terason).RESULTS: Relative to normal bodyweight (BW) when standing upright, increments of 10 mmHg LBNP from 0 to 40 mmHg while supine induced axial loading corresponding to 0%, 13 ± 3%, 41 ± 5%, 75 ± 11%, and 125 ± 22% BW, respectively. Furthermore, LBNP reduced IJVa from 1.12 ± 0.3 cm2 to 0.67 ± 0.2, 0.50 ± 0.1, 0.35 ± 0.1, and 0.31 ± 0.1 cm2, respectively. LBNP of 30 and 40 mmHg reduced cardiac stroke volume and increased heart rate while cardiac output and mean arterial pressure were unaffected. During 2 h of supine rest at 20 mmHg LBNP, temperature and humidity inside the suit were unchanged (23 ± 1°C; 47 ± 3%, respectively).DISCUSSION: The flexible GravitySuit at 20 mmHg LBNP comfortably induced mechanical loading and desired fluid displacement while maintaining the mobility of hips and knee joints. The GravitySuit may provide a feasible method to apply low-level, long-term LBNP without interfering with daily activity during spaceflight to provide an integrative countermeasure.Petersen LG, Hargens A, Bird EM, Ashari N, Saalfeld J, Petersen JCG. Mobile lower body negative pressure suit as an integrative countermeasure for spaceflight. Aerosp Med Hum Perform. 2019; 90(12):993–999.

scholarly journals Cardiovascular Response to Graded Lower Body Negative Pressure in Young and Elderly Man

2001 ◽  
Vol 86 (3) ◽  
pp. 427-435 ◽  
Author(s):  
R. van Hoeyweghen ◽  
J. Hanson ◽  
M. J. Stewart ◽  
L. Dethune ◽  
I. Davies ◽  
...  
Keyword(s):  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Cardiovascular Response ◽  
Lower Body

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.

scholarly journals Validation of lower body negative pressure as an experimental model of hemorrhage

2014 ◽  
Vol 116 (4) ◽  
pp. 406-415 ◽  
Author(s):  
Carmen Hinojosa-Laborde ◽  
Robert E. Shade ◽  
Gary W. Muniz ◽  
Cassondra Bauer ◽  
Kathleen A. Goei ◽  
...  
Keyword(s):  
Experimental Model ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Cardiovascular Response ◽  
Venous Pressure ◽  
Blood Gases ◽  
Plasma Renin ◽  
Lower Body ◽  
Central Venous ◽  
Shed Blood

Lower body negative pressure (LBNP), a model of hemorrhage (Hem), shifts blood to the legs and elicits central hypovolemia. This study compared responses to LBNP and actual Hem in sedated baboons. Arterial pressure, pulse pressure (PP), central venous pressure (CVP), heart rate, stroke volume (SV), and +dP/d t were measured. Hem steps were 6.25%, 12.5%, 18.75%, and 25% of total estimated blood volume. Shed blood was returned, and 4 wk after Hem, the same animals were subjected to four LBNP levels which elicited equivalent changes in PP and CVP observed during Hem. Blood gases, hematocrit (Hct), hemoglobin (Hb), plasma renin activity (PRA), vasopressin (AVP), epinephrine (EPI), and norepinephrine (NE) were measured at baseline and maximum Hem or LBNP. LBNP levels matched with 6.25%, 12.5%, 18.75%, and 25% hemorrhage were −22 ± 6, −41 ± 7, −54 ± 10, and −71 ± 7 mmHg, respectively (mean ± SD). Hemodynamic responses to Hem and LBNP were similar. SV decreased linearly such that 25% Hem and matching LBNP caused a 50% reduction in SV. Hem caused a decrease in Hct, Hb, and central venous oxygen saturation (ScvO2). In contrast, LBNP increased Hct and Hb, while ScvO2 remained unchanged. Hem caused greater elevations in AVP and NE than LBNP, while PRA, EPI, and other hematologic indexes did not differ between studies. These results indicate that while LBNP does not elicit the same effect on blood cell loss as Hem, LBNP mimics the integrative cardiovascular response to Hem, and validates the use of LBNP as an experimental model of central hypovolemia associated with Hem.

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