Is the AHI my cpap tells me what it corrected?

The machine is limited in that it doesn't know if we are awake or asleep. It just calls them like it sees them.
Also limited in reporting clear airway events because it really can only measure air flow and doesn't/can't measure brain waves to know if you are asleep and thoracic effort measurement which are done in a sleep study to help determine if the event meets criteria for a central event (open airway cessation of breathing).

The other night I woke up in the middle of the night with extreme nausea. I was awake for about an hour before it subsided and I went back to sleep. That hour is easily seen on the reports. I had a truckload of events get scored during that time frame and I know for a fact I was awake...so I have to toss all those out the window and not count them at all.

You may or may not have a similar thing going on with your clear airway events. Centrals are fairly common at sleep onset of post arousal and in a sleep study those are not counted. We don't have the other data available to the machine so that it could also not count them....it just reports what it senses.

The events counted during a sleep-lab diagnostic study are counted for the purpose of diagnosing, in the sense of proving to insurance that it is worth it to find out how you would do on PAP therapy.

The events counted during a sleep-lab titration are counted for the purpose of proving the benefit of treatment, in the sense of proving to insurance you benefit. The titration is done, medically speaking, mostly for the purpose of seeing if the application of PAP uncovers other breathing problems or sleep problems and to find a good ball-park pressure that seems to help stabilize breathing during sleep.

However, the events counted by a home machine are not really designed for any of the above purposes, so those home-machine-scored events should not be confused with, or compared with, those sleep-lab events. The purpose of home-machine-scored events is TRENDING. In other words, you use those numbers to see how you do over time as a comparison for you on that one machine and as a way to see what tweaks in therapy make the numbers better or worse. It's not so much what the numbers are; it is whether they are trending up, trending down, or staying the same.

Each machine uses a different way to score the events, so comparison of therapy success accross machine brands is only possible in the context of how you feel--not on the basis of the numbers the machines report on themselves.

Remember, the events scored at a sleep lab are considered to have medical validity; the events scored by a home machine are not. That does not make the home-machine reports misleading, though, since those reports are extremely useful for tracking therapy and making adjustments to it over time. Those reports should not, however, ever be misused as a way to claim to be able to judge with any true accuracy whether the therapy itself is working. It just isn't that simple. The large leak numbers are likely more important than those AHI estimates. The success of the therapy is about feeling better and having better health, not numbers reported by home machines.

There is sleep-lab-reported true AHI, and then there are home-machine-reported AHI estimates. Those are two very different things. It is a shame that they both happen to have the same name, AHI, really. They are very much two completely different indexes and are designed to be used in very different ways.

In my opinion as a patient.

Yeah, I understand, but my situation with the doctor has been a bit different. I didn't get very much REM sleep during the test, and that's the sort I have, so it didn't provide an accurate picture because at home I'm sure I must get more of it. Also, I never had a titration study done, so I don't know if more centrals appear when I use CPAP. The doctor just stuck me on APAP.

I know this isn't any "real" sleep test, but I decided to set my pressure to the lowest possible setting for the night. That way, it shouldn't really affect anything because I don't think 5 changes anything a bit. I'm just curious to see what happens then. I'm not sure if it will give an idea or just a bad night... Although all this past week with the new machine I haven't had a solid night sleep. I don't want to go back to poor sleep. I've done that my first 22 years of life! No thanks...

If you drop the pressure to 5, your AHI should go up and you should feel worse the next day.

If that doesn't happen. Let us know any details no matter how minor your think they are.

Yeah, I feel pretty sluggish. However, it wasn't one of my worst nights. I think I woke up 2 or 3 times, so too because my mask seal will not stay in place anymore. It's only a little over a week old, too. I used to wake up about 6 times a night and stay away for long periods of time. So I'm sure my numbers are much worse other times before I started using this thing. I remember reading somewhere about the possibility of intermittent sleep apnea.

Here are my numbers from a night "without" CPAP:

Clear Airway: 26
Flow limitation: 1
Hypopnea: 30
Obstructive: 10
Periodic breathing: 2 (however one was for 138 and the other was for 314. I'm not even sure what this is. I know I've looked it up but I forget
Pressure Pulse: 248
RERAs: 20.
Unknown: 3

However, I'm not sure I got really much REM sleep last night. Without CPAP I tend to always remember dreaming if I do because that's when I start having trouble. That wasn't the case last night. So I'm not sure. During my sleep study I only got a tiny bit and there were no dreams I recalled.


And here was one of the nights where my "AHI" was 6.66 with CPAP:

Clear airway: 41
Flow limitation: 6
Hypopnea: 21
Obstructive: 1
Periodic: 1
pressure pulse: 209
RERAs: 6

Other nights with it the hypopneas are down a little, but they don't go down a whole lot. So when I use it, the CAs are going up, and the obstructive down. The range for the APAP is usually 5-15. Should I maybe try changing the lower setting? Originally the doctor had talked about 8. Then the order came through for 5. I know the auto is supposed to be able to tell and all that, but maybe I'll try tinkering with it. I just haven't slept great with this new machine yet, but I think a lot of that has to do with the mask, as well. It keeps want to come apart and it also pokes me in the eye. This is what happens I guess when no one really shows you what to do and all that... Sigh.

I keep wondering, what is it about 3 in the morning? Almost every night there's where the graph spikes. For as many years back as I can remember, I've always woken up starting at 3 AM. This was prior to CPAP. Is that peculiar?

Yes you want to increase it to 8 to be closer to where it needs to be. It takes time to climb a mountain.

Ok. I'll try that then.

I was just thinking about the post made earlier on asking about if I had any centrals during the study without CPAP. There was only 1 obstructive vs. 3 centrals. There were like 10 hypopneas. I never really got a classification or anything like that. I assumed he was thinking obstructive, but I have no idea. All I know if I gave him a bunch of articles on apnea only in REM sleep and he admitted that I seemed to be right that it can be significant and that I taught him something. Who knows...

So for the past two nights I tried raising my pressure to 8 - 15 to see how I did. These were the results...


AHIApnea / Hypopnea Index 8.67
HypopneaHypopnea 1.60
ObstructiveObstructive Apnea 0.23
Clear AirwayClear Airway Apnea 6.85
RERAResp. Effort Related Arousal 1.03
Flow LimitFlow Limitation 0.34
VSnoreVibratory Snore 0.00
PB/CSRPeriodic Breathing 1.45%


AHIApnea / Hypopnea Index 6.39
HypopneaHypopnea 1.57
ObstructiveObstructive Apnea 0.00
Clear AirwayClear Airway Apnea 4.82
RERAResp. Effort Related Arousal 0.90
Flow LimitFlow Limitation 0.34
VSnoreVibratory Snore 0.00
PB/CSRPeriodic Breathing 0.51%

I know the machine can only guess about the clear airway ones, but should I be concerned the number got all the way up to 60 for how many there were in a night? I am waking up more often now during the night with nightmares again, which I hadn't had when my "AHI" was lower, and now it's going up again, and I'm having more of them.