Abstract
Pleural fluid pH measurements are used in the management of parapneumonic effusions. This study evaluated the accuracy of the pleural fluid pH and PCO2 measurement in a blood gas analyser (BGA) and the error induced by altering the aerobic environment and temperature of sample storage prior to analysis. The pH electrodes in a pH meter and a BGA were initially evaluated using aqueous reference solutions. The accuracy of pH and PCO2 electrodes was then assessed in pleural fluid tonometered to a known PCO2. The effects of aerobic compared to anaerobic storage and storage temperature, 0°C vs 37°C of pleural fluid were evaluated for errors in pH and PCO2