Mortality rate of COVID-19 patients on ventilators:
https://www.physiciansweekly.com/mortality-rate-of-covid-19-patients-on-ventilators/
An interesting posting a FReeper provided yesterday that says something similar, but believes the low oxygen to be from lost red blood cells:
https://web.archive.org/web/20200405061401/https://medium.com/@agaiziunas/covid-19-had-us-all-fooled-but-now-we-might-have-finally-found-its-secret-91182386efcb