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sawzall
Unread post  Post subject: Lots of Centrals in Auto BiPap mode  |  Posted: Thu Aug 05, 2021 12:50 pm

Joined: Thu Aug 05, 2021 11:47 am
Posts: 3
PAP Mask: ResMed AirFit F20
PAP Machine: ResMed AirSense 10 VAUTO
Pressure Setting: 4-20

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I have been using my ResMed AirSense 10 VAUTO for over two months. I was getting a lot of low oxygen desaturation events in my home sleep study. I had a CPAP titration study and need a high pressure of 20 cm-H20 when sleeping on my back. The doctor prescribed a BiPap with max IPAP of 20, min EPAP of 6, and Pressure Support of 4. I think they prescribed a BiPAP because my pressure was so high, they thought a BiPap would be more comfortable.

I used the doctor's settings in VAUTO mode for 30 days and my AHI was 11-18. The Central Apnea Index was 5-6. I didn't feel like I was getting much rest.

After doing some research, I decided to experiment with the pressure support setting.

I found that I do much better with the Pressure Support set to zero, which I think is similar to Auto CPAP mode. With PS=0, my AHI is 4-6 and my CAI is less than 2.

So I am doing OK now using PS=0. It seems like I don't really need the auto BiPAP and would do just as well with an Auto CPAP machine.

But I don't understand why I was having so many centrals in BiPAP mode.


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Pugsy
Unread post  Post subject: Re: Lots of Centrals in Auto BiPap mode  |  Posted: Thu Aug 05, 2021 2:30 pm
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Joined: Wed Aug 02, 2017 8:01 pm
Posts: 2461
PAP Mask: Bleep/DreamPort nasal mask
PAP Machine: ResMed AirCurve 10 VAuto

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For some people...actually a very small percentage of people using any sort of bilevel pressures, which includes any exhale relief, the bilevel situation simply causes some unstable breathing which ends up triggering central apneas. It's not all that common but not all that rare either.

I have a friend who gets about 15 centrals per hour on average with PS of 4 but essentially none with PS of 3. Go figure that one.
1 cm difference in PS makes a huge difference in the number of centrals that pop up.

There is long drawn out explanation as to how and why bilevel does this for some people and I don't have time to explain it right now but I have explained it not long ago her if you read some of may past recent posts.

You might want to re-evaluate your minimum EPAP though IMHO it needs to be increased to hopefully reduce the hyponea numbers and make the ugly flow limitation graph look not so ugly.

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sawzall
Unread post  Post subject: Re: Lots of Centrals in Auto BiPap mode  |  Posted: Thu Aug 05, 2021 3:16 pm

Joined: Thu Aug 05, 2021 11:47 am
Posts: 3
PAP Mask: ResMed AirFit F20
PAP Machine: ResMed AirSense 10 VAUTO
Pressure Setting: 4-20

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Thanks a million Pugsy! :)

I am glad that I am not the only one that has trouble with bilevel pressure. I think I can maybe tolerate a pressure support or exhale relief on 1. But more than that is trouble, and I am OK just leaving it at zero.

I set the min EPAP to 4 intentionally. I agree it is too low. I want to use this setting for a week to find out my average pressure, using the full auto range. My average EPAP for the last three nights is about 13. I expect my weekly average will be about the same. But I am not sure if it is a good idea to set the min EPAP this high.


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Pugsy
Unread post  Post subject: Re: Lots of Centrals in Auto BiPap mode  |  Posted: Thu Aug 05, 2021 3:53 pm
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Joined: Wed Aug 02, 2017 8:01 pm
Posts: 2461
PAP Mask: Bleep/DreamPort nasal mask
PAP Machine: ResMed AirCurve 10 VAuto

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Just because an average number is up around 13 doesn't necessarily mean we have to set the minimum that high.
Often when the minimum is more optimally set the machine might end up not going to high anyway.

All you need is a minimum close enough to what you need to hold the airway open and prevent collapse of the airway.

If it were me I would look at around 7 or 8 minimum and see what happens with the hyponea numbers which are your biggest problem.
Hyponeas are usually dealt with fairly easily with just a little more pressure baseline and you aren't having truck loads of them anyway....and with it higher the machine can go higher more quickly and deal with what is needed faster.

The FL graph...as long as you are sleeping well and feeling decent, I don't know that I would worry about it especially if you are experiencing any nasal congestion. Often FL graphs are ugly looking from nasal congestion and we can't fix that with pressure tweaks anyway.

You might do okay with PS of 1...might not.
At sometime in the future you can revisit adding PS back in if you wish.
It's not a critical issue at this point.

It doesn't really hurt anything that your machine is functioning more like an apap with some bells and whistles. Should things ever change and you happen to need more than 20 cm pressure....you machine can deal with it.

I would use whatever settings let me sleep and feel the best.

As to how many people have this weird little problem???? It can happen with plain ordinary exhale relief as well because when we use any form of exhale relief we create a bilevel situation. I suspect that you are maybe a part of less than 1% of cpap users who end up with this problem.
There are a lot more people out there using exhale relief and many forms of PS settings and they don't have this problem.

You are special. :lol:

Didn't know the 4 cm Minimum was an on purpose experiment....so get back to whatever you were doing and now since you have additional information you should be able to dial in rather quickly.

_________________
I may have to rise but I refuse to shine.


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sawzall
Unread post  Post subject: Re: Lots of Centrals in Auto BiPap mode  |  Posted: Thu Aug 05, 2021 4:18 pm

Joined: Thu Aug 05, 2021 11:47 am
Posts: 3
PAP Mask: ResMed AirFit F20
PAP Machine: ResMed AirSense 10 VAUTO
Pressure Setting: 4-20

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Thanks again pugsy. 8-)


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