Studies of Oxygen in the Venous Blood

Abstract

1. Determinations of the oxygen content and the oxygen unsaturation of the venous blood have been performed on patients with varying amounts of hemoglobin. 2. The oxygen unsaturation of the venous blood is independent of the oxygen capacity, unless the latter is reduced below the normal value for oxygen unsaturation (about 5 volumes per cent). In a polycythemic patient, for example, with 33.4 volumes per cent oxygen capacity (181 per cent hemoglobin), the venous oxygen content was. 28 volumes per cent, giving an unsaturation of 5.4 volumes per cent. Similarly, in an anemic patient with only 6.7 volumes per cent oxygen capacity (36 per cent hemoglobin), the venous oxygen was 1.5, giving an unsaturation of 5.2 volumes per cent. This means that the tissues extract from the blood all the oxygen they need with apparently equal readiness, regardless of whether the extraction leaves a great oxygen reserve in the blood as in polycythemia, or practically no reserve as in anemia. 3. The results seem to show that the resting organism does not increase its circulation until all the reserve oxygen is used. This means that the resting anemic organism does not need or use any compensation for its anemia until the hemoglobin has sunk below 30 per cent. Below that value the organism increases the blood flow in order to secure to the tissues the normal amount of oxygen.

Studies on Cyanosis

“…In one case (Determination 1) the venous blood contained no oxygen. The importance of this fact is discussed in a previous paper (21). Table III presents the values of the oxygen unsaturation 4 arranged according to decreasing values.…”

“…In a previous publication(21) this is termed rest oxygen or reserve oxygen of the blood, analogous to the reserve force of the heart muscles.4 That is, the difference between the total oxygen capacity of the blood and the venous oxygen 5. In several other unpublished determinations of oxygen unsaturation the same holds true.…”

A broad diversity in oxygen affinity to haemoglobin

“…The low oxygen carrying capacity of the blood in anemia is compensated by an increased concentration of 2,3-Bisphosphoglycerate (2,3-BPG, alias 2,3-DPG), an allosteric effector promoting the offloading of oxygen to the tissues by lowering Hb-O 2 affinity 3 . Thus, O 2 ER can adapt to meet VO 2 4 and here, the ability to release the required amount of oxygen to the tissue is of major significance.…”