Precapillary O2 Loss and Arteriovenous O2 Diffusion Shunt are Below Limit of Detection in Myocardium

Abstract
Is venous PO2 an index of tissue PO2, of end capillary PO2, or neither of these because of diffusive shunting from arterioles to venules? To evaluate diffusive shunting and venous PO2 in myocardium we determined hemoglobin (Hb) saturation in arterioles and venules and myoglobin (Mb) saturation in individual subepicardial myocytes by use of a cryomicrospectrophotometric method (Gayeski, 1981, Degner and Gayeski, 1987).