Updated: May 22, 2021 1:25:37 pm
Over the past several weeks, as the second wave of Covid-19 has devastated India and patients have struggled against an acute shortage of medical oxygen and ICU beds, a clinical intervention technique known as ‘ECMO’ has entered the vocabulary of common conversation.
In critically ill patients, when oxygen support fails, specialists may resort to mechanical ventilation to help maintain oxygenation. However, some patients are no longer able to respond to such intervention — their heart and lungs are too weak or diseased to carry out the exchange of gases that is needed to stay alive.
In these extreme cases, doctors may choose to apply ECMO or extracorporeal membrane oxygen, which acts as an artificial heart and pair of artificial lungs outside the body (thus ‘extracorporeal’), which removes carbon dioxide from the patient’s blood and adds oxygen to it.
How does ECMO work?
Originally developed in the 1960s to support newborns and infants with respiratory distress syndrome and cardiac abnormalities, ECMO has been widely adapted for use in adults only over the last five years.
The ECMO machine works by inserting a plastic tube into a large vein and/or artery through the neck, chest or groin of the patient. This tube allows the patient’s blood to flow out into an oxygenator, or artificial lung. The oxygenator adds oxygen and removes carbon dioxide from the blood, before a pump sends this blood back into the patient through a different tube, at the same frequency and force as that of the patient’s heart.
The machine is used when all other medical options have been exhausted for patients whose lungs can’t provide enough oxygen to their body or rid themselves of carbon dioxide. It can also be used for patients whose heart can’t pump enough blood to the body, and for those waiting to either get a heart or lung transplant.
How does ECMO work for Covid-19 patients?
Studies of the virus and how it affects the body for over a year have shown that in the majority of Covid-19 patients who turn serious, the infection spreads to the lungs. Studies have revealed that unlike pneumonia or influenza A or B, Covid-19 affects all five lobes of the lungs.
In the event that all five lobes of the lung are damaged, they can’t properly exchange oxygen and carbon dioxide. As carbon dioxide levels in the body increase, so does the respiratory rate, as the brain tells the body to breathe more to rid itself of this carbon dioxide. However, since the lungs are damaged and are unable to so, this carbon dioxide remains in the blood, and turns it acidic.
When a patient is brought into hospital to be put on ECMO support, a right ventricular support device (RVAD) and oxygenator within the ECMO machine are used. The RVAD is placed inside the patient through the tube that goes into the patient’s neck, down through the right atrium and right ventricle of the heart and into the pulmonary artery.
This allows for blood to be taken out of the right atrium and sent to the ECMO machine. There, it’s filtered, temperature-modulated and oxygenated, and the carbon dioxide is removed. This blood then re-enters the body through a tube placed in the pulmonary artery.
For Covid-19 patients, this accomplishes two things.
One, it takes the load off the right side of the heart, as it is essentially bypassed.
And two, by increasing the level of oxygen going into the lungs, it decreases pulmonary vascular resistance and reduces the pressure it takes to push blood through the lungs.
The ECMO process supports patients’ bodies and allows them extra time to combat the virus. This extra time is often critical for patients with extreme illness.
The average Covid-19 patient can stay on ECMO for 10-12 days. Once off ECMO, they are kept isolated while recovering in the cardiovascular intensive care unit.
ECMO has also been shown to successfully reduce the chances of a cytokine storm — in which the patient’s immune system turns on itself — which can cause a severe inflammatory response and multiple organ failure.
What risks are involved in the ECMO procedure?
A major complication that might arise is bleeding. Because of the blood thinning medication that patients need while on ECMO, they can start bleeding at different places in their body.
Also, patients who are on ECMO sometimes do not get enough blood flow to their kidneys. This can cause their kidneys to stop working, a condition known as acute renal failure.
Infection is a very real and major threat. Tubes from the ECMO machine go from outside the patient’s body directly into their bloodstream. This makes the patient extremely vulnerable to germs entering the body.
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