Ruins data???

[Gabe]

If you keep the mask on when you wake up and lie there thinking you might get some more sleep and you fidget, toss and turn and cough and sneeze, doesn't this give you a higher AHI and higher events? Isn't it better to take the mask off after you wake up? You never get a true reading of the way you slept. True or not true?

[Julie]

False, it only takes account of what happens when you're asleep - it 'knows' from the way you breathe, etc.

[Gabe]

Julie, I was told that the machine doesn't know if you are asleep or awake. Thanks.

[Julie]

It doesn't "know" the way we know consciously, but it knows all the same.

[Pugsy]

Julie, the PR System One machines don't know if we are asleep or not. They will score whatever it senses as happening whether we are awake or asleep. If I hold my breath while awake for 30 seconds I get a central event.
If I read a book for 30 minutes and have the machine on, it will likely think that odd things are going on because of irregular breathing and shows stuff happening that didn't happen.

I think that the machine that you use does say it senses awake vs asleep but the Respironics machines don't do that.

[chunkyfrog]

My machine was at zero used and zero run when I got it from our hosts.
From the first night, the time with the mask has always been greater than the time recorded.
I tend to agree that the machine knows; but I don't plan to lose any sleep over why.

[Gabe]

Chunkyfrog, it isn't whether you lose sleep over it, but as to how accurate the data is to be able to evaluate it and make adjustments. Why do anything that would distort the data? You have to know how things function.

[Mary Z]

If you keep the mask on when you wake up and lie there thinking you might get some more sleep and you fidget, toss and turn and cough and sneeze, doesn't this give you a higher AHI and higher events? Isn't it better to take the mask off after you wake up? You never get a true reading of the way you slept. True or not true?

These things won't increase your AHI. Apnea only happens while you are asleep. There was a question on another forum from a guy not meeting his compliance requirement. He had tried just letting the machine blow without wearing the mask, but that didn't work. The machine senses your breathing. Now I don't know if it can tell you're awake or not, I doubt it, except for the new Sensawake technology. If you're likely to fall back asleep, leave the mask on.

[archangle]

False, it only takes account of what happens when you're asleep - it 'knows' from the way you breathe, etc.

No, it doesn't. PRS1 machines like Gabe has do not know whether you are asleep or not and count "events" when you're awake. I have the software, and I've looked at the data it records. It counts events when I'm awake.

Some Fisher&Paykel machines have "SensAwake" that attempts to decide when you're awake. I'm not sure it ignores those results. The F&P documentation mostly talks about reducing the pressure when you're awake, not about data collection.

I'm skeptical about it actually telling the difference. Supposedly, it's really hard to clearly distinguish sleeping from waking without an EEG.

If you have an in-lab sleep test, they DO try to manually screen out the data from when you're awake.

I'm pretty sure ResMed machines don't try to sense when you're sleeping. Do any other manufacturers try to do this?

[mck]

If you keep the mask on when you wake up and lie there thinking you might get some more sleep and you fidget, toss and turn and cough and sneeze, doesn't this give you a higher AHI and higher events? Isn't it better to take the mask off after you wake up? You never get a true reading of the way you slept. True or not true?

True - but when you look at the FLOW WAVE in your software you can tell by the shape of the wave if you were sleeping or not - at least that is what I do the next day when I look at the software - someone correct me if I am wrong.

When you are awake the wave is round on the top and when you are sleeping it is pointy.

[robysue]

As archangle points out, it's the EEG data in an NPSG that determines when you're awake and when you're asleep. And if you have a 10+ second pause in breathing or some very shallow breathing in an epoch that's scored as AWAKE, the breathing "problem" is NOT scored as an apnea or a hypopnea since on an NPSG, they're looking for sleep disordered breathing---i.e. problems breathing when you are actually asleep.

Our wakeful breathing is much more irregular than our sleep breathing. During sleep, our breathing is 100% controlled by our automatic nervous system and the CO2 level in our blood is what drives our respiration. When we're awake, both our somatic (voluntary) and automatic nervous systems control our breathing. We don't think about breathing most of the time. But we sigh, decide to take a deep breath or two (or more), hold our breath momentarily (even as long as 10-15 seconds) when we're in deep concentration, yawn, and many other things. When we are AWAKE, these kinds of events are largely controlled by the somatic nervous system, and they are NOT used in the data needed to diagnose SDB even if they meet a technical standard of lasting 10+ seconds and involve little or NO airflow into your lungs.

Think of it this way: If you are all wired up for an NPSG and you decide to hold your breath as long as you can right after the tech says, "Good Night", there's no airflow at all going into your lungs for (presumably) well more than 10 seconds. But it's not recorded as an apnea because the EEG shows that you're wide awake when this period of no breathing happened.

Now--NONE of our machines has an EEG attached to it. So NONE of our machines can definitively tell whether we are awake or asleep when the hose is on our nose and the machine is on. To the best of my knowledge, no machine except for the P&R Icons with SensAwake even pretend to try to determine when you're awake and when you're asleep. And the SensAwake algorithm (from what I've read) does indeed seem to be more targeted towards reducing the pressure (slightly) when it thinks you are awake in an effort to make you more comfortable. So our machines will record an apnea any time there is no breathing detected for 10+ seconds---regardless of whether we're awake or not.

Try it out on your own machine if you don't believe me: Put the mask on your nose. Breath normally for several minutes. Then hold your breath for as long as you can (at the end of an exhale if you can). Chances are that when you look at the data, some kind of an apnea will be scored. If you play around long enough, you'll be able to discover some kind of a breathing pattern that should trigger a hypopnea to be scored. On a PR, if you breath very regularly for several minutes and then take in a couple of sudden, deep breaths you might get a RERA scored.

One caveat to the above experiments: On a Resmed S9 machine, if you use the ramp, NO events occurring during the ramp time are flagged as events. In other words, if there's a clear 15 second period of no airflow into/out of the lungs, but the ramp is on, the S9 will NOT record it as an apnea. On a PR System One machine, events that happen when the ramp is on ARE flagged as SDB events. At least that's been my experience with both the S9 and the System One. I don't know whether other machines will flag events during the ramp/delay time or not.

As to MaryZ's other point:

There was a question on another forum from a guy not meeting his compliance requirement. He had tried just letting the machine blow without wearing the mask, but that didn't work. The machine senses your breathing.

Exactly: Our machines sense breathing by measuring back pressure and air flow through the generator. So it's rather easy for the machine to tell that it's blowing its little heart out trying to maintain 10cm pressure with NO back pressure and no change in airflow---i.e. that it's losing 100% of the pressure it is trying to generate. And that's a surefire sign that there is no nose attached to the other end of the hose. Hence, the blower hours continue to increase, but the therapy hours do not. Had the guy worn his mask for four hours every night wide awake watching tv, he would NOT have run into any problems meeting compliance.

As to chunkyfrog's comment:.

From the first night, the time with the mask has always been greater than the time recorded.

Are you saying that the blower hours are less than the time you think you've worn the mask? Or are you saying the therapy hours are less than the blower hours?

Do you put your mask on FIRST and then turn the machine on?

Or do you turn the machine on and then put the mask on your nose?

[Pugsy]

Gabe.
I know your history. You admit to spending a lot of time fiddling with the mask, tossing and turning, cough etc while masked up with machine on. I have seen your reports. There are sometimes a slight increase in whatever events sometimes during up to an hour after you start the machine. You have told me that these times of "fiddling" are much less when you are really tired and go to sleep more quickly. It is quite possible that some of the flagged events are not the real deal because you might have been awake. Unfortunately the only way to know for sure is with the sleep study equipment and a tech to watch the EEG to see if you were really asleep.

To limit the chance of false events being flagged you could indeed take the mask off and turn off the machine until you get more sleepy. I think that this idea runs the risk of your falling back asleep without having the mask on. I think that this is a worse risk to take and not worth trying to get a "perfect" report with no possible awake events being flagged.

When you know for sure that you spent 30 minutes fiddling with things and you see a group of events scored during that first 30 minutes, it is obvious they aren't real in the sense of what we worry about. Just ignore them. Simple as that.

I can put my mask on and turn the machine on. Wait 5 minutes with normal breathing and I can hold my breath for 30 seconds and my machine will flag a Clear Airway obstruction. I have tried it and I can feel the little pulses of pressure when the machine is testing to see if the air flow has just stopped or has stopped because of a collapse of tissue.
We have these wonderful machines and they do a good job but they just have some limitations. They sense our breathing changes quite well, they just don't know for sure if we are asleep or not.

[Otter]

True - but when you look at the FLOW WAVE in your software you can tell by the shape of the wave if you were sleeping or not - at least that is what I do the next day when I look at the software - someone correct me if I am wrong.

When you are awake the wave is round on the top and when you are sleeping it is pointy.

I'm not going to tell you that you're wrong about your breathing pattern, but this is not true for me.

[Otter]

If you keep the mask on when you wake up and lie there thinking you might get some more sleep and you fidget, toss and turn and cough and sneeze, doesn't this give you a higher AHI and higher events? Isn't it better to take the mask off after you wake up? You never get a true reading of the way you slept. True or not true?

Yes, you can score events while awake. AHI is like the "check engine" idiot light on the dashboard of your car, though. It doesn't really tell you how you slept no matter what you do with the mask, but if you see a major change, that alerts you investigate further. I never make decisions about my settings based on AHI. I look at the detailed data. Being awake would mostly score central apneas, and if you know you lay in bed for about an hour after waking, you can ignore these. I used to breathe in a pattern that was easy to see in the data so that I'd know when I woke up or when I got done fussing with the covers and pillow. I don't bother with this anymore because I don't score as many centrals when awake. I think that subconsciously, I keep breathing to avoid scoring false events.

I'm not very concerned about centrals anyway, because I know now that I have simple OSA. Centrals aren't an issue for me, and if I see a cluster of them, that tells me I was awake. I also have a pretty good sense now for what OSA looks like in my data, and I'm not likely to confuse that with waking events. It may be that you are similar, and you can leave your mask on and ignore any cogitation apnea that appears in your data.

[archangle]

AHI is like the "check engine" idiot light on the dashboard of your car, though.

Hey, that's great Otter, I'm going to steal it.

"AHI" or machine scored apnea numbers are like the "Check Engine" light on your car. You may have forgotten to tighten your gas cap or you may have lost all the oil and your engine is about to explode. It's a good idea to investigate further.