Alpha-stat capnography for the Sorin Monolyth oxygenator

Monitoring the carbon dioxide exhaust of an oxygenator is an inexpensive method to accurately predict and control the arterial carbon dioxide tension during cardiopulmonary bypass (CPB). The partial pressure of carbon dioxide in the exhaust ventilating gas (p exCO 2) was continuously monitored from the capnograph port of the Sorin Monolyth oxygenator during CPB. At the time of routine arterial blood gas sampling, the arterial blood temperature (ABT) was recorded along with the p exCO 2 from the capnograph monitor. The arterial carbon dioxide tension (paCO 2) from the arterial blood sample analysis was then statistically analyzed and related to the p exCO 2 and ABT. The statistical relationship of p exCO 2 and ABT while employing alpha stat ventilation resulted in an exponential regression with a correlation coefficient of 0.98. The exponential regression is unique to each manufacturer's oxygenator; we have titled this the "regression signature." This regression signature can be easily learned and employed by the perfusionist during CPB as an aid in controlling oxygenator ventilation. The mean paCO 2 value obtained during the study period was 39.0 +/-2.5 mmHg. There was no statistical difference between the paCO 2 values when separated into four different blood temperature groups, ( less than 28, 28-32, 32-37, and greater than 37 degrees C).