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[Diagnosis] Odd exhale flow rate shape question
Odd exhale flow rate shape question

Can someone help me understand these attached flow rate graphs? 
I have these odd exhale breaths show up randomly but I believe they tend to be more when I have EPR set to 3. I can not seem to get my statistical flow limits under control which in turn drive my APAP pressures up. Higher pressures do  not improve the statistical flow limits so I have switched to CPAP and set the pressures myself.  Right now I seem to be caught between EPR 3 to help hypopneas and EPR 2 to improve exhale flow rate issues.   The graphs are at 7.2/4.2. and 6.8/4.8. I have tried pressures up to 12/9 but the statistical flow rates are always high and very random every night.   Many thanks.

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RE: Odd exhale flow rate shape question
The zoomed chart is showing expiratory mouth breathing and numerous inspiratory flow limits.

My question to you is how do you feel? And please be critical. Your numbers are such that your Doc will see them and say "That's great, no problem see you next year."

I would like to see you try EPR=4, but you cannot, the AutoSet is not capable. The goal of therapy is to get solid restful sleep. Are you?
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RE: Odd exhale flow rate shape question
That looks like palatal prolapse to me and your report of it occurring more often at higher EPR supports that. I believe the lack of leak rate during these periods also supports palatal prolapse over mouth breathing (which I believe should have associated leak rates).

Palatal prolapse is when your palate flips up during exhalation blocking the nasal passage. EPR creates a pressure differential which improves flow and higher EPR creates more flow/pressure difference increasing the chances of palate being pushed closed. An analogy would be wind blowing on a partially closed door, the stronger the wind the more likely the door will be blown shut.

If it is palatal prolapse then palate restrictions could also explain the inspiratory flow limitations that do not improve with pressure (compared to tongue/lower airway collapsing as is seen in majority of apnea cases). Unfortunately the few people on here that have had issues with palatal prolapse usually struggle to find settings that resolve the issue and treatments other than CPAP may be warranted. I would try to find a good ENT with experience and knowledge in restricted airways that can do an analysis of your upper airway to see if palate appears to be a source of your restriction. If it is believe to be a source of restriction they will probably recommend UPPP surgery. Normally I do not recommend UPPP surgery (since it is not reversible and rarely solves sleep apnea on its own) but in cases like palatal prolapse it is something that may be worth considering.
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RE: Odd exhale flow rate shape question
As for settings the main thing I noticed about your data is that both nights were very short and ended in hypopnea/apnea which I assumed woke you up and then you removed your mask. I would recommend EPR of 2 if that avoids most of palatal prolapse looking data and then try titrating pressure up until you can sleep most of the night without apnea issues. As Gideon mentioned titrating against how you feel is important, you do have a high number of flow limitations and this may be an issue but it may also not be an issue so try to treat the apnea as much as possible, get as much sleep as possible and see if that results in feeling satisfactory.
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RE: Odd exhale flow rate shape question

Thanks for posting these really interesting charts.
There are some similar posts on this flow rate pattern, you can search for them on this forum using the search term Palatal Prolapse.

I can duplicate these on my own flow charts at will while awake, deliberately causing palatal closure, and also see them when asleep but certainly not for such long protracted periods as yours. I plan to add some comments to an earlier post of mine when I have more data.

You don't mention whether you use a neck collar, or what other measures you are taking to control leaks, for example mouth tape.

As others have mentioned your flow limitations are too high.

However, in the meantime I have taken the liberty of editing and adding one of your charts and think it is worth thinking about.


I have added a red baseline to represent the Zero value on the Flow Rate chart.
This helps to see the fluctuations around the baseline.
(I would love to have OSCAR be able to place this Zero baseline on top of the Flow Rate chart with the option of colour selection.)

I have marked the Insp Flow Limitations in blue, notice how when your FLs increase the inspiratory excursions narrow down towards the baseline.

Then when your Flow Limit chart shows no FL (green) the Flow Rate excursions move up towards the baseline (red).
This is when you are getting reduced expiratory flow, at the extreme end of this spectrum we see the pattern of Palatal Prolapse or Palatal Closure.

I am not at all sure if this is related to neck position (in which case a soft cervical collar might help) or different stage of sleep (in which case we cannot control this), or maybe due to nasal/soft palate congestion, or indeed how this relates to pressure differentials between the nasopharynx and oropharynx, or indeed how we can manage this with machine settings.

This is yet another example of finding a balance/compromise between different factors while we sleep.

I am interested in how ResMed records Flow Limitations for Inspiration and not for Expiration. Clearly the palatal closure causes Expiratory Flow Limitation, as we can see on the Flow Rate chart, even if ResMed does not record them as such.

The question is are these a normal phase of sleep? do they disturb or awaken you? can they contribute to how you feel during the day?

Notice how your tidal Volume remains mostly stable during these periods but increases at the end of this sleep session when you have a cluster of obstructions: notably with minimal indication by ResMed that there are any Flow limitations. Yet another hint that the charts show us most of what is going on, but not everything.

Fascinating charts, many thanks.
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RE: Odd exhale flow rate shape question
In the close-in shot, I see: On your exhales, you exhale with an initial "jolt", followed by a continuous effort to exhale against a resistance. I have seen that in my charts some times. When it has been that way for me, I am either (awake or in shallow sleep) and fighting nasal flow restriction due to congestion or swelling/inflammation of nasal passages. Hope you can narrow down the possible culprits.

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