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[Equipment] What is the VPAP supposed to respond to
#1
I have noticed over the past month or two that with my weight loss that my pressures were going down. last week i had a cold and my AHI figures unsurprisingly rose. I seemed to have damaged the mask pillow with the extra more thorough cleaning I was giving my mask the hole was only the size of a pin head so I acquired a new mask. I think I discovered the damage on the day it occurred as mask leakage is zero. I started to use my new replacement Pilairo mask at first last night but felt that it had not inflated correctly, so I changed to my old Swift FX which I use whenever the Pilairo starts irritating my nose. With this change the system one gradually decided to up the pressure after each flow limitation which the machine appears to actually be creating by dropping the pressure just before recording a flow limitation whereupon it increases the pressure still further. In other words it reduces the pressure hence the flow rate detects a flow limitation and ups the pressure a bit more. Just what is the system one supposed to respond to it is not the hypopnea or apneas as it totally ignores these. On the 11th of this month my AHI was 2.39 and my machine remained at 4.5 for most of the night with a rise to 6 for half an hour at 5-5.30am;I went to bed at 11.30 and got up at 6.30 with one short bathroom visit surprisingly I had a Hypopnea, CA,VS and a OA when the pressure rose but the pressure rose before these events. My machine did not appear to respond in any way to previous events that night. On Monday with no apneas and only 3 hypopneas my machine took the pressure up from 4.5 to 10 between 11.00 and 02.30 at which time I woke.
Sorry if I have not explained it clearly and included information that may be irrelevant but, just what event is supposed to induce a rise in pressure and should not apnea /hypopnea be among these or do you think my machine is misbehaving? I would include screen shots from sleepyhead but do not know how to

Thanks

Gerry
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#2
Hi plasticplumber,
WELCOME! to the forum.!
I don't know the answer to your question but hang in there, someone will be along to help you, soon.
Best of luck to you.
trish6hundred
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#3
plasticplumber,

I want to select out a few quotes and respond to them, and hopefully that will answer some of your questions about how the System One you are using is supposed to respond to sleep disordered breathing problems.

(02-19-2014, 01:02 PM)plasticplumber Wrote: the system one gradually decided to up the pressure after each flow limitation which the machine appears to actually be creating by dropping the pressure just before recording a flow limitation whereupon it increases the pressure still further. In other words it reduces the pressure hence the flow rate detects a flow limitation and ups the pressure a bit more.
It would be really helpful if you could post a graph of the wave flow and the pressure curve zoomed in just enough to see what you are talking about.

That said, I can make some guesses about what might be going on.

The PR System One's Auto algorithm has a "search" part where the machine will periodically increase the pressure even if there has been no recent "events" to react to. The machine is analyzing the shape of the inhalations as the pressure is increased by 2 cm H2O over the course of four minutes or so. If the machine does not detect any improvement in the shape of the inhalations, the machine then lowers the pressure back down to the original level over the course of about 2 minutes or so. If the "search" results in improvements in the wave flow, the machine will continue increasing the pressure at a rate of 0.5 cm per minute until no more improvement is found. Typically the machine backs the pressure off by about 0.5cm and uses the new pressure as the new "baseline" pressure. It could be that what you are noticing is the search algorithm in action and either you are noticing the decrease back down to base pressure if no improvement is found or you're noticing that 0.5cm drop to the new baseline pressure.


Quote:Just what is the system one supposed to respond to it is not the hypopnea or apneas as it totally ignores these.
The System One responds to the following events in the following ways:

Central Apneas: The machine does NOT increase the pressure.

Snoring: The machine will increase the pressure by 1cm over about 15 seconds when a VS snore is scored. The machine will then wait for one minute to see if the snoring stops. If the snoring continues for a full minute, the machine will score another VS snore and again increase the pressure by 1 cm and wait for another minute to see if the snoring stops. The machine will keep doing this until either the snoring stops or max pressure is reached.

Flow limitations: These work in the same way that Snoring works. The machine will increase the pressure by 1cm over about 15 seconds when the shape of the inhalations has deteriorated enough to score a flow limitations. The machine will then wait for one minute to see if the the flow limitation is resovled. If the shape of the inhalations show no improvement for a full minute, the machine will score another FL and again increase the pressure by 1 cm and wait for another minute to see if the flow limitation is resolved. The machine will keep doing this until either it is happy with the shape of the inhalations (the flow limitation has been resolved) or max pressure is reached.

RERAs, Hs, and OAs: These do not work the same way that VS and FL work. First, the machine will NOT increase the pressure during one of these events; it will wait until after the event is over---this mimics what goes on in an in-lab titration study. Second, the machine will NOT increase the pressure for an "isolated" RERA, H, or OA. In other words, the machine will increase pressure for these events only if two or more of the events happen within about a 5 minute period. At the end of the second event, the System One will increase the pressure by 1cm in about 15 seconds and then it will leave the pressure alone for one full minute even if another event happens. The idea is that the machine wants to see if the 1cm increase in pressure is enough to resolve the SDB problems resolve. If an event occurs during that minute, the machine will increase the pressure by another 1cm at the end of the minute and then again wait for another full minute to see if the SDB events resolve. In general, if another event occurs within 5 minutes of the last event, the machine will again increase the pressure by 1 cm and wait for a full minute before the next pressure increase. This too mimics what goes on during a titration study in the lab---the tech does not increase the pressure for isolated Hs and OAs.

As an example: Suppose we have a stretch where we have the following events happening at the following times:

OA at 2:15:30
H at 2:22:00
H at 2:22:45
OA at 2:23:15
H at 2:24:50
OA at 2:31:15
RERA at 2:33:30

Here's how the machine responds:

OA at 2:15:30 No pressure increase since it's been more than 5 minutes since the last event

H at 2:22:00 No pressure increase since it's been more than 5 minutes since the last event

H at 2:22:45 Pressure is increased by 1 cm at the end of this event since this even occurs 45 seconds after the previous event.

OA at 2:23:15 No pressure increase since this even occurs 30 seconds after the last pressure increase; pressure IS increased by 1 cm at 2:23:45, one minute after the last pressure increase.

H at 2:24:50 Pressure is increased by 1 cm at the end of this event since this even occurs 1 minute and 35 seconds after the previous event.

OA at 2:31:10 No pressure increase because this event occurs 6 minutes and 20 seconds (more than five minutes) after the last event.

RERA at 2:33:30 Pressure is increased by 1 cm at the end of this event since it occurs 2 minutes and 20 seconds after the previous event.

Hopefully that helps you understand how the machine responds to your sleep disordered breathing.

Quote:On the 11th of this month my AHI was 2.39 and my machine remained at 4.5 for most of the night with a rise to 6 for half an hour at 5-5.30am;I went to bed at 11.30 and got up at 6.30 with one short bathroom visit surprisingly I had a Hypopnea, CA,VS and a OA when the pressure rose but the pressure rose before these events. My machine did not appear to respond in any way to previous events that night.
Again, seeing the data would help. But my guess is that the search algorithm kicked in before these events were scored. OR the VS triggered a pressure increase, and the OA happened right after the pressure increase.

Quote:On Monday with no apneas and only 3 hypopneas my machine took the pressure up from 4.5 to 10 between 11.00 and 02.30 at which time I woke.
Chances are that's the search algorithm kicking in. Flow limitations are a continuous thing, but the System One scores them as discrete events and the shape of the inspiration has to be moderately to severely flow limited for a minute or so before a FL will be scored. The search algorithm, however, will respond to very, very subtle flow limitation problems that are not severe enough to be scored as a FL.

Quote:I would include screen shots from sleepyhead but do not know how to
The easiest way is to take a screen shot and save it as a .jpg. Then upload the .jpg file to a photo sharing site like Photobucket. And link to the .jpg using the [ img ] .... [ /img ] commands. (Don't put the blanks between the brackets and the img and /img when you make the link.)
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#4
Thank you for those replies, I will examine the wave forms when I have time later today. It is really good to have a better idea of what the machine is actually looking for and that my machine is probably not just going on its own silly way without reason. My sleep pattern was much better last night so the cold probably had a lot to do with showing up these events even after the nasal congestion had subsided. At least the cold brought this effect to my notice and I have learnt a lot from it.

Gerry
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