Methods and apparatus for treatment of medical disorders such as obstructive sleep apnea and congestive heart failure are disclosed. A method involves delivering pressurized air, oxygen or other breathing gas to a patient during a respiratory cycle, where pressure of the air is decreased according to an expiratory unloading factor during expiration. The timing and magnitude of the pressure change may be fully automated and responsive to feedback from a motor load sensor, optionally in combination with a pressure sensor.