Alkaline Liquid Ventilation of the Membrane Lung for Extracorporeal Carbon Dioxide Removal (ECCO₂R): In Vitro Study

Extracorporeal carbon dioxide removal (ECCO₂R) is a promising strategy to manage acute respiratory failure. We hypothesized that ECCO₂R could be enhanced by ventilating the membrane lung with a sodium hydroxide (NaOH) solution with high CO₂ absorbing capacity. A computed mathematical model was implemented to assess NaOH-CO₂ interactions. Subsequently, we compared NaOH infusion, named "alkaline liquid ventilation", to conventional oxygen sweeping flows. We built an extracorporeal circuit with two polypropylene membrane lungs, one to remove CO₂ and the other to maintain a constant PCO₂ (60 ± 2 mmHg). The circuit was primed with swine blood. Blood flow was 500 mL × min^-1. After testing the safety and feasibility of increasing concentrations of aqueous NaOH (up to 100 mmol × L^-1), the CO₂ removal capacity of sweeping oxygen was compared to that of 100 mmol × L^-1 NaOH. We performed six experiments to randomly test four sweep flows (100, 250, 500, 1000 mL × min^-1) for each fluid plus 10 L × min^-1 oxygen. Alkaline liquid ventilation proved to be feasible and safe. No damages or hemolysis were detected. NaOH showed higher CO₂ removal capacity compared to oxygen for flows up to 1 L × min^-1. However, the highest CO₂ extraction power exerted by NaOH was comparable to that of 10 L × min^-1 oxygen. Further studies with dedicated devices are required to exploit potential clinical applications of alkaline liquid ventilation.