IN-VITRO EVALUATION OF INTRAGASTRIC PCO2 MEASUREMENT BY AIR TONOMETRY

Objective. To assess the in vitro performance of a new device, the Ton ocap(R), for semi-continuous air tonometry of regional PCO2 in the gas trointestinal tract. Methods. The tonometer consists of an air filled balloon-tipped catheter, connected to a prototype Tonocap(R) system. T he tonometer was placed in saline baths at steady-state PCO2's ranging from 0 to 105 torr, to evaluate bias, precision and reproducibility t o PCO2 measurements. The response time was defined as the time needed to detect 95% of an instantaneous change in bath PCO2. Results. The bi as of the PCO2 measurement (mean +/- SD) was -2 +/- 2% and reproducibi lity (coefficient of variation) was 2 +/- 1%. The response time was 19 +/- 2 min. Conclusions. Tonocap(R) air tonometry is simple and elimin ates most sources of error associated with conventional saline tonomet ry. The bias, precision, reproductibility and response time in vitro a re consistent with a clinically reliable device.