Orthostatic intolerance in 6 degrees head-down tilt and lower body negative pressure loading

Orthostatic intolerance follows actual weightlessness and weightlessness simulated by bed rest. Orthostasis immediately after acute exercise imposes greater cardiovascular stress than orthostasis without prior exercise. We hypothesized that 5 min/day of simulated orthostasis [supine lower body negative pressure (LBNP)] immediately following LBNP exercise maintains orthostatic tolerance during bed rest. Identical twins (14 women, 16 men) underwent 30 days of 6° head-down tilt bed rest. One of each pair was randomly selected as a control, and their sibling performed 40 min/day of treadmill exercise while supine in 53 mmHg (SD 4) [7.05 kPa (SD 0.50)] LBNP. LBNP continued for 5 min after exercise stopped. Head-up tilt at 60° plus graded LBNP assessed orthostatic tolerance before and after bed rest. Hemodynamic measurements accompanied these tests. Bed rest decreased orthostatic tolerance time to a greater extent in control [34% (SD 10)] than in countermeasure subjects [13% (SD 20); P < 0.004]. Controls exhibited cardiac stroke volume reduction and relative cardioacceleration typically seen after bed rest, yet no such changes occurred in the countermeasure group. These findings demonstrate that 40 min/day of supine LBNP treadmill exercise followed immediately by 5 min of resting LBNP attenuates, but does not fully prevent, the orthostatic intolerance associated with 30 days of bed rest. We speculate that longer postexercise LBNP may improve results. Together with our earlier related studies, these ground-based results support spaceflight evaluation of postexercise orthostatic stress as a time-efficient countermeasure against postflight orthostatic intolerance.

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Use of Lower Body Negative Pressure to Counter Symptoms of Orthostatic Intolerance in Patients, Bed Rest Subjects, and Astronauts

The Journal of Clinical Pharmacology ◽

10.1002/j.1552-4604.1993.tb01944.x ◽

1993 ◽

Vol 33 (11) ◽

pp. 1071-1085 ◽

Cited By ~ 16

Author(s):

Claire M. Lathers ◽

John B. Charles

Keyword(s):

Negative Pressure ◽

Orthostatic Intolerance ◽

Lower Body Negative Pressure ◽

Bed Rest ◽

Lower Body

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Lower-body negative pressure/ergometer exercise in bed rest: Effects on female orthostatic tolerance

Journal of Novel Physiotherapy and Rehabilitation ◽

10.29328/journal.jnpr.1001036 ◽

2020 ◽

Vol 4 (2) ◽

pp. 040-048

Author(s):

Wang Linjie ◽

Li Zhili ◽

Tan Cheng ◽

Wang Huijuan ◽

Zhou Xiangjie ◽

...

Keyword(s):

Negative Pressure ◽

Orthostatic Intolerance ◽

Lower Body Negative Pressure ◽

Bed Rest ◽

Tilt Test ◽

Control Group ◽

Orthostatic Tolerance ◽

Lower Body ◽

Interval Exercise ◽

Ergometer Exercise

Introduction: Alternatively using gradient lower-body negative pressure (LBNP) and ergometer exercise (LBNP + ergo) under a flight schedule framework was explored to detect its orthostatic capacity maintenance effects in female subjects after 15 days of -6° head-down bed rest (HDBR). Methods: Twenty-two female university students were divided into a control group (n = 8), an LBNP group (n = 7), and an LBNP + ergo group (n = 7). Ergometer exercise consisted of an interval exercise protocol with 2 min intervals alternating between 41% and 70% VO2max. Gradient LBNP was decompressed in 10 mm Hg intervals to -40 mmHg every 5 min. intermittent ergometer exercise and LBNP were alternatively performed. Tilt test was performed 2 days before HDBR (R-2), on the day of HDBR termination (R+1), and 5 days after HDBR (R+5). Results: Fifty percent of the participants (11/22) did not pass the tilt test on R+1. The orthostatic tolerance time decreased from 20 to 16.1 ± 2.1 min in the control group, to 10.0 ± 2.7 min in the LBNP group (p = 0.01) and to 16.3 ± 2.0 min in the LBNP + ergo group. The HRs and BPs were at similar level among three groups during tilt test on different test days. Compared with the control group, the LBNP + ergo group had higher SV and CO percentage changes at R+1(p < 0.023) and R+5 (p < 0.00001) during the tilt test. Conclusion: LBNP combined with ergometer exercises fails to prevent orthostatic intolerance but it induced some positive hemodynamic changes during tilt test after 15 days HDBR.

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Doppler measurement of cerebral and lower limb flow during a lower body negative pressure test for predicting orthostatic intolerance.

Journal of Ultrasound in Medicine ◽

10.7863/jum.2001.20.11.1207 ◽

2001 ◽

Vol 20 (11) ◽

pp. 1207-1217 ◽

Cited By ~ 6

Author(s):

N Tobal ◽

J Roumy ◽

S Herault ◽

G Fomina ◽

P Arbeille

Keyword(s):

Negative Pressure ◽

Lower Limb ◽

Orthostatic Intolerance ◽

Lower Body Negative Pressure ◽

Lower Body ◽

Doppler Measurement ◽

Pressure Test ◽

Negative Pressure Test

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Development of Lower Body Negative Pressure as a Countermeasure for Orthostatic Intolerance

The Journal of Clinical Pharmacology ◽

10.1002/j.1552-4604.1991.tb03644.x ◽

1991 ◽

Vol 31 (10) ◽

pp. 888-892 ◽

Cited By ~ 16

Author(s):

Suzanne M. Fortney

Keyword(s):

Negative Pressure ◽

Orthostatic Intolerance ◽

Lower Body Negative Pressure ◽

Lower Body

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Cardiovascular Responses to Maximal Graded and Acute Lower Body Negative Pressure

Journal of Aging and Physical Activity ◽

10.1123/japa.18.1.27 ◽

2010 ◽

Vol 18 (1) ◽

pp. 27-42 ◽

Cited By ~ 1

Author(s):

Juliane P. Hernandez ◽

Kristin Roever ◽

Tonya Seed

Keyword(s):

Heart Rate ◽

Negative Pressure ◽

Orthostatic Intolerance ◽

Lower Body Negative Pressure ◽

Cardiovascular Responses ◽

Tolerance Index ◽

Lower Body ◽

Age Related ◽

Per Se ◽

Blood Pressure Responses

This investigation attempted to determine whether heart-rate and blood pressure responses to maximal acute lower body negative pressure (LBNP) are exacerbated compared with maximal graded LBNP in active older (n= 9, 70 ± 7 yr) and endurance-trained younger (n= 10, 23 ± 3 yr) individuals. Heart rate increased earlier during graded LBNP in the younger group (−40 mm Hg vs. tolerance) and was significantly higher than that of the older adults at the point of tolerance. Mean arterial pressure (MAP) decreased more in the older than the younger individuals during graded LBNP. LBNP-tolerance index was significantly greater in the younger group (309 ± 52 vs. 255.6 ± 48 mm Hg/min). Acute doses of LBNP elicited slower heart-rate responses in the older group. Despite these age-related differences, MAP responses were not different between groups with acute LBNP, so age per se does not appear to predispose individuals to orthostatic intolerance.

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Modeling of Orthostatic Intolerance During Lower Body Negative Pressure

ASME 2010 Summer Bioengineering Conference, Parts A and B ◽

10.1115/sbc2010-19053 ◽

2010 ◽

Author(s):

Karen E. Etter ◽

M. Keith Sharp

Keyword(s):

Negative Pressure ◽

Orthostatic Intolerance ◽

Lower Body Negative Pressure ◽

Poor Performance ◽

Lower Body ◽

Capillary Filtration ◽

Arterial Blood ◽

Long Duration ◽

Head Up Tilt ◽

The Many

Postflight orthostatic intolerance (POI) afflicts a significant fraction of male astronauts and nearly all female astronauts when they first stand on Earth after spaceflight. Symptoms include dizziness and fainting, which can impact their abilities to perform critical tasks during the post-landing period. On the Moon or Mars, poor performance or accidents resulting from POI may have potentially catastrophic consequences due to the more hazardous conditions and lack of medical facilities. In addition, the long duration flights necessary to reach Mars may elicit adaptations that increase the risk of POI. Of the many factors that may influence POI, one of the few that may explain the gradual decline in arterial blood pressure experienced by many subjects during stand tests is the loss of blood volume by capillary filtration. Previous simulations suggest that elevated capillary filtration rates distinguish nonfinishers from finishers of stand tests [1, 2]. In this investigation, further computer modeling was undertaken to compare modeled orthostatic response to that of volunteers during graded orthostatic stress (GOS) involving head up tilt (HUT) and lower body negative pressure (LBNP), which reliably produces presyncope and is a candidate training countermeasure for preventing POI.

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