Principles & Application 

ECMO is a modified ‘heart-lung machine’ that uses a centrifugal pump that acts as an artificial heart and an oxygenator that acts as an artificial lung. ECMO is a form of life support for people with life-threatening illnesses or injuries that affect the function of their heart or lungs. ECMO keeps blood moving through the body and balances blood gasses (oxygen and carbon dioxide).ECMO does not treat lung or heart failure, but does the jobs of the heart and lungs temporarily ― allowing them to “rest." The machine pumps the blood, provides oxygen, and helps the body get rid of carbon dioxide. 

Doctors might recommend ECMO for someone affected by severe trauma or infection, cardiac arrest, lung failure, or heart failure. Doctors can use ECMO to stabilize a severely ill patient while they are determining the diagnosis or starting treatment. ECMO can support blood oxygen and circulation for someone awaiting a heart or lung transplant. 

Hence, ECMO can be used in 2 categories - rescue therapy, to buy time and allow the supported organ to recover, and bridging therapy to stabilize patients. 

The ECMO circuit consists of an access cannula in the venous system (drainage cannula), a centrifugal pump, a blood gas exchange unit, and finally, a return cannula that can be placed in the venous system (V-V ECMO) or the arterial system (V-A ECMO)

The negative suctioning pressure in the drainage cannula allows the blood to flow from the patient’s venous system to the pump, where the centrifugal force then moves the blood to the oxygenator. From here, a consistent positive pressure in the return cannulas allows blood from the oxygenator to re-enter the patient’s circulation.

The circuit itself can be functionally divided into 3 limbs:

• Drainage limb: from the drainage cannula to the pump 

• Gas exchange limb: from the pump outflow to the ‘venous’ side of the oxygenator 

• Return limb: from the ‘arterial’ side of the oxygenator to the return cannula