My guess is the old machine was waiting for the ramp to finish before starting the compliance hours. I think most of the modern machines don't bother with that. It may be that folks (the manufacturers, the DMEs, the docs, and the insurance companies) have all come to realize that it is better to find a way to pay for the machine for a patient who is having some adjustment problems and work on getting them fully compliant (in the sense of sleeping with the machine 100% of the time) rather than bean counting whether the "4 hours" were at full therapy pressure or not.
current settings Min EPAP = 4, Max IPAP = 8 and Rise time = 3
8/1/2010 sleep study results:
AHI = 3.9 [AHI = (#OA +#CA + #H w/desat) per hour]
RDI = 23.4 [RDI = (#OA +CA + #H w/desat + #H w/arousal) per hour]
Dx: Moderate OSA