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Effect of two hours head-down bedrest on orthostatic tolerance

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Author(s)
Won-Kyun ParkWoon-Jae LyoJae-Hoon BaeDae-Kyu SongE Up Chae
Keimyung Author(s)
Park, Won KyunBae, Jae HoonSong, Dae Kyu
Department
Dept. of Medical Education (의학교육학)
Dept. of Physiology (생리학)
Institute for Medical Science (의과학연구소)
Journal Title
Korean Journal of Physiology
Issued Date
1996
Volume
30
Issue
2
Keyword
Cardiovascular adaptationEpinephrineOrthostatic intolerance
Abstract
This study was carried out to determine the effect of −6∘ head-down bedrest on the cardiovascular and hormonal responses to orthostasis and to evaluate the mechanism of orthostatic intolerance. Ten healthy young men were changed the body position from −6∘ head-down or supine bedrest for 2 hr to 70 ∘ head-up tilt for 20 min. During the bedrest, there were no differences in hemodynamic and hormonal changes between the head-down and the supine positions. However, the tendency of decreased end-diastolic volume and increased cardiac contractility during the later period of 2 hr showed that the cardiovascular adaptation could be accelerated within a relatively short period in the head-down bedrest. During the head-up tilt, presyncopal signs were developed in five subjects of the supine bedrest, and one of the same subjects of the head-down bedrest. In the tolerant subjects, the increase in cardiac contractility and plasma epinephrine level during the bend-up tilt was greater following the head-down bedrest than that following the supine bedrest to compensate for reduced venous return. The intolerant subjects showed the greater decrease in end-diastolic and stroke volume, and the greater increase in heart rate during the head-up tilt than the tolerant subjects. Cardiac contractility and plasma epinephrine level were remarkably increased. However, arterial pressure was not maintained at the level for the appropriate compensation of the reduced venous return. It seems that the tolerance to orthostasis is more effective after the short-term head-down bedrest than after the supine bedrest, and the secretion of epinephrine induces the higher cardiac performance as a compensatory mechanism fur the reduced venous return during the orthostasis following the head-down bedrest than the supine bedrest.
Key words: Cardiovascular adaptation; Epinephrine; Orthostatic intolerance
Keimyung Author(s)(Kor)
박원균
배재훈
송대규
Publisher
School of Medicine
Citation
Won-Kyun Park et al. (1996). Effect of two hours head-down bedrest on orthostatic tolerance. Korean Journal of Physiology, 30(2), 237–247.
Type
Article
ISSN
0372-1582
URI
https://kumel.medlib.dsmc.or.kr/handle/2015.oak/36234
Appears in Collections:
1. School of Medicine (의과대학) > Dept. of Medical Education (의학교육학)
1. School of Medicine (의과대학) > Dept. of Physiology (생리학)
3. Research Institutues (연구소) > Institute for Medical Science (의과학연구소)
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