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No events with at-home titration.Why does pressure increase?
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jdip Offline

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Post: #1
No events with at-home titration.Why does pressure increase?
I have to wait another five weeks to see my doctor and I'm a bit confused. I know there's a lot of knowledgeable people here so I figured I'd try and post this while I'm waiting.

I've had debilitating fatigue for many years now and recently suspected maybe I had SA. So I got an at-home test done and it came back negative (barely slept that night) and the doctor told me I don't have SA according to the results. But because of my symptoms he said maybe I have UARS and sent me to do a titration. The sleep clinic I went to doesn't do in-lab titrations (seemed odd to me) and they sent me home with an S9 Autoset to sleep one night with and log data (which doesn't seem to be the method usually used to find UARS... don't know how useful that is).

I've done my own research and therefore knew about Sleepyhead and therefore imported the data before I sent the machine back. I slept really poorly again, but the machine's data seems to support that I don't have SA. Got 0.00 score for AHI and RDI. But the pressure still went up while I slept (min. was at 4.0). It seems like every time I nodded off, the pressure would increase to around 10 and wake me. But why would the pressure go up if I wasn't having any events? I read that flow limitation is sometimes looked at to determine UARS but am not sure about that. Can anyone make anything of my data?

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04-22-2015 01:35 PM
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eviltim Offline

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Post: #2
RE: No events with at-home titration.Why does pressure increase?
It's been a while since I read through the actual algorithm, but the way the auto works is fairly simplistic as I recall. If it detects trouble breathing it will bump up the pressure quickly and then slowly lower it over time. It does not wait for a full apnea event to occur.

One other thing to note if you slept very poorly with it is that deeper states of sleep can result in more apneas as your muscles relax. So if you'd made it through the whole night normally, you might have had some detectable events.
(This post was last modified: 04-22-2015 02:26 PM by eviltim.)
04-22-2015 02:25 PM
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Terry Offline

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Post: #3
RE: No events with at-home titration.Why does pressure increase?
(04-22-2015 01:35 PM)jdip Wrote:  I've done my own research and therefore knew about Sleepyhead and therefore imported the data before I sent the machine back. I slept really poorly again, but the machine's data seems to support that I don't have SA. Got 0.00 score for AHI and RDI. But the pressure still went up while I slept (min. was at 4.0). It seems like every time I nodded off, the pressure would increase to around 10 and wake me. But why would the pressure go up if I wasn't having any events? I read that flow limitation is sometimes looked at to determine UARS but am not sure about that. Can anyone make anything of my data?

The machine won't jack up the pressure from 4 to 10 for no reason. I suspect it was because your O2 dropped or because it saw something in the flow waveform that looked like an event was about to happen. The machine sees much more data than appears in the event chart.

When you get your own machine, they should set the minimum pressure close to what you need, so the pressure change won't wake you up.
04-22-2015 02:26 PM
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jdip Offline

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Post: #4
RE: No events with at-home titration.Why does pressure increase?
What you guys said makes sense. So it's not a total write-off that I wouldn't benefit from a machine then (depending on what they find). I'm kind of hoping that I do have UARS or something, so that I can finally know why I feel so tired and do something about it.

(04-22-2015 02:26 PM)Terry Wrote:  I suspect it was because your O2 dropped or because it saw something in the flow waveform that looked like an event was about to happen.

FWIW my min SpO2 was 96 and was at 99 95% of the time.
04-22-2015 02:42 PM
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Terry Offline

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Post: #5
RE: No events with at-home titration.Why does pressure increase?
(04-22-2015 02:42 PM)jdip Wrote:  What you guys said makes sense. So it's not a total write-off that I wouldn't benefit from a machine then (depending on what they find). I'm kind of hoping that I do have UARS or something,

You definitely have "something". The machine won't go from 4->10 for no reason.

If you want, you can select a section of the flow rate graph where the pressure had gone to 10 and see what the waveform looked like.
04-22-2015 03:24 PM
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jdip Offline

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Post: #6
RE: No events with at-home titration.Why does pressure increase?
(04-22-2015 03:24 PM)Terry Wrote:  You definitely have "something". The machine won't go from 4->10 for no reason.

If you want, you can select a section of the flow rate graph where the pressure had gone to 10 and see what the waveform looked like.

The flow rate waveform definitely changes when there are spikes in the pressure. I also had a lot of spikes in pulse rate all over the place. I'm anxious to see what my doctor will say. Thank you for sharing your thoughts.
04-22-2015 04:11 PM
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TyroneShoes Offline

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Post: #7
RE: No events with at-home titration.Why does pressure increase?
(04-22-2015 02:26 PM)Terry Wrote:  The machine won't jack up the pressure from 4 to 10 for no reason. I suspect it was because your O2 dropped or because it saw something in the flow waveform that looked like an event was about to happen. The machine sees much more data than appears in the event chart...

The events in AHI are hypop, central, and obstructive. The AutoSet does not raise pressure for centrals, but it will raise pressure for the other two. But it does not raise pressure until just after it sees such an event, because it can't identify that event until the event is over.

But it raises pressure for other things not in AHI, such as a vibratory snore event or a FL. If the FL reaches ~.2-.4, that will trigger a pressure raise, for instance.

It also does not raise it quickly from 4 to 10; it raises usually in 1 cm increments, so you would have to have 6 events almost directly in a row to see it raise from 6-10 quickly.

And that could also be an indication that the range is too wide. Most "wide-open" ranges are set at 5-20, so this indicates that possibly the range is at default (not set) or 4-20 on this machine.

My best guess would be that you need more pressure than 4, which is why it is climbing on you so much. You need one of two things, either a sleep lab titration study, or an intelligent adjustment of the machine in increments over time, to find out what pressure suits you.

For instance, after much fiddling (I started at 5-20) I am now at 10-14, and it rarely ever climbs even to 13 in any sleep session. Everyone is different, of course. I am untreated at AHI 55.7, but have been under 1.5 now for the last 115 days.

Others know more about this, but for UARS you may want a machine that records RDI. The AutoSet does not. You need the newest ResMed machines, or machines from Philips to do this, I think. At any rate, that is something to speak to your sleep doc about when he prescribes. None of these machines directly have any clue about your 02 sat levels, other than they might assume they become lower when there is a FL, which is a highly indirect assumption and something not actually measured, and not something that will directly invoke a raise in APAP pressure. You need an independent third-party oximeter to measure this, and if you need supplemental 02, that can be added using the xPAP as a delivery system.

One other thing, if a pressure as low as 10 wakes you, you might want to set EPR to 3 to see if this helps. This will only affect expiratory pressure, which is normally not a factor in OSA. Your inspiratory pressure remains the same.
(This post was last modified: 04-22-2015 04:24 PM by TyroneShoes.)
04-22-2015 04:20 PM
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AshSF Online

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Post: #8
RE: No events with at-home titration.Why does pressure increase?
Auto set algorithm will raise pressure for snores and flow limitation events because it assumes that these events are precursor events to hypopnea or obstructive apnea. This assumption may or may not be true for individual cases. A lot of people have flow limitations but zero Apneas.

Just a raise in pressure this way does not diagnose sleep apnea. To diagnose, you need a home sleep study (with a device like Resmed Apnea Link plus) OR a full in-lab PSG.

A very rudimentary apnea diagnosis can be made by running the machine at a fixed minimum pressure (4cm) and if the machine records H and Os, then you do have some apnea. But you won't know how severe unless it's a proper diagnostic study - in home or in lab.

Started APAP 4-20, Closed range to 7.5-14, then straight 8.0 w/ Aflex 3
RDI always below 1. But sleep much much better at straight pressure.
Started on F10, Tried Quattro Air successfully. Finally settled on P10.
04-22-2015 05:08 PM
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archangle Offline
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Post: #9
RE: No events with at-home titration.Why does pressure increase?
Did you save a copy of your SD card data? I'd love to see that because you apparently had the ResMed pulseox.

http://www.apneaboard.com/wiki/index.php..._your_data

Even without the pulseox, the S9 AutoSet will sense snores and other airflow problems and up the pressure. I wonder if it uses the SpO2 readings to adjust the pressure as well.

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04-22-2015 05:47 PM
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jdip Offline

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Post: #10
RE: No events with at-home titration.Why does pressure increase?
(04-22-2015 04:20 PM)TyroneShoes Wrote:  It also does not raise it quickly from 4 to 10; it raises usually in 1 cm increments, so you would have to have 6 events almost directly in a row to see it raise from 6-10 quickly.

And that could also be an indication that the range is too wide. Most "wide-open" ranges are set at 5-20, so this indicates that possibly the range is at default (not set) or 4-20 on this machine.

My best guess would be that you need more pressure than 4, which is why it is climbing on you so much. You need one of two things, either a sleep lab titration study, or an intelligent adjustment of the machine in increments over time, to find out what pressure suits you.

For instance, after much fiddling (I started at 5-20) I am now at 10-14, and it rarely ever climbs even to 13 in any sleep session. Everyone is different, of course. I am untreated at AHI 55.7, but have been under 1.5 now for the last 115 days.

Others know more about this, but for UARS you may want a machine that records RDI. The AutoSet does not. You need the newest ResMed machines, or machines from Philips to do this, I think. At any rate, that is something to speak to your sleep doc about when he prescribes. None of these machines directly have any clue about your 02 sat levels, other than they might assume they become lower when there is a FL, which is a highly indirect assumption and something not actually measured, and not something that will directly invoke a raise in APAP pressure. You need an independent third-party oximeter to measure this, and if you need supplemental 02, that can be added using the xPAP as a delivery system.

One other thing, if a pressure as low as 10 wakes you, you might want to set EPR to 3 to see if this helps. This will only affect expiratory pressure, which is normally not a factor in OSA. Your inspiratory pressure remains the same.

Thanks a lot for sharing your thoughts.

You're right, it wasn't a sudden increase in pressure. But when I fell asleep I would wake up after not-long (an hour or less) and find that the pressure was higher. I was not uncomfortable but I could feel the difference upon waking.

The minimum pressure was left low because it was a one-night 'titration', even though my previous ambulatory test came up negative for SA. I'm not entirely sure what my doctor was trying to accomplish with this. I suppose he just wanted to see that data/results and he told me to see 'how I feel' after sleeping with it. This was the first time I'd ever tried a CPAP so I had a good chance of not sleeping well and that's what happened. My diagnosis is still up in the air for the moment.

Good to know that the S9 AutoSet does not record RDI. I assumed it did and when I checked the RDI measurement in SleepyHead it was zero. I also read that AHI is a lot less useful than RDI when it comes to UARS. As for the O2 sat levels, the machine did know them since it was hooked up to an oximeter which I used.

Thanks for the suggestion about EPR. Seeing as this was just a 'test', I'm not too worried about being woken up by the increased pressure for the moment. I may not even need a CPAP and if I do, it will be in quite a while (doctor appointment is in a month). I can try your suggestion if ever it comes to that.

(04-22-2015 05:08 PM)AshSF Wrote:  Auto set algorithm will raise pressure for snores and flow limitation events because it assumes that these events are precursor events to hypopnea or obstructive apnea. This assumption may or may not be true for individual cases. A lot of people have flow limitations but zero Apneas.

Just a raise in pressure this way does not diagnose sleep apnea. To diagnose, you need a home sleep study (with a device like Resmed Apnea Link plus) OR a full in-lab PSG.

A very rudimentary apnea diagnosis can be made by running the machine at a fixed minimum pressure (4cm) and if the machine records H and Os, then you do have some apnea. But you won't know how severe unless it's a proper diagnostic study - in home or in lab.

Yes, I was quite upset that I was not able to do an in-lab PSG, nor an in-lab titration. For the former, I would have had to wait another 3 months. I did want to do this for the EEG though, because I'm convinced that I am not spending a lot of time in the deeper stages of sleep and I wanted to verify that. For the latter, the technician told me that they don't do that which is odd... So I've been quite disappointed with the sleep clinic that I went to (at a local hospital). But I haven't paid a penny out of pocket, so there's that at least.

(04-22-2015 05:47 PM)archangle Wrote:  Did you save a copy of your SD card data? I'd love to see that because you apparently had the ResMed pulseox.

http://www.apneaboard.com/wiki/index.php..._your_data

Even without the pulseox, the S9 AutoSet will sense snores and other airflow problems and up the pressure. I wonder if it uses the SpO2 readings to adjust the pressure as well.

I did tell SleepyHead to save a backup of the data on my hard drive for future reference. I don't know which files are required for you to view, so I just zipped everything. It's only one night, in two segments (first segment was me in bed unable to sleep, disconnecting to go to the washroom, then started again on the second segment). Let me know if the data works for you. From what I can see, the snores were minimal (I'm not a big snorer, but it happens sometimes) and there weren't any major leaks.

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04-22-2015 06:10 PM
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