Hi,
why don't you just start by checking the registration authorities of English speaking countries? This will give you an idea about the requirements for registration and the costs involved.
You will need to undergo some kind of assessment in all countries, but that's not always an exam (e.g. Australia) but could involve preparing a portfolio (e.g. NZ).
As to the job situation - I can only talk about the situation down here - there are jobs in Australia and NZ, but not as many as there were a few years ago.
With hospital respiratory and sufficient experience, I presume you'll always find a job. There's not many Specialists in this area.
Good luck,
Fyzzio