[Experimental study of pumpless ECMO during 24 hours using extracapillary blood flow type polypropylene membrane...

To remove carbon dioxide in acute respiratory failure, pumpless ECMO (extra-corporeal membrane oxygenation) experiment was carried out using extracapillary blood flow type membrane oxygenator, which was developed by our department and which has many advantages, compact, small priming volume and low pressure drop. The oxygenator is consisted with 17 cm in length, 200 microns in inner diameter, made of polypropylene with micropores. And it has 0.7 m2 of surface area and 60 ml of priming volume. In 14 canines, acute respiratory failure were made by hypoventilation (T.V. = 10 ml/kg, R.R. = 5 times/min). We compared with hypoventilation group (group 1, n = 5) and pumpless ECMO group (group 2, n = 9). Pumpless ECMO circuit is A-V bypass between femoral artery and femoral vein. The following results were obtained. 1. In group 1 severe hypoxia and hypercapnea were observed, and all 5 canines were dead within 4 hours. 2. In group 2 hypoxia and hypercapnea were improved by pumpless ECMO, and 4 in 9 lived for 24 hours. 3. Function in CO2 transfer with the P.H.O. is maintained in satisfactory condition for 24 hours. 4. The oxygenator seems to be available for long-term pumpless ECMO. 5. Degeneration of mitochondria in the acute respiratory failure was observed by electron microscopic examination. 6. Further examinations about the intracellular respiration and metabolism in pumpless ECMO should be needed.