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 (FEO ₂ ) 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 (FEO ₂ ).
Results: Whenever the FiO ₂ is greater than 21%, and the inflow line is properly connected, the FEO ₂ exiting the oxygenator is greater than 21%. The FEO ₂ falls to 21% when the inflow line is not functioning.
Conclusion: Monitoring the FEO ₂ is a more reliable way to verify O ₂ delivery to an oxygenator. An alarm can be set on the FEO ₂ monitor to alert the perfusionist if the FEO ₂ falls below a predetermined threshold so any issue with O ₂ delivery will always be recognized.