Extracorporeal Membrane Oxygenation (ECMO)

Extracorporeal membrane oxygenation (ECMO) is a form of life support that drains a patient's blood, oxygenates it and removes carbon dioxide through an external membrane lung, and returns it to the circulation. It temporarily substitutes for the function of the lungs, and in some configurations the heart, in patients whose cardiac or respiratory failure is refractory to conventional support.

Definition

Extracorporeal membrane oxygenation is a temporary mechanical life-support technique in which blood is circulated outside the body through a membrane oxygenator that performs gas exchange, supporting respiratory function (venovenous) or both cardiac and respiratory function (venoarterial) when the patient's own organs cannot.

Scope

The entry covers the principle of extracorporeal gas exchange, the main venovenous and venoarterial configurations and what each supports, the registry data describing its use, and the trial evidence in severe respiratory failure and shock. It is a reference description of the technique and its evidence base, not guidance on patient selection or device management.

Core questions

• What does ECMO replace, and how does it perform gas exchange outside the body?
• How do venovenous and venoarterial ECMO differ in what they support?
• What does the evidence show about ECMO in severe respiratory failure and shock?

Key concepts

• Extracorporeal gas exchange
• Membrane oxygenator
• Venovenous (VV) ECMO for respiratory support
• Venoarterial (VA) ECMO for cardiac and respiratory support
• Bridge to recovery, decision, or transplantation
• Extracorporeal cardiopulmonary resuscitation (ECPR)

Mechanisms

A pump drains venous blood through a circuit containing a membrane oxygenator, where oxygen is added and carbon dioxide removed across a gas-permeable membrane, before the blood is returned to the patient. In the venovenous configuration, oxygenated blood is returned to the venous system and the patient's own heart pumps it forward, so the technique supports the lungs alone. In the venoarterial configuration, blood is returned to the arterial system, providing both gas exchange and circulatory flow and thereby supporting a failing heart as well as the lungs. Because blood contacts artificial surfaces, anticoagulation and careful circuit management are intrinsic to the technique.

Clinical relevance

ECMO illustrates how the most advanced forms of organ support substitute mechanically for the heart and lungs, and the trials and registries describing it form part of the evidence clinicians appraise. This entry describes the technique and its evidence base as a reference; it does not provide criteria for selecting patients or instructions for managing the device.

Epidemiology

Use of ECMO has grown substantially over recent decades, documented by international registry reports, and expanded further during periods of high demand for respiratory support. Outcomes vary by indication, configuration, and the experience of the treating center.

Evidence & guidelines

The EOLIA trial (Combes et al., 2018) examined venovenous ECMO in severe acute respiratory distress syndrome, and registry reports from the Extracorporeal Life Support Organization (Thiagarajan et al., 2017) describe patterns of use and outcomes. Reviews such as Vincent and De Backer (2013) situate venoarterial support among the options for circulatory failure, and device trials such as DanGer Shock (Møller et al., 2024) inform the broader landscape of mechanical support in shock.

History

Extracorporeal gas exchange grew out of cardiopulmonary bypass developed for cardiac surgery and was adapted for prolonged support outside the operating room, with early success in neonatal respiratory failure. Adult use expanded as circuit technology improved and as trials and registries accumulated, and demand rose sharply during epidemics of severe respiratory failure.

Debates

When does ECMO improve outcomes in severe respiratory failure?

Trial evidence for venovenous ECMO in severe acute respiratory distress syndrome has been interpreted in different ways, with debate over patient selection, timing, and crossover affecting how its benefit is judged.

Key figures

• Alain Combes
• Robert H. Bartlett

Seminal works

• combes-2018-eolia
• thiagarajan-2017-elso

Frequently asked questions

What is the difference between venovenous and venoarterial ECMO?

Venovenous ECMO returns oxygenated blood to the venous side and supports the lungs while the heart pumps, whereas venoarterial ECMO returns blood to the arterial side and supports both the heart and the lungs.

Does ECMO cure the underlying disease?

No; ECMO temporarily substitutes for heart or lung function to buy time, serving as a bridge while the underlying condition recovers or while other decisions or treatments are pursued.