The most common conditions in which ECMO is used to support the lungs are:

• Severe pneumonia or lung infection (especially influenza (flu) or COVID)
• Pulmonary embolus (blood clot in the lung)

The most common reasons for ECMO to be used to support the heart are:

• Following a large heart attack (sudden blocked arteries to the heart)
• After open heart surgery where the heart is failing to respond to usual medications

But the list of possible causes is long.

Most people require ECMO support in a hurry and when it has not been expected. For some people there is time to explain the need and risk of ECMO beforehand, but this is less common. Some people have ECMO commenced in an emergency setting and there is no time to explain these steps beforehand.