My Newbie OSCAR Hypopnea Statistics

For the first days of my CPAP journey I struggled with an ill-fitting full face mask and an overly heated air tube with no temperature controls. Nevertheless, I managed to sleep enough to use the machine's AHI numbers to adjust my min/max pressure in auto mode and wound up at 4.5 to 7.5 cmH20. [My sleep study recommended 12 cmH20.]

Last night was my first night with a well fitted full face mask and my new ResMed AirSense machine which allowed me to set a comfortable air temperature. I set APAP pressure to 5 to 8 cmH20 with a 10 minute ramp (5 cmH20) and EPR level 1 "ramp only." After about 6 hours of sleep (which is typical for me), the machine detected no Obstructive Apnea events and 4 Hypopnea events resulting in an AHI of 0.67 I believe this is an excellent result if it is accurate. If it turns out that my hypopnea events are being underestimated or become more frequent, what adjustments would be recommended?

By the way, the data section of my sleep study report shows my AHI but does not break it down into obstructive versus hypopnea events like the OSCAR software does. During the titration portion of the study I was given a face mask that was apparently too small (based on my experience and the opinions of a certified sleep technician who worked at the same clinic and a respiratory therapist at my DME provider) and was instructed to lie on my back even though I explained that I had a fear of sleeping on my back and never do it. Was my sleep study typical or below par?

MJS,

It sounds like you are off to really good start now that you have a well fitted mask and the AirSense in a decent pressure range for you.

Pay attention to how you feel and how well you are sleeping. If those are both good AND the leaks stay under control AND your machine scored AHI is reasonably low, you can safely assume that therapy is going well.

MJS_ wrote: ↑

Fri Apr 07, 2023 8:40 am

After about 6 hours of sleep (which is typical for me), the machine detected no Obstructive Apnea events and 4 Hypopnea events resulting in an AHI of 0.67 I believe this is an excellent result if it is accurate.

That AHI data is indeed excellent. But what are the leak numbers?

If it turns out that my hypopnea events are being underestimated or become more frequent, what adjustments would be recommended?

The fix would depend on seeing the data: If the leaks are not under control, that would be the first thing to fix.

Then whether to raise the Min Pressure or the Max Pressure (or both) would really depend on the data itself. If you start to have a lot of events, and the pressure is hitting Max Pressure for extended periods of time, then Max Pressure probably needs to be raised. But if the events start happening every time the machine tries to lower the pressure all the way back towards Min Pressure, then Min Pressure would need to be raised. Of the two settings, Min Pressure needs to be high enough to prevent clusters of events from starting and Max Pressure needs to be high enough to allow the machine to increase the pressure where it wants to go when your sleep disordered breathing is at its worst. When the Min Pressure is set appropriately, that can reduce the highest pressures the AutoSet algorithm wants to use. As long as Max Pressure is above that level, things should be good.

There are people who will tell you that leaving Max Pressure at 20cm is reasonable on the grounds that the machine will only increase the pressure that much if needed. But there are those of us who find out the hard way that there is something in our breathing that causes the machine to score flow limitations that create pressure increases that don't actually smooth out the flow rate curve and do lead to disturbances in our sleep. My advice is that unless you are hitting your max pressure for significant amounts of time during the night, there's no need to increase that setting all the way up to 20cm.

robysue1 wrote: ↑

Fri Apr 07, 2023 9:38 am

That AHI data is indeed excellent. But what are the leak numbers?

If it turns out that my hypopnea events are being underestimated or become more frequent, what adjustments would be recommended?

The fix would depend on seeing the data: If the leaks are not under control, that would be the first thing to fix.

Then whether to raise the Min Pressure or the Max Pressure (or both) would really depend on the data itself. If you start to have a lot of events, and the pressure is hitting Max Pressure for extended periods of time, then Max Pressure probably needs to be raised. But if the events start happening every time the machine tries to lower the pressure all the way back towards Min Pressure, then Min Pressure would need to be raised. Of the two settings, Min Pressure needs to be high enough to prevent clusters of events from starting and Max Pressure needs to be high enough to allow the machine to increase the pressure where it wants to go when your sleep disordered breathing is at its worst. When the Min Pressure is set appropriately, that can reduce the highest pressures the AutoSet algorithm wants to use. As long as Max Pressure is above that level, things should be good.

There are people who will tell you that leaving Max Pressure at 20cm is reasonable on the grounds that the machine will only increase the pressure that much if needed. But there are those of us who find out the hard way that there is something in our breathing that causes the machine to score flow limitations that create pressure increases that don't actually smooth out the flow rate curve and do lead to disturbances in our sleep. My advice is that unless you are hitting your max pressure for significant amounts of time during the night, there's no need to increase that setting all the way up to 20cm.

Thanks for your feedback! The ResMed app gave me a "mask seal" score of 20/20. OSCAR gave me "Leak Rate" scores of: Min 0.0, Med (median?) 0.0, and the 95% stat was 15.6. I think the higher 95% score may have been caused by me consciously adjusting the mask placement and/or the headgear straps for comfort. I did not notice leaks when I was not fussing with the gear.

I knew that increasing the air pressure could help control obstructive apnea events, but I did not know it could also reduce hypopnea events.

Regarding the Max Pressure setting, I watched Youtube videos that were critical of these machines' auto-mode algorithms and biased me toward giving them a narrow pressure range in which to play. Also, my recent Sleep Study recommended a constant air pressure of 12.

It seems I may need to learn how to interpret the more detailed data or pay an expert to do it for me in order to discover how bad my hypopnea really is and what should be done about it.

MJS_ wrote: ↑

Fri Apr 07, 2023 10:05 am

I knew that increasing the air pressure could help control obstructive apnea events, but I did not know it could also reduce hypopnea events.

Most of the time hyponeas are nothing more than obstructive apneas that don't quite make the criteria for the OA flag.
That's why the "more pressure" thing is the first thought to try to reduce the number.

Hyponea....air flow reduction anywhere from 30% (this number can vary between brands) to 79% that lasts at least 10 seconds.
Obstructive apnea....air flow reduction of 80% to 100% that lasts at least 10 seconds.

I think of hyponeas as baby OAs that haven't quite grown up to earn the full adult OA flag.

MJS_ wrote: ↑

Fri Apr 07, 2023 10:05 am

Thanks for your feedback! The ResMed app gave me a "mask seal" score of 20/20. OSCAR gave me "Leak Rate" scores of: Min 0.0, Med (median?) 0.0, and the 95% stat was 15.6. I think the higher 95% score may have been caused by me consciously adjusting the mask placement and/or the headgear straps for comfort. I did not notice leaks when I was not fussing with the gear.

Those are very good leak numbers. Yes, "Med" means median in Oscar's statistical data. The 95% leake rate of 15.6 is indeed likely caused by a few minutes of consciously adjusting the mask and/or headgear. If you look at your leak line in Oscar, there are probably a very few bumps here and there where there was a perceptible leak that the machine was able to catch.

I knew that increasing the air pressure could help control obstructive apnea events, but I did not know it could also reduce hypopnea events.

The whole idea of PAP is that with enough pressure you can make all the OAs and Hs disappear. On an in-lab titration the tech typically sees with increasing pressure, the OAs disappear as they turn into Hs and the Hs turn into flow limitations. With more pressure, the remaining Hs turn into flow limitations, and with even more pressure, the flow limitations themselves start to smooth out and all the breathing looks like normal sleep breathing.

Regarding the Max Pressure setting, I watched Youtube videos that were critical of these machines' auto-mode algorithms and biased me toward giving them a narrow pressure range in which to play. Also, my recent Sleep Study recommended a constant air pressure of 12.

Folks around here never recommend leaving the machine wide open---i.e. running with a pressure range from 4 to 20. And that's for some of the reasons you saw in those videos: 4cm is just too low to control most people's apena. So OAs and Hs' start occurring every time the pressure drops below a certain threshold. And then the machine is playing catch up in terms of increasing the pressure enough to stabilize the breathing. Different brands have different auto algorithms, but for each algorithm, there is always a scenario where the algorithm is either way to slow to react or way to aggressive to react to the events. So you can see wild pressure curves that can and do disturb some people's sleep.

But if the minimum pressure is set high enough, most events are prevented and there is less likelyhood of clusters of events from occurring that in turn trigger the wild pressure swings. In other words, when the min pressure setting is increased appropriately many people find that the maximum pressure the machine actually uses goes down. In other words, if your max pressure never gets above 15cm, then it doesn't much matter if that Max Pressure setting is set to 15cm or to 20cm. They're both above where the machine wants to go. That's the rationale behind why many long time board members say to just leave the max pressure at 20.

Now I happen to use a very, very narrow pressure range myself---my IPAP is allowed to vary between 8 and 9cm and my EPAP is allowed to vary between 4 and 5cm. (Resmed VAutos use a fixed PS, and my PS = 4). I use this very narrow range for the specific reason that I am prone to aerophagia when EPAP > 6 and IPAP > 9. This narrow range does control my apnea (well enough), even though there are nights where my pressures sit at their maximum levels most of the night. I have learned (the hard way) that if I "allow" the machine to go where it wants to go, I will wind up with aerophagia. My residual flow limitations get no better (and can get worse) when the IPAP pressure is is allowed to go to 10, 11, 12, etc, and the aerophagia gets far worse the higher that IPAP goes and my sleep gets worse the more aerophagia I have.

So for me, the tradeoff of a very narrow pressure range combined with minimum pressures that are (documented on PSGs) enough to keep the AHI reasonably low is a workable solution.

My husband, on the other hand, uses an APAP and he needs a minimum pressure of 8cm to pretty much control most of his apnea. He can run in Auto mode with a pressure range of 8-20 and on a typical night his pressure may occasionally hit 10. The highest he's ever gone is about 12.5, and he's never had any problems with aerophagia. He'd pretty much have the exact same results regardless of whether he was running in 8-12, 8-15, or 8-20 simply because he so seldom gets above 12 cm of pressure. If we lowered his max pressure to 10, there would be some nights where he'd be hitting that max pressure for 10 or 15 minutes at a time, most likely due to persistent flow limitations, but because he has had the occasional cluster of events when his pressure range was set to 8-10, he would rather run in 8-20 until or unless he starts having serious problems with aerophagia or leaks.

It seems I may need to learn how to interpret the more detailed data or pay an expert to do it for me in order to discover how bad my hypopnea really is and what should be done about it.

No need to pay $$$ to an expert: We'll be happy to look at your data in Oscar or SleepHQ and tell you what you need to know. But basically if the machine is reporting your total AHI to be well less than 5, then your HI is also going to be pretty low. If the AHI is not as low as you want it to be and the HI is the main contributor, the fix is still the same as if the problem were OAs: Look at the data to determine whether your min pressure is too low or whether you've limited the machine's ability to respond by setting your max pressure too low or both.

Pugsy wrote: ↑

Fri Apr 07, 2023 10:42 am

MJS_ wrote: ↑

Fri Apr 07, 2023 10:05 am

I knew that increasing the air pressure could help control obstructive apnea events, but I did not know it could also reduce hypopnea events.

Most of the time hyponeas are nothing more than obstructive apneas that don't quite make the criteria for the OA flag.
That's why the "more pressure" thing is the first thought to try to reduce the number.

Hyponea....air flow reduction anywhere from 30% (this number can vary between brands) to 79% that lasts at least 10 seconds.
Obstructive apnea....air flow reduction of 80% to 100% that lasts at least 10 seconds.

I think of hyponeas as baby OAs that haven't quite grown up to earn the full adult OA flag.

Thanks for the clarification! I was thinking "hypopneas" were caused by my brain (i.e., "central apnea") rather than my tongue. Is the brain responsible for SOME hypopneas? If so, would this be revealed by analysis of the detailed OSCAR data?

Thanks again for your advice robysue1. I did not understand all the jargon and acronyms, but I think I got the gist.

robysue1 wrote: ↑

Fri Apr 07, 2023 10:47 am

No need to pay $$$ to an expert: We'll be happy to look at your data in Oscar or SleepHQ and tell you what you need to know. But basically if the machine is reporting your total AHI to be well less than 5, then your HI is also going to be pretty low. If the AHI is not as low as you want it to be and the HI is the main contributor, the fix is still the same as if the problem were OAs: Look at the data to determine whether your min pressure is too low or whether you've limited the machine's ability to respond by setting your max pressure too low or both.

I will likely some day avail myself of this generous and valuable service. For now, I will continue gathering data with these APAP setting for a while as long as my summary statistics and subjective experience continue to be good.

MJS_ wrote: ↑

Fri Apr 07, 2023 11:24 am

Thanks for the clarification! I was thinking "hypopneas" were caused by my brain (i.e., "central apnea") rather than my tongue. Is the brain responsible for SOME hypopneas? If so, would this be revealed by analysis of the detailed OSCAR data?

Hyponeas "can" be central in nature but it isn't common and sometimes it can be spotted on the detailed report if someone (who knows this stuff) zooms in on the flow rate but it isn't all that easy to spot the difference. I can't spot it myself when looking at hyponeas. I do good to distinguish between awake vs asleep when zooming in on the flow rate.
The machine is going to respond to hyponeas assuming obstructive though. That's just the way the auto adjusting algorithm works.

I suppose if I were to vary my pressure settings to assess the degree of (inverse) correlation between the Min pressure and my hypopnea frequency, it could provide some evidence of whether my hypopneas were obstructive or central in nature. I probably won't be doing that as long as things seem to be going okay though.

Pugsy wrote: ↑

Fri Apr 07, 2023 11:44 am

...
The machine is going to respond to hyponeas assuming obstructive though. That's just the way the auto adjusting algorithm works.

Good to know. Thanks again!