A novel, compact oxygenator
Virtually all current blood oxygenators employ hollow fibre membranes. In these devices, oxygen flows through the hollow fibres and blood flows around them. Different manufacturers organize the flow paths differently. For example, the hollow fibres may be straight with the blood flow at right angles to the fibres. Other devices have fibres wound around a bobbin. In all cases, oxygen diffuses through the fibres to oxygenate the blood and carbon dioxide diffuses from the blood through the hollow fibres into the gas (oxygen) stream. The rate of oxygen transfer is limited by the average distance that oxygen molecules have to travel from the red blood cells to the membrane. The oxygen transfer rate is then limited by how closely the hollow fibres can be packed. If they are too far apart, the resistance to transfer is too high. However, if they are too close, the fibres touch thereby blanking out part of the transfer area and hence reducing transfer rate. The hollow fibre structure also makes it impossible to achieve a smooth blood flow, with resulting blood damage and, when using whole blood, risk of blood clot growth.
Haemair is developing an oxygenator using flat membranes instead of hollow fibres. Using flat membranes enables the blood channels to be narrower without the membranes touching. The anticipated benefits of the Haemair device are a smoother blood flow path with reduced risk of blood damage and higher gas transfer rates enabling more compact devices. We show illustrations of devices tested to date.