Total arteriovenous CO2 removal:: Simplifying extracorporeal support for respiratory failure

Background. To reduce the complexity, complications, and cost of conventional extracorporeal membrane oxygenation, we have developed a technique of simplified arteriovenous extracorporeal CO2 removal (AVCO(2)R) with a low-resistance membrane gas exchanger for total CO2 removal to provide lung rest in the setting of severe respiratory failure. Methods. We initially used AVCO(2)R in healthy animals to quantify the gas exchange capabilities of the system and establish ventilator management protocols for the subsequent studies of AVCO(2)R in a large animal model of respiratory failure secondary to a severe smoke inhalation injury. Results. In healthy sheep the maximum spontaneous arteriovenous flow ranged from 1,350 to 1,500 mL/min, whereas CO2 removal plateaued at a blood flow of approximately 1,000 mL/min in which 112 +/- 3 mL/min CO2 was removed, allowing an 84% reduction in the minute ventilation of from 6.9 +/- 0.8 L/min to 1.1 +/- 0.4 L/min (p < 0.01) without triggering hypercapnia. A subsequent reduction in extracorporeal flow at a reduced minute volume led to the development of hypercapnia only if it decreased to less than 500 mL/min. We also applied AVCO(2)R in mechanically ventilated sheep with a severe smoke inhalation injury and removed 95% (111 +/- 4 mL/min) of the total CO2 production. This allowed the minute ventilation to be reduced by 95% and the peak inspiratory pressures by 52% (both p < 0.05) over 6 hours and produced no adverse hemodynamic effects. The partial pressure of arterial oxygen was maintained above 100 mm Hg at a maximally reduced minute volume. The mean AVCO(2)R now was 1,213 +/- 29 mL/min, averaging 27% +/- 1% of the cardiac output. Conclusions. We conclude that AVCO(2)R in a simple arteriovenous shunt is a less complicated technique than extracorporeal membrane oxygenation and is capable of total CO2 removal that allows a significant reduction in the minute ventilation and peak airway pressure during severe respiratory failure. (C) 1997 by The Society of Thoracic Surgeons.