ECMO (extracorporeal membrane oxygenation) is an advanced life support technique that takes over the functions of the heart and lungs outside the body when they are too severely impaired to support life. It is used in the most critical cases of cardiac arrest, cardiogenic shock, or severe respiratory failure, providing a bridge to recovery or to a definitive treatment such as a heart transplant.
How ECMO works
Blood is drawn out of the body through a cannula (a large tube), pumped through an artificial membrane that removes carbon dioxide and adds oxygen, and then returned to the body. The circuit includes a pump that replaces the heart’s function and an oxygenator that replaces the lungs’ function. The machine can support the circulation of blood around the body continuously, allowing time for the heart and lungs to rest and, in some cases, recover.
Types of ECMO
- VA-ECMO (venoarterial): supports both heart and lung function. Used in cardiac arrest and cardiogenic shock. Blood is returned to the arterial circulation, bypassing the heart.
- VV-ECMO (venovenous): supports lung function only. Used in severe respiratory failure when the heart is still pumping. Blood is returned to the venous circulation.
ECMO in cardiac arrest: ECPR
When ECMO is used during ongoing resuscitation, the technique is called ECPR (extracorporeal cardiopulmonary resuscitation). Rather than conventional CPR alone, the patient is connected to ECMO while resuscitation attempts continue. ECPR is used in specialist centres and is typically reserved for patients with refractory cardiac arrest (where standard resuscitation has not restored circulation) who are otherwise suitable candidates. It is not universally available.
Limitations
ECMO is highly invasive, resource-intensive, and carries significant risks including bleeding, clotting, infection, and limb ischaemia. It is used only in specialist centres and requires a dedicated, expert team to manage safely.
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