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Transcapillary fluid shifts in head and neck tissues during and after simulated microgravityTo understand the mechanism, magnitude, and time course of facial puffiness that occurs in microgravity, seven male subjects were tilted 6 degrees head down for 8 hr, and all four Starling transcapillary pressures were directly measured before, during, and after tilt. Head-down tilt (HDT) caused facial edema and a significant elevation of microvascular pressures measured in the lower lip: capillary pressures increased from 27.2 +/- 5 mm Hg pre-HDT to 33.9 +/- 1.7 mm Hg by the end of tilt. Subcutaneous and intramuscular interstitial fluid pressures in the neck also increased as a result of HDT, while interstitial fluid colloid osmotic pressures remained unchanged. Plasma colloid osmotic pressures dropped significantly after 4 hr of HDT, suggesting a transition from fluid filtration to absorption in capillary beds between the heart and feet during HDT. After 4 hr of seated recovery from HDT, microvascular pressures remained significantly elevated by 5 to 8 mm Hg above baseline values, despite a significant HDT diuresis and the orthostatic challenge of an upright, seated posture. During the control (baseline) period, urine output was 46.7 ml/hr; during HDT, it was 126.5 ml/hr. These results indicate that facial edema resulting from HDT is primarily caused by elevated capillary pressures and decreased plasma colloid osmotic pressures. Elevation of cephalic capillary pressures sustained for 4 hr after HDT suggests that there is a compensatory vasodilation to maintain microvascular perfusion. The negativity of interstitial fluid pressures above heart level also has implications for the maintenance of tissue fluid balance in upright posture.
Document ID
19910014391
Acquisition Source
Legacy CDMS
Document Type
Technical Memorandum (TM)
Authors
Parazynski, S. E. (Denver General Hospital CO., United States)
Hargens, Alan R. (NASA Ames Research Center Moffett Field, CA, United States)
Tucker, B. (NASA Ames Research Center Moffett Field, CA, United States)
Aratow, M. (NASA Ames Research Center Moffett Field, CA, United States)
Styf, J. (NASA Ames Research Center Moffett Field, CA, United States)
Crenshaw, A. (NASA Ames Research Center Moffett Field, CA, United States)
Date Acquired
September 6, 2013
Publication Date
April 1, 1991
Subject Category
Aerospace Medicine
Report/Patent Number
NAS 1.15:103847
NASA-TM-103847
A-91096
Accession Number
91N23704
Funding Number(s)
PROJECT: RTOP 199-14-12-04
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

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