ABSTRACT
Oxygen is the substance without which the myocardium cannot function. Prior to considering the fashion in which tracer oxygen transfer occurs from blood to tissue, this chapter examines the manner in which exchange appears ordinarily to be regulated at the level of the capillary bed, in the heart. It also examines what can be learned from interstitial space studies carried out at various levels of coronary flow in the closed-chest anesthetized dog. Labeled albumin, a vascular plasma reference, and labeled sucrose were injected into the coronary ostium and outflow dilution curves were pumped from the coronary sinus. The relative shape change of the log ratio-time plots from the high- to the low-oxygen consumption states indicates that the change in the oxygen tracer curve with demand is principally in the later parts of the curve, rather than across the whole curve.
