Determination of Tissue O2 Tensions by Hollow Visceral Tonometers: Effect of Breathing Enriched O2 Mixtures*

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Abstract
The O2 and CO2 tensions of tissues were estimated by sampling liquids that were instilled in hollow viscera and allowed to remain until they reached gaseous equilibrium with the surrounding tissue. This method proved to be a convenient in vivo system with which to study the gas tensions of some tissues under various circumstances. It was demonstrated that, under normal conditions, the O2 tension of the tissues of the urinary bladder is lower than that of its venous blood and that, during the breathing of enriched O2 mixtures, the difference in O2 tension be-tween tissues and venous blood becomes even greater. These differences are attributed to the diversion of blood flow from capillaries to vessels where gas exchange is limited. The inordinate diversion of blood from the capillary bed of the bladder during breathing of an enriched O2 mixture tended to prevent increases in the O2 tension of the tissues. Implicit in this mechanism which curtails capillary blood flow, however, is the liklihood of impairing the exchange of other substances between blood and tissues.