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

Abstract

Abstract 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 ( $${\dot{\text{Q}}}$$ Q ˙ Lung) and an ECMO circuit ( $${\dot{\text{Q}}}$$ Q ˙ ECMO) with oxygenators for CO2 removal ( $$\mathop {\text{V}}\limits^{.}$$ V . CO2) and O2 uptake ( $$\mathop {\text{V}}\limits^{.}$$ V . O2) simulated the setting of VA-ECMO with varying ventilation/perfusion ( $$\mathop {\text{V}}\limits^{.}$$ V . / $${\dot{\text{Q}}}$$ Q ˙ ) ratios and shunt. A metabolic chamber with a CO2/N2 blend simulated $$\mathop {\text{V}}\limits^{.}$$ V . CO2 and $$\mathop {\text{V}}\limits^{.}$$ V . O2. $${\dot{\text{Q}}}$$ Q ˙ Lung was estimated with a modified Fick principle: $${\dot{\text{Q}}}$$ Q ˙ Lung = $${\dot{\text{Q}}}$$ Q ˙ ECMO × ( $$\mathop {\text{V}}\limits^{.}$$ V . CO2 or $$\mathop {\text{V}}\limits^{.}$$ V . O2Lung)/( $$\mathop {\text{V}}\limits^{.}$$ V . CO2 or $$\mathop {\text{V}}\limits^{.}$$ V . O2ECMO). A normalization procedure corrected $$\mathop {\text{V}}\limits^{.}$$ V . CO2 values for a $$\mathop {\text{V}}\limits^{.}$$ V . / $${\dot{\text{Q}}}$$ Q ˙ of 1. Method agreement was evaluated by Bland–Altman analysis. Calculated $${\dot{\text{Q}}}$$ Q ˙ Lung using gaseous $$\mathop {\text{V}}\limits^{.}$$ V . CO2 and $$\mathop {\text{V}}\limits^{.}$$ V . O2 correlated well with measured $${\dot{\text{Q}}}$$ Q ˙ 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 $$\mathop {\text{V}}\limits^{.}$$ V . CO2 showed an increased bias (− 260 ml/min [− 1503 to 982] ml/min), clinically not applicable. Shunt and $$\mathop {\text{V}}\limits^{.}$$ V . / $${\dot{\text{Q}}}$$ Q ˙ mismatch decreased the agreement of methods significantly. This in-vitro simulation shows that $$\mathop {\text{V}}\limits^{.}$$ V . CO2 and $$\mathop {\text{V}}\limits^{.}$$ V . O2 in steady-state conditions allow for clinically applicable calculations of $${\dot{\text{Q}}}$$ Q ˙ Lung during VA-ECMO therapy.