How does ResMed S9 initiate breathing after an apnea event

[c0reDump]

I have the S9 Elite and having been using it since February.

The EPR is a "comfort" feature and allows exhale relief of up to 3 cm H2O relief. So if your set pressure is 10, and your EPR is set to 3, it will allow an exhale pressure of 7. If the unit detects an event (lasting 10 secs), it will immediately increase the pressure back to it's "set pressure" (regardless of EPR).

There is an option to allow EPR during ramp only, or allow the EPR to be full-time. Sounds like you had best results with it off entirely, and if you find that comfortable that's great.

For myself, I really prefer using the EPR, but I have noticed there is a trade-off. If the exhale pressure is allowed to drop too much, obstructive apnea events can start to occur. Essentially what happens is that once the exhale completes itself (against the reduced pressure provided by the EPR), the airway may collapse if you are relaxed and don't inhale right away. The S9 (in CPAP mode) waits 10 seconds before identifying that as an apnea event and forcing the pressure back to the set pressure.

The S9 will quickly respond, but the whole purpose of CPAP is to minimize those events or prevent them from occurring. On the other hand, if the set pressure is too high, I have a tendency to over-titrate and get central apnea events.

My sleep study resulted in a recommended pressure of 8. I would love to use an EPR of 3, but I need a minimum pressure of around 6.4 to prevent the OA's, and unfortunately a set pressure as high as 9.4 gets me back into centrals. I set my EPR to 2 and set pressure to 8.4 and that seems to work well for me. Maybe I can ween myself off EPR with time.

Of course the changes to EPR and pressure may be restricted if the CPAP is not set up to allow the patient to make their own changes. Some choose to refer to the clinician's manual and make their own adjustments. SleepHead is a very useful tool to help study your results.

Its a learning process, and best to monitor your results over time and not make too many tweaks at a time.

Awesome first-post DKC_Apnea!!

[Sleepster]

Essentially what happens is that once the exhale completes itself (against the reduced pressure provided by the EPR), the airway may collapse if you are relaxed and don't inhale right away. The S9 (in CPAP mode) waits 10 seconds before identifying that as an apnea event and forcing the pressure back to the set pressure.

My BiPAP immediately raises the pressure as soon as I stop exhaling. Exhalation pressure relief (EPR on your machine, Bi-Flex on mine) shuts off and to boot, the pressure rises from EPAP to IPAP.

Welcome to the forum.