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 CO(2) removal ([Formula: see text] CO(2)) and O(2) uptake ([Formula: see text] O(2)) simulated the setting of VA-ECMO with varying ventilation/perfusion ([Formula: see text] /[Formula: see text] ) ratios and shunt. A metabolic chamber with a CO(2)/N(2) blend simulated [Formula: see text] CO(2) and [Formula: see text] O(2). [Formula: see text] (Lung) was estimated with a modified Fick principle: [Formula: see text] (Lung) = [Formula: see text] (ECMO) × ([Formula: see text] CO(2) or [Formula: see text] O(2Lung))/([Formula: see text] CO(2) or [Formula: see text] O(2ECMO)). A normalization procedure corrected [Formula: see text] CO(2) 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] CO(2) and [Formula: see text] O(2) 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], r(2) 0.85 [0.79–0.88]). Blood measurements of [Formula: see text] CO(2) 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] CO(2) and [Formula: see text] O(2) in steady-state conditions allow for clinically applicable calculations of [Formula: see text] (Lung) during VA-ECMO therapy.