OSCAR data review - Low AHI Still tired

[sheepless]

your profile shows fixed cpap pressure at 11cmw. if epr is off, your ipap and epap are 11cmw. if epr is set to 3, your ipap is 11 and epap is 8. I'm not sure if your machine is cpap or apap, but with apap, it's easy to confuse the min setting with epap, but it's really all ipap unless you use epr to reduce epap.

so if somebody needs 11cmw to resolve as many oa and h as possible, but it's hard to exhale, one might need to raise pressure by the same amount as the epr setting to maintain 11cmw on exhale to keep the airway open for the start of the next inhale. that's determined by experimentation.

flow limitation is a restriction that doesn't rise to the level of an h or oa. some think of these as on a continuum of increasing restriction. without epr, the way to address flow limitation with cpap is more pressure; with apap, more min pressure. with bilevel, flow limitations may be treated by increasing the difference between epap and ipap. with resmed machines, epr is said to function similarly to a 'mini' bilevel and as such provides an additional tool.

I hope I got this right without being too confusing. I'm sure others will clarify anything I got wrong.

[cwbolton]

your profile shows fixed cpap pressure at 11cmw.  if epr is off, your ipap and epap are 11cmw.  if epr is set to 3, your ipap is 11 and epap is 8.  I'm not sure if your machine is cpap or apap, but with apap, it's easy to confuse the min setting with epap, but it's really all ipap unless you use epr to reduce epap.

so if somebody needs 11cmw to resolve as many oa and h as possible, but it's hard to exhale, one might need to raise pressure by the same amount as the epr setting to maintain 11cmw on exhale to keep the airway open for the start of the next inhale.  that's determined by experimentation.

flow limitation is a restriction that doesn't rise to the level of an h or oa.  some think of these as on a continuum of increasing restriction.  without epr, the way to address flow limitation with cpap is more pressure; with apap, more min pressure.  with bilevel, flow limitations may be treated by increasing the difference between epap and ipap.   with resmed machines, epr is said to function similarly to a 'mini' bilevel and as such provides an additional tool.

I hope I got this right without being too confusing.  I'm sure others will clarify anything I got wrong.

That along side bonjour's comments made a lot of sense, thank you i do feel i have much better understanding now.

[alexp]

What is important to understand is that SDB (sleep disordered breathing) have two main bad consequences on your body  :
- Desaturates your blood O2 level
- Wake you up

Fundamentally, apneas and hypopneas are events that desaturates your blood (and also wake you up).

RERAs are all the other breathing events that do not have a significant impact on your O2 level but that are stilll waking you up.

Typically, most doctors only care about the first consequence. I don't know why, probably because it's pretty obvious that lacking O2 is dangerous to your body and it's easy to measure. So they'll fix the apneas and hypopneas and call it a day. And hopefully you feel better and not tired anymore. That's why they are always focusing on keeping your AHI under 5.

But even though, your AHI is under 5,  you may still be experiencing a significant amount of RERA, which means you are still waking up a lot. It can have a big impact on how tired you feel. That's why it's important to get ride of these remaining events and that's why some people still feel tired even though their daily AHI is always under 2.

Adding some kind of pressure support is usually the way you deal with the remaining flow limitations.

One thing to note is the initial test i had was the oximetry but they found no real oxygen desturation throughout the night, i think they said they look for a 6% drop to be a candidate for CPAP but they did not see that with myself, they only saw pulse rate irregularities hence the need for a polysomnography which is what confirmed the diagnosis, the doctor did comment on how my oxygen saturation levels hardly dropped during sleep, not sure if you need to know that? 

RERA's would show up in OSCAR though wouldnt they, or is a flow limitation an example of a RERA? 
I dont understand your last line, when you say pressure support, is this EPR? 

Thanks again im doing my best to learn, i thought i knew a fair bit until i looked into OSCAR!

The cpap machines try to flag RERA events but they are not very good at it in my experience. You can spot them manually pretty easily though.
Here's an exemple :

   

See how the top of the inhalation is flattening and how the amplitude of the inhalation curve is decreasing over time? That a typical flow limitation. What happens is you start to inspire but as you do there is some resistance and you need to work harder to draw air in your lungs. Now see the breaths I have circled in red at the end of the sequence? Do you see how messy they are compare to the steady rate just before? This usually means you woke up and you may have woken up because the flow limitations were bothering you. That's a potential RERA. The idea is that if you solve the flow limitations, you won't experience these microarousals.

You have to be careful though. Oscar is great but you have only one signal to try to decipher how you are sleeping. It's not a full sleep study with EEG where you can tell if you are sleeping or not, if you are working hard to breath, ... So take it with a grain of salt but if you see this pattern happening again and again during your NREM sleep, there's a good chance you are dealing with residual RERAs. I think in this case it's worth it to try to get ride of them and see if it makes you feel better. Like Bonjour wrote, don't chase numbers but try to understand what's happening and see if it makes you feel better.

Just to give you another example, here's a typical series of breaths I had when my pressure was set to 8 and here's how it looks after switching to a bilevel. I switched to a bilevel because I was still experiencing a lot of potential RERA and increasing my minimum pressure wasn't cutting it and was starting to give me unpleasant side effects. The pressure support is set to 4.

   

Hope this helps 

[howeyb]

Following this with interest because I too my AHI under control (below 1) but am still waking up frequently.
I have started using EPR 3 with max pressure of 8 and noticed my flow limitations have decreased. Can you explain how you can tell from the OSCAR graphs when you are in REM sleep? Thx

[alexp]

Following this with interest because I too my AHI under control (below 1) but am still waking up frequently.
I have started using EPR 3 with max pressure of 8 and noticed my flow limitations have decreased. Can you explain how you can tell from the OSCAR graphs when you are in REM sleep? Thx

Yes, it's pretty simple but I don't know if it works for everyone. 

First, you have to understand how sleep cycles work. A typical night looks like this :


There are two important things to note in this diagram. First of all, the cycles are approximately 90 minutes apart (this can vary a bit if you didn't have enough REM sleep the night before). Second, the last cycles are usually a bit longer because as the night goes on, the duration of your Rem sleep increases. Typically, if you are in your first cycle, you'll probably just spend like ten minutes in REM sleep but during the last cycle it can be up to almost one hour.

So now that you know where REM sleep should happen, you just need to look at your respiratory rate in Oscar to find it. Your breath in REM sleep is usually messy and not steady at all compare to NREM sleep. So if you look into your respiratory rate graph, you should be able to spot it.

For instance, my respiratory rate is pretty steady averaging 14 all night long except for a couple of spots where it gets really bumpy. These bumps are always somewhere around 90 minutes apart. Here's an example :

   

The periods I circled in red are the one I'm describing. The first happens like 80 minutes after I fell asleep and it lasts about 10 minutes so it fits the description above. I woke up between the first and second episode but if you add up the length of time I was sleeping, it works. The final clue is when I look at my flow rate chart during these episodes, it all over the places as well and it goes back to normal right after it :

   

So because of all of this, I believe I'm in REM sleep during those periods of time. This is not a scientific proof, just observations. You can't be certain it's REM sleep without EEG but I see the same pattern every night so I'm pretty confident it's the truth in my case. I don't know if everyone can use the same method though.

Edit : Another example, (I woke up before the end of the third REM period so that's why it so short) :

   

[sheepless]

thanks for that description alexp. something to learn with every visit to the AB forum!

[howeyb]

Thanks very much. I am going to have a closer look at my graphs. This forum is so helpful!

[cwbolton]

Following this with interest because I too my AHI under control (below 1) but am still waking up frequently.
I have started using EPR 3 with max pressure of 8 and noticed my flow limitations have decreased. Can you explain how you can tell from the OSCAR graphs when you are in REM sleep? Thx

Yes, it's pretty simple but I don't know if it works for everyone. 

First, you have to understand how sleep cycles work. A typical night looks like this :


There are two important things to note in this diagram. First of all, the cycles are approximately 90 minutes apart (this can vary a bit if you didn't have enough REM sleep the night before). Second, the last cycles are usually a bit longer because as the night goes on, the duration of your Rem sleep increases. Typically, if you are in your first cycle, you'll probably just spend like ten minutes in REM sleep but during the last cycle it can be up to almost one hour.

So now that you know where REM sleep should happen, you just need to look at your respiratory rate in Oscar to find it. Your breath in REM sleep is usually messy and not steady at all compare to NREM sleep. So if you look into your respiratory rate graph, you should be able to spot it.

For instance, my respiratory rate is pretty steady averaging 14 all night long except for a couple of spots where it gets really bumpy. These bumps are always somewhere around 90 minutes apart. Here's an example :



The periods I circled in red are the one I'm describing. The first happens like 80 minutes after I fell asleep and it lasts about 10 minutes so it fits the description above. I woke up between the first and second episode but if you add up the length of time I was sleeping, it works. The final clue is when I look at my flow rate chart during these episodes, it all over the places as well and it goes back to normal right after it :



So because of all of this, I believe I'm in REM sleep during those periods of time. This is not a scientific proof, just observations. You can't be certain it's REM sleep without EEG but I see the same pattern every night so I'm pretty confident it's the truth in my case. I don't know if everyone can use the same method though.

Edit : Another example, (I woke up before the end of the third REM period so that's why it so short) :

Alexp thank you for that info its amazing what we can all learn from eachother, i decided to take what you explained here and apply it to my own data however i see my respiratory rate data is not like yours as you can see below, what does this look like to you? 

Thanks

[alexp]

Here's my guess based on where you have spikes in your resp. rate and where your flow chart is a bit messy. Again this is just a guess 

   

[cwbolton]

Hi All,

I've given it about a week now after increasing the pressure by 1 and nothing else, i am still seeing flow limitations on my graph but the last 4 days it does seem to have improved, last night is a good example, i do feel better overall and have gone from needing to nap daily to only napping once every 2/3 days, although i don't feel what i'd consider normal but i have definitely seen an improvement.

Could anyone suggest what my next step might be, would you raise the pressure by one again or play with the EPR?

Thanks