Number of Events and AHI

[kirbini]

I have a fairly elemental question - I least I think it is. The goal of cpap tx seems to be get to the lowest AHI as is possible. If I have an AHI of 19 on night one and an AHI of 3 on night two does that mean that on night one the cpap was not able to correct enough events that there were still several that were not treated and on night two there may have been as many events as on night one but they were treated and thus lowered the AHI to 3? Does that make sense? I have never really understood how this works.

[Pugsy]

Well....it depends if you slept on night one or not. There can be night's with a lot of false positive flagging which can elevate the AHI but if we aren't asleep...it doesn't count in terms of evaluation of the effectiveness of the therapy.

But if you actually slept and the AHI is high...then obviously the apnea events weren't well prevented and the goal is to prevent as many as possible. Now we don't go chasing AHI of 0.0 but we want it as low as possible.

Now as to why they didn't get prevented...either the pressure settings weren't optimal or you had the kind of apnea events that the pressure couldn't prevent them. Like central apneas (clear airway flags on the OSCAR software and some machines) we can't prevent or treat with more pressure except with a very special machine.

So yes...the goal is to keep the AHI low because with each apnea event there comes the likelihood of maybe oxygen level drops (depends on how many you have and how long they last) and the potential of the apnea event disturbing sleep and causing a wake up and wake ups when we have too many of them mess with the sleep cycles and we feel like crap during the day because we don't get enough good sleep quality.

[LSAT]

His previous posts listing all his medical problems and meds need to be considered.

[Pugsy]

His previous posts listing all his medical problems and meds need to be considered.

Yeah, well...might be nice if there had been a link to that history wouldn't it?

I addressed the basic question. Seemed like a general question so I gave a general answer.

I didn't know if he wanted an answer that covered his issues or just a general answer.
Telling me night one had an AHI that is high and night two didn't without giving me more details doesn't leave much room for me to expand without knowing more details.

I don't have the time to go searching for past history and all that and I can't remember all the details of every member here that gets help.
I gotta have some history or at least a link to that history if someone wants more than a general answer....I gotta have more than a general question.

One of the reasons we like for people to stick to one thread when they come up with random questions...makes reviewing the history easier and faster and more accurate.

[kirbini]

No, I was not asking for help on my particular problem. What I discern from the answers is that when one does a sleep study, in order to determine the number of events they do not use pressure to get a preliminary reading so they know how serious the apnea is. And then, I suspect they gradually increase pressure to find where they can eliminate the apnea events and then that is the pressure that is recommended. Is this correct? That is basically my question.

If that is the case, then I may have an AHI of 3 for the night but the number of events that were prevented could have been 100?

[Miss Emerita]

I have a fairly elemental question - I least I think it is. The goal of cpap tx seems to be get to the lowest AHI as is possible. If I have an AHI of 19 on night one and an AHI of 3 on night two does that mean that on night one the cpap was not able to correct enough events that there were still several that were not treated and on night two there may have been as many events as on night one but they were treated and thus lowered the AHI to 3? Does that make sense? I have never really understood how this works.

If you have an AHI of 19 on night one, that means you had an average of 19 events PER HOUR. An AHI of 3 means an average of 3 per hour. I think you're asking whether on night two there were potential events that were prevented by the machine. Unfortunately there is no way to know that. However, if one setting consistently yields a low AHI over time and another consistently yields a high AHI over time, it's a good bet the settings are making a difference in heading off events before they can happen.

I looked up your previous thread here: viewtopic.php?t=179781 I'm concerned that your AHI may still be quite high, with a large number of CAs. As you know, those can't be treated by the machine you have. You were going to look into getting an ASV machine; any progress there?

[Miss Emerita]

No, I was not asking for help on my particular problem. What I discern from the answers is that when one does a sleep study, in order to determine the number of events they do not use pressure to get a preliminary reading so they know how serious the apnea is. And then, I suspect they gradually increase pressure to find where they can eliminate the apnea events and then that is the pressure that is recommended. Is this correct? That is basically my question.

If that is the case, then I may have an AHI of 3 for the night but the number of events that were prevented could have been 100?

Saw this right after I posted. A sleep study is intended to see how you do when you are not using a PAP machine. A titration study starts with some likely-seeming settings and then changes them during the night until the AHI looks good. Sometimes people have a "split" study: first part of the night is a sleep study, then they wake you up, put a mask on you, and hook you up to a machine to do titration (finding the optimal settings).

If you have a particular question in mind, it'd be useful to know what it is.

[Pugsy]

Yes, your assumption is basically correct assuming the apnea events are obstructive in nature can be prevented with more pressure. When in a lab they titrate or keep experimenting with pressures going upwards until they get to a point where the bulk of the obstructive apnea events are prevented.

Central apneas cannot be prevented or treated with more pressure and in some situations more pressure can make them worse so they won't try increasing the pressure if all they see are central apneas.

Your situation is a bit more than what is commonly done though. Your situation is a bit more complex. You are special and have special needs and the normal way of doing things gets muddied up a bit since you are special.
Doesn't mean it isn't fixable but does mean we have to sometimes go about things a little differently like turning off exhale relief.

But the main goal...is to have an AHI where the central apneas and the OAs and hyponeas (OAs and hyponeas are usually obstructive) is at a nice low level where your sleep isn't disturbed.

Central apneas...with your machine...we can't do anything in terms of pressure increases to prevent or deal with them.
But we can try to prevent them from happening in the first place (or at least to a nice low occurrence) if we can figure out what is triggering them.

If I remember right didn't we try turning off exhale relief and that gave us a marked reduction in central apneas?
Have you had high central apnea count nights since we turned off exhale relief?

[kirbini]

These answers satisfy my questions. I will be getting a new machine soon that will hopefully treat the complexity in my particular situation. At that time, I will need some help. As I said, it may seem elemental as a question but now I understand clearly how the AHI is determined and why and the goal of reducing it to the lowest possible number. In all these years, I never really understood this.

Thank you all.

[Pugsy]

Ahhhh... now I remember....we have altitude and centrals and exhale relief turning off didn't help and the centrals were sometimes horrible and sometimes not so bad.

Sorry...I had a rough night last night and I didn't remember who you were. and didn't have time to go back and look at your past posts and my brain is mush today. Now I remember who you are.

Yep...the machine you are getting will be a good thing. We will get it all sorted out and I predict it won't take long.

You were just asking general questions just for general education....it all makes sense now.