An oxygenator or artificial lung adds oxygen to the patient’s blood and removes carbon dioxide.
In open heart surgery, a heart-lung-machine is used for temporary replacement of the functions of both the heart and the lungs. This is necessary to enable the surgeon to perform the complicated surgical procedure in a motionless field. Both heart and lungs are rested during surgery. The oxygenator with membranes inside is the main element in the heart-lung-machine, responsible for gas exchange.
In intensive care and interventional pneumology, innovative artifical lungs provide extracorporeal removal of carbon dioxide and oxygen enrichment of the blood. This gives the human lungs time to heal. Similar to heart surgery, special membranes in the membrane ventilator assume the fuction of the pulmonary alveoli.
In both applications, a heat exchanger is often used. As large volumes of blood are channeled outside the patient’s body, temperature fluctuations may easily occur. The heat exchanger allows adjustment of the patient’s blood temperature. This way the body temperature can be regulated according to the necessities of the medical procedure.
For oxygenation, blood is drained from the venous circulation in a blood reservoir by a suction pump, passed through the oxygenator, and then subsequently pumped back into the arterial circulation, often via an arterial filter.
Inside the oxygenator, blood is channelled along capillary membranes. The inner lumen of the fibres is streamed with oxygen or oxygen enriched air. Oxygen diffuses through the membrane into the blood, while carbon dioxide diffuses out of the blood into the gas stream and thereby is removed. For oxygenation a hydrophobic capillary is necessary to avoid entrance of water or plasma into the membrane wall during the procedure.
A heat exchanger can be added to the oxygenation system. While in contact with warm or respectively cold water, the blood temperature can be regulated up and down.
CO₂ removal can be performed less invasive as compared to complete blood oxygenation. Depending on the exact patient requirements and condition, this may even be performed without a pump by using the pressure gradient from the arterial to the venous system. Blood flow and gas exchange surface area are often smaller than for full blood oxygenation, as no total takeover is required, but rather a support of the lungs.