Special tubes called cannulas are put into the blood vessels that go directly into your child's heart or bloodstream. Your child's doctor chooses the size of the tubes based on his or her size, age, weight and the reason why ECMO is being used. The cannulas transfer the blood from the child's heart by using a pump to push the blood through tubes to the machine where the blood receives oxygen and the carbon dioxide is removed. Next the blood is warmed to body temperature. Finally, the warm blood goes through another cannula back your child's body.
Look at the following pictures of the ECMO circuit/machine. They are labeled to help you understand how the blood flows from the child through the cannulas, into the machine and back to the child.
What are the modes of ECMO support?
Veno-Venous (VV): This type of ECMO provides support for the lungs only. One or two cannulas are placed in large vein(s) on the side of the neck or in the groin area at the top of the leg. Your child's heart will continue to work normally. The ECMO machine will drain the blood from the vein through the cannula, oxygen will be added to the blood, carbon dioxide will be removed, and then the blood is warmed and returned back to the right side of the heart through the cannula. The child's heart pumps the oxygenated blood to the body, so that the lungs have time to rest and recover.
Veno-Arterial (VA): VA ECMO provides support for both the lungs and the heart. Two cannulas are placed in large vessels on the side of the neck, directly into the chest (while the chest is covered with a sterile protector) or into the groin vessels. The ECMO machine will drain the blood from the vein, add the oxygen and remove the carbon dioxide, warm the blood and then return the blood to the artery and "pump" the blood through the body. This method allows the blood to "bypass" the heart and lungs, allowing them to rest and get better.