Is respiratory therapy a good prerequisite to being a nurse anesthetist or anesthesiologist assistant?

That is a very long way to do it. I knew a res. therpist who returned to school (to become a nurse). He said it didn't help him (get a job as a new grad nurse at all).

nope. waste of money and time. the 2 are different animals. google the requirements in your state and for national certification/license

The road to becoming a nurse anesthetist, from nursing school to board eligibility, is 8-9 years minimum. Adding 2 years of respiratory therapy (and likely another year or two of working as an RT before entering nursing school) will not give you any significant advantage. The SHORTEST route to an anesthesia career is the anesthesia assistant, which from start of undergraduate classes to completion of the masters AA program can be 6 years. Know that there are fewer employment opportunities and less autonomy being an AA versus a CRNA, and the pay can be lower.