Microchannel technologies for artificial lungs: (1) theory

The feasibility of developing micro channel artificial lungs is calculated for eight possible strategies: 12 and 25 μm circular channels imbedded in gas-permeable sheets, 12 and 25 μm high open rectangular channels with gas-permeable walls, 12 and 25 μm high broad open channels with support posts and gas-permeable walls, and two 40 μm high screen-filled rectangular channels with gas-permeable walls. Each strategy is considered by imposing a pressure drop maximum of 10 mm Hg and limiting the possibility of shear-induced blood trauma. The pressure drop limit determines the acceptable channel length and required size to oxygenate 4 L/min of venous blood. Circular channels imbedded in open-pore, gas-permeable materials are especially attractive. With 12 μm channels, such a device would require 140 million, 0.8 mm long channels, but the total size of the gas-exchange section would be only 57 ml and a blood prime of only 13 ml. Also attractive are 12 μm high broad open channels with support posts and 40 μm screen-filled rectangular channels. The total size of the former would be 250 ml with a blood prime of 13 ml, and the total size of the latter would be 270 ml with a blood prime of 27 ml.