Membrane Oxygenators: They are more physiological and are similar to natural lungs. There is separation of blood and gas by membrane across which gas exchange takes place. There are two types. (1) True membrane, (2) Micro porous membrane oxygenators:

i) True Membrane Oxygenator: There is no contact between blood and gas at any time. It is more expensive and needs larger priming volume.

ii) Micro Porous Membrane Oxygenator: At the beginning of perfusion, there is containing between blood and gas across the micro pores. In a short lime, protein coaling of micro pores occurs, severing direct contact. However after several hours of use, he functional capacity of the membrane decreases. So they are not useful for prolonged use as in extra corporeal membrane oxygenator (ECMO),