Performance of pH monitoring systemin vivo

In vivo tests were performed on a pH monitoring system. For this purpose 12 catheters were introduced into the arterial bloodstream of dogs. In the tip of the catheters (6F) a pH-sensitive ISFET sensor and an Ag/AgCl reference electrode were incorporated. Blood pH was varied by ventilation changes and injection of acidic and basic solutions into the animal’s blood. After stabilisation and in vivo calibration the output of the microprocessor-controlled pH monitor was compared with that of an in vitro pH/blood-gas analyser. The average deviation of the monitor output was 0·016 pH over a measurement period of 4 h. The maximum deviation observed was 0·06 pH. The system’s response is fast enough for monitoring changes in blood pH in clinical conditions.