ECLS stands for Extracorporeal Life Support, a treatment that uses a machine to do the work of the heart, the lungs, or both when a patient’s own organs are too sick to keep up. You’ll often hear it called ECMO (Extracorporeal Membrane Oxygenation), and the two terms are essentially interchangeable. ECLS is a last-resort option, used only after ventilators, medications, and other therapies have already been tried.
How the Machine Works
The basic idea behind ECLS is straightforward: blood is drawn out of the body through a large tube called a cannula, run through a machine that adds oxygen and removes carbon dioxide, then pumped back in. The circuit has four main components working together. A mechanical pump moves the blood. A membrane oxygenator acts as an artificial lung, handling gas exchange. A heat exchanger warms the blood back to body temperature so it doesn’t chill the patient. And tubing connects everything between the patient and the machine.
The goal is to give damaged organs time to rest and heal. While the machine handles gas exchange or circulation, the heart and lungs aren’t working as hard, which can allow them to recover from injury, infection, or surgery.
Two Types: Lung Support vs. Heart and Lung Support
There are two configurations of ECLS, and the choice depends on which organs need help.
Venovenous (VV) ECLS supports the lungs only. Blood is pulled from a large vein, oxygenated by the machine, and returned to another vein near the heart. The patient’s own heart still pumps that freshly oxygenated blood to the rest of the body, so the heart needs to be functioning reasonably well for this approach to work. In some cases, a special double-channel cannula allows blood to leave and return through a single insertion site instead of two.
Venoarterial (VA) ECLS supports both the heart and lungs. Blood is drawn from a large vein but returned directly into a large artery, bypassing the heart entirely. This means the machine is not only oxygenating the blood but also pushing it through the body, taking over the heart’s pumping role. Two cannulas are placed, typically in the neck or groin.
How the Tubes Are Placed
Getting a patient connected to the ECLS circuit requires inserting large cannulas into major blood vessels. The most common access points are the internal jugular vein in the neck and the femoral vein or artery in the groin. The right side of the body is preferred for both locations because the veins run in a straighter path toward the heart, making cannula placement more reliable.
Most cannulations are done percutaneously, meaning the tubes are threaded in through the skin using a guidewire technique rather than open surgery. This can happen at the bedside in an ICU, in a catheterization lab, or even in an emergency room. Doctors typically use ultrasound or other imaging to guide placement. One practical tradeoff: a cannula in the groin limits how much a patient can move around. In some cases, the team will start with a groin-and-neck setup for speed, then convert to a single neck-based cannula within a day or two so the patient can sit up and eventually walk while still on the machine.
When ECLS Is Used
ECLS is reserved for the sickest patients, those whose lungs or heart are failing despite aggressive conventional treatment. For lung failure, it’s typically considered after a patient with severe acute respiratory distress syndrome (ARDS) hasn’t improved with mechanical ventilation, sedation, and being positioned face-down to help the lungs open up. These patients have dangerously low oxygen levels that can’t be corrected any other way.
On the cardiac side, VA ECLS can support patients whose hearts are too weak to maintain blood pressure and circulation. One specialized application is called E-CPR, where the machine is connected during active cardiac arrest when standard CPR isn’t restoring a heartbeat. Observational data have consistently linked E-CPR to better survival in select patients experiencing cardiac arrest inside a hospital, and recent randomized trials suggest it can also improve survival with good neurological recovery for out-of-hospital cardiac arrest, provided care is delivered within a well-coordinated system.
ECLS also serves as a bridge to organ transplant. For patients awaiting a new set of lungs, the machine can keep them alive and, in some cases, awake and mobile until a donor organ becomes available.
How Long Patients Stay on ECLS
The duration varies widely depending on why the patient needs support and whether their organs are recovering or they’re waiting for a transplant. For patients bridged to lung transplant, studies across multiple countries show a median support time ranging from about 7 to 21 days, with most falling in the 8 to 13 day range. Shorter durations are generally associated with better outcomes.
Some patients on bridge-to-transplant ECLS are kept awake and even encouraged to walk while connected to the machine. Across published studies, anywhere from 23% to 85% of bridge patients were awake and ambulatory during support, a wide range that reflects differences in how sick patients were at the start and how aggressively rehabilitation was pursued.
Survival Rates
Survival depends heavily on the patient’s age, the reason for ECLS, and which type of support is used. According to data from the international ELSO Registry covering tens of thousands of cases, survival to hospital discharge is highest for newborns with respiratory failure, at about 68.5%. The lowest survival rate, around 29.5%, is seen in adults who receive E-CPR during cardiac arrest. Most other patient groups fall somewhere between those figures.
Risks and Complications
ECLS requires blood thinners to prevent clots from forming in the circuit, and that creates a constant tension between clotting and bleeding. Bleeding is the most common complication. Gastrointestinal bleeding occurs in roughly 3% of patients on VA ECLS, and that rate climbs to 7 to 9% among patients who also develop a stroke.
Stroke is a serious concern. In patients on VA ECLS, ischemic stroke (caused by a blood clot blocking flow to the brain) occurs in about 3.2% of cases, while hemorrhagic stroke (bleeding in the brain) occurs in about 1.4%. Patients who develop either type of stroke also tend to experience higher rates of other complications, suggesting that stroke is often part of a broader pattern of instability rather than an isolated event.
Coming Off the Machine
The process of disconnecting a patient from ECLS, called weaning, is gradual and closely monitored. For VV ECLS, the team watches for signs that the patient’s own lungs are recovering. When the lungs can handle 50 to 80% of gas exchange on their own and oxygen levels stay acceptable on moderate ventilator settings, doctors begin dialing down the machine’s support. They reduce the gas flow through the oxygenator and check blood oxygen levels frequently, typically every hour after each adjustment. If the patient’s oxygen saturation drops below 88% or their breathing rate spikes above 30 to 35 breaths per minute, the trial is paused and full support is restored.
For VA ECLS, weaning focuses on the heart. The team gradually reduces the pump flow while monitoring heart function with continuous ultrasound imaging. They’re looking for a blood pressure that holds above a minimum threshold, adequate oxygen levels, and an ejection fraction (the percentage of blood the heart pushes out with each beat) of at least 25 to 30%. Any sign that the heart can’t keep up, such as rising lactate levels in the blood or worsening heart function on imaging, means the patient goes back to full support and the team tries again later.