Original Article

Pumpless Arterial-Venous Extracorporeal CO₂ Removal During Acute Lung Injury

¹ Division of Circulation Technology, School of Allied Medical Professions, The Ohio State University
² Children's Hospital, The Ohio State University

^* Address correspondence to: Richard Tallman, PhD, Division of Circulation Technology, School of Allied Medical Professions, The Ohio State University, 1583 Perry St. Columbus, Ohio 43210-1234

Abstract

Acute Respiratory Distress Syndrome (ARDS) is associated with high morbidity and mortality. It has been shown that extracorporeal CO₂ removal (ECCO₂R) can be used to supplement mechanical ventilatory support for ARDS patients. This makes it possible to reduce the amount of positive pressure ventilation, thus reducing cardiovascular compromise and barotrauma, promoting lung rest and healing.

We have been evaluating a pumpless arterial-venous ECCO₂R circuit with a priming volume of approximately 150 ml. A 0.8 m² hollow fiber membrane oxygenator was studied in 5 dogs (average weight= 27.8 kg) anesthetized with sodium pentobarbital. A femoral artery and vein were cannulated with 17 Fr cannulae. The blood flow through this circuit averaged 1.11 1/min or approximately 23% of the animal's cardiac output. Acute lung injury was induced with oleic acid, (100 mg/kg). Following lung injury, the pulmonary shunt increased by 69% over baseline, while the pulmonary artery pressure increased from 12.7 to 18.7 mmHg. Despite this lung injury, pump less arterial-venous ECCO₂R was able to support all of the animal's CO₂ exchange without ventilating the native lungs, which were held inflated with oxygen at 5 cmH₂O.

The results of this study indicate that a small, highly efficient, low resistance gas exchanger can completely supplant the need for artificial ventilation during pumpless arterial-venous bypass, even with severe respiratory distress. This simple method of ventilatory support should prove to be an important adjunct to positive pressure ventilation.