Distribution of the myocardial tissuePO2 in the rat and the inhomogeneity of the coronary bed

Publisher Website
Google Scholar
Abstract
The structural inhomogeneity of the myocardial capillary bed is simulated by microcirculatory units (MCU's) in a diffusion model. This simulation is based on MCU's in which the arrangement of the capillary ends (concurrent structure, partial and total countercurrent structure, helical structure) as well as the structure and supply parameters are varied. The variation of these parameters is based on own measurements of the intracapillary HbO2 saturation as well as on the following parameters from the literature: frequency distribution of capillary distance and capillary radius, mean capillary length or capillary section length respectively, arterial and mean venousPO2, mean coronary blood flow, mean O2 consumption and diffusion conductivity. The analysis of O2 supply of the normoxic rat heart shows that an O2 diffusion shunt is obligatory except for MCU's with an extremely large capillary distance or with a concurrent capillary structure. Therefore the minimal tissuePO2 lies at the level of the capillary venousPO2 of a MCU. The maximum of the totalPO2 frequency distribution in the normoxic rat myocardium lies at 25±5 mm Hg, i.e. above the mean venousPO2 (20 mm Hg). TissuePO2 values between 0 and 5 mm Hg amount to 0.5%, i.e. they are extremely rare. TissuePO2 values of 0–1 mm Hg represent less than 0.2%.