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Autoset does not set the right pressure
#1
Autoset does not set the right pressure
I were a silent reader of the Apnea Board Forum for many years and decided to step out to share my experience.

I have been bothered with leak for many years.  I tried chin strap, mouth tape, full-face mask and they did not help much.  Late last year I replaced the ResMed S9 with AirSense 11 and decided to spend time fixing the leak.  My doctor suggested to do a sleep study so I had one a couple weeks ago.  The main result was "A best CPAP setting of 7 cmH2O effectively improved sleep disordered breathing during REM sleep".  Based on the result my doctor set the pressure to 7 - 8 cmH2O.  To my surprise the leak had reduced to almost zero and the AHI is about the same as before.  I set the pressure between 8 and 16 cmH2O before because I thought autoset would use the right pressure for the treatment.

When I first saw my doctor last year I showed him the OSCAR screenshots and he said he did not believe in any of those numbers.  He said how could such a machine with limited sensors measure so many parameters.  It turns out he is right.  What do you think?

I attached OSCAR screenshots before and after the pressure changed.


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#2
RE: Autoset does not set the right pressure
When you had the larger range the machine was responding to Flow Limits (a precursor to an "event") by raising the pressure.
But, that extra pressure was creating leaks at the mask (you would have to tighten the mask down to get rid of that). The leaking pressure would also reduce your actual therapy, as well as increase humidifier water consumption, noise etc.. so yes it's a mess.
Your new setting looks okay. If you're feeling good, all is well.
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#3
RE: Autoset does not set the right pressure
The main points of my post are 1) So many users complain about leak which may be fixed by lowering the pressure. 2) We probably cannot trust the CPAP machines to set the pressure and provide measurements.
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#4
RE: Autoset does not set the right pressure
Before you went to the limited pressure adjustment, you were not using EPR. That has somewhat helped your high flow limitation which has now dropped from 0.22 to 0.15 in the 90% flow limit statistic. Still quite high, but improved. I think you need to realize that you used to have a median pressure of 11.6 with no exhale relief. This gave you pressure of 11.6/11.6. You are now enjoying 8.0/5.0 (inhale/exhale). I'd like to see you gradually increase the maximum pressure to see where the leaks become a factor and we can see if those flow limits can come down a bit. I think you will ultimately find a maximum pressure of between 10 and 12 to be beneficial with the EPR.
Sleeprider
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#5
RE: Autoset does not set the right pressure
Hi Sleeprider, thank you so much for reviewing my CPAP data. Your reply makes me read about EPR and flow limitation. I now understand uncorrected flow limitation is also a concern. I'll gradually increase the pressure to find an optimal point where both leak and flow limit is low.
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#6
RE: Autoset does not set the right pressure
One of the premises appears to be; mask leaks should be addressed by reducing pressure. This is just wrong. Mask leaks are addressed by adjusting the fit or possibly changing the mask. Where would you be, if your therapy consistently required 16-18cm?

You are also drawing conclusion based on a comparison between two misconfigured APAP settings, with a limited data view.

The previous configuration (8-16), your minimum pressure was way to low, we know this because it almost immediately jumped well beyond the minimum and typically stayed well above the minimum. The volatility, is also consistent with an inadequate minimum pressure.

Your new setting is even worse, inadequate minimum and maximum, we know this because the device immediately jumps to the maximum and effectively stays there, it is sensing indicators that suggests it needs to raise its pressure and can't. That plateau is a huge red flag.

But what is most alarming is the statement that your doctor made about not believing the numbers and not understanding how a device with limited sensors could measure so many parameters. This just demonstrates he knows little about about the devices and their settings. It is not supported by trials, testing and experiences by experts on this forum.

Set your maximum back to 16, increase your minimum 8, initially around 11, turn on EPR, and adjust your mask fit.

Your doctor was not right.
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#7
RE: Autoset does not set the right pressure
(05-15-2022, 09:00 AM)Dog Slobber Wrote: Your doctor was not right.
What was the doctor not right about?
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#8
RE: Autoset does not set the right pressure
(05-15-2022, 12:51 PM)dataq1 Wrote: What was the doctor not right about?

His alleged statement about not believing the numbers because a machine with limited sensors could not measure so many parameters.
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#9
RE: Autoset does not set the right pressure
(05-15-2022, 01:24 PM)Dog Slobber Wrote: His alleged statement about not believing the numbers because a machine with limited sensors could not measure so many parameters.
Well, the doctor is right about the limited sensors when compared to a NPSG. 
Fact remains that many of the "Oscar reported numbers" are derived values based on the manufacturer's algorithms to treat and quantify direct measurements.

So, yeah, in that respect, the doctor is probably not well informed. (as far I'm aware many  NPSGs are initially evaluated using ResScan, which has the same evaluative capabilities as the software in our home appliance - e.g.  for Flow Limitations.

I originally thought that you were saying that the "doctor was not right" in prescribing 7 - 8 based on Sleepytom's sleep study. Sleepytom reported that his AHI remained the same but leaks (probably mask hyperinflation vs. fit) reduced to almost zero.
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#10
RE: Autoset does not set the right pressure
Hi Dog Slobber, thank you for the comments.
1) I think my P10 nasal pillow fits very well and I tried different ways to address the mask leak issues to no avail.
2) I think the only misconfiguration was EPR. It is set to Auto and I did not remember why it was Off in last few months. From OSCAR I can see EPR was Ramp Only on 1/25/22 and the Large Leak was 40%.
3) Regarding pressure, that is the point I want to make -- in my case autoset did not set the pressure correctly. Do you trust the CPAP machine more than the sleep study?
4) Regarding my doctor, I am also not happy that he did not look at the OSCAR printouts I brought to him. I wish I could find a sleep doctor who can spend time reviewing the OSCAR data and help me to find the optimal CPAP settings. I can even work with the doctor remotely with Zoom sessions. Do you have any recommendation?
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