Understanding min pressures

[AMK]

Let's say my pressure is 8-20. Let's say that one night I have one of my hour-long apnea fests, and immediately prior to the fest my pressure was no lower than 9.6. It seems like in my experience that if I were to raise my min pressure to 8.4 it would make a difference, even if during the night the actual pressure goes no lower than 9.6. Does this make sense? Am I misunderstanding? If my min pressure during the night never goes lower than 9.6, does my min pressure need to be higher than that if I experience one of these nightmare clusters?

[Julie]

No, if your pressure remains above a min. setting almost all the time, lowering the setting would not have an effect However don't go by only one or 2 nights... go with a week or so to see if it goes lower more than e.g. one time to a small extent (which shouldn't matter in the grand scheme). IF your clusters (on Sleepyhead) show that your pressure at those times (again, more than 1-2 nites) rises, that would be expected of course but unless it rises to e.g. 11 and stays there routinely for the clusters (or otherwise) there may not be a point in raising it... though I guess you could experiment a bit.

[jnk...]

I believe generally, as a rule of thumb, in getting your minimum to at least within 2cm of what you need most of the night.

So, for example, if someone needs 9.6cm most of the night but the machine is set at a minimum of 4, that treatment may be less than perfect for that user. I would raise that minimum up to at least 7.6.

For some of us, that doesn't matter at all, since our machines, like your machine, generally respond well to early indications of coming obstruction. So my belief is that for most people, that machine will have the pressure near what they need unless their apneas just so happen to come out of nowhere--a rare occurrence in my book.

That said, for some of us, getting the minimum up close to what we need most of the night can help the numbers. So if there is no reason (such as maybe a comfort issue or swallowing air) to leave the minimum low, then trying a higher minimum for a week or two, just to see if that helps, should be no problem at all. To my mind, if a doc trusts a user with a machine set to a maximum of 20, that doc shouldn't mind if the user decides to try a slightly higher minimum than 8 to see if that helps to optimize PAP for that user. If it turns out that raising your minimum increases your home-machine-reported AHI on average over a week or two, you can always set your minimum back down where it was. Depends on how comfortable you are with keeping track and with experimentation. Your doc may encourage you to play around with your minimum pressure if there is no reason not to. The docs rarely have time to tweak treatment for what works best to us in our homes. If it makes reported AHI lower, it should be considered by all to be a good thing. Make slow small moves and see what that does to the averages over time, not a quick large move then judging by one or two nights.

Does that answer help? Or did I miss the point of your question entirely. I do that sometimes. Feel free to restate your question or to ask further questions for clarification.

[TedVPAP]

Let's say my pressure is 8-20. Let's say that one night I have one of my hour-long apnea fests, and immediately prior to the fest my pressure was no lower than 9.6. It seems like in my experience that if I were to raise my min pressure to 8.4 it would make a difference, even if during the night the actual pressure goes no lower than 9.6. Does this make sense? Am I misunderstanding? If my min pressure during the night never goes lower than 9.6, does my min pressure need to be higher than that if I experience one of these nightmare clusters?

Yes. Your minimum pressure matters even if you do not go below it. The algorithms are not perfect so user involvement benefits most people. You want the minimum pressure set close to where your maximum pressure needs are. How close??? Based on my personal experience, within 3 cm-H2O of my maximum needed pressure.

[Arlene1963]

I would set the minimum pressure higher, maybe around 9.

[Pugsy]

How close the minimum might need to be to the max is going to be very individual in needs. I might see 18 on some occasions on APAP but I certainly don't need the minimum to be anywhere near that 18 to be able to do a good job holding the airway open.
The minimum only needs to be close enough at the time that the machine wants to climb for it to hold the airway open and prevent the airway from collapsing.

So as long as the minimum can get to where it needs to be in a timely fashion it doesn't necessarily have to be all that high.

Right now my minimum is 7 with EPR of 3 and max of 20.

Here the machine goes close to 18 and gets the job done.


and here the machine doesn't have to go up very much to get the job done. For me to set my minimum anywhere close to the max shown above would be way overkill in terms of needs.

[AMK]

Yeah, I worded my question badly, though the answers still help. I'll try again. Pressure 8-20. Post-ramp, the min pressure the whole night never goes below 9.6. It is 9.6 immediately prior to a one-hour apnea fest. Would raising the min pressure to, say, 9, still help, even though as I said the min pressure never went below 9.6 the whole night? If I understand jnk and Ted correctly, the answer is, "Yes."

[TedVPAP]

How close the minimum might need to be to the max is going to be very individual in needs. I might see 18 on some occasions on APAP but I certainly don't need the minimum to be anywhere near that 18 to be able to do a good job holding the airway open.
The minimum only needs to be close enough at the time that the machine wants to climb for it to hold the airway open and prevent the airway from collapsing.

So as long as the minimum can get to where it needs to be in a timely fashion it doesn't necessarily have to be all that high.

Right now my minimum is 7 with EPR of 3 and max of 20.

Here the machine goes close to 18 and gets the job done.


and here the machine doesn't have to go up very much to get the job done. For me to set my minimum anywhere close to the max shown above would be way overkill in terms of needs.

The Resmed algorithm appears to be working very well for you.

[TedVPAP]

Yeah, I worded my question badly, though the answers still help. I'll try again. Pressure 8-20. Post-ramp, the min pressure the whole night never goes below 9.6. It is 9.6 immediately prior to a one-hour apnea fest. Would raising the min pressure to, say, 9, still help, even though as I said the min pressure never went below 9.6 the whole night? If I understand jnk and Ted correctly, the answer is, "Yes."

Post a sleepyhead chart and we can use the data to give you a better assessment.

[jnk...]

jnk's answer was a wishy-washy "maybe," and a tip of the hat to the value of safe experimentation, just for the record.

@Pugsy, I have a related question for you on the S10 for Her, if you have time, but I'll start another thread to ask it in order to keep from derailing this thread. Ah, never mind. I just found your answer from 2014 to the same question I just had. So it's covered.

[Pugsy]

jnk's answer was a wishy-washy "maybe," and a tip of the hat to the value of safe experimentation, just for the record.

Pugsy's answer would also be a wishy-washy "maybe".

I think I understand what you are wondering and I do remember your ugly clusters in the for "her" algorithm mode and you happen to be one person who we know it doesn't work well for you.
I don't know that increasing the minimum will make any difference in your situation because once your pressure goes up it doesn't seem to go back down to the initial minimum. So there's no urgent need to increase it (as long as it can get to where it needs to be in your situation from wherever it is starting from) nor is there an urgent need to not increase the minimum as long as minimum pressure setting is comfortable for you as a starting point.

Now if your pressure routinely went back down to that initial minimum and the variations in pressure themselves caused a problem then maybe a different story.

Personally...I don't know that it will change anything in terms of results (numbers) and it is unknown if limiting the range will affect sleep quality or not.
Hence the wishy washy maybe. I have been there and done that with the changing of minimum pressure up to a lot more than what I might technically need and it didn't change a thing when I did it except make it more uncomfortable at the beginning of the night.
Didn't change AHI or sleep hours or sleep quality or pretty much anything and that's why I use the least amount of minimum pressure as I can get by with.

[AMK]

Thanks Pugsy. I hate the clusters because superficially my overall AHI might be fine but I'll wake up sometimes feeling brain damaged from one huge cluster. The one you remember was in September. After that incident I set the machine to regular apap and raised my min to 7.6, then 2 weeks later raised my max to 17 and then in October raised it to 20 because I was still having clusters where the machine could not go high enough. After a few more nights with clusters, in November I raised the min to 8. This month I've had a couple of clusters from 9-20 mins long where the machine doesn't attempt to reach its max.

[Pugsy]

If you are still seeing the ugly clusters and you think they are impacting how you feel then by all means try more minimum but you may need more than you think for whatever is causing those things.

I thought you had them all beat down and not happening any more or extremely rare thing if they popped back up again.

Interesting thing...I just downloaded SH (it's been a while) and I happened to see a night with AHI of 4 something and I had a couple of clusters like you used to have in the for Her mode where the machine didn't increase as expected. First time since I have been using the for Her mode that I have had that happen to me.

[AMK]

If you are still seeing the ugly clusters and you think they are impacting how you feel then by all means try more minimum but you may need more than you think for whatever is causing those things.

I thought you had them all beat down and not happening any more or extremely rare thing if they popped back up again.

Interesting thing...I just downloaded SH (it's been a while) and I happened to see a night with AHI of 4 something and I had a couple of clusters like you used to have in the for Her mode where the machine didn't increase as expected. First time since I have been using the for Her mode that I have had that happen to me.

What do you make of that? Was it that the machine couldn't go as high as you needed, or that it just didn't increase?

[Pugsy]

What do you make of that? Was it that the machine couldn't go as high as you needed, or that it just didn't increase?

It goes higher (and has gone up to 18 in the past at times) but obviously not as high as needed on this night or as high as it has gone on other nights.
I really don't know what to make of it except it looks like the Flow Limitations were minimal so maybe they didn't drive the pressures enough.

I am pretty sure it is REM related since I know my OSA and pressure needs are worse in REM...and past experiments with building a wall to prevent supine sleeping showed that supine sleeping really didn't change things in terms of the clusters or pressure needs...
But as for why this happened last night I have no idea and this is the first time I have seen anything like this since switching to the for Her mode in early Sept.

It was a week ago last night and I don't remember anything any different but that was a week ago so that doesn't mean much.
Nothing stood out back then or I would have uploaded from SH sooner most likely.

For now it's just one of those things I will make a mental note of and scratch my idea and laugh and blame it on the aliens messing with me.
For the last 14 days...the AHI has been either less than 2.0 and more often less than 1.0..and the bulk of my reports look like the ones I posted above with very minimal events and AHI less than 0.5.

Now the 18th...I did fly back from Vegas that morning but that's the only thing really different in my usual very boring life...that and Sunday night I did partake of a very small amount of the legal recreational drug MJ but I did that Friday, Sat and Sunday nights (different experiment there) and the other nights didn't show anything out of the ordinary.
For the time being since this qualifies as a very, very rare fluke "off" night I will just make a mental note and keep an eye out to see if/when it happens again. I have had weird stuff show up before and never return so I don't spend a lot of time worrying about stuff like this unless I see it start to develop into some sort of pattern. Like the time I once has 17 centrals in 17 minutes. Sure got me to scratching my head for a bit but never happened again.

While similar to what you had happen...not nearly as ugly as yours was.

So at this point I won't be doing anything except maybe watching the old reports a bit closer when I download (and I still won't be doing it daily or even weekly).