scholarly journals Approximate Entropy in Analysis of Cardiovascular Response to Lower Body Negative Pressure Test

2018 ◽  
Author(s):  
Agnieszka Strok ◽  
Gerard Cybulski ◽  
Anna Gąsiorowska ◽  
Wiktor Niewiadomski
Keyword(s):  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Cardiovascular Response ◽  
Approximate Entropy ◽  
Lower Body ◽  
Pressure Test ◽  
Negative Pressure Test

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.

Orthostatic intolerance during a 13-day bed rest does not result from increased leg compliance

1993 ◽  
Vol 74 (1) ◽  
pp. 286-292 ◽  
Author(s):  
F. M. Melchior ◽  
S. M. Fortney
Keyword(s):  
Orthostatic Intolerance ◽  
Lower Body Negative Pressure ◽  
Bed Rest ◽  
Venous Occlusion ◽  
Orthostatic Tolerance ◽  
Lower Body ◽  
Pressure Test ◽  
Before And After ◽  
Negative Pressure Test ◽  
The Relationship

Increased leg compliance (LC) has been proposed as a mechanism for orthostatic intolerance after spaceflight or bed rest. Using venous occlusion plethysmography with mercury-in-Silastic strain gauge, we evaluated LC before, during, and after a 13-day head-down (-6 degrees) bed rest in 10 men. LC was measured by the relationship between the increased calf areas (in cm2) at thigh cuff occlusions of 20, 30, 50, 70, and 80 mmHg. Orthostatic tolerance was evaluated by a presyncopal-limited lower body negative pressure test (PSL-LBNP) before and after bed rest. The 10 subjects were divided into TOL (n = 5) and INT (n = 5) groups for which the orthostatic tolerance was similar and lower after bed rest, respectively. For TOL (INT) before bed rest, calf area increases were 2.2 +/- 0.5 (SE) (1.3 +/- 0.4), 3.5 +/- 0.7 (2.3 +/- 0.5), 5.0 +/- 0.9 (3.5 +/- 0.6), 5.6 +/- 0.9 (4.4 +/- 0.6), and 6.4 +/- 1.1 (4.7 +/- 0.6) cm2 for thigh occlusion pressures of 20, 30, 50, 70, and 80 mmHg, respectively. Neither for INT nor for TOL were these results significantly changed by bed rest. These results suggest that other mechanisms than increased LC have to be taken into account to explain the decreased orthostatic tolerance induced by this 13-day bed rest.

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

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

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.

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