C-FLEX is Respironics name for their method of exhalation relief.In a C-Flex machine the pressure is reduced momentarily when the machine senses that the user has started to exhale. In a technical disucssion Respiroonics shows that the pressure is reduced the moment the machine senses the user starts to exhale. The amount of reduction is controlled by the C-Flex setting on the machine. After a fixed time, the machine reverts to the set pressure.
It is NOT the same as a biPAP. With a BiPAP machine, 2 pressures are delivered by the machine. One pressure while the user inhales, and a second, lower pressure, while the user exhales. This article also shows how C-Flex is used in BiPAP therapy.
Sometimes users using C-Flex find that they are waking up because they are panting/breathing rapidly, a phenomenon WillSucceed suggests might be due to a phenomenon called "Breath Stacking". This happens when the C-Flex pressure reduction cycle ends before the user has finished exhaling. When this happens SOME users are triggered into inhaling before they have completed exhaling, so they don't flush all the CO2 out of their lungs. It is this premature inhalation action that is called "breath-stacking" and causes CO2 to overload in the user's lungs. Then the CO2 overload in the lungs triggers the panting/rapid breathing as the user's body tries to blow off the excess CO2.
In order to stop this happening go into the clinical menu on the machine and turn off the C-Flex feature or try reducing the amount of C-Flex from the user menu.
This Sleep Apnea Wiki article is under constuction.