Patent ID: 7252088

Claim:
A method of operating a machine for the treatment of sleep apnea comprising: providing a machine for the treatment of sleep apnea that operates on D.C. power, wherein the machine includes a motor and compressor that are operationally coupled with a mask for delivering pressurized air to a patient; providing a power supply system for providing D.C. power to the sleep apnea machine, wherein the power supply system includes: an A.C.-to-D.C. converter for receiving an A.C. power input and converting the A.C. power into a D.C. power output; a rechargeable battery operationally coupled with the D.C. power output of the A.C.-to-D.C. converter; and a D.C.-to-D.C. converter operationally coupled with the rechargeable battery and the D.C. power output of the A.C.-to-D.C. converter, wherein the D.C.-to-D.C. converter receives a D.C. voltage within a range having a minimum and a maximum and outputs a D.C. voltage at a fixed level for powering the machine for the treatment of sleep apnea; and activating an audible alarm sufficient to wake a sleeping patient when the rechargeable battery is nearly depleted and A.C. power to the A.C.-to-D.C. converter fails but not activating the audible alarm when the rechargeable battery is able to provide power sufficient to operate the machine for the treatment of sleep apnea.