Can you please tell me if it's my fault my dad is on a ventilator?

Probably not.: Obviously, i don't know what's going on specifically, but you should talk to your dad's doctors and nurses. There can be a lot of emotion and guilt when a patient is admitted to the icu, and if you are having trouble dealing with it you should ask for help. Most icus have counselors, social workers, or pastoral care staff that can assist you, but they may not know you need them if you don't ask.