Fraction of expired oxygen: an additional safety approach to monitor oxygen delivery to the heart lung machine oxygenator

Background: Monitoring oxygen delivery to the oxygenator of a heart lung machine (HLM) is typically accomplished with an O-2 analyzer connected to the gas inflow line. It is assumed when the FiO(2) is greater than 21% that oxygen is being delivered to the oxygenator. However, this assumption is imperfect because the connection of the inflow line to the oxygenator is downstream from the O-2 analyzer. FiO(2) monitoring will not alert the perfusionist if the inflow line is not actually connected to the oxygenator. Measuring the fraction of expired oxygen (FEO2) is a more reliable way of monitoring O-2 delivery. Methods: An O-2 analyzer was placed on the scavenging line that is attached to the exhaust port of oxygenator (FEO2). Results: Whenever the FiO(2) is greater than 21%, and the inflow line is properly connected, the FEO2 exiting the oxygenator is greater than 21%. The FEO2 falls to 21% when the inflow line is not functioning. Conclusion: Monitoring the FEO2 is a more reliable way to verify O-2 delivery to an oxygenator. An alarm can be set on the FEO2 monitor to alert the perfusionist if the FEO2 falls below a predetermined threshold so any issue with O-2 delivery will always be recognized.

Automated summary

Using FEO2 to monitor oxygen delivery is more reliable than FiO(2) monitoring and can promptly detect issues with oxygen delivery. An alarm can be set to alert the perfusionist if FEO2 falls below a predetermined threshold.