CONTINUOUS MEASUREMENTS OF INTRAVASCULAR OXYGEN TENSION IN NORMAL ADULTS*

Abstract

Arterial and venous oxygen tensions were measured with the continuously-recording oxygen electrode adapted by Tsao and Vadnay. The arterial oxygen tension in normal adults fluctuates over a range of 10 to 20 mm Hg, which is directly related to changes in the respiratory pattern. Any change in respiration will be reflected in a change in arterial oxygen tension, and the effects of hyperventilation and breath holding are considerable. Thus in normal adults there is a constant varying arterial oxygen tension of significant degree, and a single sample analysis may not represent a mean value for the individual. Oxygen (50% and 100%) given by face mask, causes a rise in brachial arterial tension within 4 to 12 seconds and equilibrium is reached in 1 to 1. 5 minutes. With discontinuance of oxygen administration, return of arterial oxygen tension to previous levels occurs in 2 to 4 minutes. With 100% oxygen breathing, antecubital venous oxygen tension changes in an unpredictable fashion. Four responses noted were: slight elevation in venous oxygen tension; little change except for an occasional spike; virtually no change unless carried over a prolonged period; no change with oxygen administration, but elevations of venous oxygen tension for a few minutes after discontinuance of 100% oxygen breathing.