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Pressure Settings using Nasal and Full-face mask
#1
Pressure Settings using Nasal and Full-face mask
I have been using a dreamwear nasal mask for approximately 5 weeks with good success.  My only complaint is that my leak rate is high (>25) on some nights, while my AHI can be <3.  I know I am opening my mouth which is causing it to become dry during the night and I assume the higher leak rate.  I have tried a dreamwear full-face mask for two days now, and my leak rate is now approx. 10, yet my AHI has increased to 11.

I have been adjusting my settings gradually over the weeks and am currently set to MIN 9.6, MAX 11, no EPR (ResMed Autoset 10).  My question is does alternating masks sometimes require different settings in pressure to get the desired results.  For example, at MIN 9.0 I have no issue breathing with the nasal mask, but at the same MIN pressure I feel like I'm starving for breath while wearing the full-face.  Why would my AHI be 11 with a full-face, yet AHI of 3 with the nasal?

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#2
RE: Pressure Settings using Nasal and Full-face mask
Physics.
First, make sure you set your machine to the correct mask type.
I can't find it but different masks have different intentional leak rates. This impacts the flow through the mask. Also masks have different volumes. Volume acts like a buffer. The bottom line is that different masks have different physical characteristics which require the machine to compensate differently. This means that in general a FFM would require slightly different settings than a nasal mask or pillows., typically a 1 or 2 cmw difference
Fred Bonjour - Project Manager and Lead Tester for OSCAR - Open Source CPAP Analysis Reporter 
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#3
RE: Pressure Settings using Nasal and Full-face mask
Thanks for your input. Yes, I change the mask type. I wasn’t sure if that actually did something, or if it was more for record keeping.
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#4
RE: Pressure Settings using Nasal and Full-face mask
If I understand it, that mask setting on the machine adjusts or compensates for mask types in some way. It seems kinda like the sport button in some cars, modifying input responses.
Dave

I'm not a doctor in real or fictional life. My posts include opinions based upon user experience regarding CPAP therapy and should not be considered medically professional direction or advice.


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#5
RE: Pressure Settings using Nasal and Full-face mask
I suggest you post an OSCAR daily chart.With data we may be better able to advise you. See the links below for how to format and organize your data and how to post.
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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.

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#6
RE: Pressure Settings using Nasal and Full-face mask
Is the reason why a ff mask requires extra pressure just because there is extra volume in the mask or is it because (or also because) there is extra volume in the mask and (even with a probable larger vent area) there is still more opportunity to re-breath co2 and so you need extra pressure to neutralize the co2 by forcing it out more strongly?

If you use a ffm at a certain pressure, and set the machine to pillows instead of full face, is there more or less opportunity to be re-breathing co2?

Does the sleep dr have to say ---if you are going to use a ffm then I'm going to have to raise your pressure or is it done by the machine and so-to-speak the machine gives an adjusted result (from the true pressure) on the screen and on the report which Oscar uses?
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#7
RE: Pressure Settings using Nasal and Full-face mask
The initial assumption is that you will use the same type mask you used in the sleep study. IMHO rarely is your initial setup correctly optimized for you.
When you change mask types you change the delivery interface for your machine. Going from Pillow (or Nasal) to Full Face Increases the delivery system volume, and the intentional leak rate, These impact the co2 wash, your breathing triggers.
The machine does make some changes but it is always prudent to review your settings after a change and adjust as needed.
Fred Bonjour - Project Manager and Lead Tester for OSCAR - Open Source CPAP Analysis Reporter 
OSCAR

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New to Apnea? Helpful tips to ensure success
Soft Cervical Collar
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INFORMATION ON APNEA BOARD FORUMS OR ON APNEABOARD.COM SHOULD NOT BE CONSIDERED AS MEDICAL ADVICE. ALWAYS SEEK THE ADVICE OF A PHYSICIAN BEFORE SEEKING TREATMENT FOR MEDICAL CONDITIONS, INCLUDING SLEEP APNEA. INFORMATION POSTED ON THE APNEA BOARD WEB SITE AND FORUMS ARE PERSONAL OPINION ONLY AND NOT NECESSARILY A STATEMENT OF FACT.
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#8
RE: Pressure Settings using Nasal and Full-face mask
Each mask type has a finite, but fixed, internal volume.  When your two lungs are emptied during exhalation, they flush the interior of any mask many times over.  It's just that what they flush it with is 'exhaust' air...which is 'spent' air.  The machine needs to purge this and to supply clean, oxygenated, air as soon as it can.  So, while nasal pillows, the kind that press up against and slightly into the nares, are small and easily refilled with clean air by the machine, the larger full-face masks have probably 12 times the internal volume, your nose notwithstanding.  Our machines need to 'know' which mask interior they're clearing of spent air.

It also seems that different mask types have different 'normal' leak rates for the typical wearer, and this too is compensated for.

Them crafty engineers think of everything!  Too-funny
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#9
RE: Pressure Settings using Nasal and Full-face mask
Thanks everyone. Looking forward to another night of good sleep.
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#10
RE: Pressure Settings using Nasal and Full-face mask
This is a follow-up post.  Things have been pretty consistent.  Using the nasal mask, I can keep the pressure between 9 and 11 and all is good.  Only problem is I have high leak rates.  Attached is last night, nasal mask, high leak rate, low AHI.

What I'm finding with the FF mask is that even setting MAX at 14.5 it doesn't look to be enough pressure to control AHI.  Leak rate is low, but AHI is high.  

I'm suspecting that its better to go with the nasal mask despite the high leak rate.  Further, I'm not sure that I should take the pressure up any higher with the FF mask.  My lungs feel like balloons as it is.  Would someone please be gracious enough to confirm they agree.  Thanks.


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