CPAPs aerosolize on exhale, they aren't closed loop like hospital ventilators. It's not about cleaning just the machine but decontaminating the whole room.
Is it not possible to route the exhaust through a filter? If a couple millimeters of masks can stop it surely a canister style filter would more than do th job.
I can see some pretty easy hacks for dealing with that. Putting a hose on the outlet and filtering with electret material or UVC. Healthcare in the US is regulated to the nth degree, but at this point it seems that a slightly imperfect solution is better than nothing, and testing a solution like this for viability should be easy in any hospital that can test for COVID-19.