ECMO (extracorporeal membrane oxygenation) replaces the functions of both the heart and the lungs.
This expensive end stage device seems to have created a Lazarus effect in at least one case.
https://www.nydailynews.com/coronavirus/ny-er-doctor-with-coronavirus-says-tocilizumab-saved-his-life-20200414-24bdl5m7fjfjpowkfedirbood4-story.html