As mentioned, ECMO is a treatment for respiratory failure. There are obviously more conventional treatments for these problems, however if the patient condition worsens, increases in conventional mechanical ventilation and other treatment can actually do permanent damage to the lungs.

If the patient does survive, this damage will lessen the chances for normal recovery and quality of life.

The key is to start ECMO before the the irreversible changes occur. Several "classic" diseases and conditions meet this description.