Flow Limitations don't make sense

[Personxyz]

I'm trying to lower my FL at the moment but what I'm seeing on sleepyhead doesn't make sense. I thought that given what FL is, the correct way to reduce it would be to increase the fixed pressure or increase the min pressure on an auto machine. Maybe you could also lower the EPR. I've tried raising the pressure and turning EPR off and both lead to the FL going up significantly. The 2 screenshots I've posted are just one example but having looked through my data this seems to be a consistent occurrence. Wearing a soft cervical collar doesn't seem to help either. Does anyone have an explanation as I'm completely confused?

   
   

[Crimson Nape]

I have a flow limit problem as well. I knew that a setting of 10cm prevented most OA's and hypopneas, so I set the EPR to 3 and my starting pressure to 13cm. On exhale I'll be at 10cm. My FL's were reduced to an average .05

Basically the rule-of-thumb is, Set the starting pressure to a pressure that eliminates most of the OA's and hypopneas and add the EPR value to it.

[Sleeprider]

You will often hear me recommend using as much EPR as you can tolerate when flow limitation is an issue, and I will also limit maximum pressure, where flow limitations are driving pressure higher than needed for efficacy with OA and H. Using EPR will reduce flow limitation and hypopnea.

The principles of how this works come from the standard titration protocols for bilevel (BiPAP/VPAP) therapy. In bilevel, a person usually starts with a minimum EPAP pressure and a pressure support of 4.0. So the titration may begin at an IPAP of 8.0 and EPAP of 4.0 (8.0/4.0). Titration protocols recommend increasing EPAP and IPAP to until obstructive apnea are resolved. Once obstructive apnea is taken care of, the protocol recommends increasing IPAP for hypopnea, flow limitation and snoring. Pressure support is the difference between IPAP and EPAP, so we treat FL, H and snores with pressure support.

With your Resmed CPAP you have EPR which is analogous to the inverse of pressure support, provided you think in terms of bilevel titration. Let's say you need a CPAP pressure of 8.0 to resolve obstructive apnea, but that still leaves you with flow limits or hypopnea. We could set the CPAP pressure to 11.0 and use EPR at 3.0 to achieve a therapy pressure of 11.0/8.0. This is bilevel in a nutshell, and this strategy has therapeutic applications beyond just comfort. With a Philips Dreamstation, the use of Flex does not have the same bilevel effect, so the only choice with that machine is to increase pressure; but with the Resmed, we can use bilevel principles to get better therapy at lower overall pressures.

[Personxyz]

Thanks for the info sleeprider.

I'm sorry if I'm missing something obvious but I still don't understand how EPR or EPAP actually can reduce FL. It seems from reading what you said that IPAP is stopping the obstructive apneas, hypopneas, flow limitations etc.

Using your example, the PAP pressure is set at 11 which takes care of all the different types of sleep breathing issues. Then the EPR is set at 3 which leaves an EPAP of 8. If 8 is good enough to resolve obstructive apneas in your example but not things like hypopneas or FL I don't understand how the EPR helps with the actual therapy for hypopneas or FL, that makes it seem like the IPAP is doing all the therapy. It makes EPR seem like it's there for comfort e.g less chance of aerophagia, easier to breathe.

Having said this, I look back through previous threads in the forum and increasing the EPR does seem to help FL, I just don't understand how. The only theory (likely wrong) that I have is that a high EPAP would make it more difficult to breathe out as you would be directly fighting against the incoming air pressure from the machine. That could lead to struggling to breathe and which could show on your machine/sleepyhead as flow limitation. EPR would then help solve this problem.

I guess I'm just trying to learn as much as possible to help with my treatment, I really do appreciate the things you've taught me.

[Sleeprider]

I was saying in that example 8.0 becomes the EPAP and stops OA. Your IPAP of 11 (PS 3), is what is left to treat hypopnea and flow limitation. We are using bilevel terminology to describe, or think of a CPAP function. With the Airsense 10, you only have 3-cm of pressure support to work with, so the effect is limited. It's a little mind-bending to talk about CPAP in bilevel terms, because those settings are not present on CPAP. That's what I do, and you asked where the rationale comes from. I really don't think you need to make that leap as long as you understand that it is the difference between IPAP and EPAP that can help with H, FL and snores, and not just pressure increases.