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What is correlation of HI and CI with pressure change?
#1
Question 
I have seen several posts that indicate that too high pressure may produce centrals and that too low leads to excessive Hypopneas.

After 3 month on APAP therapy at 15 -20 pressure w/EPR=3, my 30 day average OI=0.24, HI=1.94, CI=1.27. AHI=3.45.

My doc reduced the pressure to 12-19 w/EPR=OFF last week (included in last 30 days). Now past week OA=0.0, HI=5.93, CI=0.87. AHI=6.79. AS expected CI went down, HI went up and OA no impact. 90% pressure 30 days = 16.18, last week 90% p=15.54

Would it be worthwhile to increase the pressure min up to 14 and keep EPR off for next week to see if the Hypopneas go back down and the CA, OA remain low? Is there a so called sweet spot for pressure?


It does not matter how slowly you go as long as you do not stop. --Confucius
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#2
(05-02-2016, 05:12 PM)Ed1101 Wrote: I have seen several posts that indicate that too high pressure may produce centrals and that too low leads to excessive Hypopneas.

After 3 month on APAP therapy at 15 -20 pressure w/EPR=3, my 30 day average OI=0.24, HI=1.94, CI=1.27. AHI=3.45.

My doc reduced the pressure to 12-19 w/EPR=off last week (included in last 30 days). Now past week OA=0.0, HI=5.93, CI=0.87. AHI=6.79,
This is a good example of "If it ain't broke don't fix it."

Why did the doc feel compelled to lower your pressure and tell you to turn the EPR off? Were you complaining about the difficulty of breathing with the machine? Were you saying anything about feeling like the machine was rushing your breaths?

I ask because given those numbers at 15-20 with EPR = 3, there was no a priori reason to mess with the pressures at all. And unless you were complaining specifically about the way EPR feels, there was no good reason to tell you to go from EPR=3 to EPR=OFF.

Quote:AS expected CI went down, HI went up and OA no impact. 90% pressure 30 days = 16.18, last week 90% p=15.54
The difference in 90% pressures is probably not statistically significant. But with a lower min pressure of 12, the machine has to do a lot more "chasing" events (and flow limitations and snoring) to get the pressure up to the level where it effectively keeps your airway open. When the min pressure was set to 15, the pressure was already high enough to prevent most of your OAs and Hs from occurring. Now that the min pressure is set to 12, a lot more Hs are getting through while the machine is reacting to them by increasing the pressure from 12 to 15. And the machine is also probably lowering the pressure back down to the point where it no longer effectively keeps your airway open, and that also lets more Hs occur.

It's also worth pointing out that the reduction in OAI from 0.24 to 0.0 and the reduction in CAI from 1.27 to 0.87 is probably not statistically significant. But the increase in HI from 1.94 to 5.93 IS statistically significant. And it's a change that's in the WRONG direction.

Quote:Would it be worthwhile to increase the pressure min up to 14 and keep EPR off for next week to see if the Hypopneas go back down and the CA, OA remain low? Is there a so called sweet spot for pressure?
Yes, there is often a sweet spot for pressure. That sweet spot depends on each individual's airway.

I think that you should increase the min pressure back up to 14 and see what happens.

I also would say this about EPR: If you are more comfortable with EPR turned OFF, then leave it off. But if you were more comfortable with EPR = 3, then turn it back on. The numbers when you had EPR = 3 were fine---as long as you are sleeping well and starting to feel a bit better.

You have to keep this in mind: Until you are sleeping well with the machine, you won't feel much better. If a particular change in settings makes you more comfortable and keeps the AHI < 5, you can concentrate more on how you are feeling than on chasing a super low AHI.
Questions about SleepyHead?
See my Guide to SleepyHead
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#3
EPR on some people (me!) will help cause CA's. A pressure increase can also induce CA's. A CA is akin to sticking you head out the window of a fast moving auto and trying to breathe. The initial pressure increase tells your brain not to breathe but eventually you overcome this resistance. You might try increasing the lower pressure a little at a time to let your body adapt to the new pressure. I would try an increase of 1cm or less. See how that plays out. I see that you have SleepyHead. Look at the Median and the 90(95) Percentile values. These values along with the AHI and how you feel will help in trying to find the "Sweet Spot".

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#4
Thanks robysue - Just a note, I have never felt bad or shown symptoms of daytime sleepness. I actually cannot see any difference in my personally perceived sleep with CPAP. My wife of 53 years says I am sleeping better with CPAP. I was fine with 15-20 and EPR=3. I never liked the ramp function and have it at 5 min and start pressure at 8cm.

I was curious what my indexes were in the sleep study so I ask my Doc about the centrals because my sleep study AHI=86 while my 3 months on APAP showed only 1-2 times AHI>5 (even the first night was < 3). The doc said that my study had not determined my optimum pressure? He lowered the pressure by Rx to 12-18, but scheduled my next appointment for six months? Since this pressure change last week, I have not felt as good in the AM, not excessively sleepy but I felt I am not sleeping as well. I have had less problems with leaks however which were, of course, more prevalent at 15-20.

You are correct that the APAP is ramping up and down and comparing my flow limitation graph is substantially higher than at 15-20.

I also observe in SH, that most of the CA's at 15-20cm were when I am just starting to go to sleep or just after I go back to bed after my single bathroom call arount 2-3AM. Sometime see CA's when I am first waking up in the morning also? Now at lower pressure the CA's are more scattered.

I plan to change the min pressure up 1cm per week and see if the overall AHI comes down below 5 as it was before the lower pressure. Starting tonight at 13-20cm. Since nothing much bothers me except large leaks, I will leave the EPR=OFF for now. Too many changes at once may obscure the results.

Thanks All Smile
It does not matter how slowly you go as long as you do not stop. --Confucius
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#5
(05-02-2016, 05:39 PM)robysue Wrote:
I think that you should increase the min pressure back up to 14 and see what happens.

I also would say this about EPR: If you are more comfortable with EPR turned OFF, then leave it off. But if you were more comfortable with EPR = 3, then turn it back on. The numbers when you had EPR = 3 were fine---as long as you are sleeping well and starting to feel a bit better.

Increased the pressure back to 14 and EPR=3. Working well. Average AHI < 3. Received a new mask & headgear 4 days ago. Initially leaks alternating between low and massive. Takes some time to get the new headgear adjusted correctly. Old head gear had streached out to the point thet the upper velcro would not attach.

(05-02-2016, 05:39 PM)robysue Wrote: You have to keep this in mind: Until you are sleeping well with the machine, you won't feel much better. If a particular change in settings makes you more comfortable and keeps the AHI < 5, you can concentrate more on how you are feeling than on chasing a super low AHI.

Interestingly, no matter what my AHI (86 in sleep study or < 3), I never realized I was not sleeping well. I never felt bad or had symptoms usually mentioned in the forum. I see no real change, but my wife says I sleep better. However, on large leak nights she does not sleep well and I feel like I have been up all night. As a naval aviator flying 12 hour electronic recon missions in Vietnam, I often went 24 hours without sleep so I know how that feels. Mission now is to re-establish low leaks on a nightly basis.

Thanks for your recommendations.Thanks

It does not matter how slowly you go as long as you do not stop. --Confucius
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#6
(05-17-2016, 06:24 AM)Ed1101 Wrote: Increased the pressure back to 14 and EPR=3. Working well. Average AHI < 3. Received a new mask & headgear 4 days ago. Initially leaks alternating between low and massive. Takes some time to get the new headgear adjusted correctly. Old head gear had streached out to the point thet the upper velcro would not attach.

If you have not tossed the old headgear yet, try washing and soaking it in very hot (not boiling) water. Let it soak a long time - couple hours. Then lay it out on a dish towel to dry out of the sun. There are numerous threads of people getting extended life from them and one step is to shrink them by washing and soaking in hot water.

Never hurts to have a spare if it works.
I am not a Medical professional and I don't play one on the internet.
Started CPAP Therapy April 5, 2016
I'd Rather Be Sleeping
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#7
(05-02-2016, 05:27 PM)Ed1101 Wrote: Is there a so called sweet spot for pressure?
Absolutely; and the settings for Min, Max, EPR, and Ramp, all effect it!
Data collection and tend analysis on my first 20 weeks of therapy indicate that when the pressure rises above 15.8 , I start seeing and increase in CA's.

When the minimum is lower than 12.6 I see an increase on OA

running EPR at all three settings with the min and max set as described above. Had no effect on # OA or CA events.
However, the number of HI increased with EPR off and the number of RERA increases with EPR on 3. I run my EPR on 2 because I have less awaking's (a longer sleep cycle)

With ramp off;running "Mask Fit" allow you to check for leaks before falling asleep, since leaks typically because the wake people up.

An increase in HI from turning EPR off is somewhat predictable since it is harder to exhale (more work) with EPR off.
2004-Bon Jovi
it'll take more than a doctor to prescribe a remedy

Observations and recommendations communicated here are the perceptions of the writer and should not be misconstrued as medical advice.
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#8
OrangeBear, I have been monitoring the 90% pressure and it is staying around 15-15.5. In my study the max pressure reached was 15 and there were some HI then but few. I have checked the leaks as you stated but the sometimes start up later in the early morning. 15 Cm is a lot of pressure. Without mask liners, the pressure just blows the mask seal aside. With liners the leak is mostly around bridge of the nose - narrow nose. I have used the Resperonics "liquid gel" nose guards and have recently added a small mole skin to it as it is thin. Did not work last night … blew right past it. Once leaks start very difficult to stop without redoing the whole process.
Thanks for the insight.

FrankNichols, Thanks, I will try that wash and shrink.

It does not matter how slowly you go as long as you do not stop. --Confucius
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#9
(05-17-2016, 01:37 PM)Ed1101 Wrote: OrangeBear, I have been monitoring the 90% pressure and it is staying around 15-15.5. In my study the max pressure reached was 15 and there were some HI then but few. I have checked the leaks as you stated but the sometimes start up later in the early morning. 15 Cm is a lot of pressure. Without mask liners, the pressure just blows the mask seal aside. With liners the leak is mostly around bridge of the nose - narrow nose. I have used the Resperonics "liquid gel" nose guards and have recently added a small mole skin to it as it is thin. Did not work last night … blew right past it. Once leaks start very difficult to stop without redoing the whole process.

Thanks for the insight.

You 90% is higher and narrower than mine. I run 13.4 to 14.8. It runs higher on the nights I eat in the evening.

I would expect your sweet spot to bracket around that 90% number. I would try 14-17 if it was me. This setting is closer to your original prescription and should get the numbers moving back down. I see robysue also recommended a min of 14.

After a week on the new setting if the HI is still high, you may want to try increasing the EPR to see it's impact at the same MIN/MAX setting.
2004-Bon Jovi
it'll take more than a doctor to prescribe a remedy

Observations and recommendations communicated here are the perceptions of the writer and should not be misconstrued as medical advice.
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