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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
1

The role of the hydrostatic indifferent point in governing splachnic blood pooling during orthostatic stress

Diehl, Ursula Anne 01 May 2011 (has links)
The response of the circulatory system to gravity and hydrostatic forces has been well studied, for example the hydrostatic indifferent point (the location at which pressure does not change with posture) of the venous system has been established to be an important determinant of orthostatic responses and it has been found to be located near the diaphragm. However, the role of the abdomen has been less researched; for example, it appears that the concept that the abdominal compartment may have its own hydrostatic indifferent point has been overlooked. The goal of the present study was to establish the location of the abdominal hydrostatic indifferent point (HIPab) and to test the hypothesis that binding of the lower abdomen would shift the location of the HIPab cranially. Intra-abdominal pressure was measured using a modified wick needle technique in the supine and upright posture before and after binding of the lower abdomen in 7 anesthetized rats. In the unbound condition, the HIPab was located 5.2 ± 0.3 cm caudal to the xyphoid, meaning the hepatic veins were exposed to relatively large negative interstitial pressures during head-up tilt. Binding of the lower abdomen significantly (p <0.05) shifted the HIPab cranially by 1.7 cm. Thus, the relatively caudal location of the HIPab causes a relatively large hepatic transmural pressure owing to the fall in interstitial pressure during upright posture. The cranial shift of the HIPab by binding of the lower abdomen lessens the fall in hepatic extramural pressure and thereby protects the hepatic veins from distension.

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