Oxygen Measurements in Animals

Abstract

Measurements of oxygen partial pressure (PO 2) and blood oxygen saturation (SO 2) are not equivalent to measurements of blood fl ow, but, on a moment-to-moment basis, the most critical job of the circulation in most organs is the delivery of oxygen. One of the important reasons for studying blood fl ow in the fi rst place is the hope that it will be a surrogate for tissue metabolism and the condition of the tissue, but the ability to understand normal physiology or pathophysiology on the basis of blood fl ow measurements alone is limited. Coupling blood fl ow measurements with blood oxygen saturation measurements provides more information about retinal metabolism, as discussed further below. Tissue oxygen measurements on their own, without simultaneous blood fl ow measurements, show the result of what the circulation provides to the cells. Information about oxygen is therefore critical to an understanding of the performance of the retinal and choroidal circulations under physiological and pathological conditions.