Extracorporeal CO2 Removal by Respiratory Electrodialysis: An In Vitro Study

We previously described a highly efficient extracorporeal CO2 removal technique called respiratory electrodialysis (R-ED). Respiratory electrodialysis was composed of a hemodiafilter and a membrane lung (ML) positioned along the extracorporeal blood circuit, and an electrodialysis (ED) cell positioned on the hemodiafiltrate. The ED regionally increased blood chloride concentration to convert bicarbonate to CO2 upstream the ML, thus enhancing ML CO2 extraction (VCO2ML). In this in vitro study, with an aqueous polyelectrolytic carbonated solution mimicking blood, we tested a new R-ED setup, featuring an ML positioned on the hemodiafiltrate after the ED, at increasing ED current levels (0, 2, 4, 6, and 8 A). We measured VCO2ML, electrolytes concentrations, and pH of the extracorporeal circuit. Raising levels of ED-current increased chloride concentration from 107.5 +/- 1.6 to 114.6 +/- 1.3 mEq/L (0 vs. 8 A, p < 0.001) and reduced pH from 7.48 +/- 0.01 to 6.51 +/- 0.05 (0 vs. 8 A, p < 0.001) of the hemodiafiltrate entering the ML. Subsequently, VCO2ML increased from 27 +/- 1.7 to 91.3 +/- 1.5 ml/min (0 vs. 8 A, p < 0.001). Respiratory electrodialysis is efficient in increasing VCO2ML of an extracorporeal circuit featuring an ML perfused by hemodiafiltrate. During R-ED, the VCO2ML can be significantly enhanced by increasing the ED current.