Oxygenator exhaust capnography: an in vitro evaluation.
The aim of the study was to examine whether oxygenator exhaust capnography could be used to monitor blood carbon dioxide tension in an in vitro cardiopulmonary bypass model. Carbon dioxide tension in the oxygenator's exhaust gas was measured by a capnograph and compared with that in the blood measured by blood gas analysis. Also investigated was the relationship between the capnograph's measurements and blood pH. The effects of gas and blood flow, temperature, and pH on the measurements were examined. A good correlation was found between PCO2 measured by the capnograph and by the blood gas analyzer (r = 0.997, P < 0.001). When the capnograph's results were corrected for 95% oxygen, the accuracy improved further. There was a significant correlation between oxygenator exhaust PCO2 and temperature (rs = 0.843, P < 0.05), but the difference in PCO, was small in the range examined. No significant correlation was found between oxygenator exhaust PCO2 and blood or gas flow. A reasonable correlation between blood pH and oxygenator exhaust PCO2 (r = 0.965, P < 0.001) was found, but the metabolic component of pH could be altered without correlation with exhaust PCO2 (rs = 0.203). In conclusion, oxygenator exhaust capnography was used with reasonable accuracy and reliability to monitor blood PCO2 in an in vitro cardiopulmonary bypass model.
Alston
R P
RP
University Department of Anaesthesia, Glasgow Royal Infirmary, Scotland, UK.
McNicol
J
J
D001784:Blood Gas Analysis; D019296:Capnography / Q000379:methods*; D002245:Carbon Dioxide / Q000097:blood*; D002315:Cardiopulmonary Bypass; D006801:Humans; D006863:Hydrogen-Ion Concentration; D010107:Oxygenators, Membrane
D002245:Carbon Dioxide