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 (AVCO2R) 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 AVCO2R in healthy animals to quantify the gas exchange capabilities of the system and establish ventilator management protocols for the subsequent studies of AVCO2R 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 AVCO2R 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 AVCO2R flow was 1,213 +/- 29 mL/min, averaging 27% +/- 1% of the cardiac output.


CONCLUSIONS
We conclude that AVCO2R 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.
Brunston
R L
RL
Department of Surgery, University of Texas Medical Branch and Shriners Burns Institute, Galveston 77555-0528, USA.
Zwischenberger
J B
JB
Tao
W
W
Cardenas
V J
VJ
Traber
D L
DL
Bidani
A
A
D000818:Animals; D001166:Arteriovenous Shunt, Surgical / Q000379:methods*; D002245:Carbon Dioxide / Q000097:blood*; D005112:Extracorporeal Circulation / Q000379:methods*; D005260:Female; D012131:Respiratory Insufficiency / Q000628:therapy*; D012756:Sheep; D015208:Smoke Inhalation Injury / Q000150:complications
D002245:Carbon Dioxide