The ResMed S9 CPAP machine series was roughly available between the years 2010-15.  Its predecessor was the popular line called S8 series.  The S8 was a very compact unit due to having a robust motor, individual operating components, and a built in power supply vs the S9 which now has an external transformer.

 Any professional or commercial driver who is using CPAP is required by the DOT (department of transportation) to provide a compliance report of usage.  Drivers have mentioned DOT is needing compliance of using the device for at least 4 hours a night, 70-75% of the time in order to be passed.