Obstructive apneas persist despite high pressure (20/16 cm)

[deltadave]

While these algorithms are quite accurate when they call centrals, there are frequent instances when centrals may be mislabelled as obstructive.

Deltadave, can you elaborate on this a bit?

And am I understanding what you say correctly if I think you are saying:

When one of the algorithms labels an apnea as a central (clear airway) apnea, there's a high probability that the apnea is indeed a central one.

But ....

Many (how many?) central apneas wind up being scored as OAs by the machine algorithms.

And hence for a person with significant numbers of centrals on their sleep studies, the machine computed CAI should be considered a lower bound for the true CAI under treatment.

While that may be the gist of it, I think there are too many factors to make a rule (i.e., 67% of OAs in x patient are centrals because the CAI is >5, 10, 20 whatever). For instance, this thread suggests that a FFM may cause an OA to register as a central. In a dramatic example, bandnuts showed dozens of OAs, that, since this was clearly a CSR pattern, were centrals (he pulled the original images, this is a ghost from a crawler):



Without NPSG, trying to make this differentiation takes a bit of detective work.

[NapsZ]

Hi DeltaDave, thanks for the extremely detailed post on what to look for when being examined by an ENT doctor. I'll print out your post and make sure I go through every single word with the doctor. You have probably saved me from a lot of wrong directions! Thanks.

If you don't mind me asking, did you go through surgery? Was it successful?

P.S. Yeah I don't know what to make of the Resmed detection algorithm. When I zoom in to the detailed flow charts I can see the little high frequency wiggles it uses to estimate airway impedance. But there must be a fairly arbitrary cutoff between what is considered a central and what is considered an obstructive. And in reality surely there is a continuous extent to which an airway may be blocked?

[sickwithapnea17]

thanks for the post! I think I have mostly centrals now but if I had osa then I would consider tonsil surgery. my doctors say though it's better to keep them in. I'm having memory problems too and tiredness and some asthma attacks that feel like heaviness in my chest. my FEV 1 is in the 70s.
I can't sleep on my 18/14 pressure- I keep waking up but the lab says that it gives me 97% O2 so maybe I should try? I'm just so exhausted and sick of this disease

[deltadave]

If you don't mind me asking, did you go through surgery? Was it successful?

I did not have surgery, do not use xPAP, and probably (I am somewhere between skeptical to cynical about everything) have any SDB.

Periodically have RLS, probably have concommitant PLMs, otherwise a "Student in the Study of Sleep".

[deltadave]

BTW, another surgical area in SDB is the nose (septum, turbinates, etc.). Get familiar with Empty Nose Syndrome if they want to take that apart.

[deltadave]

Another Fun Thing To Know:

The 2004 paper Kezirian et al.: Serious Complications After Uvulopalatopharyngoplasty showed

The overall incidence of 30-day serious complications (including death) was 1.6% (51/3130).

but Death was only 0.2% (7/3130).

If they say they're going to do a UP3, you could ask them "How many UP3s have you done, and how many guys have you had die on you?"

If they reply "Over 3000, but nobody died", I suppose there's a couple ways you could analyze that....

[robysue]

Deltadave, can you elaborate on this a bit?

And am I understanding what you say correctly if I think you are saying:

When one of the algorithms labels an apnea as a central (clear airway) apnea, there's a high probability that the apnea is indeed a central one.

But ....

Many (how many?) central apneas wind up being scored as OAs by the machine algorithms.

And hence for a person with significant numbers of centrals on their sleep studies, the machine computed CAI should be considered a lower bound for the true CAI under treatment.

While that may be the gist of it, I think there are too many factors to make a rule (i.e., 67% of OAs in x patient are centrals because the CAI is >5, 10, 20 whatever).

I'm glad to know I was getting the gist of what you were saying. And I understand that there are way too many factors to take into account for a "rule". So interpret that "how many?" in my comment as---"how many is hard to determine for any given patient because there isn't a hard fast reliable rule"'

And the example, even as a ghost image, was illuminating. Thanks for posting it. I always learn a lot from your posts regardless of what name you're posting under

[NapsZ]

Hi DeltaDave, just googled "Empty Nose Syndrome". Oh wow. Who would have known those stubby turbinates would be so essential. Always good to know all the possible side effects ..!

I really would prefer to just get CPAP working properly over any surgical options. It's similar reasoning to my continuing to wear contact lenses, even after friends have (successfully) gotten laser eye surgery .. "But isn't it a lot of trouble, cleaning them every day and taking them in and out of your eyes?" .. "Yeah, but I don't have to worry about side effects from slicing parts of my cornea off .."

[NapsZ]

An update for everyone. I saw an ENT doctor this morning, to see if he could figure out which anatomical features were causing my obstructive apneas.

He did exactly what DeltaDave outlined -- stuck an endoscope up my nostrils and poked around, also asking me to making a snoring sound (he told me this was his version of Muller's maneuver).
His findings:

1. I have a severely deviated septum and enlarged turbinates, but this isn't causing the apnea, just nasal congestion.
2. Nothing wrong with my soft palate or tonsils, I would be a poor candidate for UPPP surgery.
3. I do have a rather large tongue base, and my jaw is set back against a narrow throat. It is the hard muscle base of my tongue relaxing to fill up my throat that causes the obstruction.
4. Surgical options for this are limited (things like jaw advancement, complicated and painful).
5. But I'd be an excellent candidate for a dental device, a mouthpiece I wear that would shift my jaw forward a few millimeters and keep my tongue in place. He gave me a referral to a "prosthodontics" dentist.

Basically he said CPAP/BiPAP was the way to go, and that using a dental appliance could reduce significantly the pressure needed to keep my airway open, thus making the therapy more effective and tolerable.

So I'm going to look into these dental appliances. Maybe I'll get one of the over the counter ones (stop snoring aid?) first and see if it has any effect on the CPAP data, and if it looks promising I'll go ahead and get the full custom device.

[NapsZ]

Hi everyone! I am happy to report that I've optimized a set of pressure conditions where my xPAP treatment is now fully effective (AHI 2.5).

The key realization was that once my obstructive events got started, they became progressively harder to resolve.
Thus in using auto-adjust mode, it proved to be essential to start at a pressure that already eliminated most of the events, and then to use the higher pressures to eliminate the residual events.

Original conditions: MIN EPAP = 10 cm, MAX IPAP = 20 cm, PS = 4 cm
Final conditions: MIN EPAP = 16 cm, MAX IPAP = 20 cm, PS = 0 cm

I established the minimum effective pressure by systematically trying out CPAP conditions night after night (4, 8, 12, 16, 18 cm).
Anything less than 16 cm was completely useless.

Here is an example of a night on 8 cm CPAP. Lots of events, many of long duration (max 80-100 sec).



And here is a night on 16 cm CPAP, which eliminates some, but not all, of the events. I would have nice long stretches where I was sleeping peacefully, but there would be periods where there was just not enough pressure to force the airway to be open. These trains of events would cause me to notice my mask being on, and I would tend to take it off in the middle of the night as well. So it was an imperfect solution.



Then I allowed the machine to adaptively adjust the pressure within a range of 16 to 20 cm. The result is a nearly complete elimination of obstructive events, consistent and reproducible over the last 3 nights:



If I track the applied pressure, I can see the machine cranking up as soon as it notices the events starting, which is enough to force the airway open. Interestingly, just running it continuously at a higher pressure (say 18 cm) is not effective -- the time rate of change of pressure seems to play a role.

As a side benefit, with the events gone, I sleep more soundly and keep my mask on all night, which makes the therapy even more effective. These past days I've awoken so comfortably I wondered whether the machine was actually on -- then realized it was actually blowing 20 cm!

Lessons learned in self-titrating:
-- For adaptive algorithms, the minimum pressure needs to be set at at the minimum EFFECTIVE therapeutic pressure. In my previous trials, I used 10 cm. The machine never had a chance to get to where it needed to go before the train of obstructive apneas took over. The common practice of setting it at 4 cm is likely ineffective. THE LOWER BOUND PRESSURE SHOULD BE SET HIGH.
-- The UPPER BOUND PRESSURE should be set JUST HIGH ENOUGH TO ELIMINATE RESIDUAL EVENTS (say during REM sleep).
Reading forum posts in hindsight, I think others have had similar experiences in adjusting their pressures.

Also, as I mentioned previously, I am exploring combination oral appliance therapy. My mouthpiece should arrive in another 2 or 3 weeks. This will hopefully enable me to use lower pressures, and may help with other side-effects too (like "chipmunk cheeks" and a very dried out mouth).

But I am delighted to have established an effective baseline therapy and am looking forward to seeing improvements related to the resolution of the condition over the next months. Thanks to everyone for their helpful suggestions.

[avi123]

See what happened when the poster Dave was imposed to a pressure of 20 cm:



viewtopic.php?f=1&t=69947&p=648160&hili ... ts#p648160

[chilliman64]

Also, as I mentioned previously, I am exploring combination oral appliance therapy. My mouthpiece should arrive in another 2 or 3 weeks. This will hopefully enable me to use lower pressures, and may help with other side-effects too (like "chipmunk cheeks" and a very dried out mouth).

But I am delighted to have established an effective baseline therapy and am looking forward to seeing improvements related to the resolution of the condition over the next months. Thanks to everyone for their helpful suggestions.

hello NapsZ, I was wondering your your mandibular device worked out