Here, courtesy of cpap.com's mailing list, is the TSA's official web page on Travelers with Disabilities and Medical Conditions.
[...] TSA has established a program for screening of persons with disabilities and their associated equipment, mobility aids, and devices. Our program covers all categories of disabilities (mobility, hearing, visual, and hidden). As part of that program, we established a coalition of over 70 disability-related groups and organizations to help us understand the concerns of persons with disabilities and medical conditions. These groups have assisted TSA with integrating the unique needs of persons with disabilities into our airport operations.
Includes pages about CPAP machines, wheelchairs, Assistive Devices and Mobility Aids, and quite a lot more. Think they've taken a bit of flak over this stuff? Take advantage of it if you need to.