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.

Daily generation of a footward fluid shift attenuates ocular changes associated with head-down tilt bed rest

2020 ◽  
Vol 129 (5) ◽  
pp. 1220-1231
Author(s):  
Justin S. Lawley ◽  
Gautam Babu ◽  
Sylvan L. J. E. Janssen ◽  
Lonnie G. Petersen ◽  
Christopher M. Hearon ◽  
...  
Keyword(s):  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Bed Rest ◽  
Lower Body ◽  
Fluid Shift ◽  
Gravitational Gradients ◽  
Ocular Changes

Choroid measurements appear to be sensitive to changes in gravitational gradients, as well as periods of head-down tilt (HDT) bed rest, suggesting that they are potential indicators of early ocular remodeling and could serve to evaluate the efficacy of countermeasures for SANS. Eight hours of lower body negative pressure (LBNP) daily attenuates the choroid expansion associated with 3 days of strict −6° HDT bed rest, indicating that LBNP may be an effective countermeasure for SANS.

Lower-body negative pressure restores leg bone microvascular flow to supine levels during head-down tilt

2015 ◽  
Vol 119 (2) ◽  
pp. 101-109 ◽  
Author(s):  
Jamila H. Siamwala ◽  
Paul C. Lee ◽  
Brandon R. Macias ◽  
Alan R. Hargens
Keyword(s):  
Negative Pressure ◽  
Repeated Measures ◽  
Simulated Microgravity ◽  
Near Infrared ◽  
Lower Body Negative Pressure ◽  
Lower Body ◽  
Calf Circumference ◽  
Fluid Shift ◽  
Microvascular Flow ◽  
Flow Head

Skeletal unloading and cephalic fluid shifts in microgravity may alter the bone microvascular flow and may be associated with the 1-2% bone loss per month during spaceflight. The purpose of this study was to determine if lower-body negative pressure (LBNP) can prevent microgravity-induced alterations of tibial microvascular flow. Head-down tilt (HDT) simulates the cephalad fluid shift and microvascular flow responses that may occur in microgravity. We hypothesized that LBNP prevents HDT-induced increases in tibial microvascular flow. Tibial bone microvascular flow, oxygenation, and calf circumference were measured during 5 min sitting, 5 min supine, 5 min 15° HDT, and 10 min 15° HDT with 25 mmHg LBNP using photoplethysmography (PPG), near-infrared spectroscopy (NIRS), and strain-gauge plethysmography (SGP). Measurements were made simultaneously. Tibial microvascular flow increased by 36% with 5 min 15° HDT [2.2 ± 1.1 V; repeated-measures ANOVA (RMANOVA) P < 0.0001] from supine (1.4 ± 0.8 V). After 10 min of LBNP in the 15° HDT position, tibial microvascular flow returned to supine levels (1.1 ± 0.5 V; RMANOVA P < 0.001). Tibial oxygenation did not change significantly during sitting, supine, HDT, or HDT with LBNP. However, calf circumference decreased with 5 min 15° HDT (−0.7 ± 0.4 V; RMANOVA P < 0.0001) from supine (−0.5 ± 0.4 V). However, with LBNP calf circumference returned to supine levels (−0.4 ± 0.1 V; RMANOVA P = 0.002). These data establish that simulated microgravity increases tibial microvascular flow and LBNP prevents these increases. The results suggest that LBNP may provide a suitable countermeasure to normalize the bone microvascular flow during spaceflight.

LLower body negative pressure reduces jugular and portal vein volumes, and counteracts the cerebral vein velocity elevation during long-duration spaceflight

2021 ◽  
Author(s):  
Philippe Arbeille ◽  
Kathryn A. Zuj ◽  
Brandon R. Macias ◽  
Douglas J. Ebert ◽  
Steven S. Laurie ◽  
...  
Keyword(s):  
Portal Vein ◽  
Negative Pressure ◽  
Jugular Vein ◽  
Lower Body Negative Pressure ◽  
Venous Blood ◽  
Upper Body ◽  
Cerebral Vein ◽  
Fluid Shift ◽  
Cross Sectional ◽  
Long Duration

Purpose: Cephalad fluid shifts in space have been hypothesized to cause the spaceflight-associated neuro-ocular syndrome (SANS) by increasing the intracranial-ocular translaminal pressure gradient. Lower body negative pressure (LBNP) can be used to shift upper-body blood and other fluids towards the legs during spaceflight. We hypothesized that microgravity would increase jugular vein volume (JVvol), portal vein cross-sectional area (PV), and intracranial venous blood velocity (MCV) and that 25mmHg LBNP application would return these variables towards preflight levels. Methods: Data were collected from 14 subjects (11 male) before and during long-duration ISS spaceflights. Ultrasound measures of JVvol, PV, and MCV were acquired while seated and supine before flight and early during spaceflight at days 45 (FD45) and late (FD150) with and without LBNP. Results: JVvol increased from preflight supine and seated postures (46 ± 48 % and 646 ± 595 % on FD45 and 43 ± 43 % and 702 ± 631 % on FD150, p<0.05), MCV increased from preflight supine 44 ± 31 % on FD45 and 115 ± 116 % on FD150 (p<0.05), PV increased from preflight supine and seated (51 ± 56 % and 100 ± 74 %) on FD150 (p<0.05). Inflight 25mmHg LBNP restored JVvol, and MCV to preflight supine and PV to preflight seated level. Conclusions: Elevated JVvol confirms the sustained neck-head blood engorgement inflight, while increased PV area supports the fluid shift at the splanchnic level. Also, MCV increased potentially due to reduced lumen diameter. LBNP, returning variables to preflight levels, may be an effective countermeasure.

scholarly journals Lower-body negative pressure decreases noninvasively measured intracranial pressure and internal jugular vein cross-sectional area during head-down tilt

2017 ◽  
Vol 123 (1) ◽  
pp. 260-266 ◽  
Author(s):  
William Watkins ◽  
Alan R. Hargens ◽  
Shannon Seidl ◽  
Erika Marie Clary ◽  
Brandon R. Macias
Keyword(s):  
Intracranial Pressure ◽  
Tympanic Membrane ◽  
Internal Jugular Vein ◽  
Negative Pressure ◽  
Jugular Vein ◽  
Lower Body Negative Pressure ◽  
Cross Sectional Area ◽  
Lower Body ◽  
Sectional Area ◽  
Cross Sectional

Long-term spaceflight induces a near visual acuity change in ~50% of astronauts. In some crew members, postflight cerebrospinal fluid (CSF) opening pressures by lumbar puncture are as high as 20.9 mmHg; these members demonstrated optic disc edema. CSF communicates through the cochlear aqueduct to affect perilymphatic pressure and tympanic membrane motion. We hypothesized that 50 mmHg of lower-body negative pressure (LBNP) during 15° head-down tilt (HDT) would mitigate elevations in internal jugular vein cross-sectional area (IJV CSA) and intracranial pressure (ICP). Fifteen healthy adult volunteers were positioned in sitting (5 min), supine (5 min), 15° HDT (5 min), and 15° HDT with LBNP (10 min) postures for data collection. Evoked tympanic membrane displacements (TMD) quantified ICP noninvasively. IJV CSA was measured using standard ultrasound techniques. ICP and IJV CSA increased significantly from the seated upright to the 15° HDT posture ( P < 0.05), and LBNP mitigated these increases. LBNP at 25 mmHg reduced ICP during HDT (TMD of 322.13 ± 419.17 nl) to 232.38 ± 445.85 nl, and at 50 mmHg ICP was reduced further to TMD of 199.76 ± 429.69 nl. In addition, 50 mmHg LBNP significantly reduced IJV CSA (1.50 ± 0.33 cm2) during 15° HDT to 0.83 ± 0.42 cm2. LBNP counteracts the headward fluid shift elevation of ICP and IJV CSA experienced during microgravity as simulated by15° HDT. These data provide quantitative evidence that LBNP shifts cephalic fluid to the lower body, reducing IJV CSA and ICP. NEW & NOTEWORTHY The current study provides new evidence that 25 or 50 mmHg of lower body negative pressure reduces jugular venous pooling and intracranial pressure during simulated microgravity. Therefore, spaceflight countermeasures that sequester fluid to the lower body may mitigate cephalic venous congestion and vision impairment.

The Transplanted Human Kidney Does Not Achieve Functional Reinnervation

1994 ◽  
Vol 87 (1) ◽  
pp. 13-20 ◽  
Author(s):  
Jesper Melchior Hansen ◽  
Ulrik Abildgaard ◽  
Niels Fogh-Andersen ◽  
Inge-Lis Kanstrup ◽  
Palle Bratholm ◽  
...  
Keyword(s):  
Negative Pressure ◽  
Filtration Rate ◽  
Lower Body Negative Pressure ◽  
Renal Plasma Flow ◽  
Baseline Period ◽  
Lower Body ◽  
Transplant Recipients ◽  
Noradrenaline Infusion ◽  
Control Subjects

1. Previous histological studies have demonstrated partial reinnervation of the human transplanted kidney. However, it remains unknown whether this reinnervation is of any functional significance. 2. The effects of noradrenaline infusion (2 μgh−1kg−1) and lower body negative pressure (−27 mmHg) on renal haemodynamics, sodium excretion and tubular function were investigated in 25 renal transplant recipients and 10 normal subjects. Sixteen of the transplant recipients had all been transplanted for more than 27 months, and nine had all been transplanted for less than 2 months. 3. After an overnight fast, the subjects were water-loaded, and clearance studies were performed with a 1 h baseline period, a 1 h period with noradrenaline infusion, another 1 h baseline period, and a final 1 h period with lower body negative pressure. 4. During noradrenaline infusion the relative decrease in effective renal plasma flow, glomerular filtration rate and clearance of lithium and sodium was significantly more pronounced in the long-term transplanted patients than in the control subjects. 5. Lower body negative pressure only depressed the glomerular filtration rate significantly in the control subjects. Further, the relative decrease in effective renal plasma flow and clearance of lithium and sodium was significantly greater in the control subjects than in the two groups of transplanted patients. 6. The present study thus demonstrated that in short- and long-term transplanted kidneys in man, supersensitivity to circulating noradrenaline and an inadequate response to lower body negative pressure was present. This strongly suggests that the human transplanted kidney remains functionally denervated.

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.

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

1988 ◽  
Vol 65 (4) ◽  
pp. 1752-1756 ◽  
Author(s):  
M. A. Frey ◽  
G. W. Hoffler
Keyword(s):  
Heart Rate ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Peripheral Resistance ◽  
Older Men ◽  
Lower Body ◽  
Fluid Shift ◽  
Arterial Blood ◽  
Age Related ◽  
Older Subjects

Responses of 21 women and 29 men (29-56 yr of age) to -50 Torr lower body negative pressure (LBNP) were examined for differences due to sex or age. Responses to LBNP were normal, including fluid shift from thorax to lower body, increased heart rate and peripheral resistance, and decreased stroke volume, cardiac output, and Heather index of ventricular function. Mean arterial blood pressure did not change. Comparison of responses of the women to responses of an age-matched subset of the men (n = 26) indicated the men had larger relative increases in calf circumference and greater increases in peripheral resistance during LBNP than the women, whereas the women experienced greater increases in thoracic impedance and heart rate. Analyses of responses of the 29 men for age-related differences indicated older subjects had greater increases in peripheral resistance and less heart rate elevation in response to LBNP (P less than 0.05 for all differences, except sex-related heart rate difference, where P less than 0.10). Based on these data and the data of other investigators, we hypothesize the age-related circulatory differences in response to LBNP are due to a reduction in vagal response and a switch to predominant sympathetic nervous system influence in older men. We cannot exclude the possibility that diminished responsiveness in the afferent arm of the baroreceptor reflex also plays a role in the attenuated heart rate response of older men to LBNP.

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