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Autopap questions on how it works
#1
New to AutoPAP, been on CPAP for over a decade, though.

My understanding: Give it a minimum and maximum range. Machine will adjust pressure within that range to maintain the "sweet spot".

How does the algorithm seem to work? When does it decide it's found the best setting? Does it adjust upward until it stops sensing improvements over a certain period of time and stop? Or does it adjust until it reaches some AHI target value and then stop? Or is there another way?
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#2
For me it seems to try and analyze my flow rate to predict events, and try different techniques to stop them. Sometimes it will sit at the lowest pressure and periodically spike the pressure before returning to minimum. Other times it will actually raise the pressure a bit and stay there for a while.
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#3
I am not a PR expert by any means since I have only used Resmed. Generally the autos increase pressure when they encounter apneas, flow restrictions, or snores. They will increase pressure until they no longer sense any of the foregoing. If no more reason they wil reduce the pressure until they detect one of the aforementioned apnea events or precursors. For the Respironics machines-if the machine has found a happy place pressurewise for a while it will temporarily increase the pressure to see if it makes any improvement and then drop back if it does not. If it is at a high pressure, it will the same thing in reverse. That is, it will drop the pressure slightly to see if things get worse. If they do, it will raise the pressure back up.

That is a crappy, oversimplified explanation of generally how autos work.

Best Regards,

PaytonA
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#4
The Respironics machines are much slower to respond to obstructive events than a Resmed, so it is important to have the minimum pressure high enough to provide most of the needed therapy, letting the machine adjust higher as needed. A general rule-of-thumb would be to set minimum pressure approximate 2-cm less than the 90% pressure you have recorded over the past week.

You can change Sleepyhead in Preferences to report the average and 90% rather than median and 95%. The Philips auto will increase pressure in response to snores, flow limitation, volume reductions (hypopnea) and obstructive events. It will only increase enough to where those events are mostly stopped, then will slowly fall back towards minimum pressure until another obstructive precursor is detected. In addition, the machine increases pressure 1.5 cm over 2-minutes, every 20 minutes during the night to "test" a higher pressure. It usually drops back to the baseline pressure unless it detects an improvement at the higher pressure. This gives Philips auto machines a characteristic saw-tooth pressure pattern.
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#5
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#6
(10-10-2016, 11:48 AM)Sleeprider Wrote: The Respironics machines are much slower to respond to obstructive events than a Resmed, so it is important to have the minimum pressure high enough to provide most of the needed therapy, letting the machine adjust higher as needed. A general rule-of-thumb would be to set minimum pressure approximate 2-cm less than the 90% pressure you have recorded over the past week.

You can change Sleepyhead in Preferences to report the average and 90% rather than median and 95%. The Philips auto will increase pressure in response to snores, flow limitation, volume reductions (hypopnea) and obstructive events. It will only increase enough to where those events are mostly stopped, then will slowly fall back towards minimum pressure until another obstructive precursor is detected. In addition, the machine increases pressure 1.5 cm over 2-minutes, every 20 minutes during the night to "test" a higher pressure. It usually drops back to the baseline pressure unless it detects an improvement at the higher pressure. This gives Philips auto machines a characteristic saw-tooth pressure pattern.

I did see a setting in the clinician menu on my PR Dreamstation that tells it to start at the 90% pressure of the last x number of sessions or hours. This should help keep it from having to hunt too far.

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#7
SmartRamp will start the pressure at 90% of the last 30 hours, but it does not fix the problem if the machine then drops below an effective therapeutic pressure, resulting in more events. My preference would be to set the minimum pressure at 90% minus 2 cm. That will be more comfortable starting, and will ensure the machine is always in range to make needed increases.
______________________________________________
Organize your SleepyHead Data
Post your SleepyHead Data from Imgur
Robysue's Beginner's Guide to Sleepyhead
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