Hi Kelly
I checked with my London respiratory doctors about me flying, (a four hour flight from the UK to Malta) and they said I was ok and gave me the go ahead. We decided however not to fly this year because of the airstrikes and the volcanic ash problem and went by ferry to France instead,
So, i'm afraid I can't help any more than to say, my doctors were ok with it, and didn't have any special instructions for me.
I would worry too about picking up a virus, as the air system in the plane is notorious for picking up coughs and colds, so a mask might be a good idea,
Alison