Intravascular Membrane Oxygenation and Carbon Dioxide Removal with IVOX: Can Improved Design and Permissive Hypercapnia Achieve Adequate Respiratory Support During Severe Respiratory Failure?

Abstract: The intravenacaval oxygenator and carbon dioxide removal device (IVOX) conceived by Mortensen at CardioPulmonics is a diffusion–limited device capable of removing 30% of CO₂ production of an adult at normocapnia with minimal reduction in ventilator requirements. Through mathematical modeling, an ex vivo venovenous bypass circuit to model the vena cava and animal models of severe smoke inhalation injury, the practice of permissive hypercapnia has been established to enhance CO₂ removal by IVOX. By allowing the blood PCO₂ to rise gradually, the CO₂ excretion by IVOX can be linearly increased in a 1: 1 relationship. Experimental and clinical studies have shown that CO₂ removal by IVOX increased from 30–40 ml/min at normal blood PCO₂ to 80–90 ml/min at PCO₂ of 90 mm Hg. In addition, IVOX with permissive hypercapnia allowed a significant reduction in minute ventilation and peak airway pressure. Design changes could also improve the performance of IVOX. Increased surface area and mixing with more fibers and crimping in new prototypes of IVOX significantly increased CO₂ removal and oxygen transfer. Active mixing in the blood to decrease the boundary layer resistance can further enhance gas exchange of IVOX. In conclusion, gas exchange by the current design of IVOX is limited, and improvements in design are needed for it to become a more clinically applicable device. Permissive hypercapnia can significantly enhance CO, removal by IVOX as well as significantly reduce ventilator requirements.