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Altered baroreflex control of forearm vascular resistance during simulated microgravityReflex peripheral vasoconstriction induced by activation of cardiopulmonary baroreceptors in response to reduced central venous pressure (CVP) is a basic mechanism for elevating systemic vascular resistance and defending arterial blood pressure during orthostatically-induced reductions in cardiac filling and output. The sensitivity of the cardiopulmonary baroreflex response [defined as the slope of the relationship between changes in forearm vascular resistance (FVR) and CVP] and the resultant vasoconstriction are closely and inversely associated with the amount of circulating blood volume. Thus, a high-gain FVR response will be elicited by a hypovolemic state. Exposure to microgravity during spaceflight results in reduced plasma volume. It is therefore reasonable to expect that the FVR response to cardiopulmonary baroreceptor unloading would be accentuated following adaptation to microgravity. Such data could provide better insight about the physiological mechanisms underlying alterations in blood pressure control following spaceflight. We therefore exposed eleven men to 6 degrees head-down bedrest for 7 days and measured specific hemodynamic responses to low levels of the lower body negative pressure to determine if there are alterations in cardiopulmonary baroreceptor stimulus-FVR reflex response relationship during prolonged exposure to an analog of microgravity.
Document ID
20040089964
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Convertino, V. A.
(Laboratory for Aerospace Cardiovascular Research Brooks Air Force Base, TX 78235, United States)
Doerr, D. F.
Vernikos, J.
Date Acquired
August 21, 2013
Publication Date
May 1, 1994
Publication Information
Publication: Journal of gravitational physiology : a journal of the International Society for Gravitational Physiology
Volume: 1
Issue: 1
ISSN: 1077-9248
Subject Category
Aerospace Medicine
Distribution Limits
Public
Copyright
Other
Keywords
NASA Program Space Physiology and Countermeasures
NASA Discipline Cardiopulmonary
NASA Discipline Number 14-10
Non-NASA Center
NASA Center ARC

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