Intravascular membrane oxygenator and carbon dioxide removal devices: A review of performance and improvements

The first intravascular oxygenator and carbon dioxide (CO2) removal device (IVOX), conceived by Mortensen, was capable of removing 30% of CO2 producti on of an adult at normocapnia with a measurable reduction in ventilator req uirements. Through studies of mathematical modeling, an ex vivo venovenous bypass circuit to model the human vena cava, animal models of severe smoke inhalation injury, and patients with acute respiratory failure, the practic e of permissive hypercapnia has been established to enhance CO2 removal by IVOX. By allowing the blood pCO(2) to rise gradually, the CO2 excretion by IVOX can be linearly increased in a 1:1 relationship. Experimental and clin ical studies have shown that CO2 removal by IVOX can increase from 30 to 40 ml/min at a normal blood pCO(2) to 80 to 90 ml/min at a pCO(2) of 90 mm Hg . In addition, IVOX with permissive hypercapnia allows a significant reduct ion in minute ventilation and peak airway pressure. Active blood mixing to decrease the boundary layer resistance in the blood can significantly impro ve O-2 transfer by up to 49% and CO2 removal by up to 35%. Design changes c an also improve the performance of IVOX. Increased surface area with more f ibers and enhanced mixing by increased fiber crimping in new prototypes of IVOX significantly increased CO2 removal. Other groups have used alternativ e designs to address the limited performance of intravascular gas exchange devices. With improved design and patient management, clinically meaningful gas exchange and reduction in mechanical ventilatory support may be achiev ed during treatment of severe respiratory failure.