ECMO (Extracorporeal Membrane Oxygenation) 

ECMO (Extracorporeal Membrane Oxygenation) is a life-saving procedure involving the use of a machine to give temporary support to the heart and/or lungs. An Extracorporeal Membrane Oxygenation treatment also known as the Bridge to Lung Transplant is used in patients with acute respiratory failure or end-stage lung disease as a bridge to Lung Transplant. In other words, Bridge to Lung Transplant is for patients who cannot survive without a lung transplant.

ECMO, as a Bridge to Lung Transplant: Definition & Overview

Extracorporeal Membrane Oxygenation or ECMO is a machine that temporarily provides heart and lung support to patients through the use of a Veno-Venous (VV) or Veno-Arterial (VA) cannula. For Lung Transplant patients, VV-ECMO is primarily used for patients that need pulmonary support only. This machine works by pumping blood from a vein through an oxygenator that adds oxygen to the blood and removes carbon dioxide and then pumping the oxygenated blood back into a vein. VV-ECMO basically allows the lungs to rest while the patient is waiting for a Lung Transplant. On the other hand, VA-ECMO is used in patients that need both pulmonary and cardiac support; however, this type of ECMO is rarely used for patients on the waiting list for Lung Transplant.

Reasons for Using an ECMO as a Bridge to Lung Transplant

An Extracorporeal Membrane Oxygenation (ECMO) machine, in most cases, is utilized for patients with severe acute respiratory failure that requires treatment before a Lung Transplant surgery. In addition, an ECMO can also be used as a bridge to Lung Transplant for patients with any of the following:

Acute Respiratory Failure

Acute respiratory distress syndrome (ARDS) or any other acute respiratory failure that does not respond to mechanical ventilation or other treatment. Acute respiratory distress syndrome (ARDS) can present with a spectrum of symptoms ranging from mild to severe respiratory distress and decreased oxygen levels (hypoxemia). Conditions such as trauma, pneumonia, sepsis, and aspiration can lead to ARDS which may require treatment with an ECMO.

End-Stage Chronic Lung Disease

End-stage chronic lung disease includes pulmonary fibrosis, chronic obstructive pulmonary disease (COPD), emphysema, cystic fibrosis, or other chronic lung diseases that may require a Lung Transplant.

Pulmonary Hypertension

Pulmonary hypertension (PH) is a condition characterized by abnormally high blood pressure in the pulmonary artery. This condition may lead to right heart failure and profound respiratory failure requiring extracorporeal oxygenation.

Bronchial Obstruction

Bronchial obstruction due to tumors or other causes that lead to acute respiratory distress and respiratory failure.

Lung Transplant Complications

Following Lung Transplant, patients may present with graft dysfunction or other complications such as infections, which may lead to acute respiratory failure requiring an ECMO as a bridge back to the Lung Transplant.

Refractory Hypoxemia or Hypercapnia

Hypoxemia or hypercapnia that is not responsive to treatment or mechanical ventilation.

Pediatric Patients

In some cases, an ECMO can also be used as a bridge to Lung Transplant in pediatrics for respiratory failure due to lung disease and malformation.

How does ECMO Work for a Lung Transplant Patient?

In summary, an Extracorporeal Membrane Oxygenation is basically a machine that offers temporary cardiac and pulmonary support to patients with acute respiratory failure or who need a Lung Transplant. This machine takes over the work of the lungs giving it time to rest and heal while the patient waits for a Lung Transplant. Following are some of the ways on how an ECMO works for a Lung Transplant patient:

VV-ECMO setup

In the first place, a cannula is inserted into a major vein (such as the femoral and internal jugular veins) that allows the machine to pump blood out of the body; the blood is then pumped through the VV-ECMO circuit. In the VV-ECMO circuit, the blood is oxygenated and de-carbonated. Lastly, the re-oxygenated blood is pumped back into the major vein, most commonly the internal jugular vein, the subclavian vein, or the superior vena cava.

Rest for the Lungs

The VV-ECMO circuit performs the work of the patient’s lungs, providing the much-needed oxygenation and ventilatory support required to allow the patient’s lungs to rest.

Blood Flow and Oxygenation

The VV-ECMO circuit provides sufficient flow and oxygenation, which in turn promotes adequate organ perfusion that would otherwise be limited due to lung injury. By doing so, it prevents oxygen deprivation, which could lead to lung damage, brain damage, renal failure, etc.

Monitoring

The VV-ECMO circuit must be closely monitored to prevent complications. For example, medical workers have to ensure that the machine is not the source of infection or coagulation problems. In addition, the rate of flow of the machine and its oxygenation must often be checked and monitored.

Procedure for initiating ECMO

The VV-ECMO cannulation is performed by a specialist under local anesthesia. The specialist accesses the vena cava through either the femoral vein or the internal jugular vein. This procedure can alternatively be done in the operating room under general anesthesia. The patient is then connected to the machine (the VV-ECMO circuit). The specialist then tunes the VV-ECMO according to the specific needs of the patient. Moreover, it is important to keep a close watch on the patient throughout the whole procedure.

Health workers that are handling the VV-ECMO circuit have to constantly monitor the patient for any signs or development of infection or other complications. Additionally, they constantly monitor the overall condition of the patient and may determine the need to prescribe certain medication. In addition, the patient is put on a ventilator to assist with breathing while the VV-ECMO circuit provides the lungs with the oxygenation it needs. The VV-ECMO circuit basically promotes rest for the patient’s lungs.

Benefits of Using ECMO as a Bridge to Lung Transplant

Following are some of the benefits of using an ECMO as a bridge to a Lung Transplant:

The ECMO machine provides crucial support to patients presenting with acute respiratory failure, thereby stabilizing them and allowing for the introduction of other forms of treatment.

Lung Protection and Rest

ECMO provides the required oxygenation and ventilation of patients, thereby giving their lungs a much-needed rest. This would be beneficial to patients with acute respiratory distress syndrome (ARDS), chronic obstructive pulmonary disease (COPD), or other lung problems since it helps to prevent additional lung damage or complications.

Protecting Other Organs

ECMO provides oxygenation and ventilation that can help prevent other organ damage and promote organ function.

Buying Time for a Donor Lung

ECMO can buy time for critically ill patients who cannot afford the time it takes to find a donor lung. Therefore, it can be used as a bridge to a Lung Transplant for those patients who cannot be weaned off the ventilator.

Bridge to Further Treatment or Lung Transplant

ECMO can act as a bridge to further treatment or a Lung Transplant for patients with acute respiratory failure. This would allow patients to be put on a waiting list for a Lung Transplant while they recover and regain their health.

Risks and Complications of Using ECMO

An Extracorporeal Membrane Oxygenation, a bridge to a Lung Transplant, is mostly indicated for patients with acute respiratory failure or other severe conditions. In addition, the Extracorporeal Membrane Oxygenation can present with a number of risks and complications such as:

Infection

Since an ECMO is an invasive procedure that requires the insertion of several large catheters into the vena cava, there is a possibility that complications such as infection may arise.

Bleeding

An ECMO patient is put on anti-coagulants to prevent the formation of clots within the machine; however, this may lead to other complications such as severe bleeding.

Blood Clots

Blood clots may also form within the VV-ECMO circuit leading to various complications depending on where the clot is located. For example, if a blood clot travels to the brain it may lead to a stroke.

Organ Dysfunction

An ECMO may also lead to malfunction of organs such as the kidneys, liver, and brain.

Right Heart Failure

ECMO is closely associated with right heart failure which leads to various complications.

Post-ECMO and Following Lung Transplant Surgery

Once there is an available donor lung, the patient will have to undergo Lung Transplant surgery. Once the surgery is done, the patient will be closely monitored for any complications and appropriate interventions will be administered if needed. In addition, the patient will be required to take immunosuppressive drugs to prevent transplant rejections. The patient may also begin pulmonary rehab to aid in their recovery. In the end, the patient will be transferred to another facility where they will be monitored to ensure that the donor lungs are working appropriately.

ECMO as a Bridge to Lung Transplant Survival Rate

The survival rate of patients that are placed on an ECMO as a bridge to a Lung Transplant varies. In most cases, the survival rate to a Lung Transplant from patients on an ECMO is high as most patients survive on an ECMO until a donor lung becomes available. The survival rate of patients on an ECMO as a bridge to a Lung Transplant is between 60 and 70% one year after the procedure. On the other hand, following a Lung Transplant the survival rate is even higher at between 85% one year after surgery and 50 to 60% five years after surgery.