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Pressure Question
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rdonchann Offline


Posts: 10
Joined: Jul 2015

Machine: S9
Mask Type: Full face mask
Mask Make & Model: resmed
Humidifier: resmed
CPAP Pressure: unsure
CPAP Software: Not using software

Other Comments:

Sex: Male

Post: #1
Pressure Question
I have been doing some reading and have not found an answer to my question.
I see most of you that are on an auto machine set a range. Let's say 9-13. I can see and have experienced the reasoning behind having a bottom number. Until the machine adjusts up to the area of your top number it makes breathing hard and is not fun. Why limit the top number? In other words, why not have a range of 9-20? If your number is 12 and you set the top to 13 in theory the machine will always be in the range you need, but why not have the top at 20? The way I understand it, the machine will not go higher and run 19 if all you need is 12. What is the advantage to limiting the range? What happens if my number is 12 and the range is 9-13 but a position or some other reason causes me to need 16 briefly and the machine doesn't go there because of the limit?
07-14-2015 08:35 AM
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MobileBasset Offline

Advisory Members

Posts: 198
Joined: May 2015

Machine: ResMed AIRCURVE 10 V Auto
Mask Type: Nasal mask
Mask Make & Model: Fisher Paykel Zest
Humidifier: Integrated
CPAP Pressure: 10 (minE 6,maxI 12, PS 3)
CPAP Software: ResScan SleepyHead Other Software

Other Comments:

Sex: Female
Location: Florida

Post: #2
RE: Pressure Question
This may not be the best reason but it is one reason that caused me to tighten my limits.
I have experienced leaks that temporarily disrupt the machine's best operation and cause it to increase pressure above what I am used to, or need, which wakes me up. Where as if I decrease the upper limit to just a little above where it wants to operate, these short leaks just occur without incident.

if you can't decide then you don't have enough data.
07-14-2015 09:13 AM
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OpalRose Offline


Posts: 3,027
Joined: Nov 2014

Machine: PR System One REMstar Auto 560 with A Flex
Mask Type: Nasal pillows
Mask Make & Model: AirFit P10 For Her
Humidifier: REMStar heated humidifier with heated hose
CPAP Pressure: Auto Cpap 10-13 AFLEX 1
CPAP Software: SleepyHead EncoreBasic

Other Comments: Started CPAP Therapy October 23, 2014

Sex: Female
Location: Northeast Ohio, USA

Post: #3
RE: Pressure Question
I try to keep a tight range because my APAP responds to Flow Limations, RERAs and snores by raising the pressure. Sometimes it raises it way too much and according to sleepyhead, there are no apneas occuring when it decides to raise pressure. This increase in pressure, if too high disturbes my sleep, so I have to "tame the beast."

MobileBassit is correct. If you have a lot of leaks, and if too many, the machine sometimes raises pressure which can wake you up. One reason why you have to control leaks.

(This post was last modified: 07-14-2015 09:28 AM by OpalRose.)
07-14-2015 09:27 AM
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under pressure Offline

Preferred Members-2

Posts: 139
Joined: Feb 2014

Machine: ResMed Airsense 10 Autoset
Mask Type: Full face mask
Mask Make & Model: F&P Simplus
Humidifier: Integrated
CPAP Pressure: 11 - 14
CPAP Software: ResScan SleepyHead

Other Comments: Also use F&P Icon Auto and Z1 Auto for travel and Backup

Sex: Male
Location: Colorado

Post: #4
RE: Pressure Question
There are several reasons one might want to limit upper number the most important being that some people begin to experience more Central Apneas due to higher pressures. Other reasons might be increased problems with aerophagia or stomach bloating from higher pressure forcing air into stomach; increased leaks around mask.

In my case the Resmed is overly sensitive to Flow Limitations for my particular circumstances and wants to keep increasing pressure due to Its sensing these FLs. It will want to go way up past my prescribed pressure and if I let it go to these higher pressures I begin to experience all the problems listed above, but most notably the increase in Central Apneas/Clear Airway Apneas.

The first versions of Auto machines could actually experience a form of run away pressure increases so it was more important in the earliest versions to set an upper limit, but the newer generations of Auto machines don't suffer from those issues at this point.

If you are an individual that does not have an issue leaving the top wide open, then no problem, go ahead and leave the top at 20 cm, but for some folks it does create problems. It's funny that both my Resmed machines (S9 and Airsense Autos) want to keep increasing pressure, but my other Auto machines (F&P Auto Icon, Z1 Auto, and Transcend Auto) don't react the same way, they all top out either right at my prescribed pressure or just slightly above, so my conclusion is this happens due to the fact that each manufacturer uses their own proprietary Auto Algorithm - and from studying Sleepyhead graphs it looks like the Resmed Algorithm is much more sensitive to Flow Limitations in terms of increasing pressure.
07-14-2015 09:41 AM
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quiescence at last Offline

Advisory Members

Posts: 753
Joined: Nov 2014

Machine: REMstar System One with Autoflex
Mask Type: Full face mask
Mask Make & Model: Quattro AirFit F10
Humidifier: yes typical setting = 4
CPAP Pressure: 5-13 Autotritrating CPAP
CPAP Software: SleepyHead EncoreBasic

Other Comments: CMS-50F Plus oximeter /w SPO2 Assistant software. Avowed mouth-breather switching to nose-breathing

Sex: Male
Location: US

Post: #5
RE: Pressure Question
the first time I adjusted my top limit down from 20 is the morning after the bad night where it climbed to 15. Boom, I will not subject myself to that anymore. Luckily, my pressures don't slam against my current top, but if they did, I would have to choose between lowest AHI and best fit comfort and sleep quality. I think of this as obtaining the lowest practical AHI.


Dedicated to QALity sleep.
You'll note I am listed as an Advisory Member. I am honored to be listed as such. See the fine print - Advisory Members as a group provide advice and suggestions to Apnea Board administrators and staff concerning Apnea Board operation and administrative policies. Membership in the Advisory Member group should not be understood as in any way implying medical expertise or qualification for advising Sleep Apnea patients concerning their treatment.
07-14-2015 12:27 PM
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