APAP behavior puzzling to me

[TyroneShoes]

My S9 Autoset seems to behave in ways I do not understand.

What I thought I understood was that it begins at the lowest pressure in the range that is set, and only raises pressure after a obstructive event or in case of a leakage event, and I am not even sure it is designed to respond to leakage by raising pressure.

But according to SH it seems to be raising pressure a cm or two at a time randomly. IOW, there seems to be no concurrent events associated with the changes (raises) it makes to pressure.

So I must be missing something about how this is supposed to work. Can someone clear up for me what might be going on here?

TIA

[Ghost1958]

Never had a Resmed machine but autos pretty much either respond to events or to changes in the wave form they are programmed to see as event precursors and adjust a bit to prevent the event in the first place which is ideal if the machine can accomplish that.

It cant always do that though and reponds after an event that did slip thru in an attempt to prevent further ones. Some Autos respond faster some slower. But something in the waveform is a trigger to the machines programming to respond.

[Galactus]

The unit works in the be background to prevent events, it does not really respond to them. It responds to what it sees in the flow graph and uses an algorithm to raise or lower pressure in advance of events. It does it's best to keep a pattern of breathing so that it is proactive rather than reactive. Hope that helps.

[DeepBreathing]

It also reacts to flow limitations which could be precursors to an apnea (see Galactus' post above). If you turn on the flow limits graph in Sleepyhead you might see a correlation.

[Crimson Nape]

I just changed my S9 to a VPAP with a setting of 8-12 from a CPAP 10cmH2O. It turns on at 8 and ramps right up to 12 in about 30 seconds. It seems to ignore the minimum setting and go straight for the maximum. It has done this for the past 5 nights. I was going to post about this problem until I saw this thread. I'm going to do a Cold Boot and see if that helps.

[TyroneShoes]

The unit works in the be background to prevent events, it does not really respond to them. It responds to what it sees in the flow graph and uses an algorithm to raise or lower pressure in advance of events. It does it's best to keep a pattern of breathing so that it is proactive rather than reactive. Hope that helps.

It does, and thanks.

I want to clarify something where I mis-spoke. The term "randomly" implies that there is no reason for pressure to rise, and obviously there are reasons.

As far as lowering pressure, I think I understand that better than I understand why it raises pressure. My understanding is that in the absence of events or precursors, it lowers naturally on a percentage-per-minute basis, which seems pretty reasonable. That also seems to be borne out by a "ski-slope" response as it comes back down in the SH graph.

Your explanation of raising pressure seems pretty reasonable too. It is I guess pretty comforting that the APAP can do this (which is why I found it puzzling that my sleep doc told me to brick this thing at straight 8).

It seems like what I have heard so far is that it does not respond to CAs, because raising pressure would not really help, and that it does not respond to OAs until after one passes (assuming it could not predict via a precursor and was somewhat blindsided by that happening).

Its all very interesting stuff. I did notice that leak events do not seem to make any difference, but I did see it go up about 1.5 cm in response to a single large snore event. I will have to take a closer look at whether there is a correlation between auto-pressure and flow limitation.

[Terry]

It seems like what I have heard so far is that it does not respond to CAs, because raising pressure would not really help, and that it does not respond to OAs until after one passes (assuming it could not predict via a precursor and was somewhat blindsided by that happening).

Its all very interesting stuff. I did notice that leak events do not seem to make any difference, but I did see it go up about 1.5 cm in response to a single large snore event. I will have to take a closer look at whether there is a correlation between auto-pressure and flow limitation.

I have no idea if your particular machine does this, however there are flow patterns that can be detected before apneas occur, and the pressure adjusted to stop them from ever happening.

[Sleeprider]

I just changed my S9 to a VPAP with a setting of 8-12 from a CPAP 10cmH2O. It turns on at 8 and ramps right up to 12 in about 30 seconds. It seems to ignore the minimum setting and go straight for the maximum. It has done this for the past 5 nights. I was going to post about this problem until I saw this thread. I'm going to do a Cold Boot and see if that helps.

We don't know from your post what AHI or other events are being recorded on the baseline, so have you observed an improvement? What happens if you open the top end to 14? The machine programming is seeing something in your breathing patterns that cause the pressure increase. If it wasn't required, it stays at the lowest setting. I doubt a power-off cycle will change that.

[TyroneShoes]

I just changed my S9 to a VPAP with a setting of 8-12 from a CPAP 10cmH2O. It turns on at 8 and ramps right up to 12 in about 30 seconds. It seems to ignore the minimum setting and go straight for the maximum. It has done this for the past 5 nights. I was going to post about this problem until I saw this thread. I'm going to do a Cold Boot and see if that helps.

There are two ways of looking at this.

First, it may be that this does not sound like it is working correctly. It seems that an APAP starts at the minimum pressure in the set range, and only goes up if it has a reason to, such as responding to breathing feedback and SA events. If the machine climbs up to the top of the range this quickly, it may be operating differently than what should be expected, as it does not seem that it even has time to respond to breathing feedback. And if little else has changed, why would the behavior of the machine change abruptly, unless it was not working properly?

On the other hand, it may be that your min pressure should be 12 or above, and there was indeed an abrupt change (in setting an APAP range over operating it as a brick). The straight 10 may be an educated guess based on a sleep study, and was too low in the first place.

8-12 is not a significantly large range, and not significantly different than straight 10. So maybe the machine really is seeing something immediately that is telling it to go to the top of its current set range. This is the advantage of APAP over CPAP in that it has the intelligence to titrate your pressure automatically based on feedback. IOW, it may be operating absolutely correctly.

Regardless, and speaking as an Engineer, my experience tells me that a cold boot seems like a reasonable thing to try, and it is non-invasive and can't really make anything worse. I am curious to see if it helps (odds are not that good, but it's worth a shot), so please post back your results.

I would also take this up with your sleep doc and your DME.

[vsheline]

I just changed my S9 to a VPAP with a setting of 8-12 from a CPAP 10cmH2O. It turns on at 8 and ramps right up to 12 in about 30 seconds. It seems to ignore the minimum setting and go straight for the maximum. It has done this for the past 5 nights. I was going to post about this problem until I saw this thread. I'm going to do a Cold Boot and see if that helps.

Hi sgearhart,

You no longer have an S9 AutoSet? You now have the S9 VPAP Auto?

Obstructive Sleep Apnea is usually highly positional, with flat on our back usually the worst.

Can you try sleeping only on your side?

If using the Ramp, what is the Start a Pressure and Ramp Time?

What therapy mode is your machine set to?

If therapy mode is Auto, what are the settings for EPAP, Max IPAP, and Pressure Support?

If therapy mode is S (Synchronous), what are the settings for EPAP and IPAP?

If therapy mode is CPAP, what are the settings for Pressure and EPR?

Take care,
--- Vaughn