scholarly journals Lower Body Negative Pressure Counters Internal Jugular Vein Engorgement during Simulated Microgravity

2015 ◽  
Vol 29 (S1) ◽  
Author(s):  
Shannon Baird ◽  
Brandon Macias ◽  
Alan Hargens
Keyword(s):  
Internal Jugular Vein ◽  
Negative Pressure ◽  
Simulated Microgravity ◽  
Jugular Vein ◽  
Lower Body Negative Pressure ◽  
Lower Body

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 Internal Jugular Vein Volume Pulsatility during Head‐Down Tilt and Lower Body Negative Pressure

2021 ◽  
Vol 35 (S1) ◽  
Author(s):  
Andrew Robertson ◽  
Robert Amelard ◽  
Courtney Patterson ◽  
Richard Hughson
Keyword(s):  
Internal Jugular Vein ◽  
Negative Pressure ◽  
Jugular Vein ◽  
Lower Body Negative Pressure ◽  
Lower Body

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.

scholarly journals Nightly Sustained Lower Body Negative Pressure Attenuates Reductions in Cerebral Blood Flow Associated with Simulated Microgravity

2021 ◽  
Vol 35 (S1) ◽  
Author(s):  
Christopher Hearon ◽  
Katrin Dias ◽  
James Macnamara ◽  
John Marshall ◽  
James Leidner ◽  
...  
Keyword(s):  
Blood Flow ◽  
Cerebral Blood Flow ◽  
Negative Pressure ◽  
Simulated Microgravity ◽  
Lower Body Negative Pressure ◽  
Lower Body

Aortic baroreflex control of heart rate after 15 days of simulated microgravity exposure

1994 ◽  
Vol 77 (5) ◽  
pp. 2134-2139 ◽  
Author(s):  
C. G. Crandall ◽  
K. A. Engelke ◽  
V. A. Convertino ◽  
P. B. Raven
Keyword(s):  
Heart Rate ◽  
Mean Arterial Pressure ◽  
Arterial Pressure ◽  
Negative Pressure ◽  
Simulated Microgravity ◽  
Lower Body Negative Pressure ◽  
Lower Body ◽  
Baroreflex Control ◽  
Neck Pressure ◽  
Change In Mean

To determine the effects of simulated microgravity on aortic baroreflex control of heart rate, we exposed seven male subjects (mean age 38 +/- 3 yr) to 15 days of bed rest in the 6 degrees head-down position. The sensitivity of the aortic-cardiac baroreflex was determined during a steady-state phenylephrine-induced increase in mean arterial pressure combined with lower body negative pressure to counteract central venous pressure increases and neck pressure to offset the increased carotid sinus transmural pressure. The aortic-cardiac baroreflex gain was assessed by determining the ratio of the change in heart rate to the change in mean arterial pressure between baseline conditions and aortic baroreceptor-isolated conditions (i.e., phenylephrine + lower body negative pressure + neck pressure stage). Fifteen days of head-down tilt increased the gain of the aortic-cardiac baroreflex (from 0.45 +/- 0.07 to 0.84 +/- 0.18 beats.min-1.mmHg-1; P = 0.03). Reductions in blood volume and/or maximal aerobic capacity may represent the underlying mechanism(s) responsible for increased aortic baroreflex responsiveness after exposure to a ground-based analogue of microgravity.

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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