Well, you don't want to check everything and risk it being lost or damaged, so I would suggest you take it as carry-on. We have yet to fly with DS's vest because our last trip, he didn't have it yet, but we flew several times with a nebulizer, cooler with meds... We put his nebulizer in a carry-on, along with a small lunch box cooler that had one of those ice packs we got in the mail with his tobi to keep his tobi & pulmozyme and liquid meds cool. I asked the pharmacy for smaller pill bottles, so I didn't have to take the ginormous containers a 3 month supply comes in -- so I could take just enough meds for a week or so trip (did have extras in case of flight delays). And I placed all the pill bottles in a smaller baggie.
Do you have a hill-rom vest? I know a couple people here have just packed everything in a carry-on size spinner (samsonite) or rolling suit case and placed everything in that for ease of transport. Hill Rom now has a duffle bag with wheels, though. Medical equipment is considered exempt from your carry-on luggage allotment. Some people carry a letter along from their doctor.
The only issue we had in all our travels is the local airport took us aside to scan our "breathing apparatus" -- nebulizer. Then made DH plug it in. Otherwise, no issues.
