Traveling with your CPAP can sometimes be a hassle. However, with proper preparation, it can be very easy. If you are flying with your CPAP, you can bring your CPAP machine on the airplane with you and it will not count as one of your carry-on items. Never check your CPAP machine because through normal luggage handling procedures it can easily be broken. You may want to call ahead and find out your airline's procedures for carrying your CPAP machine on the airplane to prevent any delays through security. We have learned that many airlines will not let you use your CPAP machine during the flight because it is not a life-sustaining device. You may want to contact your airline to see if you can make special arrangements.
From Air Transat website
A CPAP (Continuous Positive Airway Pressure) machine will be accepted as a carry-on if it fits the standard carry-on size of 23 x 40 x 51 cm (9 x 16 x 20 in). Due to the excess weight of these machines, we ask that you limit your other carry-on to the bare minimum that is required for your personal needs during flight.
Note: The distilled water used by this device is exempted from the liquid restrictions of carry-on baggage. We recommend that passengers carry supporting documentation from their doctor to facilitate pre-board screening.