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.

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.

Thigh Cuff Effects on Venous Flow Redistribution During 4 Days in Dry Immersion

2020 ◽  
Vol 91 (9) ◽  
pp. 697-702
Author(s):  
Philippe Arbeille ◽  
Danielle Greaves ◽  
Laurent Guillon ◽  
Stephane Besnard
Keyword(s):  
Left Ventricle ◽  
Ejection Fraction ◽  
Jugular Vein ◽  
Residual Effect ◽  
Cerebral Vein ◽  
Fluid Shift ◽  
Venous Flow ◽  
Additional Measure ◽  
Dry Immersion ◽  
Vein Diameter

PURPOSE: The objective was to quantify the venous redistribution during a 4-d dry immersion (DI) and evaluate the effect of thigh cuffs.METHODS: The study included nine control (Co) and nine subjects wearing thigh cuffs during the daytime (CU). Ultrasound measures were performed Pre-DI, on day 4 AM (D4 AM) and D4 PM: left ventricle stroke volume and ejection fraction (SV, EF), jugular vein volume (JVvol), portal vein diameter (PV), and middle cerebral vein velocity (MCVv). An additional measure of JVvol was performed on Day 1 after 2 h in DI.RESULTS: After 2 h in DI, JVvol increased significantly from Pre in both groups, but increased more in the Co compared to the CU subjects (Co: 0.27 0.15 cm3 to 0.94 0.22 cm3; CU: 0.32 0.13 cm3 to 0.64 0.32 cm3). At D4 AM, SV and EF decreased from Pre (SV: 111 23 cm3 to 93 24 cm3; EF: 0.66 0.07 to 0.62 0.07). JVvol was slightly increased (Co: 0.47 0.22 cm3 CU: 0.35 014 cm3). MCVv and PV remained unchanged from Pre-DI. No difference was found between the two groups for any of the parameters measured. From D4 AM to PM, no significant change was observed for any parameter.CONCLUSION: The results confirm that DI induces, during the first 2-3 h, a significant cephalic fluid shift as observed in spaceflight. During this early phase, the thigh cuffs reduced the amplitude of the fluid shift toward the head, but after 4 d in DI there was only a slight memory (residual) effect of DI on the jugular volume and no residual effect of the thigh cuffs.Arbeille P, Greaves D, Guillon L, Besnard S. Thigh cuff effects on venous flow redistribution during 4 days in dry immersion. Aerosp Med Hum Perform. 2020; 91(9):697702.

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.

Abstract 14436: Nightly Lower Body Negative Pressure Redistributes Blood Volume and Prevents Maladaptive Vascular Remodeling Induced by Microgravity

Circulation ◽  
2020 ◽  
Vol 142 (Suppl_3) ◽  
Author(s):  
Katrin A Dias ◽  
Christopher M Hearon ◽  
Gautam Babu ◽  
John E Marshall ◽  
James P Macnamara ◽  
...  
Keyword(s):  
Blood Volume ◽  
Negative Pressure ◽  
Vascular Remodeling ◽  
Lower Body Negative Pressure ◽  
Venous Pressure ◽  
Bed Rest ◽  
Lower Body ◽  
Long Duration ◽  
Sustained Reduction ◽  
Area And Volume

Introduction: During space flight and ground based simulations of microgravity, transmural distending pressure increases in resistance vessels above the level of the heart, causing maladaptive vascular remodeling over time. Lower body negative pressure (LBNP) mimics gravity by redistributing blood volume and reinstating hydrostatic gradients, and may preserve vascular structures above the heart while in microgravity. Methods: Ten healthy subjects (5 female, 29 ± 9 years) completed three days of supine (0°) bed rest with and without eight hours of nightly LBNP (-20mmHg) in a randomized, crossover design. Area and volume of the choroid, a highly vascularized layer of the eye sensitive to changes in hydrostatic gradients, were assessed using optical coherence tomography on the first and last day of bed rest. Central venous pressure (CVP) was measured during spontaneous breathing with a peripherally inserted central catheter. Results: CVP increased significantly from the seated to supine position (+9.1 ± 2.4mmHg, P < 0.001), leading to choroid engorgement over three days of supine bed rest (choroid area: +0.09 mm 2 95% CI 0.04 to 0.13, P = 0.0014; choroid volume: +0.37 mm 3 95% CI 0.19 to 0.55, P = 0.0011). Nightly LBNP caused a sustained reduction in supine CVP (5.7 ± 2.2mmHg to 1.2 ± 1.4mmHg, P < 0.001), indicating effective redistribution of blood volume and significantly attenuated the increase in choroid area (3.5% control vs. 0.9% LBNP, P = 0.0164) and volume (3.8% control vs. 1.8% LBNP, P = 0.0040) compared to control (Figure). Conclusions: Nightly LBNP caused caudal redistribution of blood volume that partially reinstated hydrostatic gradients and mitigated the increase in choroid area and volume by 74% and 53%, respectively. These findings illustrate that normalizing transmural distending pressures during simulated microgravity preserves vascularized structures above the level of the heart and may prevent adverse remodeling during long duration spaceflight.

Short-term variability of blood pressure: effects of lower-body negative pressure and long-duration bed rest

2012 ◽  
Vol 303 (1) ◽  
pp. R77-R85 ◽  
Author(s):  
Federico Aletti ◽  
Manuela Ferrario ◽  
Da Xu ◽  
Danielle K. Greaves ◽  
J. Kevin Shoemaker ◽  
...  
Keyword(s):  
Blood Pressure ◽  
Negative Pressure ◽  
Lower Body Negative Pressure ◽  
Venous Pressure ◽  
Bed Rest ◽  
Pressure Effects ◽  
Lower Body ◽  
Arterial Baroreflex ◽  
Long Duration ◽  
Cardiopulmonary Baroreflex

Mild lower-body negative pressure (LBNP) has been utilized to selectively unload cardiopulmonary baroreceptors, but there is evidence that arterial baroreceptors can be transiently unloaded after the onset of mild LBNP. In this paper, a black box mathematical model for the prediction of diastolic blood pressure (DBP) variability from multiple inputs (systolic blood pressure, R-R interval duration, and central venous pressure) was applied to interpret the dynamics of blood pressure maintenance under the challenge of LBNP and in long-duration, head-down bed rest (HDBR). Hemodynamic recordings from seven participants in the WISE (Women's International Space Simulation for Exploration) Study collected during an experiment of incremental LBNP (−10 mmHg, −20 mmHg, −30 mmHg) were analyzed before and on day 50 of a 60-day-long HDBR campaign. Autoregressive spectral analysis focused on low-frequency (LF, ∼0.1 Hz) oscillations of DBP, which are related to fluctuations in vascular resistance due to sympathetic and baroreflex regulation of vasomotor tone. The arterial baroreflex-related component explained 49 ± 13% of LF variability of DBP in spontaneous conditions, and 89 ± 9% ( P < 0.05) on day 50 of HDBR, while the cardiopulmonary baroreflex component explained 17 ± 9% and 12 ± 4%, respectively. The arterial baroreflex-related variability was significantly increased in bed rest also for LBNP equal to −20 and −30 mmHg. The proposed technique provided a model interpretation of the proportional effect of arterial baroreflex vs. cardiopulmonary baroreflex-mediated components of blood pressure control and showed that arterial baroreflex was the main player in the mediation of DBP variability. Data during bed rest suggested that cardiopulmonary baroreflex-related effects are blunted and that blood pressure maintenance in the presence of an orthostatic stimulus relies mostly on arterial control.

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.

Sign in / Sign up

Export Citation Format

Share Document