ACCURACY OF THE TONOMETRIC FUNCTION OF RECYCLED GASTRIC TONOMETER CATHETERS

We investigated the accuracy of recycled gastric tonometer catheters, using a prospective laboratory model, within the Intensive Care Unit o f a University teaching hospital. Ten used tonometer catheters and thr ee new catheters were exposed to known constant PCO2 levels between 23 -65 torr (3.06-8.66 kPa) in a gas mixing chamber, at a temperature of 35.5-38 degrees C and a relative humidity >95%. The tonometer balloons were primed with normal saline, and after a 30-minute equilibration t ime, the saline was sampled for PCO2 measurements. Steady-state PCO2 ( PCO2(ss)) and gastric mucosal pH (pHi) values were derived using a cor rection factor and the Henderson-Hasselbalch equation. There was no di fference in the mean or distribution of PCO2(ss) values between recycl ed and new catheters. The PCO2(ss) values of recycled catheters were w ithin the 95% confidence limits of those of new catheters. Individual catheter values did not differ significantly from each other (ANOVA P= 0.05). Using an arterial HCO3-. value of 21 mmol/l, the calculated pHi values of used catheters varied <1.5% of the mean pHi of new catheter s. The tonometric performance of recycled gastric tonometer catheters was similar to that of new catheters when tested in vitro.