Cardiovascular deconditioning during weightlessness simulation and the use of lower body negative pressure as a countermeasure to orthostatic intolerance.
The cardiovascular function is one of the main disturbed by weightlessness: it is particularly affected by the astronaut's return to Earth, where symptoms linked to the cardiovascular deconditioning syndrom appear in the following forms: (1) orthostatic intolerance with its risk of syncope: (2) higher submaximal oxygen consumption for an equivalent work load. Lower Body Negative Pressure (LBNP) is intended to stimulate the venous system of the lower limbs; however, the specific effects of periodical LBNP sessions on the orthostatic intolerance have never been studied. With this objective in mind, 5 volunteers took part in two recent antiorthostatic bedrest experiments for 30 days. In the first experiment 3 subjects were submitted to several sessions of LBNP experiment per day and 2 others were controls; in the second experiment the LBNP group of the 1st one became controls and vice-versa. Two orthostatic investigations were performed: (1) 5 days before the bedrest; (2) at the end of the 30 day bedrest period. The results showed: (1) when the subjects were control, a high orthostatic intolerance post bedrest with 3 syncopes and one presyncopal state during the first minutes of the tilt test; (2) when the subjects were submitted to LBNP sessions, no orthostatic intolerance.
Guell
A
A
Centre National d'Etudes Spatiales, Toulouse, France.
Braak
L
L
Pavy Le Traon
A
A
Gharib
C
C
D000328:Adult; D000337:Aerospace Medicine; D001127:Arginine Vasopressin / Q000378:metabolism; D001510:Bed Rest; D001794:Blood Pressure; D018493:Cardiovascular Deconditioning / Q000502:physiology*; D002395:Catecholamines / Q000378:metabolism; D005069:Evaluation Studies as Topic; D018495:Fluid Shifts; D006339:Heart Rate; D006801:Humans; D007024:Hypotension, Orthostatic / Q000517:prevention & control*; D008150:Lower Body Negative Pressure; D010953:Plasma Volume; D012083:Renin / Q000097:blood; D012084:Renin-Angiotensin System / Q000502:physiology; D018667:Tilt-Table Test; D014667:Vasopressins / Q000378:metabolism; D018544:Weightlessness Countermeasures; D018474:Weightlessness Simulation
D002395:Catecholamines; D014667:Vasopressins; D001127:Arginine Vasopressin; D012083:Renin