TOTAL RESPIRATORY SUPPORT WITH TIDAL FLOW EXTRACORPOREAL-CIRCULATION IN ADULT SHEEP

A novel pressure gated tidal flow extracorporeal circulation (TF ECC) device was developed, and it was hypothesized that it could provide to tal respiratory support in apneic adult sheep without adverse hemodyna mic or cardiac effects. The circuit consisted of a single lumen cannul a, computer driven tubing occluders gated by circuit pressure, a nonoc clusive peristaltic blood pump, a spiral coiled membrane lung, and a h eat exchanger. Six paralyzed, anesthetized adult sheep were instrument ed and TF ECC was instituted via cannulation of the right atrium. Tota l respiratory support was provided by the circuit during an apneic per iod of 6 hours. Echocardiography was performed with the animal instrum ented (baseline) and after 2 hours of TF ECC. Circuit blood tidal volu me was 172.6 +/- 18.0 cc, resulting in a TF ECC flow of 71.1 +/- 10.1 cc/kg/min. At the end of the study period, PaCo2 was 35.5 +/- 7.6 mmHg , p(a)O(2)) was 91.2 +/- 30.6 mmHg, and pulmonary artery oxygen satura tion (SPAO2) was 95 +/- 5%. Hemodynamic stability was maintained with no significant differences at baseline and after 6 hours in mean arter ial pressure, mean pulmonary artery pressure, or heart rate noted. Ech ocardiographic evaluation showed preserved fractional shortening of th e left ventricular (LV) septal-lateral dimension (baseline 32.4 +/- 11 .4 %; 2 hours 34.8 +/- 8.4 %). This study demonstrates TF ECC provides total respiratory support without adverse hemodynamic effects, and pr eserved LV function.