OXYGENATOR PERFORMANCE

OXYGENATOR PERFORMANCE
•     Oxygenator function can be assessed by delta pressure and post membrane blood gas analysis
•     "Delta pressure" is the pressure between pre and post oxygenator pressure
•     When resistance in the oxygenator increases, delta pressure increases
•     It means that the oxygenator is clogged or clotted or obstructed
•     It is the earliest sign of oxygenator failure
•     Post membrane blood gas analysis also reflect the efficacy of oxygenator
•     Post membrane PO2 should be >150 mmHg and CO2 <40> •     Post oxygenator PO2 depends on blood flow rate
•     If the blood flow is >capacity of oxygenator, hemolysis occurs and blood gases may show hypoxia
•     In case of oxygenator dysfunction you need to distinguish between oxygenator dysfunction and hypermetabolic condition.
•     The determination of oxygenator function is made by calculating the oxygen consumption of patient and comparing this to known gas transfer capacity of the oxygenator.
•     If the calculated amount is within range of predicted O2 or CO2 transfer,then the oxygenator is performing according to specifications and the patient is in hypermetabolic state or an inappropriate oxygenator is used.
•     If the gas transfer is less than the predicted value, then the oxygenator maybe malfunctioning and may need to be changed.
•     Vo2=Q.(Ca-Cv) wherein Vo2 is oxygen transport, Q is blood flow rate, C is oxygen content, a and v are arterial and venous values.
•     The difference of O2 in inlet and outlet gas concentrations can be multiplied by total gas flow rate to determine the O2 transfer rate - 
Vo2=Q.(FIO2 - FEO2) where FIO2 and FEO2 are inlet and outlet gas oxygen fractions respectively
•     Measure of oxygenator performance is "reference flow rates" given by manufacturer and Association for advancement of medical instrumentation.
CO2 Reference Flow-
Is defined as maximum flow of blood with
•     Hb of 12g/dl
•     Zero base deficit
•     Oxygen saturation of 65%
•     At temperature of 370C
that can enter the oxygenator and subsequently leave oxygenator with CO2 content decreased by 38ml/L
O2 Reference Flow-
Is defined as maximum flow of blood with
•     Hb of 12g/dl
•     Zero base deficit
•     Oxygen saturation of 65%
•     At temperature of 370C
that can enter the oxygenator and subsequently leave oxygenator with O2 content increased by 45ml/L
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Reference - Manual of Extracorporeal Membrane Oxygenation (ECMO) in the ICU by Poonam Malhotra Kapoor 
-Cardiopulmonary bypass- Principles and Practice by Glenn P. Gravlee

- by Dr Amarja