ECMO is hard. That survival was poor in a handful of early cases in China (1/15 with 2 unresolved) is a good start, but there is a lot more information available...and more relevant information.

In North America and Europe, where docs are more experienced with ECMO and were better versed in treating covid-19 (thanks in no small part to the experiences of the Chinese), the success rate seems to be MUCH better.

I was basing my gross estimate on the following data:

Among well over 1000 patients in a larger database?
survival 55% among resolved cases (about half are unresolved)
https://www.elso.org/COVID19.aspx

A later study in China: 3/7 discharged (with 1 unresolved)
https://journals.lww.com/asaiojournal/Fulltex...for.4.aspx

West Virginia University study: mortality 10/32 (17 unresolved)
DOI: 10.1097/MAT.0000000000001185

This all fits with observations that ECMO lowered mortality rates for ARDS patients with SARS, MERS, and H1N1.

If the survival rate is anything like the 1/3 - 2/3 suggested by the data, a patient coming off life support is a textbook case of "anecdote."