To the Editor:

Tay et al¹ provide an excellent overview on the practical management of venovenous extracorporeal membrane oxygenation (VV-ECMO). The physiologic basis for the proposed algorithms should be discussed to provide clarity to the readers.

Firstly, a preoxygenator O₂ saturation threshold of >80% was suggested for cannula repositioning to address recirculation. Based on the Fick Equation (assume negligible dissolved O₂), where Qs = systemic flow; Qp = pulmonary flow; VO₂ = oxygen consumption; CaO₂, CvO₂, CpaO₂, and CpvO₂ = arterial, venous pulmonary artery, and pulmonary venous oxygen content, respectively; and O₂SatA, O₂SatCV, O₂SatPV, and O₂SatPA = arterial, central venous, pulmonary venous, and pulmonary arterial oxygen saturation, respectively.