Tiberius himself hasn't been previously covered in the sub, so anything specific to his case is more than welcome.

In the meantime, here are some previous posts on ancient coma care in general:

Caligula and his coma has been asked about before, but received no surviving responses. In the meanwhile, I did turn up some answers regarding comatose care before modern medicine:

• A now-deleted user on the medical side of things.
• u/jpallan offers insight on Henry VI.
• Bonus: u/itsallfolklore has a post on how the comatose were socially regarded; not directly medical, but related and interesting.