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Leg intravenous pressure during head-up tilt
Jan T Groothuis1, Fleur Poelkens, Constantijn W Wouters
1Radboud Univ. Nijmegen Medical Centre, Dept. of Physiology, Geert Grooteplein-noord 21, 6525 EZ Nijmegen, The Netherlands.
Journal of Applied Physiology (Bethesda, Md. : 1985)
|July 19, 2008
Summary
During orthostatic challenges, leg venous pressure measurements confirm that hydrostatic pressure equally affects leg arterial and venous pressures. This validates assumptions used in calculating leg vascular resistance under changing body positions.
Area of Science:
- Physiology
- Cardiovascular Research
Background:
- Leg vascular resistance calculations assume hydrostatic pressure equally affects arterial and venous pressures during orthostatic challenges.
- The presence of venous valves raises questions about continuous hydrostatic column formation and leg venous pressure accuracy.
Purpose of the Study:
- To measure intravenous pressure in the great saphenous vein during head-up tilt.
- To compare measured leg venous pressure with calculated hydrostatic pressure.
Main Methods:
- 12 healthy individuals underwent 30 and 70 degrees head-up tilt.
- Intravenous pressure in the great saphenous vein was measured.
- Measurements were compared to hydrostatic pressure calculated from the heart to medial malleolus height difference.
Main Results:
- No significant differences were found between measured intravenous pressure and calculated hydrostatic pressure at 30 degrees (47.2 vs. 46.9 mmHg) and 70 degrees (83.9 vs. 85.1 mmHg).
- Steady-state venous pressure was reached within 95 seconds at 30 degrees and 161 seconds at 70 degrees tilt.
Conclusions:
- Measured leg venous pressure closely matches calculated hydrostatic pressure during orthostatic challenges.
- The assumption of equal hydrostatic pressure contribution to leg arterial and venous pressures is supported.
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