Personalised energy targeting during venovenous ECMO: serial assessment of resting energy expenditure reveals phase-dependent metabolic demand and systematic discordance with predictive equations

Background In patients receiving extracorporeal membrane oxygenation (ECMO), metabolic demand varies dynamically across the disease course, while conventional indirect calorimetry in ECMO patients underestimates measured energy expenditure (measured EE) because a substantial proportion of gas exchange occurs across the membrane lung. Specialised protocols can overcome this limitation and measure EE directly during ECMO. However, no adult study has yet compared serial measured EE measurements with concurrent energy intake to assess feeding equipoise or to quantify the temporal variability that personalised nutrition must address. Methods Post-hoc analysis of prospectively collected data from 9 adult patients receiving venovenous ECMO for acute respiratory distress syndrome at Charité — Universitätsmedizin Berlin. Measured-EE was assessed using the MEEP protocol (75 valid measurements). Feeding equipoise was assessed as the ratio of actual energy intake to measured EE (equipoise: 80–110%). Discordance analysis compared measurement-based classification with hypothetical ESPEN-guided nutrition (25 kcal/kg/day) using adjusted body weight (primary) and actual body weight (sensitivity analysis). Results Median measured EE was 1923 kcal/day (interquartile range, 1594–2222). The ECMO circuit accounted for 60.5% ± 18.2% of total gas exchange. Feeding equipoise was achieved on only 30 of 75 measurement days (40%); patients were overfed on 44% and underfed on 16%. ESPEN 25 kcal/kg/day with adjusted body weight misclassified feeding equipoise on 55% of days (concordance 45%); actual body weight yielded concordance of 49%. The respiratory quotient (0.908 ± 0.131) did not correlate with the feeding ratio (ρ = 0.024). Conclusion Both actual feeding practice and standard predictive equations failed to match measured energy requirements regardless of body weight choice. The substantial intra-individual measured EE variability and the progressive decline in extracorporeal gas exchange contribution support a phase-specific, personalised approach guided by serial assessment of measured EE rather than static weight-based targets.