Flow limit targets?

[Jlfinkels]

Is there a specific target for flow limits? I've been searching looking for information, but have not had any luck so far.

For example, here is a typical OSCAR chart for me on an average night. I'm still a bit groggy in the morning at times and noticed I do wake up a few times during the night. Based on notes I scribble when I wake the timing coincides with the pressure increases in response to the flow limits.

I was using a pressure of 8-20 with an EPR of 3, but noticed my 95% was around 14 and 99.5% was 15 so I limited it to 15 for now to see what happens. It seems no matter what I do with pressure the flow limits remain in the same range. If I change EPR the flow limits increase, so I left it at 3.

If the limits I have are not worth messing with I'm fine leaving it as is and focusing on sleep quality.

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[Pugsy]

You omitted some critical information.

Are you experiencing any nasal congestion at all? This is critical because sometimes nasal congestion can show up with increased activity on the FL graph. We can't do a thing with FLs caused by nasal congestion by machine setting tweaking...nasal congestion FLs must be dealt with by the usual nasal congestion treating measures.

And...how are you sleeping and feeling in general. While FLs can disturb sleep they don't always disturb sleep.
How you feel and sleep is always a critical part of any evaluation.

Limiting the max does absolutely nothing except maybe keep the machine from dealing with something it wants to deal with.
We don't normally limit the max unless the machine going higher creates a significant problem...like aerophagia, leaks, centrals.
That 95% number....all it means is you were AT OR BELOW that number for 95% of the night. That's all it means and the OR BELOW part of the definition is extremely important.

There is no overall set standard for acceptable FL graph numbers or activity levels...not nearly as clear cut as AHI numbers or leak numbers. Instead multiple factors have to be evaluated.

Since you can't really increase the pressure support any more than the 3 cm with your machine and making use of EPR....about the only other choice is to increase the minimum pressure...with no guarantee it will help all that much but you can certainly give it a try.
Whether it is needed or not though....depends on the answers to the above questions.

[Jlfinkels]

Thanks, I should know better by now than to leave out information. Mea culpa!

In answer to your questions I have varying degrees of congestion and use nightly nasal sprays (Fluticasone and Azelastine) which helps a lot. I on rare occasion get awoken by a clogged nostril, almost always on the pillow-side nostril, but it is rare.

I definitely have some nasal constriction regardless due to deviated septum and some kind of "collapse", apologizes but I don't remember specifically what the ENT said, but he did suggest surgery if it gets too bad. I've learned that when you go to a surgeon for advice, don't be surprised when the answer involves surgery, so I decided to delay making a decision on surgery until all other sleep quality options are explored.

Sleep quality is definitely better than pre-CPAP, but always looking for more improvement as some mornings I am a bit groggy. I did limit the upper end as I had issues with leaks and wake-ups when pressure was above 18 with both a FFM and nasal pillows. Of course I'm only 9 months into therapy and am willing to try things to improve sleep quality including increasing the max.

As always, thanks Pugsy for your thoughtful response.

[Pugsy]

Ah...it is within the realm of possibilities that at least some of the activity on the FL graph is related to nasal congestion issues and we can't fix those issues with minor little tweaks of the machine. It is something we just have to accept and make a decision if the activity is worth trying to deal with by whatever means.
Sometimes the cure is worse than the disease kind of thing.

The sometimes congestion with the side that is down....probably the normal "nasal cycle" thing...google it if you don't already know about it. I get it myself sometimes as well. I don't get it all the time and have never been able to actually isolate a cause for when I do.
And I don't have any pre-existing nasal issues like you have.

You could try more minimum pressure and it might help a little bit but don't be surprised if you don't see a lot of change.
It would at least answer a question that is probably in the back of your mind...one way or the other.
As long as the more minimum doesn't created a problem...hurts nothing to try it.

As long as you are sleeping decently for the most part and feeling decent during the day....I don't see any urgent need to go trying to kill those FLs at this time especially since we have to accept that we might not be able to kill them anyway if they are nasal in origin.
BUT....I have done experiments just to see if some little change actually does anything...and it often answers the "what if " question.

Limiting the max in your situation...probably an acceptable idea since we know that most likely the machine wants to go higher rarely and probably may be related to nasal FLs...and going higher causes leaks which do end up causing a problem.
An acceptable trade off.

Your choice if you want to experiment a bit...you always have a choice but I don't see an urgent need.
While the FL graph is a bit active...it could be partly nasal related for one thing and the other thing it really isn't all that horrible in the grand scheme of things even if not nasal related.
I have seen much worse... Like this person below.

[Jlfinkels]

Thanks. I'll experiment with increasing the minimum a bit and see what happens. My AHI has been good for quite a while with these settings so no real reason to increase the max at this time, unless you recommend otherwise.

[Pugsy]

An occasional kiss of the pressure line to 15 probably isn't a big deal but if you start seeing prolonged periods up at that 15 cm max line...maybe consider a small increase to maybe 16 or so...keep it below the 18 cm level where leaks are waking you up and still maybe let the machine kill whatever it wants to kill...all the while understanding that if it is nasal congestion FLs it is trying to kill that it won't work. If the FLs the machine wants to kill (remember it doesn't know if the FLs are in the nose or the airway itself) are from nasal congestion....no amount of pressure is going to resolve those anyway.

Watch your reports...if you start seeing that the pressure goes higher for longer on the nights where you know you have more nasal congestion then you know the nose is the cause and not much you can do about it other than the usual stuff we try to reduce nasal congestion.

[Jlfinkels]

Thanks!

Any value in borrowing a Vauto to see if a bipap would make a difference? If the FL's are not a big problem then I don't want to mess with them, but am curious if it would make much difference.

[Pugsy]

Thanks!

Any value in borrowing a Vauto to see if a bipap would make a difference? If the FL's are not a big problem then I don't want to mess with them, but am curious if it would make much difference.

Be careful when borrowing the VAuto.... we have a little saying...when you go real bilevel you won't want to go back. First time I ever tried PS of 4 I said to myself....I gotta get one of these...and it was a borrowed machine.
If you can try a VAuto....and it doesn't cost you anything to try it....by all means give it a go.
It probably won't make much of a difference in overall AHI but you might find that it does help a bit more with the FLs if you use PS of 4 or 5...and you might actually like it like I did. Most people do...a few don't though.
Remember always a big YMMV sticker with anything related to cpap or sleep apnea.

If you do decide to try it....don't go over 5 PS unless you watch the centrals really close. There are some people who find that more PS causes centrals. It's relatively rare but it can happen.
I have a friend who gets about 15 centrals per hour with PS of 4 and essentially none with PS of 3..go figure that one.
I can use PS of 4 or 5 and not have any centrals to speak of. I haven't tried 6 PS though other than a brief trial where I found it simply wasn't all that comfortable so never tried sleeping with that much PS.
I think Palerider uses a PS of 6 and just loves it....no increase in centrals.


Also there are a few more tweaks available with the VAuto in terms of the timing of the respirations that some people find useful and greatly adds to overall comfort.
Me...personally....I have always put "comfort" in the critical category for optimal therapy because if we aren't comfortable then we don't sleep so great and this whole cpap thing revolves around sleep.
Some people pooh pooh off "comfort" and not being important but not me....If I am not comfortable then I don't sleep so great and without sleep then the rest of this stuff doesn't really matter much IMHO.

Your pressures tend to run in the mid teens...that alone might be worth looking at that 4 cm PS simply from comfort and exhale relief.
So yeah...if you can borrow one and try it...definitely worth trying for several reasons....
just be careful...you might be like me and while it really doesn't make all that much difference in the overall data on the reports...You might fall in love just from the ease of breathing and comfort aspect and those puppies aren't cheap and getting insurance to pay for them just because "it feels so good" won't fly.

Now you might try it and just hate it....but the odds are you will like it. Very few people who try that type of bilevel machine with more ability to have a higher PS end up hating it. They are in a very small minority.

[CyberSpiff]

Thanks. Same questions here.

[palerider]

I was using a pressure of 8-20 with an EPR of 3, but noticed my 95% was around 14 and 99.5% was 15 so I limited it to 15 for now to see what happens. It seems no matter what I do with pressure the flow limits remain in the same range.

Because you're changing the wrong setting.
What you did was effectively nothing. You want to raise the minimum pressure, not mess with max.

[Jlfinkels]

Because you're changing the wrong setting.
What you did was effectively nothing. You want to raise the minimum pressure, not mess with max.

I did raise the min from 8 to 10 and lowered the max from 20 to 15. I'm thinking of raising the min to 12 and the max to 18. At least for a few nights to see how it goes. Happy to try other ideas.

[palerider]

Because you're changing the wrong setting.
What you did was effectively nothing. You want to raise the minimum pressure, not mess with max.

I did raise the min from 8 to 10 and lowered the max from 20 to 15. I'm thinking of raising the min to 12 and the max to 18. At least for a few nights to see how it goes. Happy to try other ideas.

Changing the max pressure doesn't do anything *unless* the machine is trying to go past your max setting. Leaving it at 20 keeps that setting from preventing the machine to respond to your varying needs.

Looking at your charts, a min pressure of 12 looks like it'll be more successful.

[Jlfinkels]

Very good points. I’ll try bumping it to 12-20 and see what happens. Easy enough to change.

[Jlfinkels]

Quick check-in. I've settled down to an 11-16 range as the 12-20 felt a bit high. My sleep and numbers are good, FL is down a few points and fairly consistent. Both Palerider and Pugsy were spot on with their recommendations of raising the minimum as even a tiny boost made the difference. I'll continue with these numbers for a while and check OSCAR again in a week. Still hoping to borrow a friends spare Vauto to give it a whirl, but won't know until the weekend.

Thanks guys!

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[zonker]

Quick check-in. I've settled down to an 11-16 range as the 12-20 felt a bit high. My sleep and numbers are good,

good work!!