You really should contact the airline and make arrangements with them for any special needs you have. They should also be made aware of your situation in case anything happens to you inflight. They need to have emergency contact numbers for you. You should be sure to ask a doctor if it is indeed safe for you to fly. Pressurization seriously affects the lungs. Generally, aircraft pressurize to an altitude of around 8000' - this is comfortable for healthy individuals but can put stress on the cardio-vascular system. You do not want to be the cause of 200+ people having to divert into a foreign airport in the middle of the night. It is not safe for you, and causes an emergency on the part of the crew and all the other passengers.
Surgery