Abstract
We investigated the accuracy of recycled gastric tonometer catheters, using a prospective laboratory model, within the Intensive Care Unit of a University teaching hospital.
Ten used tonometer catheters and three 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°C and a relative humidity >95%. The tonometer balloons were primed with normal saline, and after a 30-minute equilibration time, the saline was sampled for PCO2 measurements. Steady-state PCO2 (PCO2(ss)) and gastric mucosal pH (pHi) values were derived using a correction factor and the Henderson-Hasselbalch equation.
There was no difference in the mean or distribution of PCO2(ss) values between recycled and new catheters. The PCO2(ss) values of recycled catheters were within 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 catheters.
The tonometric performance of recycled gastric tonometer catheters was similar to that of new catheters when tested in vitro.