Another ResScan question

It is typical for my ResScan report to show 1 to 4 apneas during the night. I am puzzled that I don't see the pressure rise to try to prevent them. I am running in auto mode with pressures from 9 to 13. I have seen apneas located during times where the pressure was only 9. They usually last 10-12 seconds. I expected to see the pressure rise to 13 but it hardly ever does during these displayed events. My titrated pressure is 12. Can someone explain this to me?

bump

Doesn't anyone know the answer to this question?

It's answered in another thread, Resmed doesn't respond to apneas over 10 cm by design. Jim

shooter wrote:I have seen apneas located during times where the pressure was only 9. They usually last 10-12 seconds. I expected to see the pressure rise to 13 but it hardly ever does during these displayed events. My titrated pressure is 12.

You seem to have some misconceptions about the way APAP treatment works. No APAP machine will make any pressure change during an apnea.

Any pressure changes will occur either prior an apnea due to specific identfiable events, or after the apnea based on its occurance. Pressure chanages are also not instantaneous events but occur over a period of time, as sudden pressure changes will wake many users. Even with slow pressure changes some users find pressure variations disturb their sleep.

Also, it is not at all surprising that you are experiencing apneas at 9cm if you were titrated at 12cm. You should be running your minimum APAP pressure fairly close to you titrated pressure, 9 to 13 is too wide a range. Try running 11 to 13.

A Resmed APAP flow generator will certainly respond to apneas arising from precursor hypopneas at over 10cm, but it will very deliberately not respond to "frank" apenas (that is apneas with no precursor events) at over 10cm, to avoid the possibility of triggering central apneas in some users.

Cheers,

Bill
l

Jim
You were REALLY helpful. Thanks a lot! (NOT!)

Bill

On the night in question the pressure changed from 9 to 12 several times. In two instances the pressure was at 12 and 45 minutes later it dropped back to 9 and the apneas appeared each on top of a hypopnea. Both of these were at 9.

[/quote]
"You seem to have some misconceptions about the way APAP treatment works. No APAP machine will make any pressure change during an apnea."
[/quote]

I may very well have misconceptions......Thats why I am asking questions.

[/quote]
"You should be running your minimum APAP pressure fairly close to you titrated pressure, 9 to 13 is too wide a range. Try running 11 to 13."
[/quote]

How is this different than running in CPAP mode at 13 with EPR = 3? (or 2)

[/quote]
"A Resmed APAP flow generator will certainly respond to apneas arising from precursor hypopneas at over 10cm, but it will very deliberately not respond to "frank" apenas (that is apneas with no precursor events) at over 10cm, to avoid the possibility of triggering central apneas in some users."
[/quote]

When you say it will certianly respond....what is the nature of the response? Is it immediate or some time later? If later, how much later?
My clinical manual says "Initial pressure increases are rapid, but the rate of increase diminishes as the pressure approaches 10 cm"
I was surprised to see no significant pressure increase at the time of these detected apneas nor even shortly after. Or could these be centrals that are being ignored?

Just trying to learn from you folks with more experience!

Thanks

billbolton wrote:

shooter wrote:I have seen apneas located during times where the pressure was only 9. They usually last 10-12 seconds. I expected to see the pressure rise to 13 but it hardly ever does during these displayed events. My titrated pressure is 12.

You seem to have some misconceptions about the way APAP treatment works. No APAP machine will make any pressure change during an apnea.

Any pressure changes will occur either prior an apnea due to specific identfiable events, or after the apnea based on its occurance. Pressure chanages are also not instantaneous events but occur over a period of time, as sudden pressure changes will wake many users. Even with slow pressure changes some users find pressure variations disturb their sleep.

Also, it is not at all surprising that you are experiencing apneas at 9cm if you were titrated at 12cm. You should be running your minimum APAP pressure fairly close to you titrated pressure, 9 to 13 is too wide a range. Try running 11 to 13.

A Resmed APAP flow generator will certainly respond to apneas arising from precursor hypopneas at over 10cm, but it will very deliberately not respond to "frank" apenas (that is apneas with no precursor events) at over 10cm, to avoid the possibility of triggering central apneas in some users.

Cheers,

Bill
l

Bill just to add to your comments

A Resmed cpap when over 10 CMs won't respond to a no-flow apnea for the reason you stated but also because if there were no pre-cursor events (these are identified via flow-lims and or snores & including the 'flattening' data ), the machine quite rightly says this has to be a central & for that reason won't try to respond whilst it is in progress.

Increasing pressure during an apnea or a central, is a no-no for a cpap machine (but increasing pressure is a central is being detected on an SV type machine does happen).

I will start a thread about a situation I recently looked at for someone where it was clear to me the machine was trying to respond to a no-flow apnea with pressure because the set up on the machine for that patient was not adequate for the persons situation.

I'll call it 'Story of an AVAPS user where the setup was wrong'

DSM

OK, can anyone point me to a detailed description of how my ResMed APAP actually works?

shooter wrote:OK, can anyone point me to a detailed description of how my ResMed APAP actually works?

This explains a few things about the thinking behind the way ResMed autos work.

http://www.resmed.com/en-au/assets/docu ... 0906r1.pdf

The idea when using a ResMed is to get AI below 1 consistently, if you can, and to work to get AHI as low as you can, eventually, but not to compare your numbers to users of other machine brands. Generally speaking, a few apneas a night shouldn't be a big deal, especially if they aren't long apneas. And a ResMed counts minor flow limitations as estimated hypopneas.

The advice you have gotten here, to put your bottom number, your minimum, within one or two cm of your titrated pressure is good advice in the majority of cases, if your titration was done well. There is usually no need to worry about what your top number, your maximum, is set at, unless your pressure sometimes runs up higher than you need. In that rare case, you might want to lower your maximum.

That is my personal understanding anyway.

jnk

That article was helpful and informative. Thanks

I still have a couple of questions...
Am I correct in assuming that the three or four apneas, that sometimes show up in my reports, are probably central and not obstructive?

What is the difference if any, between running my machine in auto mode with pressures between 11 and 14 or running it in cpap mode with pressure set to 14 and EPR set to 3? Is there an advantage or disadvantage to one or the other?

shooter wrote:jnk

That article was helpful and informative. Thanks

I still have a couple of questions...
Am I correct in assuming that the three or four apneas, that sometimes show up in my reports, are probably central and not obstructive?

What is the difference if any, between running my machine in auto mode with pressures between 11 and 14 or running it in cpap mode with pressure set to 14 and EPR set to 3? Is there an advantage or disadvantage to one or the other?

I'm no expert, but I'll give those questions a shot.

There is no reason to assume your apneas are centrals, though they could be centrals occurring when you transition between sleep stages. If they are pressure-induced centrals, they should balance out as you stay on PAP therapy. Your titrated pressure should be safe, and if pressure-induced centrals were that big of a deal, autos wouldn't be as popular as they are, I don't think.

AS for auto versus straight cpap with EPR:

Running an auto, with a small range of pressures, works very well for some. Others find they do better at one straight pressure, and only use the auto mode for occasional self-titration as part of their decision-making process if their numbers deteriorate while in straight CPAP mode. The pressure changes that occur with auto mode seems to disturb some people more than others--it just depends on how sensitive a person is to such changes. A number here swear by straight CPAP being more restful sleep compaerd to how they feel after using an auto. Others swear by auto mode. People who are prone to positional apneas, on their back for example, may benefit from an auto set to cover their needs in all positions. That's a theory anyway. You will need to find what works best for you in practice.

EPR is a form of pressure relief that allows your exhale pressure to be lower than your inhale pressure. Some find that to be very soothing as they fall asleep. But you need to watch your numbers to make sure EPR isn't letting too many apneas through. Some find they have to raise their straight pressure a cm or two when using EPR.

Hope that helps. If I got anything wrong, someone should correct me. I am only a patient educated here at cpaptalk.com.

jeff