Physiological Investigations of Extracorporealco2-removal with Regard to Clinical Application

221 PHYSIOLOGICAL INVESTIGATIONS OF EXTRACORPOREALCO2-REMOVAL WITH REGARD TO CLINICAL APPLICATION. K. Mottaghy, R. Bey., B. Oedekoven, A. Lester and D. Schaich-Lester Advanced lung diseases with respiratory insufficieny are usually treated by respiratory therapy. In more serious cases an increase of venti lation parameters over physiological ~lues in combination with enhancement of oxygen concentrations is necessary in order to overcome the pathophysiological diffusion barrieres. Barotraumas and oxygen toxicity can be the following complications. A promising approach seemed to be the extracorporeal membrane oxygenation (ECMO) until 1976. Since the oxygenator should replace the total function of the natural lung in a long time perfusion (up to weeks), the biotechnical d i f f icu l ties such as large membrane areas, high extracorporeal flow rates and disturbances in governing the blood c lot t ing system, are reasons that this method could be regarded as a disappointment. Fortunately the new idea of extracorporeal C02-elimination promises a new succcsfull alternat ive, which is based on recent positive clinical results. Here we report about the physiological aspects of this method, where in experiments with dogs and sheeps, undergoing a veno-venous bypass, the CO 2 is eliminated so that the natural venti lation could be reduced (down to respiratory frequencies of only 3 or 4min -• with a blood flow rate below 40% of cardiac output. The blood gas data of the animals could be maintained at Dhysiological ranges. This was even the case in the status of apnoe up to 12 h by sl ightly flushing the lung with oxygen. Analytical considerations together with experimental measurements allow to derive the important relationships between the blood flow rate, the demanded C02-elimination rate and the low respiratory frequency. 223