Ghastly Pressure Spikes - Please Help!

[Sleeprider]

Your median pressure is still near 11.0, so you don't spend much time at your set minimum of 7.0. If the higher starting pressure is a problem for you, then just gradually step up minimum pressure towards 9.0 and work into it. Any increase above your current minimum will help with less pressure fluctuation. I think flow limits are what drives your pressure, so try taking out some of the maximum pressure to about 13 cm. That may end up being more comfortable and still effective. The persistence of your flow limits suggests you might do better with bilevel and higher pressure support, which would allow for lower EPAP pressure. Your AHI is excellent as-is, so a lower maximum pressure seems like it won't hurt anything.

[DaveSkvn]

Hi Sleeper49,

A few points.

1) From your initial Oscar graph it seems the machine is detecting worsening "flow limitations" and then responding to them. The process goes something like: (A) something physically changes to restrict your breathing (B) the machine detects there is an issue, © the machine responds to the issue (D) your body processes the machine response. 

   

When all that is happening there is a parallel process: (A) something physically changes to restrict your breathing (B) your body responds to the restriction © you are "woken up" to respond to the issue. There is a race between the two processes. If your body gets to "wake up" before the machine response is processed by your body then you have poor therapy.

For an auto CPAP the minimum pressure really needs to be the level that covers most events without any need for detection or response. That is why 11 will probably be much better.

2) The bad news: there are some "physical changes to restrict your breathing" that CPAP cannot deal with. They do not seem to respond to increased pressure. The classic that I have recently discovered applies to me is "positional apnea" which kicks in when I roll onto my back. 

https://www.apneaboard.com/wiki/index.ph...onal_Apnea

If you have some such issue, an auto machine will detect it and ramp up the pressure to the maximum. It will fail to deal with it (because pressure does not work on it) and you either have
poor sleep because of the issue itself or because of air being pumped into your stomach / mask leaks / air being blasted up your nose. If you have a fixed machine, it won't attempt to deal with it and, unless it turns into a full Apnea / Hypopnea, it will not be visible or reported (outside Oscar).

There is a possibility that your issue is not pressure responsive. 

3) The better news: an aid to deal with this is wearing a soft surgical collar. I recently bought one for less than $10 off ebay and wore it for the first time on Monday evening. Its not a complete solution but it is a vast improvement.

   

It may or may not be of use to you but for $10 its worth a try.


4) You ask about "Flow Limitation". "Flow Limitation" seems to have two meanings. In a CPAP / Oscar-graph sense it is a chain of breaths on diminishing strength. Its a like a hyponea but not as severe. It is intended to detect RERAs or the arrival of Apean/Hypopnea-style breathing. This is useful when dealing with OSA. There is another meaning. That is stable breathing that is limited by some obstruction. The height of the breath graphs does not diminish but stays constant (I've called it "waveform flow limitation"). The top of the "inspiration curve" (that is the bit above the middle line) becomes flattened. There is however something partially blocking the airway - this can result in daytime sleepiness by a different mechanism to OSA. It is more typical of UARS. "Waveform flow limitation" is picked up by Resmed CPAP machines but shown at a much lower value than OSA style "flow limitations". Have a look at the detail of your "flow rate" graph when a "flow limitation" is detected and see if the height is stable but the tops are flatter than when you are awake.

   

[Dormeo]

Let me add a bit more about flow limitations. They can come about via limiting factors in the nose or further down, in the pharynx.

If they originate in the nose, then the machine can't really do much of anything anything about them, because the nose tissues are too rigid to respond to air stenting. So if you have a stuffy nose, you need to work on that directly.

But FLs can also originate further down, where the soft tissues lining the pharynx can become lax during sleep. Air stenting can help to push those tissues back and keep the airway fully open. Dave gives you information about several shapes you'll see in your flow rate if you're having FLs. In addition, you may see one or two dents in the top of the inspiration curve, or a plateau with a bit sticking up from it on one side or the other or in the middle.

Some people with heavy FLs aren't bothered by them; others are quite sensitive to FLs. So it's good to see what, if anything, can be done to address them. In my own case, I switched to a bi-level machine and now use pressure support of 5, which really cleaned up my FLs. Do I sleep better for that reason? It's hard to say, because I have other night-time problems, especially pain, and it can be hard to sort out what factors are in play. But I do get some good nights nowadays, and I didn't when my FLs were heavy.

I agree with Dave that FLs can be positional, so trying a soft cervical collar is certainly one thing you can do. EPR (or pressure support) is the main machine-based tool for FLs that can respond to stenting. The pressure boost when you begin to inhale can help you complete the breath more smoothly. I do sometimes see people whose FLs benefit somewhat from higher pressure, but I don't think that's common.

[Sleeper49]

Thanks everyone for your very helpful replies, especially on flow limitations. The ENT doctor I saw did say that I have a narrow throat and a deviated septum, so it's plausible that these two factors are responsible in for the flow limitations. When I compare my flow limitation graphs between (i) the 'awake' state; and (ii) during flow limitation state, the latter does show a more levelled peak, with 1-2 kinks in it.

Also tried out Sleeprider's suggested settings (min 11 max 13, EPR 3) last night to see where it will get me. I was generally comfortable, and the 95% flow limitation dropped to 0.08 (though the 99.5% flow limitation ratio went up to 0.59). However, found that I had multiple RERAs and obstructive apnea events. Sleep was generally disrupted and I had to sleep in an additional hour to compensate for the disruption. 

I also found myself waking up in the middle of the night before 5am, partially rolled on my back, so I guess I probably experienced positional apnea.     

Attached a screenshot below of the original result before I embarked on a quest to reduce my flow limitations.     

For tonight, I'll try Sleeprider's other suggested setting of min 11, max 11 (i.e. constant pressure) and EPR 3.

[Dormeo]

Sleeprider also suggested using the regular PAP mode. You might go back to that.

[Sleeper49]

Thanks Dormeo, DaveSkvm. Results from last night (min 11, max 11, EPR 3) as attached. 

   

Overall, had quite a poor night of sleep, waking up several times (at least 3 times that I recall). Stats show a number of obstructive apnea events and some RERAs. Wasnt brain fogged this morning, but felt sluggish and memory recall was poor. And needed an additional 45 min of sleep to compensate. 

If doesnt improve, I'm inclined to go back to APAP min 8.4 and max 15 without EPR. At this setting, I had AHI 0.0 to 0.4, could breathe quite easily, and was the best I felt in the day. However, I'd pair it with a soft cervical sleep collar as advised, to rule out the likelihood of flow limitations arising from positional apnea events.

[Sleeprider]

I think using fixed pressure took away the variation of pressure as a factor. Compared to 12/24, your flow limit was slightly lower but no significant changes in therapy efficacy or comfort. We can now see more clearly how flow limits are clustered and associated with events. If you allow a higher maximum pressure of 14, the Autoset pressure will increase along with changes in flow limits and my intercept some of the OA events, however, I think your solution lies in resolving positional apnea and perhaps in the use of bilevel pressure using more pressure support.

[DaveSkvn]

As @Sleeprider says that was a useful exercise but clearly not an acceptable final state. The flow limits towards the end of the night are not good. Upping the max to 14 has minimal downsides.

One question is at what pressure level you'll start to experience "aerophagia" (swallowing air) which tends to wake you up by itself. I recently found I start to get it at 13 which is quite low but I am slightly built. Others can manage 20. If you start to wake up with air in the stomach / bloating then the max pressure may be too high for your particular physiology and it may need to be reduced to a level where that doesn't happen.

I see your respiration rate was normally about 16 breaths per minute but was above 20 for 5% of the time. Looking at your respiration rate graph, did it wander about randomly or was it raised for a specific period (perhaps matching a cluster of flow limitations about 06:00)?

By setting a constant pressure we can see that the flow limitations are grouped and get worse as the night wears on. From my non-specialist understanding this broadly follows REM sleep phases. Did your sleep study show worse AHI during REM sleep?

[Sleeper49]

Thanks Sleeprider and Dave. I've just purchased a cervical collar, and it should arrive within the week. So will post my results after trying it out.

To Dave's question, I took a look at the sleep study results to see if there's any correlation between the clustering of obstructive apnea and hypopnea events and the phase of sleep. 

- Of the 5 OA clusters I had, 2 were during REM, 3 during N2 and N3. 
- And of the 12 hyponea clusters I had, 5 were during REM, 5 during N2, 2 during N3. 
- There was a 10min window around 4am (just 2-3h before waking) when I experienced 3 hypopneas and 3 OA, all during REM, and it was sufficient to push me up to a brief period of wakefulness.

[Sleeper49]

I've one more question! For those who have succeeded in optimising their settings (e.g. after optimising the adjustments for flow limitations etc) what has been your experience like in terms of cognitive improvement? 

Asking because I've to make a job transition about a year from now, and am aware of my limits what I can and cannot realistically accomplish, depending on how this recovery journey goes. I've probably had OSA since 20 years ago when I was a teen, so I am also circumspect about how fast (and much) the improvements will look like.