Diffusion of Oxygen and Carbon Dioxide Through Teflon Membranes

1) The platinum polarograph provides an accurate method of measuring oxygen transmission through different membranes. 2) High oxygen transmission through Teflon membranes is confirmed. 3) Measured values of oxygen transmission for a Clowes-type oxygenator are approximately one-third to one-half those obtained by polarographic measurements. This discrepancy is discussed. 4) The measured transmission of carbon dioxide through Teflon is very low compared to the figures obtained for oxygen at physiological pressures. Behavior of the two gases is dissociated and depends on their individual partial pressures. Data are presented which suggest that diffusion of gases through Teflon membranes can be predicted best from the behavior of the gases in dry air. This is important since diffusion through biological membranes depends on the behavior of gases in liquids. Apparently use of the dry membrane Teflon in an oxygenator results in carbon dioxide retention. The data indicate that the samples of cellophane and polyethylene tested are only slightly wettable and also show relatively poor ability to transmit carbon dioxide. Wettable cellophane has a favorable diffusion ratio. 5) It is suggested that no present benefit can be derived from improved oxygenation in membrane oxygenators because the limiting factor is the diffusion of carbon dioxide. A Teflon oxygenator, for instance, must be used at less than 25 per cent efficiency as far as oxygenation is concerned to prevent carbon dioxide retention.