Smargie’s Therapy Thread...in Need of ASV Advice

Smargie wrote: ↑

Thu Aug 29, 2019 10:25 am

But some simple advice about when to consider if and when I should increase pressure again would also be very hellpful.

I can answer your other question later, but for this, you can zoom in on the time leading up to your hypnopnea. Check the Pressure graph and see if pressure support is at it's maximum (you can move the cursor and it will tell you the amount of pressure support where the green line is intersecting the graph). Here's an example where PS Max is set to 10.4 and the machine is maxed out in trying to respond to the hypnopnea:


If you see a situation like this, you may benefit from increasing PS Max. As Pugsy said, hypnopneas can be obstructive or central in nature. An ASV machine introduces a third variation: a hypnopnea that would've been a pure central apnea (cessation of breathing) but the triggered breaths got you to take in some air. Unfortunately the latter situations are also ripe for swallowing air from increased pressure, so it may be a trade-off between comfort and treatment.

Thanks for responding, idlewire. I understand what you mean now, but my pressure graph doesn't show PS.


Also, doesn't it look like there was another central before the hypopnea?

Anyone care to weigh in on how long to give a new setting a chance before considering another change?

Smargie wrote: ↑

Thu Aug 29, 2019 5:39 pm

Thanks for responding, idlewire. I understand what you mean now, but my pressure graph doesn't show PS.

On your chart, "Pressure" is IPAP, so to figure out PS, you would take that and subtract EPAP. So, for example if "Pressure" is 12 and EPAP is 4, your PS is 8. You'll have to exclude glitchy times when it says EPAP is 0, those won't be meaningful.

I can tell looking at the mask pressure that those largest spikes are very likely at your PS Max. Based on that, you could have improvement with increasing your PS Max. We only limited your max pressure in the first place due to discomfort with air swallowing. How are you doing with that? I've noticed positional effects myself (e.g., I swallow more air laying on my right side than my left).

If you are doing okay with that, your numbers are not that bad, if it were me I would raise PS Max by a mere 0.2 each night until you find that sweet spot between treatment and discomfort.

Thanks idlewild. I've gone over graphs of the past few days and you're right about PS getting close to its' max at times. The last 4 nights have been pretty good, though--the last 2 my AHI was even below 1.0. Hopefully the increase I made in PS max from 8 to 9 is starting to do the trick and this is a trend. But your plan of raising it by increments of 0.2 sounds very reasonable and if my AHI starts to go up again I will try it. I did notice a small increase in aerophagia when I bumped it up to 9, but it's still tolerable at this point.

When thinking about where to raise the pressure to get increased IPAP, my first thought was that it would be most comfortable to raise the EPAP minimum. What initially really bothered me and made me unable to sleep when I first started the ASV on the prescribed settings was the feeling that I was getting more air on inhalation than my lungs could accommodate. When we lowered the pressure settings to something more tolerable I was finally able to sleep, but not for very long periods because of the aerophagia.

I just realized that I don't really understand what pressure support is. I was under the impression that it was the bursts of air you get when you have centrals. Now I understand that that's incorrect since all bilevels have it, not just the ASV. I understand how to calculate it, but beyond that it's the difference between EPAP and IPAP I haven't been able to find other definitions. Is it the back up that is the bursts of air? What keeps the machine from providing more IPAP when it's at a maximum of 23?

I'm pretty embarrassed that I don't really understand these basic functions--I thought I had it down.

Pressure support is simply the difference between inhale and exhale.
Your ASV machine has a PS that will auto adjust how much of a difference it thinks you need based on what is happening.
Higher PS is needed briefly when you have a central apnea or maybe the hyponea on occasion.
It's brief and can vary with each breath depending on what the machine thinks it needs to fight and of course how much it can vary depends on what it feels you need and the limitations that might be set.

So sometimes you may need all that PS of 8 or 9 or maybe even a little more but more inhale feeds the aerophagia monster...so we limit PS for that reason.
If you had increased EPAP then you would have had higher IPAP all the time and not just some of the time...pretty much guaranteed to open the door for the aerophagia monster to return. Using a higher PS limit allows the machine to increase IPAP only when needed vs all the time with an all the time increase in EPAP/IPAP if you had increased EPAP minimum.
Ideally we would just open up the PS max and let the machine sort its needs out but in your situation it very well would cause aerophagia issues that are significant.

Anytime there is a difference between inhale and exhale there is PS...most machines have a fixed PS though or if it roams around a bit it does the roaming a bit slower but with your ASV machine it does it rather quickly. You spend a minimal time with higher IPAP.
Gives you the greatest chance of keeping the door closed on the aerophagia monster.

When you have an inhalation pressure greater than exhalation pressure, your breathing is "supported" because the added pressure makes it "easier" to breathe -- less effort is required to take in the same quantity of air.

If you were to hold everything else about your breathing constant -- your respiration rate, inhalation time, breathing intensity, degree of partial obstruction (if any) -- then as you changed the amount of pressure support, you would change the amount of air you inhale. So when your breathing parameters change -- and they are all encapsulated in "Minute Ventilation" -- the ASV alters the amount of pressure support in an attempt to keep your level of ventilation steady rather than changing too abruptly. This prevents central apneas by keeping your CO2 levels from changing too much.

Although a lot of emphasis is usually placed on the "backup rate" (triggered breaths), the above is what the ASV is spending most of its time doing, and the degree to which it does it successfully is the degree to which you won't need any triggered breaths (barring any other established cause for your central apnea, the main "drive to breathe" while asleep is mediated by CO2 levels).

I think I'm finally starting to get it. You've both been very helpful Pugsy and idlewide. Thank you so much!

Hello again...things had been going smoothly so I haven’t been around for awhile. I’m back for more help from you kind people.

First off, my new laptop stopped powering on. So I won’t be able to supply graphs until I either get it fixed or try to boot up my crappy old one. I thought I’d try posting a question without data first to see if anyone has any insights.

About 2 months ago the ASV started to wake me up several times a night. It’s hard to know what exactly was going on...it felt like the pressure was ramping up really high and I’d often get a pretty dry mouth. About a month ago I stopped using it at all because it consistently woke me after 60 to 90 minutes of first falling asleep and my mouth would be super dry. I was getting more sleep without it (I know, I know...poor quality sleep!). Between having had surgery, quite possibly having contracted a mild case of Covid -19 and the broken laptop I haven’t gotten around to tackling the issue till now. I did try it again for a few nights after my hiatus. The same thing happened and this time my AHIs got up to 17.

Any thoughts or do you need the data to be able to help? I was thinking that increasing the PS max up from 9 incrementally might be a first step.

Have you ever tried a full face mask (not doing so is the likely reason you're drying out from mouth breathing)?

Smargie wrote: ↑

Fri May 01, 2020 3:24 pm

Any thoughts or do you need the data to be able to help? I was thinking that increasing the PS max up from 9 incrementally might be a first step.

well, hello. welcome back. yeah, data is always good but i can maybe suggest some remedies.

have you considered using something to keep your mouth closed? (i know my wife makes several such suggestions to me!) some use tape, some use a chinstrap. what i have found that works for me-

viewtopic/p1089718/viewtopic.php?f=1&t= ... s#p1086296

this works for me and it may work for you. i modify it somewhat but it's still jay's superb method at the heart of it.

also, i use a firm foam cervical collar in conjunction with this.

lastly, there are xylimelts. this is a wee lozenge that you place between tooth and cheek. it disolves slowly overnight, promoting saliva.

whatever. hope you find what works for you.

Thanks, Julie and Zonker.

I’m generally not a mouth breather. It only seems to happen when the pressure is too high.

Smargie wrote: ↑

Fri May 01, 2020 5:46 pm

Thanks, Julie and Zonker.

I’m generally not a mouth breather. It only seems to happen when the pressure is too high.

Yes... but life changes, and when you're asleep, how can you be sure?

Welp, I suppose it’s possible I’m breathing through my mouth occasionally. I’m a terrible teeth grinder, though. Actually more of a teeth clencher. I recently cracked my bite guard which impressed my dentist because apparently the fancy expensive one I had was supposed to be indestructible. I imagine it would be hard to breathe through your mouth with your jaws clenched though not impossible. I do it even when I’m daydreaming so I’m pretty sure I do it all night long.

Hello back to you, Zonker! How is the Northwest treating you? I remember when I first started this thread, before you suggested I change the name, it was about chipmunk cheeks. There were many suggestions like the ones you just made and someone suggested we start a thread with photos of people’s handmade solutions to various problems. You posted a pic of yourself in full regalia and someone said you looked like you’d been kidnapped. Once we got my setting right the mouth problems stopped.

I’ll work on my laptop issues (but it will take some time because I think I have to buy a new power cord) and in the meantime I’ll try my chinstrap.