Transcapillary fluid shifts in tissues of the head and neck during and after simulated microgravity

S. E. Parazynski, A. R. Hargens, B. Tucker, M. Aratow, J. Styf, A. Crenshaw

Research output: Contribution to journalArticlepeer-review

87 Scopus citations


To understand the mechanism, magnitude, and time course of facial puffiness that occurs in microgravity, seven male subjects were tilted 6° head-down for 8 h, 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 27.7 ± 1.5 mmHg (mean ± SE) pre-HDT to 33.9 ± 1.7 mmHg by the end of tilt. Subcutaneous and intramuscular interstitial fluid pressures in the neck also increased as a result of HDT, whereas interstitial fluid colloid osmotic pressures remained unchanged. Plasma colloid osmotic pressure dropped significantly by 4 h of HDT (21.5 ± 1.5 mmHg pre-HDT to 18.2 ± 1.9 mmHg), suggesting a transition from fluid filtration to absorption in capillary beds between the heart and feet during HDT. After 4 h of seated recovery from HDT, microvascular pressures in the lip (capillary and venule pressures) remained significantly elevated by 5-8 mmHg above baseline values. During HDT, urine output was 126.5 ml/h compared with 46.7 ml/h during the control baseline period. These results suggest that facial edema resulting from HDT is caused primarily by elevated capillary pressures and decreased plasma colloid osmotic pressures. The negativity of interstitial fluid pressures above heart level also has implications for maintenance of tissue fluid balance in upright posture.

Original languageEnglish (US)
Pages (from-to)2469-2475
Number of pages7
JournalJournal of Applied Physiology
Issue number6
StatePublished - 1991
Externally publishedYes


  • colloid osmotic pressures
  • edema
  • head-down tilt
  • hydrostatic pressure gradient
  • interstitial fluid pressures
  • orthostasis
  • transcapillary pressures

ASJC Scopus subject areas

  • Physiology
  • Physiology (medical)


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