What Is ECMO?

A ventilator can only do so much. It pushes air into the lungs and hopes the lungs can still trade gases — but when lungs are too sick to take in oxygen, or a heart is too weak to move blood around, pushing harder doesn't fix the problem. That's the gap ECMO fills. ECMO — extracorporeal membrane oxygenation — takes blood out of the body, adds oxygen and removes carbon dioxide through an artificial membrane, and returns the blood, doing the gas-exchange work outside the body while the heart and lungs rest. It doesn't cure anything. It buys time.

ECMO vs a ventilator: support from outside, not inside

The contrast is worth spelling out, because the two are often confused. A ventilator works through the lungs: air travels down a breathing tube, and the patient's own lung tissue still has to pass oxygen into the blood. Our guide to a ventilator and how it works covers that side in detail, and the breathing tube itself is explained in our article on endotracheal intubation. ECMO works around the lungs: large tubes (cannulas) placed in big blood vessels carry blood to a pump and an oxygenator, where gas exchange happens across a membrane, and the warmed, oxygen-rich blood flows back. Because the exchange no longer depends on injured lung tissue, the ventilator can usually be turned down to gentler settings — which is the point. Rest, for an organ, means not being forced to work at full stretch while it heals.

The video at the top: an explainer centred on babies

The recording at the top of this page, "ECMO Explained" (just under four minutes), introduces ECMO through its use in infants who are sick because of breathing or heart problems. Its own description states the purpose plainly: to provide enough oxygen while allowing time for the lungs and heart to rest or heal. That infant framing is worth knowing before you press play — ECMO is also used in older children and adults, and the circuit it shows works on the same principle at any age. A second, more specialist recording on this site, "Start of CRRT circuit within ECMO" (just over a minute), shows a kidney-support circuit being started within an ECMO setup — a glimpse of how these systems are combined and managed by intensive care teams, rather than a general introduction.

Two ways to return the blood: VV versus VA

ECMO comes in two main configurations, and the difference is where the blood goes back. In venovenous (VV) ECMO, blood is taken from a vein and returned to a vein. The oxygenator does the lungs' gas-exchange work, but the patient's own heart still pumps the blood around the body — so VV support is used when the lungs are the failing organ, as in severe pneumonia and other causes of respiratory failure. In venoarterial (VA) ECMO, blood is returned to an artery instead, so the circuit helps with pumping as well as gas exchange — support for both heart and lungs, used when the heart itself is failing, the situation described in our overview of heart failure. Same machine, same membrane; a different job, decided by which organ needs the help.

What a day on ECMO actually involves

From the outside, ECMO looks quiet: the patient rests in an intensive care bed, usually deeply sedated, while the circuit hums beside them. Inside that quiet is constant work. A specialist team watches the pump, the oxygenator, pressures and blood tests around the clock, because blood running through an artificial circuit tends to clot — medicines that thin the blood are usually part of care, and the balance between clotting and bleeding is one of the main things the team manages day to day. ECMO is only offered in specialist centres with that team in place. It continues for as long as it is helping — while the underlying problem is treated and, everyone hopes, begins to recover. When the heart or lungs show they can take over again, support is reduced in a trial, and the cannulas come out. When they can't, ECMO has still done its one honest job: it gave the body time that it wouldn't otherwise have had.

References & further reading

• MedlinePlus Medical Encyclopedia — Extracorporeal membrane oxygenation: https://medlineplus.gov/ency/article/007234.htm
• MedlinePlus — Respiratory Failure: https://medlineplus.gov/respiratoryfailure.html
• MedlinePlus — Heart Failure: https://medlineplus.gov/heartfailure.html
• Nemours KidsHealth — Extracorporeal Membrane Oxygenation (ECMO): https://kidshealth.org/en/parents/ecmo.html
• Extracorporeal Life Support Organization (ELSO) — Resources for ELSO and ECMO: https://www.elso.org/ecmo-resources.aspx

Frequently Asked Questions

Is ECMO a cure?
No — and that's the most important thing to understand about it. ECMO does the gas-exchange work (and, in VA mode, some pumping work) so the heart and lungs can rest, but recovery depends on the underlying illness or injury improving with treatment. ECMO buys time; it doesn't fix the cause.

How is ECMO different from a heart-lung bypass machine?
They're cousins, not twins. A bypass machine supports a patient for the hours of an operation, in theatre, with the chest open. ECMO is designed to run for much longer — days and sometimes longer — at the bedside in intensive care, through cannulas in large vessels. The principle of pumping and oxygenating blood outside the body is shared.

How long does someone stay on ECMO?
It varies widely with the reason for support and how recovery goes, from days to, in some cases, several weeks. There's no standard timetable; the team reassesses continuously and trials reducing support when the heart or lungs begin to recover. Your own team can talk through what they're watching for in your family member's case.

Can anyone receive ECMO?
No. It's a major, resource-intensive treatment offered in specialist centres, and teams weigh whether the underlying problem has a realistic chance of recovering and whether ECMO's risks are justified for that person. Those decisions are individual and clinical — this page deliberately doesn't set out eligibility rules, because they belong to the treating team and the centre's specialists.

MedicalVideos.com has published trusted medical videos since 2007. The site was founded by Dr. Mohamed Ibrahim, MD, PhD — physician-scientist.

Educational only — this article is general information about ECMO, not medical advice and not a diagnosis. Decisions about ECMO belong to the specialist intensive care team caring for the individual patient.