Therapy using Lumis 150 ST

[Geer1]

Imo some of his symptoms are not related to sleep disordered breathing but that said settings are still being fine tuned to optimize therapy and comfort.

I wouldn't consider IVAPS as treatment for respiratory failure and a normal (or near normal) PFT has nothing to do with sleep disordered breathing. His hypoventilation during normal sleep and especially during rem sleep is an issue (especially if interrupting rem sleep) that can cause symptoms and should be treated.

My understanding is that his CO2 is elevated both during sleep and when he was awake during lung function tests. To me that is further evidence that CO2 issue is more related to something else rather than sleep disordered breathing although the primary place CO2 issue was noted on sleep study was with fixed pressure CPAP which is not ideal for CO2 levels especially in someone with an underlying CO2 issue.

As far as IVAPS goes I think we were pretty close. A slightly lower PS range (I am thinking 3-6) to avoid high TV periods and help stimulate a bit more spontaneous breathing is worth considering as well as a slightly lower MV target may be warranted since desats don't appear to be an issue until MV is less than 5. This combination should reduce machine driving his respiration although as noted in my previous response the detailed views of these periods look better than I expected and I don't think they are a significant issue at the recent settings, I just don't think he needs that level of assistance as I don't think his breathing/lung function is as bad as originally thought.

It will be interesting to follow this and especially interesting to see what is found when looking into the causes of the CO2 as that could be more of a factor than sleep quality right now.

[LarissaH]

I wouldn't consider IVAPS as treatment for respiratory failure 

iVAPS is totally targeted towards respiratory failure:

""iVAPS is ResMed’s unique volume-assurance mode that intelligently and automatically tailors therapy to patients’ individual breathing needs. It is designed to target each patient’s alveolar ventilation, and auto-adjusts to maintain that target and improve blood gases."

Trust me, this part I have memorized, especially when it comes to insurance reimbursement (in the USA anyway).

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My understanding is that his CO2 is elevated both during sleep and when he was awake during lung function tests. 

During wake?  I did not see that part.  Can you point me to that, or was that part of a separate conversation?

[StuartC]

Larissa, let me recap the way things have worked to clear a few things up.

1. I was diagnosed with OSA in 2013 but have only been on fixed CPAP since 2017 with AHI < 2 and still feeling crap
   
2. I have known for some time that my daytime SpO2 levels are frequently / typically lower than normal (90 - 95% with occasional dips below 90%).  However, I got an O2ring last year that showed that almost every night I desaturated three to four times, at 90-ish minute intervals, to a level of about 85% with an average total of 10 minutes below 90%.  That got me the new sleep study.
   
3. Every sleep study that I have had showed that desaturations to occur during REM but all of the previous studies has obstructive apneas also occurring at the time.  Presumably the assumption was that the apneas were causing the desats.  The O2ring alongside my CPAP data, and then the latest sleep study, showed that the desats occur even without apneas present.
   
4. The sleep study showed that I started the night with normal CO2 but that it became high while using fixed CPAP even though I had high SpO2 levels.  The study then tried BiPAP with AVAPS and that successfully reduced my CO2 levels that night.  That resulted in a recommendation to use Bilevel with AVPAS, which got me the Lumis - but it didn't get me any settings for that Resmed machine since the sleep study was done using a Philips machine.  Hence this thread on the forum.
   
5. The lung function test is a wildcard.  It was not requested by the respiratory specialist, but rather by a rheumatologist (who was scraping the bottom of the barrel).  The test was actually done before the sleep study but I only got the results about a week ago.  The spirometry part of the test was reported as "normal" but apparently that is possible with some lung disorders.  The breath diffusion capacity test, which measures the absorption of CO (not CO2), reported "elevated gas transfer" with suggestions of a couple of possible causes, the one I find most plausible is a left-to-right shunt, but even that is just a statistical guess.
   

So, I have no idea of what my CO2 levels are during the day - they have never been tested.  I know that my SpO2 can be normal at times, when I am active and my heart is pumping hard (> 100 bpm just walking around normally).  My SpO2 is more likely to be below 95% with my pulse still typically above 80 bpm, when I am sitting quietly.  SpO2 less than 80% when awake is less predictable, though there are a few situations I might bet on.

Nor am I being treated for respiratory failure, simply for hypercapnia and REM-related hypoxemia.  Do I need iVAPS for that?  Not sure because I can get good SpO2 results using ST mode, perhaps even S mode (and I think I have worked out why I could not do that on fixed CPAP with EPR, but that is a topic for another post, maybe even a different thread).  I also think I have worked out that a VAPS mode was recommended from the sleep study because that is what the Philips titration guide / equivalent document instructed then to use when hypoventilation / hypercapnia was detected - and because it worked.  S and ST modes were not tried on the night.

I still have no idea of CO2 levels during sleep following the sleep study since I cannot measure and record those overnight at home.

I do now have a referral to a new respiratory specialist but no idea how long it will take to get an appointment.  The journey continues

[LarissaH]

Nor am I being treated for respiratory failure, simply for hypercapnia and REM-related hypoxemia.  

OK but this is precisely my point.  Hypercapnia in the face of hypoxemia is the very definition of respiratory failure, but a normal PFT makes that virtually impossible!

Home CO2 monitoring is readily available here in the States (we've done it plenty of times) and it should be available there somewhere.

Back to researching the impossible, it was suggested earlier in the thread that the elevated CO2 could be due to a compensated metabolic alkalosis.  Other than the aforementioned sarcoidosis IDK the rest of your history but if that were the case, the hyperventilation of iVAPS would be sending your normalized pH into the allkalotic range, making you feel...

That's a good question.  How exactly do you feel?  Fatigue?  Sleepiness?  Exhaustion?  Weakness?  Many of those downloads look like you're actually sleeping pretty well.  Perhaps what you're trying to treat doesn't actually need treating.

Hoping you find a solution!

[StuartC]

The primary key to my situation seems to be REM.  While I am awake, nothing to see.  Asleep during NREM, respiratory effort is fine and oxygen is fine even if CO2 might not be.  But during REM, my respiratory effort decreases, which can be seen as reduced respiratory rate accompanied by reduced tidal volume.  This leads to both hypoxemia and hypercapnia.  Rubicon has suggested on this forum that this could be caused by "hemidiaphragm paralysis", which makes some sense but needs proper investigation.  

I have found CO2 meters available, but only for single measurements displayed in the moment, often requiring a nasal cannula.  I need something that will measure and record CO2 overnight, similar to the O2ring.  Anyone ...?

How do I feel? From the minute I wake, headache, fatigue, brain fog, cognitive difficulties such as memory challenges around names and words, joint pain, muscle pain and weakness generally but in right arm and thigh particularly, post exertion fatigue and more.  I only work part time and not in my original profession as an engineer.  Is all of this caused by a REM-related sleep disorder?  Don't know, probably not.  Will using the Lumis make all of this go away?  Same answer.

But it is generally accepted that sleep apnea is worth treating in terms of preventative effects against a variety of other conditions.  Surely hypoxemia is as well.  So I do think it is worth treating.  A better question might be whether I need the complexity of iVAPS to do that?   Watch this space, I might still work out an answer to that one.

[Geer1]

Respiratory failure is a pretty drastic term in my eyes. IVAPS is meant for treating hypoxemia or as Resmed puts it respiratory insufficiency. Issues like this could be physical or neurological (akin to central apnea) and it isn't really obvious which is the case here.

I mistakenly read the CO diffusion test results as as CO2. I'll have to read up more on that test but assume it might tell something about CO2 levels as well.

[StuartC]

It is time I updated this thread since I do have iVAPS working, quite well in fact.

When I left off previously, I switched to S/T mode with EPAP = 5, IPAP = 9 amd fixed BR = 11 using an Evora Full mask. I soon increased BR to 12, which I then used as my baseline.  I went on to experiment with a few changes, mostly related to fixed and intelligent backup rates but I also switched between my Evora Full and a Vitera, I decreased T Rise from 900ms to 600 ms and (briefly) IPAP = 10.  I also tested therapy with Covid, but that was not part of the plan!

As I tested, I did not really see anything remarkable or consistent with respect to AHI, RR, Vt, Mv or SpO2.  The only parameters that I did see change were decreases in the rates of spontaneous trigger and cycle.  I eventually worked that I could reasonably successfully use those pressure settings with iBR on and Target Patient Rate (TPR) set to 15.  

While doing off of these tests, I established that my oxygen desaturations corresponded to Mv levels below about 5.5 L.  So I set my Va target such that my Mv target was 5.3 L.  I had originally thought to set the target lower but that also translated into a Vt target of 350 ml (about 80% of my typical Vt) or 5.1 ml.kgIBW, and I thought that might  be low enough.  Then I switched to iVaps with EPAP = 5, PS Min = 4 (IPAP min = 9) and PS Max = 5 (IPAP max = 10), just to see what would happen.  It worked! My desaturations were reduced.  For what is it worth, I often scored low or zero AHI.

This appears to be the key to iVAPS therapy, for me at least.  In non-REM, fixed EPAP/IPAP is fine.  But during REM, my RR drops, my MV follows and my SpO2 goes along.  So what iVAPS needs to do is stay out of the way during nREM.  Then, during REM, it needs to increase PS to maintain Mv at a volume below my typical nREM value but high enough to maintain an acceptable SpO2.

It was at that time that I first saw my new pulmonary / sleep specialist.  She was P*ssed! She could not believe that I had an ST machine and was using a mode that "is not used very often" without having an actual diagnosis to require it - beyond the sleep study that is.  Her response was to send me for a sleep study without CPAP, at a lab of her choosing of course, and to refer me to a neurologist (first available appointment next year).

By the time I went for the sleep study, I had worked out that I needed to increase PS Max to 6 (IPAP Max to 11).  I did that the night after the study and results were better.  My desaturations were further reduced, often only with the one in the middle of the night (2nd REM) below 90%.

When I saw her again she told me, rather forcefully, to "stop changing your settings" and I simply told her I had no need to change them because it was working.  She also backed down from her initial umbrage to admit that she could see why I had the ST machine and why the iVAPS mode was correct and working.  But, of course, she wanted to confirm settings, so she sent me for a titration sleep study.

That was a split study with the first half using my machine and the second half using the lab's AVAPS.  My machine worked beautifully, keeping CO2 below 45.  The AVAPS didn't do as well. They manage to keep it below 60, but had to go higher than IPAP of 11 to do so.  The only comment I managed to get from the sleep tech was that if I sleep on my back, I needed to increase my pressure.  But I did not think I was seeing results suggesting much back sleeping, so I initially blew it off.  

However, I bought an inexpensive security camera with a micro SD card.  Well that showed that I do sleep on my back - a lot.  I also noticed that the histogram from my O2ring showed that my oxygen levels were less than 95% more often than they were above 95%.

When I saw the specialist for the follow-up, she said my settings were fine, don't change anything.  She also suggested that if I could sleep only on my sides, I would not need a CPAP.  That is despite me deauturating during every REM while using fixed CPAP regardless of position.  

So, of course, I went home and changed the settings.  First I increased PS Min to 5 (IPAP Min = 10) and about a week later I increased PS Max to 7 (IPAP Max = 12).  That has worked really well.  I have had 0 AHI 14 of the 20 nights since that change.  My lowest SpO2 has been 91 and I now have more readings every night >= 95% than less.

And that's it.  I have my appointment with the neurologist in January to (maybe) work out why this therapy is effective, or at least to try determine whether my issues will be progressive.  In the meantime, I have my settings fixed.

Or have I?  My non-REM Mv has increased since increasing PS, so I wonder if I need to slightly increase my target Mv, which might improve my ability to reduce that one stubborn desaturation that still occurs in the middle of the night (REM, on my back).  My PS is still being limited at times by my PS max setting, and I wonder if the PS difference should be 3, not 2 (what do people say? It will only go there if it needs to).  And then there is that one magical day that I had on the 20th of April (I remember the date well) where I had more energy in one day than I have had in any week (month?) in the past ten years.  It was the day after I set PS Min and Max to 6 and 9 (IPAP Min and Max to 11 and 14).  I am not planning to rush into anything but I am so tempted to test that far!

Rubicon and Geer1, My deepest thanks for all the support and help that you provided.  I could not have got to where I am on my own.

Charts attached (all with EPAP = 5, iBR on, TPR = 15, Target Mv = 5.3 L, Evora Full mask and soft cervical collar used):

• 2 July, PS Min = 4, PS Max = 5 (IPAP Min = 9, IPAP Max = 10)
  
• 7 November, PS Min = 4, PS Max = 6 (IPAP Min = 9, IPAP Max = 11)
  
• 20 December, PS Min = 5, PS Max = 7 (IPAP Min = 10, IPAP Max = 12)
  

[Jay51]

I have learned a lot about IVAPS from reading your threads and posts.  I would consider you an expert on IVAPS.  I used to use IVAPS but now use AVAPS.  

Today I learned of aPCV (Assisted Pressure Control Ventilation).  I did some online research.  This thread explains it a little bit:  Long time CPAP user still fatigued 


If you have any thoughts or opinions about it, I would like to hear it.  Especially on how you think it would compare to IVAPS?  And what do you think about its different settings?  

Thank you very much.

[StuartC]

Today I learned of aPCV (Assisted Pressure Control Ventilation).  

If you have any thoughts or opinions about it, I would like to hear it.  Especially on how you think it would compare to IVAPS?  And what do you think about its different settings?  

I have said this on the other post but is sounds like the PAC (Pressure Assist Control) mode on the ResMed ST / ST-A machines.  The description for that is:

The inspiration time is preset in the PAC mode. There is no spontaneous/flow cycling. The inspiration can be triggered by the patient when respiratory rate is above a preset value, or time triggered breath will be delivered at the set Backup Rate.

This description and the settings that I see in the clinical guide make it look like S/T mode but with fixed inspiration time and non-spontaneous (mandatory) cycle.  I do not know enough to suggest when that would be better than S/T mode, but I personally prefer the idea of spontaneous cycle.  

It should be possible to determine tidal volume / minute vent by setting PS in the same way as S/T mode, though possibly with more certainty and less variability.  However, it is an open loop control strategy so there is not the certainty that iVAPS / AVAPS modes give since those are closed loop, feedback control strategies.  The strength of the VAPS modes is that they adjust PS to respond to changes, which S/T and PAC does not.

[Jay51]

Thank you very much for explaining that Stuart.