Evaluation of CO₂ removal rate of ECCO₂R for a renal replacement therapy platform in an experimental setting

Background A critical parameter of extracorporeal CO 2 removal (ECCO 2 R) applications is the CO 2 removal rate (VCO 2 ). Low‐flow venovenous extracorporeal support with large‐size membrane lung remains undefined. This study aimed to evaluate the VCO 2 of a low‐flow ECCO 2 R with large‐size membrane lung using a renal replacement therapy platform in an experimental animal model. Methods Twelve healthy pigs were placed under mechanical ventilation and connected to an ECCO 2 R‐CRRT system (surface area = 1.8 m 2 ; OMNIset®, BBraun, Germany). Respiratory settings were reduced to induce two degrees of hypercapnia. VCO 2 was recorded under different combinations of PaCO 2 (50–69 or 70–89 mm Hg), extracorporeal blood flow (ECBF; 200 or 350 mL/min), and gas flow (4, 6, or 10 L/min). Results VCO 2 increased with ECBF at all three gas flow rates. In severe hypercapnia, the increase in sweep gas flow from 4 to 10 L/min increased VCO 2 from 86.38 ± 7.08 to 96.50 ± 8.71 mL/min at an ECBF of 350 mL/min, whereas at ECBF of 200 mL/min, any increase was less effective. But in mild hypercapnia, the increase in sweep gas flow result in significantly increased VCO 2 at two ECBF. VCO 2 increased with PaCO 2 from 50–69 to 70–89 mm Hg at an ECBF of 350 mL/min, but not at ECBF of 200 mL/min. Post‐membrane lung PCO 2 levels were similar for different levels of premembrane lung PCO 2 ( p = 0.08), highlighting the gas exchange diffusion efficacy of the membrane lung in gas exchange diffusion. In severe hypercapnia, the reduction of PaCO 2 elevated from 11.5% to 19.6% with ECBF increase only at a high gas flow of 10 L/min ( p < 0.05) and increase of gas flow significantly reduced PaCO 2 only at a high ECBF of 350 mL/min ( p < 0.05). Conclusions Low‐flow venovenous extracorporeal ECCO 2 R‐CRRT with large‐size membrane lung is more efficient with the increase of ECBF, sweep gas flow rate, and the degree of hypercapnia. The influence of sweep gas flow on VCO 2 depends on the ECBF and degree of hypercapnia. Higher ECBF and gas flow should be chosen to reverse severe hypercapnia.