Intravascular membrane oxygenation and carbon dioxide removal - A new application for permissive hypercapnia?

Pressure limited ventilation or 'lung rest' may prevent further exacerbation of acute lung injury from high airway pressures. A therapeutic goal of an intracorporeal oxygenation and carbon dioxide removal device (IVOX) is reduction of airway pressures. We noted increased IVOX CO₂ removal as mixed venous CO₂ increased in experimental animals. However, we recognize the limited clinical utility of removing approximately 30% of venous CO₂. Therefore, intentional hypoventilation to limit airway pressures (mild permissive hypercapnia) was used in 5 patients with respiratory failure, and again we noted improved CO₂ removal with increasing mixed venous CO₂ concentrations. Preliminary calculations demonstrate that a CO₂ gradient of approximately 70 mm Hg is needed to remove 100 ml CO₂/min. The use of more aggressive permissive hypercapnia protocols with IVOX may permit further reduction in airway pressure without problems of severe respiratory acidosis.