Intracorporeal CO₂ removal and permissive hypercapnia to reduce airway pressure in acute respiratory failure: The theoretical basis for permissive hypercapnia with IVOX®

Initial studies have shown that the intravascular oxygenator and carbon dioxide removal device (IVOX, Cardiopulmonics, Inc., Salt Lake City, UT) removes approximately 30% of VCO₂. After noting increased CO₂ removal with increased venous CO₂, we developed a conceptual analytical model based on data obtained from patients and laboratory experiments. Increasing the CO₂ gradient across the hollow fiber membranes of IVOX increases the operating efficiency of the device. Using the patient management technique of permissive hypercapnia (limiting tidal volumes, respiratory rates, and airway pressures) serves to increase the CO₂ gradient across the membrane. The conceptual analytical model predicts that a PaCO₂ of 75-80 mm Hg is required to obtain a CO₂ gradient that results in IVOX CO₂ removal of approximately 90-100 ml CO₂/min. This technique may allow a broader application of both permissive hypercapnia and IVOX in acute respiratory failure.