Low AHI but still fatigued

[isaacsmith]

Hello,

I've been using CPAP for a month now, while I can tell an improvement in my asthma upon waking I still feel very fatigued every day. My latest week's average AHI is 4.16: 0.86 obstructive, 2.30 hypopnea, and 1.00 Clear Airway.

Some background:

A little over a year ago I started having daytime fatigue and was always waking up tired. I feel extremely groggy and just generally bad all the time, as well as had increased difficulty breathing upon awaking. After some research I suspected sleep apnea, so I saw a local sleep medicine doctor. He had me do an in-lab sleep study, then said I didn't have apnea and should look for other causes of my fatigue.

I've spent the last year being checked for everything from hypothyroidism to vitamin D deficiency, with no result. Since my symptoms matched sleep apnea so exactly I decided to try CPAP on my own, since machines are so cheap nowadays (well, relative to constant medical bills). My first full night of CPAP resulted in an AHI of 18.26, but over the weeks my AHI decreased as I tweaked settings and became accustomed to CPAP. Now, most nights are between 4 and 6.

I'm using a Phillips DreamStation 500 Auto with an pressure range of 7 to 20, and a Respironics Nuance nasal pillow. I'm a side sleeper. Some nights the pillow shifts and leaks, waking me up, so I'm shopping for a nasal mask to try.

SleepyHead shows that hypopnea events make up the bulk of my AHI, followed by clear airway events. The events are all scattered over an entire night, instead of just at certain times. Here's a screenshot of last night's graphs (a mask slip woke me up at 02:00):



A couple questions:
Can a low AHI still cause severe fatigue?
Does the amount of hypopneas and CAs indicate central sleep apnea?

[Pugsy]

Hyponeas are usually obstructive in nature....partial closure of the airway.
Centrals are when the airway is totally open but no air is moving.

Your number of CAs/centrals isn't enough to think central apnea.

While your AHI isn't horribly high..it's a little higher than I would want to see if this were my report especially since you are showing some RERAs, FLs and snores all of which are related to airway trying to close.
I think a little more minimum pressure is in order to try to reduce those hyponeas and reduce the RERAs, FLs and snores a bit more.
Will it mean you won't feel fatigued? Don't know but it's worth trying.

Couple of questions
Do you wake often during the night or sleep soundly for the most part? Is 7 to 8 hours what you normally get?
Do you take any medications of any kind and if so, what?

[isaacsmith]

I think a little more minimum pressure is in order to try to reduce those hyponeas and reduce the RERAs, FLs and snores a bit more.
Will it mean you won't feel fatigued? Don't know but it's worth trying.

Thanks for the advice, I'll try increasing the minimum and see if it helps.

Couple of questions
Do you wake often during the night or sleep soundly for the most part? Is 7 to 8 hours what you normally get?
Do you take any medications of any kind and if so, what?

I wake up once or twice a night, usually to adjust my nasal pillow. I'm ordering a new mask to try soon, which will hopefully that issue.

I've taken 10mg of Zyrtec daily for the last several years. I've tried switching to different antihistamines, it made no difference to my fatigue.

[Pugsy]

Once or twice a night isn't an inordinate number of wake ups. Some wake ups are normal anyway.
I was just wondering if you had an inordinate number of wake ups and if you did that might explain some of the fatigue.
Obviously some meds have fatigue as a side effect also.
Is it fatigue you are feeling or excessive sleepiness....some people say one thing and it's really the other and they really aren't necessarily the same thing?

Some people do say they notice a marked difference between an AHI of 4.0 and below 2.0...I never did but enough people say they can tell the difference that I don't pooh pooh them off. So you do have some room for improvement that might help. Your overall report has more clutter than I would like to see if it were my report because of the other stuff showing up (like the RERAs, FLs & snores) which along with a slightly higher than we might want to see AHI that could potentially be a factor in sleep quality in general.
Worth trying to fix just in case you get lucky and cleaning things up a little helps you feel better.

Remember though that these machines only fix stuff related to sleep apnea and if your cause for your fatigue isn't related to sleep apnea the best "numbers" in the world won't necessarily let you feel those good numbers. There's a really long list of potential culprits for not feeling as good as we would like besides sleep apnea. I know that we all would like for the cpap machine to fix all our problems but the hard cold truth is that it sometimes can't fix stuff not related to what it is designed to fix.

[RiverDave]

Can't help with the OP, but what's up with the correlation between higher pressure and lower leak rate pressure and spike in snoring?

[Pugsy]

Can't help with the OP, but what's up with the correlation between higher pressure and lower leak rate pressure and spike in snoring?

His machine shows a different leak rate graph line and the leak rate line will increase as the pressure increases because that top leak line includes the vent rate and vent rates increase as the pressure increases. Even at his highest leak he isn't anywhere near near large leak territory.

Now as to why the pressure went up? It wasn't because of the VS2 snores...these machines don't increase pressure for VS2 snores but they will increase it for the other snores and FLs and hyponeas/OAs and very likely something we can't see on the reports.
I suspect that the 4:40 to 6:00 time frame where the pressure went up was either related to sleeping position (probably rolled over onto his back) or REM stage sleep...both of which it is common for OSA to be worse and/or need more pressure to keep the airway open.

Given that was the only real time the pressure changed much...I am betting he rolled over onto his back. I am pretty sure that if it was REM related we would have seen pressure increases at other parts of the night. We get 4 to 6 REM cycles a night with 7 hours of sleep if the sleep is fairly solid.

[isaacsmith]

Once or twice a night isn't an inordinate number of wake ups. Some wake ups are normal anyway.
I was just wondering if you had an inordinate number of wake ups and if you did that might explain some of the fatigue.
Obviously some meds have fatigue as a side effect also.
Is it fatigue you are feeling or excessive sleepiness....some people say one thing and it's really the other and they really aren't necessarily the same thing?

In my case it's definitely fatigue. I feel pretty sleepy as well after waking, but once I'm fully awake I don't feel sleepy. I usually can't fall asleep during the day, when I try to nap I just lie in bed awake.

Some people do say they notice a marked difference between an AHI of 4.0 and below 2.0...I never did but enough people say they can tell the difference that I don't pooh pooh them off. So you do have some room for improvement that might help. Your overall report has more clutter than I would like to see if it were my report because of the other stuff showing up (like the RERAs, FLs & snores) which along with a slightly higher than we might want to see AHI that could potentially be a factor in sleep quality in general.
Worth trying to fix just in case you get lucky and cleaning things up a little helps you feel better.

Hopefully I do feel a difference getting it down some more, guess we'll see.

Remember though that these machines only fix stuff related to sleep apnea and if your cause for your fatigue isn't related to sleep apnea the best "numbers" in the world won't necessarily let you feel those good numbers. There's a really long list of potential culprits for not feeling as good as we would like besides sleep apnea. I know that we all would like for the cpap machine to fix all our problems but the hard cold truth is that it sometimes can't fix stuff not related to what it is designed to fix.

My various doctors and I have gone through a number of other possibilities, although given the caliber of physicians in my semi-rural area it's quite possible something was missed. Regardless of whether it's the cause, I'd still like to treat it for my asthma and heart's sake. (No heart problems that I know of, but have read OSA can cause heart problems with age.)

[RiverDave]

Thank you Pugsy! I've been away from the science for a while. People are far more knowledgeable than I used to be. I appreciate it!

[kteague]

Guessing that the suggested pressure adjustment will yield results in a better looking report, and that over time you'll begin to feel better.

Was there any mention of limb movements in your overnight study?

[AMK]

Pugsy, how would you recommend that the OP raise the min pressure? From 7 to 8, or in smaller increments?

[Goofproof]

Pugsy, how would you recommend that the OP raise the min pressure? From 7 to 8, or in smaller increments?

Ha,ha! 1 cm change (7 to is the same as blowing air in a glass of water less than .4 inches deeper. Jim

[Pugsy]

Pugsy, how would you recommend that the OP raise the min pressure? From 7 to 8, or in smaller increments?

The choices are limited with a Respironics machine. It only offers 0.5 cm increments.
Not like your machine that offers 0.2 cm increments.
It's really up to him as to how he wants to go up and will likely do what was done in the past as he has already started lower and worked up.
Whatever he is comfortable with doing. Some people like to go up really slowly and other like to take bigger jumps.
I don't know that 0.5 cm more is going to do much but I have been pleasantly surprised in the past with a relatively small increase in the minimum.

I was once in a similar situation and I decided to experiment with results by increasing the minimum above where the AHI was nice and low and stable just to see if it changed things much.
First I was using minimum of 9 and had reports similar to what the OP posted above...so I increased the minimum to 9.5 and it reduced things a little but not enough to suit me so then I went to min of 10 and the AHI reduced to below 2.0 and stayed that way for quite a while. Then I decided to see if I could make it lower so I gradually increased the minimum in 0.5 cm increments (stayed 1 week at each change) so over a period of 6 weeks made my way up to 13 cm minimum. The AHI never really changed from the 1.0 to 2.0 I was at with 10 cm minimum. So there comes a point when we can't clean up things with more pressure and since I didn't notice any difference in how I felt or slept along with no real change in the AHI I went back down to 10 cm minimum.

An increase of 0.5 cm might bring about a significant change...it also might not. Doesn't hurt a thing to go slowly though.
So really it's what he wants to do in this situation. There's no urgent need to take a bigger jump at one time. Now if his AHI was running 6 to 9...then yeah...a bigger jump is likely needed and I wouldn't spend much time with tiny increments if it were me unless I wasn't comfortable with the increase.

[AMK]

Thanks, Pugsy; that makes sense. If a person has to get on top of a terrible AHI then more dramatic changes are needed.

[isaacsmith]

Thanks everyone for the advice, I'm going to go ahead and try a minimum pressure of 10 tonight and see if it changes anything.

[Pugsy]

Oh my...a gutsy one.
Good luck.