A respiratory gas exchange catheter: In vitro and in vivo tests in large animals

Objectives: Acute respiratory failure is associated with a mortality of 40% to 50%, despite advanced ventilator support and extracorporeal membrane oxygenation. A respiratory gas exchange catheter (the Hattler Catheter) has been developed as an oxygenator and carbon dioxide removal device for placement in the vena cava and right atrium in the treatment of acute respiratory failure to improve survival. Methods: Differing from a previously clinically tested intravenous gas exchange device (ie, IVOX), the Hattler Catheter incorporates a small, pulsating balloon surrounded by hollow fibers. The pulsating balloon redirects blood toward the fibers, enhances red cell contact with the membrane, and significantly improves gas exchange so that smaller catheter devices are still efficient on insertion and can be inserted through the jugular or femoral vein. Devices were tested in mock circulatory loops and in short-term (8 hours) and long-term (4 days) experiments in calves to study the effect of various sized balloons and the anatomic location of the device in the venous system as a function of hemodynamics and gas exchange. Results: In vitro performance in water demonstrates an oxygen delivery (Vo(2)) of 140 +/- 8.9 mL . min(-1) . m(-2) and a carbon dioxide removal (Vco(2)) of 240 +/- 6.1 mL . min(-1) . m(-2). Acute in vivo experiments demonstrate a maximum carbon dioxide consumption of 378 +/- 11.2 mL . min(-1) . m(-2). Devices positioned in the right atrium had an average carbon dioxide exchange of 305 mL . min(-1) . m(-2), whereas in the inferior vena cava position carbon dioxide exchange was 255 mL . min(-1) . m(-2). Devices have been tested long term in calves, with gas exchange rates maintained over this time interval (carbon dioxide consumption, 265 35 mL . min(-1) . m(-2)). Plasma-free hemoglobin levels at the end of 4 days have been 4.8 3.2 mg/dL. Hemodynamic measurements, including a decrease in cardiac outputs and increased mean pressure decreases across the device become significant only with the larger balloon (40-mL) devices (P < .05, 40-mL vs 13-mL devices). Autopsies show no end-organ damage. The device linearly increases its carbon dioxide output with progressive hypercapnea, predicting its ability to meet tidal volume reduction in the therapy of respiratory failure. Conclusions: Progress has been made toward developing an intravenous gas exchange catheter to provide temporary pulmonary support for patients in acute respiratory failure.