Estimating cardiac output based on gas exchange during veno-arterial extracorporeal membrane oxygenation in a simulation study using paediatric oxygenators

Veno-arterial extracorporeal membrane oxygenation (VA-ECMO) therapy is a rescue strategy for severe cardiopulmonary failure. The estimation of cardiac output during VA-ECMO is challenging. A lung circuit ([Formula: see text]_Lung) and an ECMO circuit ([Formula: see text]_ECMO) with oxygenators for CO₂ removal ([Formula: see text]CO₂) and O₂ uptake ([Formula: see text]O₂) simulated the setting of VA-ECMO with varying ventilation/perfusion ([Formula: see text]/[Formula: see text]) ratios and shunt. A metabolic chamber with a CO₂/N₂ blend simulated [Formula: see text]CO₂ and [Formula: see text]O₂. [Formula: see text] _Lung was estimated with a modified Fick principle: [Formula: see text]_Lung = [Formula: see text]_ECMO × ([Formula: see text] CO₂ or [Formula: see text]O_2Lung)/([Formula: see text]CO₂ or [Formula: see text]O_2ECMO). A normalization procedure corrected [Formula: see text]CO₂ values for a [Formula: see text]/[Formula: see text] of 1. Method agreement was evaluated by Bland-Altman analysis. Calculated [Formula: see text]_Lung using gaseous [Formula: see text]CO₂ and [Formula: see text]O₂ correlated well with measured [Formula: see text]_Lung with a bias of 103 ml/min [- 268 to 185] ml/min; Limits of Agreement: - 306 ml/min [- 241 to - 877 ml/min] to 512 ml/min [447 to 610 ml/min], r² 0.85 [0.79-0.88]). Blood measurements of [Formula: see text]CO₂ showed an increased bias (- 260 ml/min [- 1503 to 982] ml/min), clinically not applicable. Shunt and [Formula: see text]/[Formula: see text] mismatch decreased the agreement of methods significantly. This in-vitro simulation shows that [Formula: see text]CO₂ and [Formula: see text]O₂ in steady-state conditions allow for clinically applicable calculations of [Formula: see text]_Lung during VA-ECMO therapy.