Does my AirSense 10 Autoset Misidentify CAs

[notam2]

Hi Everyone,

I was recently diagnosed with sleep apnea and got my ResMed AirSense 10 Autoset last week.  Trying to optimize my therapy now to get rid of a bunch of OAs I'm having.  When looking at my sleep data through Oscar, I was getting concerned because I was picking up a couple CAs most nights.  It makes me hesitant to up my pressure to get rid of the OAs if I'm having CAs.  However, upon digging down and looking at the flow rate around the CAs, I noticed that most of the surrounding breaths did not have a nice bell curve, but rather they had sawed off tops which I understand to be indicative of obstructive apneas.

Does anybody know how the ResMed algorithm differentiates between OA and CA?  I'm assuming that the algorithm looks for a breathing pause followed by a breath that resembles a bell curve (ish).  The thing is, other breaths surrounding the apnea could clearly indicate the presence of an obstructed airway which makes me believe that its the obstruction that caused the apnea rather than my brain failing to initiate a breath.

Three examples of these apneas are attached.

If these are in fact misidentified OAs I'd be a lot more confident increasing my pressure until the point where the apneas disappear.

Thoughts?

[SarcasticDave94]

It would be good practice to show a full not zoomed OSCAR with left panel for context. What did your detailed diagnostic sleep study show regarding apnea events count and type? Lots of PAP beginners get some Central Apnea/CA when first starting?

[notam2]

Full panel attached.  My diagnostic study showed an AHI of 102, all of which was obstructive.  ZERO CA events.

My titration study showed that I started picking up CAs at 13 cmw and higher.  However, by looking at these three CAs I'm starting to question whether my titration study was correct about those CAs.  If they used the same algorithm that ResMed is using here, they could be making the same mistake.

It makes me wonder if there is a physics-based explanation for why the first breath after the apnea is more bell-curve-ish.  Kind of like motors that need a higher starting amperage but only for an instant until the motor starts moving.

[Geer1]

Titration study is far more capable of determining if an apnea is central or obstructive case in point they use effort belts, if they scored central apneas then you must not have been trying to breath.

These machines on the other hand try to determine type of apnea based on flow/pressure data alone and are prone to making mistakes.

Your clusters of obstructive apnea (as well as very high ahi during sleep study) are indications of positional apnea. Try treating that and see if it helps.

http://www.apneaboard.com/wiki/index.php...onal_Apnea

[SarcasticDave94]

I think most test sites tend to use Respironics, at least on almost all my tests were. I think you are needing more Min/EPAP pressure to combat the obstructive events. And you are at or near higher pressure requirements that a ResMed VAuto makes sense. Most PAP patients get a few CA at the beginning. I am not following you on questioning your study results, but if you had the actual report, it can be redacted for privacy and attached in a post. We can look at it and comment.

[notam2]

Titration study is far more capable of determining if an apnea is central or obstructive case in point they use effort belts, if they scored central apneas then you must not have been trying to breath.

This was my original thought as well.  However, after using my cpap for a week I've looked at the handful of CAs that have been flagged, and none of them really look like CAs to me.  They all look like OAs.  Since my machine is set to go up to 16, if I was having CAs from 13+ I would have expected to see them during the past week, but given the absence of believeable CAs I wonder about how the sleep study was scored.

The sleep lab titrated me to 15 cmw and they were scoring MAs at 12 cmw and CAs from 13 cmw.  At the end of the titration the tech told me he would have liked to try bipap but he ran out of time.  The titration study got my AHI down to around 8 point something at 12, 13, 14, and 15 cmw fixed pressure, and I'm actually doing much better with an auto-titrating machine than a fixed pressure.

Also, I didn't know there was such a thing as an MA.  I figure either you're trying to breathe (in which case its a OA) or you aren't (in which case its a CA).  Is an MA when you try to breathe a little?  Or when you stop trying to breathe but they know that an obstruction is present?

I had talked to my sleep doc about the interpretation of the titration.  She was going to prescribe me a fixed pressure cpap machine at 12 cmw, but given the sleep tech's comments at the titration I pushed to get an autoset so that it could "finish the job" of titrating me.  To qualify for funding for the autoset, the titration study would have to show either positional apnea or apnea that was dependent on sleep stage.  Since I slept on my back for the entire titration and didn't change position, the doc said she couldn't interpret the results as positional apnea.  She did however interpret the results as clusters of apneas happening when I was in REM sleep so that I could get the autoset.

From what I've read in that link to positional apnea, I see that my sleep doc may have been misinformed and I could have positional apnea even if I didn't change my position from back to side (etc.) during the titration, and that it might be linked to a kink in my neck.

What I posted here was my worst night sleep of the week.  The machine actually has my AHI down to around 1 point something most nights this week (which is considerably better than the results of the fixed pressure titration).

What do you think of reducing the EPR from 3 to 2 so that the expiratory pressure is bumped up a little, which has the effect of increasing the min pressure by 1 but only on the expiratory side.  Also, are CAs triggered by higher inspiratory pressure, or by higher expiratory pressure?

Much thanks for the help with this.

[Geer1]

If your normal night is AHI of 1.something then your apnea sounds like it is mostly treated.

As mentioned it is highly unlikely they incorrectly scored apnea during the sleep study. They monitor your actual effort and the only way to score a central apnea is with no effort.

Mixed apnea is a thing and most commonly starts as a small central during which time an obstruction forms (because of airway inactivity) and even though your body attempts to start breathing it can't.

Actually looking at your original examples again the first example shows what I think was obstruction but not a full 10 seconds so not labelled as an apnea, followed by a central/mixed apnea labelled as an obstruction apnea (at that point you were probably awake and changing position or something) that might have started as a sleep transition central apnea (after arousal from the first obstruction) then this is followed by what looks like a central apnea but the one beginning of a partial breath near the end and then large recovery breaths afterwards make me wonder if there is an obstructive nature to it as well.

I can kind of distinguish that by the pressure oscillation amplitude (larger in obstructive apnea, smaller in the central case in point 1st "OA" vs following CA). One other thing that gives some information is the cardiogenic oscillations (small bumps in flow rate caused by heart beat), these are only visible in central apnea or paused breaths but they are present at the beginning of the "OA" making me think it was a mixed apnea (you can see that the oscillation amplitude briefly starts out small which I think kick starts your respiratory drive but you have obstruction at that point).

The second example posted shows reduced breath amplitude followed by an apnea that shows cardiogenic oscillations, has low amplitude FOT and was probably correctly labelled a central apnea again followed by some strange large amplitude arousal breathing. Similar to the final example although there was some odd breathing prior to that central so you might not have even been asleep at that point.

If you aren't regularly seeing clusters of obstruction apnea like that then it could have just been an odd night where you shifted forward or something creating a strongly kinked neck. Or it could potentially be mislabeled central apneas. These machines are prone to mislabeling apnea in tougher cases because they don't collect enough data to do so 100% effectively.

Central apnea is usually triggered by higher pressure support (difference between EPAP and IPAP), sometimes by higher pressure (not sure EPAP or IPAP matters or is the specific trigger other then like I say PS often the cause more so then pressure) and in some cases even just the pressure waveform can cause centrals by forcing you to breath in a manner body isn't used to. You probably used a Phillips Respironics machine during titration and that has a slightly different waveform which might have been part of the picture.

Reducing EPR to 2 reduces PS which might help with centrals, EPAP simultaneously increasing could help with obstructive apneas (EPAP is what holds airways open) but the one downside is that reduced pressure support negatively impacts flow limitations (restricted breaths) which you show signs of in a periodic nature (probably coinciding with rem sleep which is common). It could be tried but I don't know that it would be the answer.

What I still wonder is if this is positional apnea. If so then treating it using the other techniques may allow you to use lower pressures which then might avoid centrals caused by pressure. I would try adjusting pillows, maybe a collar or force yourself to sleep on side a couple nights to see if that causes improvements.

[SarcasticDave94]

I don't remember but has positional Apnea and a soft collar been discussed? This may be the cause of the Obstructive Apnea clusters. If so no pressure edit will help. If it's not positional then pressure will need an increase. And I think a VAuto will be better for you due to your higher pressure needs.

[notam2]

You are correct in regards to the Respironics machine which I believe the sleep lab used during the titration.

Couple things: My titration study showed a fair number of hypopneas happening even at 13 cmw to 15 cmw fixed pressure cpap. Being on the autoset at 12-16 cmw and EPR = 3, I'm basically on a bilevel machine with EPAP set to 9-13 and PS=3. This setting has pretty much wiped out the hypopneas but replaced them with flow limitations and RERAs. Over the past 7 days, I've averaged 0.34 RERAs per hour, and I haven't had a full night of uninterrupted sleep. I initially chalked this up to adjusting to life with a cpap, but maybe what I need is even more pressure support, say PS=4. The periodic flow limitations posted above are pretty consistent with what I've been seeing all week.

I've currently got a one month trial of the autoset. I was a little afraid that they'd pull the autoset from me and stick me with a fixed pressure cpap, but I think the data over the last week makes a good case that something periodic in nature is going on and I'm benefiting from the auto adjustments, especially since its AHI is much better than what they achieved during the fixed pressure titration. That said, I think I'm going to make an appointment with my sleep doc and ask if she can increase PS to 4 to treat my RERAs and flow limitations, and get a full night's sleep. I realize I need to keep an eye on the CAs, but they seem to be 3 or fewer per night and maybe when my body adjusts to the lower CO2 levels they'll disappear (or so I'm hoping). Of course, this means I need to try to talk my sleep doc into prescribing me a trial of the VAuto.

At the same time I'll try to treat my positional apnea by doing my best not to tuck my chin while I'm sleeping, and see if it helps out.

Does this plan sound reasonable?

Much thanks again with the help.

[Geer1]

This is one of the frustrations with titration studies. Some techs still don't understand the best way to treat some of these issues and they get too focused on trying to make the problem go away with pressure alone. My most recent sleep study is going to have the same issue, still waiting on the results but my understanding is that she titrated me up to 12 cm pressure trying to treat RERA's but never used any amount of pressure support.

If you read enough literature on the subject (such as Resmed and Philips Respironics titration guides) EPAP treats obstructive apneas (by holding open collapsing airways) whereas pressure support treats hypopneas and RERA's (both caused by partially restricted airways). Sometimes extra pressure will help hold a partially restricted airway open further and fix the issue but many times pressure support is required.

Your sleep study still had hypopneas present because your airways were fully open (or as open as PAP pressure was going to make them) but airways were still restricted. Like you say APAP pressure support is partially treating your hypopneas but leaving some flow limitations (and potentially RERA's although you haven't posted data to make me believe RERA's are present in an amount that is an issue). For the record these machines absolutely suck at interpreting RERA's and the 0.34 number you referenced is probably nowhere near accurate (if it is then you have no breathing issues other then the short periods of what looks to be positional apnea).

Your APAP results from a doctors point of view are going to look good enough. In talking with doctor I would focus on saying that you don't feel comfortable (difficulty exhaling is a good point, especially if there is some truth in that) and that you don't feel that you are getting good enough results. Bring up the point that titration study didn't resolve all breathing issues and that the sleep tech wanted to try bipap and you wonder if it would help. Then can try to talk doctor into trial of vauto or getting a 2nd titration study that focuses on bipap depending on what doctor is willing to do.

CA's aren't an issue unless you start having like 5 CAs per hour. Everyone has them in small numbers and many "CAs" flagged by these machines are not real and are post arousal when you hold your breath, roll over, transition back to sleep etc.

I think trying to confirm the positional apnea is worthwhile now. If you normally sleep on back I would be curious what your results look like if you force yourself to sleep on side.