Geer1 wrote: ↑Tue Dec 10, 2019 1:03 am
slowriter wrote: ↑Mon Dec 09, 2019 4:49 pm
Yes. Effectively, EPR (and PS) allows you to tolerate higher inspiratory pressure.
I did want to add a bit to my response to geert's question.
When they do the bilevel titration, they first raise the EPAP until they eliminate obstructions.
They then raise the IPAP until they eliminate hyponeas and RERAs.
Beyond comfort (which is critical to good sleep), I'm not sure if there are other benefits to the EPAP/IPAP gap. Everything I've suggests there is.
Here is a titration protocol guide I was looking at the other day.
https://www.sleepapnea.com/downloads/10 ... fGuide.pdf
Page 11, they raise EPAP until obstructions are eliminated. IPAP is then raised to eliminate partial obstructions (flow limitations). This makes sense as the EPAP is required to maintain an open airway and then IPAP helps open the airways further during inhalation (and the pressure difference helps speed up air intake).
I believe it is the higher pressures that are reduced your flow limitation, I don't see how increasing PS/EPR would do that(unless doing so raises pressure as it did in your cause).
I do think there are at least theoretical benefits to a larger PS/EPR though and that would be more effective CO2 clearance. If you have a flow restriction that does not expand with increased pressure then the only way to increase flow through that passage is to increase the pressure differential as simply increasing the pressure does not change the differential pressure which is what determines flow. Higher PS/EPR does change the differential pressure though and it can make breathing more efficient. This is the same effect that can cause centrals in some patients (too effectively clearing CO2 leading to the brain thinking it doesn't need to breath).
Yes, I think that all makes sense.
So at minimum PS and EPR allows one to balance the need for higher inspriratory pressure to combat the RERAs, with the higher expiratory pressure intolerance that comes with it. If you can't sleep at the higher pressures, then what's the point, after all?
But while I can't find the medical study references at the moment, I do think the gap also makes for more efficient breathing, as you note.
This is only two data points, but below are two closeups from my experience: one is on CPAP at a fixed pressure of 12 (and EPR 3). The other is on bilevel, with EPAP of 6 and PS of 6, so IPAP of 12. In other words, they are the same pressure on inspiration.
Notice a difference? Does the difference matter?
Caveats: the vauto machine does have other breathing-related settings that may influence the flow graphs, beyond pressure. Also, there's a gap of a couple months.

- Screenshot from 2019-12-09 06-30-07.png (9.81 KiB) Viewed 14570 times

- Screenshot from 2019-12-09 06-32-11.png (10.01 KiB) Viewed 14570 times