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Oxygen transport in vasculature

Oxygen is supplied to the avascular region of arterial wall by diffusion from the luminal blood and from the vasa vasorum. The abnormalities in this supply of oxygen are linked with the conditions of hypoxia or hyperoxia, which accelerates the human atherosclerosis by initiating a chain reaction of self sustaining metabolic abnormalities. The changes in the supply of the oxygen to the avascular arterial wall have always been a subject of research over the period of past few decades. This research aims at finding the oxygen concentration distribution in normal artery as well as its pathophysiologic counterpart. This includes i) various degrees of area occlusion representing a wide range of stenoses for ii) flow rates varying from basal to hyperemic conditions, and iii) effect of the viscosity changes due to hematocrit (Hct) variations. The coupled flow and oxygen transport equations in luminal blood flow and oxygen consuming arterial wall are solved and validated with previous studies.

Figure 1 shows the contour plot of the oxygen concentration distal to a moderate occlusion in a stenotic artery at basal flow condition. In the region immediately distal to stenosis closed concentric iso-contours of oxygen concentration similar to the flow streamlines are observed. This is due to the flow separation downstream of the stenosis. The oxygen transport across the concentration contours occurs only by diffusion.

 

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Fig 1. Contours of oxygen concentration distal to stenosis.

 

Figure 2 shows the effect of hematocrit (Hct) variations on the radial pO2 profile for the basal flow (50 ml/min) and the hyperemic flow (180 ml/min). Hct variations from 25% to 65% cause the pO2 in the medial region to drop by ~ 20% for the basal flow (arrow in Fig. 2A), while to increase by ~ 13% for the hyperemic flow (arrow in Fig. 2B).  Thus, current results with the moderate stenosed artery indicate that reducing Hct might be favorable in terms of increasing O2 flux and pO2, min in the medial region of the wall for the basal flow, while higher Hct is advantageous for the hyperemic flow beyond the diverging section.

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Fig 2. Radial pO2 variation in the recirculation region for the basal flow (A) and the hyperemic flow (B).

 

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by zopeown last modified 2015-05-26 12:05