Extra Corporeal Membrane Oxygenation (ECMO)
ECMO or Extracorporeal Membrane Oxygenation is a type of Mechanical Circulatory Support device that performs the role of the heart and lungs externally. Blood is taken out of the body, it goes through the ECMO machine that oxygenates the blood with the help of an oxygenator and it is then sent back into the body and pumped to the different organs. A person is put on ECMO for one of two reasons — when there is a heart failure/pump failure or when there is a lung failure. The ECMO machine is controlled by a perfusionist or a nurse with advanced training in ECMO.
What are the uses of ECMO?
ECMO can be used as a bridge to transplant. This is used for patients with heart failure who are awaiting a heart transplant. Once the transplant is performed, the patient is taken off ECMO. ECMO can also be used as a bridge to definitive therapy. Patients with bad lungs following a severe infection are put on ECMO to give the lungs a rest till it can recover. Once the lungs recover, they are taken off ECMO.
How does an ECMO machine work?
The ECMO machine is connected to a patient through cannulae (plastic tubes). The tubes are placed in the large veins and arteries in either the leg, neck or chest. The ECMO machine now pumps the oxygen-low blood from the patient’s body to an artificial lung (oxygenator). This oxygenates the blood and removes the carbon dioxide, just like our lungs. Once done, the ECMO machine sends the blood back to the patient via a pump with the same force that the heart would normally exhibit. Based on the condition of the patient, the settings on the machine can be adjusted to give them the required heart and lung support.
How is the cannulation done?
Previously, surgeons used to open the chest (sternotomy) and put one cannula into the venous system or the right atrium from where the body is taken out of the body and another cannula into the aorta where the oxygenated blood is returned to the body. But nowadays, with modern technology, we do what is called percutaneous peripheral ECMO. In percutaneous peripheral ECMO, the cannula is put into the femoral vein. This drains the blood, it gets oxygenated and then it is given back to the femoral artery in the groin (VA-ECMO) or jugular vein (VV-ECMO).
What are the types of ECMO?
There are two types — venoarterial (VA) ECMO and venovenous (VV) ECMO. VA-ECMO can be used for heart and lung support, while VV-ECMO is used for lung support only. In VA-ECMO, venous blood from the inferior vena cava (a large vein that carries deoxygenated blood from the lower body into the right atrium of the heart) is drained through a cannula often placed in the femoral vein. The blood passes through the oxygenator where it is oxygenated before being sent back to the arterial system through the femoral artery. In VV-ECMO, blood from the inferior vena cava is drained through a cannula often placed in the femoral vein. The blood passes through the oxygenator and it is then returned to the venous system through the internal jugular vein.