Which indication suggests that recirculation is occurring in ECMO?

Recirculation in ECMO occurs when a portion of the blood that has already been oxygenated returns to the patient before it can fully circulate through the system. This phenomenon is detrimental as it results in inefficient oxygen delivery to the patient.

When there is high pre-oxygenator SO2 (indicating that the blood entering the oxygenator is well-oxygenated), coupled with low patient SaO2 (indicating that the arterial blood saturation in the patient is low), this suggests that the well-oxygenated blood is recirculating back to the circuit instead of adequately delivering oxygen to the patient’s tissues. Consequently, the patient is unable to benefit from the oxygen that is being provided, reflecting ineffective oxygenation and the presence of recirculation.

This combination of high pre-oxygenator SO2 and low patient SaO2 serves as a clear indication that the intended function of ECMO—that is, to oxygenate and support the patient—is being compromised by recirculation, thereby highlighting an opportunity to evaluate the positioning of the cannulas or assess for any issues within the circuit design or function.