Fortunately, the answer is even easier than you think. Thanks in part to the Americans with Disabilities Act, airlines have to provide you accommodations to carry your CPAP machine (or BIPAP/AutoPap or other respiratory device). Also as CPAP machine’s are increasingly common, a great number of travelers every day are flying with their CPAP machines.
Domestic airlines are required to allow you to bring your CPAP machine with you on the airplane without the machine and its equipment counting towards your carry on luggage allowance. International rules may vary of course. It is generally recommended that she bring your machine on the plane with you, rather than checking your machine with luggage, in the event that you have lost luggage and have no access to your CPAP machine for several days.
The TSA will opt to put your machine through the scanner, and may require you to open the bag to visually inspect the machine. It is of course recommended to keep the machine fairly clean and sanitary, and best practices would be to put this in a sealed Ziploc bag so that he can be inspected in a sanitary fashion.
Rarely if you are chosen for inspection, your machine may be closely inspected by a TSA agent along with the rest of your carry on luggage.
While it is not a requirement of the TSA, having a doctor’s prescription or order with you may help in the event of further questioning by the TSA. This may be even more important when traveling internationally, and may also prove beneficial should you damage or machine or need a replacement machine or supply while out of town.
In general, it is fairly easy to travel with your CPAP, but does require a little bit of planning and packing ahead of time. And of course, don’t forget that if traveling internationally electrical adapters or transformers may be needed.