DEVELOPMENT AND VALIDATION OF A TECHNIQUE FOR CONTINUOUS MONITORING OF GASTRIC INTRAMUCOSAL PH

A novel method for continuously monitoring gastric intramucosal PCO2 a nd pH was developed and tested. Gas was continuously circulated throug h a modified balloon-tipped catheter connected to an external closed s ystem fitted with an infrared CO2 sensor to monitor PCO2. Performance of the capnometric recirculating gas tonometry (CRGT) system was teste d in vitro using an equilibration chamber and in vivo in six anestheti zed dogs. Serial PCO2 measurements were made using CRGT and compared w ith intermittent PCO2 values obtained by conventional tonometry cathet ers. In the animal experiments, gastric intramucosal PCO2 and pH were determined before and after inducing hypoxia by decreasing the FIO2 to 0.08. After initial placement, PCO2 determined by the CRGT reached a near plateau within 45 min, and at that time point values were compara ble to those obtained by conventional intermittent tonometry. Signific ant increases in gastric intramucosal P-CO2 were detectable by CRGT wi thin 5 min of inducing systemic hypoxia, and there was a concomitant s ignificant decrease in intramucosal pH. Continuous monitoring of gastr ic intramucosal P-CO2 and pH is feasible, has potential advantages ove r conventional methods, and can provide significant trending informati on over intervals as short as 5 min.