Finding 95%

[napstress]

Several people have mentioned doing straight CPAP at one's 95% pressure, based on their APAP range. I would think that the 95% would change, based on what range I'm working with. For example, when my range is 5–8, my 95% is 7.5, but it could be different if my range were 7–10.

Any advice on finding out one's 95% pressure without spending a month playing with different ranges? I suppose I could set the max super-high (for me, say 12cm) for a week, and if it never goes there, it never goes there and I would know my 95%. Does that seem like a sound experiment?

My titration study suggested 4-9, but never did capture supine REM. When I wake up at night, I am always on my back.

[Lizistired]

Several people have mentioned doing straight CPAP at one's 95% pressure, based on their APAP range. I would think that the 95% would change, based on what range I'm working with. For example, when my range is 5–8, my 95% is 7.5, but it could be different if my range were 7–10.

Any advice on finding out one's 95% pressure without spending a month playing with different ranges? I suppose I could set the max super-high (for me, say 12cm) for a week, and if it never goes there, it never goes there and I would know my 95%. Does that seem like a sound experiment?

My titration study suggested 4-9, but never did capture supine REM. When I wake up at night, I am always on my back.

My problem with the 95% method is that the pressure always wants to go to the top of what ever range I set, and then it causes aerophagia. I had a lot of arrousals during my PSG's so I keep my pressure low and steady and my AHI stays around 0.3.
I think actually have UARS, but my PSG AHI of 11 was just enough to call it OSA.

[Sloop]

Several people have mentioned doing straight CPAP at one's 95% pressure, based on their APAP range. I would think that the 95% would change, based on what range I'm working with. For example, when my range is 5–8, my 95% is 7.5, but it could be different if my range were 7–10.

I thought APAP ranges were set to a specific range? If so, finding you 95% is simple math. With your example of a 5-8 range, your delta is 3. 95% of 3 is 2.85. Add that number to 5 and you get 7.85.

[robysue]

Like any rule---the 95% pressure setting rule for straight CPAP is a guideline that works for many, but not for all.

Does the pressure range you use affect the 95% pressure level? Of course it can. Obviously, if you are hitting the max pressure multiple times during the night, the 95% would likely go up if the max pressure was increased. And if you never get off of the min pressure setting during the night, then it's possible that lowering the min pressure could lower the 95% pressure setting. So it's important to remember that the 95% pressure level should be established when you are using a wide enough pressure range on the APAP that you are not repeatedly hitting the max all night long and your also not staying at the min all night long. But running the machine wide open may not work for someone with aerophagia problems since the pressure can increase past what is strictly needed to control the worst of the OSA/UARS.

I max out my IPAP for very long periods each night---as in my IPAP = max IPAP for well over 50% on most nights. About 1/3 of the time, my EPAP stays at its max of 6cm for close to half the night. And like Lizistired, whenever I increase the Max IPAP, flow limitations and intermittent snoring will drive my 95% pressures up to near the top of where ever I set their ranges. And running with those higher pressures, even for short periods of time, typically leads to aerophagia, less comfort, more arousals, and me generally not feeling as well in the daytime. And allowing the machine to use higher pressures doesn't usually reduce the AHI that much, nor does it seem to really "fix" the snoring or reduce the FLs.

So for me: I find sleeping well with the machine at my current pressure levels and a long term AHI around 1.5 or 1.6 beats sleeping poorly with the machine set with a higher Max IPAP that would allow it to find a true 95% pressure level.

[robysue]

Several people have mentioned doing straight CPAP at one's 95% pressure, based on their APAP range. I would think that the 95% would change, based on what range I'm working with. For example, when my range is 5–8, my 95% is 7.5, but it could be different if my range were 7–10.

I thought APAP ranges were set to a specific range? If so, finding you 95% is simple math. With your example of a 5-8 range, your delta is 3. 95% of 3 is 2.85. Add that number to 5 and you get 7.85.

No, you are misinterpreting the meaning of 95 percentile pressure level.

If your pressure is AT or BELOW 6.2 cm for 95% of the time the machine was running during the night, then your 95% pressure level is 6.2 cm. It doesn't matter if the pressure range was set from 4-20 or 5-10 or 6-8.

For more details on how the statistics work, see my Average, Median, 95% numbers: A guide to those who don't remember their introductory stats

[avi123]

Several people have mentioned doing straight CPAP at one's 95% pressure, based on their APAP range. I would think that the 95% would change, based on what range I'm working with. For example, when my range is 5–8, my 95% is 7.5, but it could be different if my range were 7–10.

Any advice on finding out one's 95% pressure without spending a month playing with different ranges? I suppose I could set the max super-high (for me, say 12cm) for a week, and if it never goes there, it never goes there and I would know my 95%. Does that seem like a sound experiment?

My titration study suggested 4-9, but never did capture supine REM. When I wake up at night, I am always on my back.

Reply,

If you check your results in a graph then you can tell if the 95% pressure stated in the Stats is "almost" correct. I say "almost" b/c a study published in 2008 complained that APAPs at that time did not show 95% pressures correlated with formulas and PSG sleep studies.


I deleted the rest of my post b/c it related to Resmed and you have Respironics.

[Pugsy]

Like Robysue says, to find the most accurate 90/95% pressure one has to use a wide enough range to let the figures establish their pattern. It also has to be done long term. SleepyHead let's us choose 90 or 95 % numbers.

A while back I did some review of my data for my 90% (that is what Respironics reports with Encore software) and with my APAP pressures of 10 min and 20 maxi my 90% pressure was around 12.5 cm using 6 months of data. Interesting to note that my overall average pressure was just under 12 cm. One month would probably give me similar numbers but haven't checked them. Some individual nights I might have a 90 % pressure of 16 and I have seen 18. Those nights were rare but they did happen maybe one or two nights a week. No way would I want to use straight 16 or 18 all night. If doing straight cpap and trying to base it on 90% number then I might do 12 or 13.

Since I have been lucky enough that the times I saw the much higher pressures never disturbed my sleep nor caused any aerophagia problems then it works well for me to have a wide range. I do it now with the bilevel machine in auto mode. Sometimes there are times when I see 16 to 18 cm but the bulk of the night I stay well below those higher numbers.
I might go a week and never see above 14 and next week go to 18 briefly every night. I even have nights where there is minimal pressure change from my minimum and the 90% pressure was merely 11.

Sometimes the 90/95% pressure number happens to correlate pretty close to the overall average and sometimes it doesn't.
It isn't the holy grail of numbers that works ideally for everyone though.

[napstress]

Thanks for responding, everyone!

My problem with the 95% method is that the pressure always wants to go to the top of what ever range I set, and then it causes aerophagia. I keep my pressure low and steady and my AHI stays around 0.3.

I have gone as high as 10 for my max, as well as doing straight CPAP at 8, and (thank the merciful gods) have not experienced aerophagia. So I'm thinking that it is probably safe for me to experiment with going higher. My AHI on 5-8 is around 2.9 (RDI on SH is 4.6). Since some people have mentioned feeling a noticeable difference with going down from there, I would like to see if I do, too.

But running the machine wide open may not work for someone with aerophagia problems since the pressure can increase past what is strictly needed to control the worst of the OSA/UARS.

I'm thinking I'd like to keep extending the max until I reach the aerophagia level and then back off a bit, provided that it does make my AHI as pretty as Lizzie's and RobySue's —and that I feel better. Of course, light sleep from CAs might do me in before the aerophagia hits! So far on 6min-10max, which is this week's pressure, I've been doing OK with the CAs.

allowing the machine to use higher pressures doesn't usually reduce the AHI that much, nor does it seem to really "fix" the snoring or reduce the FLs.

This is good to know. I've been wondering about the FLs. Maybe I'll just focus on capturing the REs, which are always higher than the OAs and Hs. The REs comprise 38% of all my events at the 5-9 and 4-4 settings, so I'm thinking greater pressure might capture them—and they might be worth capturing. Even at 6-10, they quite often come in clusters.

It also has to be done long term. (....) A while back I did some review of my data for my 90% (...) and with my APAP pressures of 10 min and 20 maxi my 90% pressure was around 12.5 cm using 6 months of data. (....) One month would probably give me similar numbers but haven't checked them. Some individual nights I might have a 90 % pressure of 16 and I have seen 18. Those nights were rare but they did happen maybe one or two nights a week. No way would I want to use straight 16 or 18 all night. If doing straight cpap and trying to base it on 90% number then I might do 12 or 13.

Do you think my doing it for a month would be sufficient? What about two weeks and keeping an eye out for one or two anomalies?

Maybe each week I will inch up both my min and my max by 1cm to the point where I hit aerophagia or am sleeping lightly with high CAs. Then I'll setting on straight CPAP at the 90/95% from the range just below that. Even though I spend most of my time at 5 (in the 5-8 range) and 6 (in the 6-10 range), I'd like to keep the range tight so the machine can quickly move up to address events. Is my thinking around this correct? Would anyone modify this plan?

[Guest]

It's not that complicated (or at least it shouldn't be).
Just pick a pressure and set your machine to it. Then use it for a week or two and decide whether you need to tweak it or not.
Usually, a pressure somewhere between the "average" and "90%" is a reasonable place to start.
Using the "90%" pressure is like trying to nail Jello to a wall.......it's a moving target from night to night.

[myconoclast]

Does anyone know how the 90th percentile pressure is actually calculated in Sleepyhead? I've noticed that my 90th percentile numbers seem high based on the pressures that I see when I just eyeball the graph, so I took a closer look at some of my nights.

For 7/15, Sleepyhead is showing a 90th percentile of 11.54. I slept a total of 8 hours and 44 minutes (so 524 minutes total). As you can see from the data posted below, there is only one time period when my pressure climbed above 11. A generous estimate of the time spent at or above a pressure of 11 is 40 minutes (from 9:50 to 10:30), so I was at or above a pressure of 11 for 40/524 = 7.63% of the time. So I don't see how my 90th percentile could be 11.54. Is there something I'm missing?

[napstress]

Does anyone know how the 90th percentile pressure is actually calculated in Sleepyhead? I've noticed that my 90th percentile numbers seem high based on the pressures that I see when I just eyeball the graph, so I took a closer look at some of my nights.

For 7/15, Sleepyhead is showing a 90th percentile of 11.54. I slept a total of 8 hours and 44 minutes (so 524 minutes total). As you can see from the data posted below, there is only one time period when my pressure climbed above 11. A generous estimate of the time spent at or above a pressure of 11 is 40 minutes (from 9:50 to 10:30), so I was at or above a pressure of 11 for 40/524 = 7.63% of the time. So I don't see how my 90th percentile could be 11.54. Is there something I'm missing?

I've noticed the same thing. On the Statistics page it says that for the Last 30 Days, my 95% pressure is 9.00, which is not possible b/c in that time I spent 13 days with pressures set to 5-8, 6 days at 4-4, and 5 days at 6-10. During those times I rarely hit 8 or higher and didn't stay there long.

[Pugsy]

Do you think my doing it for a month would be sufficient? What about two weeks and keeping an eye out for one or two anomalies?

It all depends on how often you might have random times where the maximum pressure is significantly higher than what you normally see. How high it goes and how long it stays there and how often. Example...overall average maybe 11 but might see 17 cm for an hour or so each night compared to the maximum never getting above 13 ever. The wider the difference the longer you need to evaluate things to get an overall picture of things. If you don't see much difference then a week or two would probably be sufficient.

FWIW...aerophagia...the only time I ever had it bother me was this night here.
viewtopic.php?f=1&t=67883&p=631376&hili ... mb#p631376
I have hit 18 cm often but never for very long and no problems with aerophagia. I think that time spent at the higher pressures is also a factor in the chances of having problems with aerophagia and not just a pressure number.
The above link also contains a report showing extremely high 90% pressure which would likely really mess with a weekly 90% number but not so much with a monthly number. I don't think I still have that week in my software (did something stupid and my Encore erased my data) but if I do I will go pull that week's 90% numbers to see what that looks like and compare to my 6 month number.
You might get lucky and not have any aerophagia problems at all.

Regarding SleepyHead and its calculations....I have seen some other discrepancies also with the % figures. I haven't bothered evaluating % pressures but for sure % leaks sometimes don't match up with ResScan reports (reported in a thread not long ago). Sometimes spot on and sometimes way off. Mark is aware of the bug. SleepyHead is Beta software so we just deal with it. If it is a critical need and difference then a person needs to use Encore or ResScan to evaluate things.

[napstress]

Thanks, Pugsy, for analyzing this with me.

It all depends on how often you might have random times where the maximum pressure is significantly higher than what you normally see. (....) The wider the difference the longer you need to evaluate things to get an overall picture of things. If you don't see much difference then a week or two would probably be sufficient.

Thanks, Pugsy. This makes a lot of sense.

I've also been wondering about if I do a range of, say, 4-12cm. If I hang out at 4 or 5 most of the time, it could take a long time to get up to a therapeutic level when the events kick in. If that happens most of the time, then my 90% would look lower than is actually therapeutic, right? I do know that at 5-8, my 90% is 7.5. So now I'm thinking if I do a bit higher with a little overlap, then compare the two numbers, I could get a 90% that is generally accurate for most of the time.

Incidentally, last night at the highest range I've done, my AHI was actually higher than it usually is. But I had the Allergy Fit from Hell, which I'm sure skewed things. I'm kind of despairing as it occurs to me that the numbers generated during Allergy Season are probably not very reliable, and that I should probably wait until November before doing this. But I am longing to feel rested through getting my RDI as low as possible and getting good sleep consolidation!

How high it goes and how long it stays there and how often

What is your method for seeing this? I'm tempted to look at Encore's % MaP on the Daily Events Per Hour and Summary of Daily Events Per Hour grids. But I don't know what might be statistically significant: 10% of time at max pressure?

aerophagia...the only time I ever had it bother me was this night here. (....) I think that time spent at the higher pressures is also a factor in the chances of having problems with aerophagia and not just a pressure number.

How brave you were to conduct that experiment! It was also interesting to see Dori's response that everyone is so different. Yes, it does sound right that it was the extended period at the higher pressures that tipped the scales for you.

Regarding SleepyHead and its calculations....(....) Mark is aware of the bug.

Ah, thanks!

[Pugsy]

Pugsy wrote: How high it goes and how long it stays there and how often


What is your method for seeing this? I'm tempted to look at Encore's % MaP on the Daily Events Per Hour and Summary of Daily Events Per Hour grids. But I don't know what might be statistically significant: 10% of time at max pressure?

Real scientific measurement...I eye ball it. I just let the machine do its job. Once I established the minimum pressure that I wanted then I just shrugged my shoulders when I saw the nights with higher 90 % numbers.
I rarely had prolonged time spent with the higher pressures. You can get the MaP from the Encore reports if you want to go into that much detail. Remember, I am lazy and don't do any more work than I have to and I wasn't trying to isolate an effective 90% pressure because I have no need to try straight cpap.
Here are a couple of examples of the random nature that I have seen. a 11 cm 90% number and a 15cm. I have seen 18 fairly often but pretty much always short term.
Here's one where I had some time at some higher pressures.


And then I also have these nights with no real increases at all.

[DoriC]

So on the 3/30 data, the higher pressure seems to correspond with an increase in your leak rate, right? Otherwise, your data is completely boring!