Properties of synthetic membranes in extracorporeal circuits

Membranes with capabilities which promise to produce a clinically effective artificial lung are now available. Silicone rubber, 1 8 mil Teflon, and cellophane all transfer carbon dioxide satisfactorily. These substances, as well as the thicker films of Teflon, appear to be adequate for oxygen transfer, although cellophane does it rather poorly. Turbulence is of considerable importance in the transfer of oxygen. A fruitful line of investigation might be that of evaluating the maximal degree of turbulence that one can introduce to an oxygenating system without producing blood damage. One could use the Reynolds ∗ number as a guide to quantitating the degree of turbulence produced and perhaps devise a scheme that produces even greater turbulent flow than that which we have described. Perhaps other membrane substances could be considered or those previously discarded could be re-evaluated in the light of improved turbulent flow. For example, cellophane, which is a wettable membrane and theoretically more desirable, might be made to transfer oxygen more satisfactorily, with improved flow characteristics. Other wettable membranes might also be devised and tested. One might suggest that the ideal gas exchange membrane would be one that is wettable, durable, easily fabricated into lung units, and sufficiently thin. It would need to provide adequate carbon dioxide and oxygen transfer in a highly turbulent flow system which also involves a tolerable amount of blood damage.