In vivo performance of the pH tissue electrode during acute acid-base changes in the dog

The ROCHE tissue pH-electrode was tested in acute animal experiments under various metabolic conditions. In anesthetized dogs an electrode was placed in the subcutaneous tissue of the scalp, neck, and axilla. Simultaneous with the continuous measurement of tissue pH, the overall acid-base balance of the animal was measured discontinuously at 5-min intervals by means of indwelling arterial and venous catheters. Various forms of acidosis and hypoxia were produced in the experimental animal and the sensitivity of the electrodes in relation to their site was tested. A high correlation between the continuously measured tissue pH values and the corresponding arterial and venous actual blood pH values were found in the physiologic pH range. With acute changes of acid-base balance no correlation could be found in the acidotic range.