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Auto CPAP Pressure - Does this make sense?
#1
I have a Dreamstation Auto CPAP machine. It was purchased new within the last six months or so. It's set at 10-15, with no inhale/exhale pressure relief. I'm putting in two graphs that I think cover the issue at hand. Feel free to ask for anything additional you might deem relevant.

In the first graph on 12/24, I highlighted the period of time from 3:36am to 4:38am approx. During that time I had only one event. It was a RERA at 3:48am that lasted 33 seconds. The air pressure remained at the minimum setting of 10 until 4:03am, approx 15 minutes after the RERA. the air pressure then fluctuates as shown in the graph during a period of time where there were no events. It almost appears to be a wave function.

[Image: AB1.jpg]

In the second graph on 12/25, I highlighted the period of time from 13:17am to 13:27am approx. During that time I had two events. They were an OA and a Hypopnea. The air pressure remained at the minimum setting of 10 before, during and after the events.

[Image: AB2.jpg]

In my mind, the pressure range should be adjusting when I have events and not adjusting when I don't. Am I looking at this correctly? Is there a potential issue with my machine?
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#2
I'm not a PR machine expert. Sleeprider is really the go to guy.
In the first graph, the pressure is not really rising -- it's sending out a burst of 1 cm-water triangular pulses. It's "hunting" for something. Note that is always returns to the 10 cm baseline.

PR machines are not as aggressive at raising pressure compared to ResMed machines. In the second graph, you have a 7 second OA at 13:19:30. It's really a none event as an event must last 10 seconds by definition. Why a 7 second was scored -- I do not know. Then at 13:25:00, you have an Hypopnea. It's from the waxing then waning of flow amplitude. You seem to take larger breaths around 13:24:20, then waning which gets flagged as an hypopnea based on reduced flow.

There's nothing really unusual here; that I see. Perhaps Sleeprider can expand on the topic.
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#3
Thank you for the reply. As Robert Frost said, miles to go before I sleep. Clearly I need to dig deeper into the knowledge base. I'll keep at it for a couple more months and increase my sample size. My AHI is consistently under 2.8, usually 1.5 or less. Perhaps I'm looking for ghosts where there aren't any.

I am very appreciative for the brain power here on this board. I don't get that same feeling from my provider.
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#4
OldVet,
Here is a small excerpt from the Beginners Guide to SleepyHead.

Question: I had an OA and the machine didn't increase the pressure. Why didn't it increase the pressure to blow through the event and open my airway and end the apnea?

Answer: While APAPs and Auto bi-levels are designed to respond to OAs with pressure increases, they are NOT non-invasive ventilators and they CANNOT trigger inhalations. (The fancier ASV machines ARE non-invasive ventilators and can trigger inhalations). If the machine is going to increase the pressure in response to an OA, it will wait until the OA is over and you are breathing again before it increases the pressure.

Moreover, the auto-algorithms are designed to NOT respond to isolated OAs and Hs: Unless two or more events happen relatively close to each other (as in within about 2 minutes of each other), an APAP or Auto bi-level machine is programmed to NOT increase the pressure.

You can read more here:
http://www.apneaboard.com/wiki/index.php...SleepyHead
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#5
In plain English the waves are the PR machines hunt and peck algorythem.
And the PR machines don't raise pressure for one single event.
Except flow limitations. It will raise pressure for each and every flow limitation or snore it senses.
You machine is working perfectly sir.
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