Therapy using Lumis 150 ST

[Rubicon]

S or ST mode is looking quite attractive right now until I can get more capnograph information.

FA1 on both accounts.

[Rubicon]

While iVAPS responds instantaneously, monitored stuff is trended so often lags, but I think this example makes it crystal as an obvious spontaneous breath switches off IntelliBreath:

[StuartC]

Yes, all it takes is one single breath. They are just few and far between.

Maybe Geer1 is right about setting RR to 12 simply because then iBR only activates at 8, not 8.7 (is that really better?) and maybe I have a better chance of triggering that single breath to end controlled RR.

I don't know. But I think I need to call it quits for tonight, not thinking straight right now.

Thanks

[Geer1]

This machine targets two aspects of your breathing, minute ventilation and respiration rate.

If your respiration rate falls below 2/3rds of target RR then it will start to work to speed up your breathing with IBR. If you don't spontaneously breath it will maintain target RR until you start to do so.

If your MV falls below target it will try to increase it by increasing PS to force you to take deeper breaths.

Your bodies breathing is driven by CO2. If CO2 is low your body doesn't think it needs to breath and as it increases your body increases respiratory drive. With this machine your CO2 levels are primarily driven by target MV. If you target too high of an MV the extra PS/MV decreases CO2 levels too much and your respiratory drive decreases by decreasing RR. Sometimes this occurs in a consistent manner (12 RR instead of 13) whereas others it can fluctuate on/off (apnea, recovery breaths, periodic breathing type of stuff).

On your CPAP your spontaneous RR may have been 13 because PS/EPR was only 3. On S mode with PS of 5 your spontaneous RR was probably slightly less but still sounds like around 13. On IVAPS your average PS on most settings has been 7+ because of high target ventilation and this is forcing body to decrease RR to try and maintain the ventilation/CO2 levels it wants to.

I am not opposed to S mode and I think it is likely adequate for the most part. The only thing IVAPS adds is the ability to maintain ventilation when your respiration is depressed momentarily (bad periods in rem sleep). If you aren't having obvious desaturations I would think the S mode is doing a good enough job. If you are having desaturations then perhaps IVAPS becomes warranted. Jumping all the way from fixed pressure CPAP to AVAPS in the sleep study was a large jump and the reality is that basic bilevel may adequately treat your breathing at this time (maybe not in the future as disease progresses though).

That said you can make IVAPS act more like S mode by simply handcuffing it. So far you keep using settings that drive it to interfere (higher/ideal RR and MV). If you try targeting RR and MV below normal spontaneous breathing then your spontaneous breathing should kick back in the majority of sleep and machine should only really take over in moments of significant respiratory depression. The reason low RR hasn't really worked out for you so far is because target MV was almost always too high on those settings so your body just accepted the lower RR.

If you use something like RR of 11 or 12 and target MV of 5.5 for example should leave you breathing spontaneously the majority of the time but still has the ability to maintain your RR or MV if it drops to these levels (whereas S mode just lets it drop more if that would happen spontaneously). This machine does not try to lower your MV or RR (if MV or RR are above target) so having low targets doesn't hurt and just promotes spontaneous breathing. The key is just having the targets high enough so that the machine helps if/when needed.

As far as capnograph information is concerned I believe what you would see is that at almost all of these settings tried so far your CO2 levels are good if not low. I imagine even 3 or 4 PS keeps you close to decent and 4-6 is probably around the sweet spot with higher PS only required at the odd times of respiratory depression but that is just my opinion/guesstimate.

[Geer1]

For further clarification S mode is the same as IVAPS except

a) No backup rate so RR can decrease as body sees fit. If you set target RR low on IVAPS then it will act similar.
b) PS does not increase if your MV decreases. If you set target Va low on IVAPS it will act similar and rarely increase PS to try and increase MV.

If you use the same EPAP and PS/PSmin setting then your body gets the same support regardless of low IVAP targets.

The one other difference is that I believe on S mode you can use easybreath waveform but I have assumed you are using the same waveform settings.

[StuartC]

I have attached an interesting extract from last night's charts.  Note that the minimum y-axis value for the RR chart is set to 9, which is above the calculated iBR lower limit of 8.67.  The recorded RR is never as low as 9, so it should not be triggering iBR.  Of course, it is always possible that 8.67 is being rounded to 9 and the minimum RR, which OSCAR records as 9.44, could also be rounded to 9.  That would be a simple, but frustrating, explanation.  However, there is another possible explanation.

You will notice that I have identified four zones in the chart:

• Zone 1 is iBR active at RR = 13.  Note that this is really the dotted line that I have drawn in because the OSCAR reports the value to be 14.  This is a charting issue that is common with data historian systems.  (30 years ago, it used to be a significant marketing point for multi-million dollar distributed control systems that had fixed this.)  In Zone 1, Vt is 495, MV is 6.6 and IPAP is 12.3.  Zone 1 ends with a single spontaneous breath that occurs before the iBR trigger.
  
• Zone 2 is spontaneous breathing and the RR immediately decreases.  OSCAR shows this as a steady decline, but the first four breaths after the spontaneous breath all have total time of approximately 6 seconds, which is a RR of approximately 10.  I have drawn in another dotted line to illustrate the immediate step change in RR but recognize that the decreasing line plotted by OSCAR is almost certainly a perfectly valid moving average.  In Zone 2, Vt increases but MV still drops.  IPAP increases, which shows that it is responding to MV, not Vt.  IPAP very quickly reaches IPAP max, which means that the MV continues to drop.
  
• Zone 3 is the reintroduction of controlled RR.  As I said above, it could be triggered by RR (rounded) = iBR lower limit (rounded = 9.  But it also happens to be the minimum value of MV.  So it is possible that iBR is being triggered by MV (converted to Va) being too far below the Va controller set point.  In Zone 3, Vt levels off, then decreases, MV increases and IPAP decreases below IPAP max.
  
• Zone 4 is steady iBR control again.
  

If MV below set point is the event that re-initiates iBR control, then we could try to prevent this by increasing IPAP max.  But if RR didn't drop, we would not even be in that position and need to consider it.

The thing that has been bothering me is the sleep study recommendation for Vt of 580 to 600 ml, which is 20% higher that what is achieved in the chart attached.  I have reached out to someone to try get a better understanding of this figure.  I gather it is very specific to the Philips machine used in the sleep study and may not transfer well to other machines or, especially, to other brands with different VAPS algorithms.  The person that I spoke to is able to seek advice from ResMed, so I am hopeful that I will get more information sometime in the future.

I still have to post last night's overall results.  Spoiler alert, it was eventful and I have decided something because of it.

[StuartC]

Last nights chart is attached. 

• iBR ran for basically the whole night. 
  
• The desaturation at about 2:30 (probably REM) is interesting because Vt and MV went up, allowing IPAP to actually drop to IPAP min. 
  
• The most significant event is that I woke early with significant pain in my ribs / chest. 
  

The pain is not a new thing, so I did not panic (or call the ambos), but it was worse than I have had before.  I just stopped using the machine and rested propped upright with several pillows.  While doing that, I decided that I have had enough with iVAPS, for now.  Too much guesswork based on too little firm knowledge.

I have a reference point in S mode at EPAP = 5 and IPAP = 10.  I am planning to use that to switch to ST mode with BR = 10.  Then I plan to progressively increase IPAP to establish the relationships with Vt, MV and RR.  Reduced / decreasing RR will indicate when I have increased IPAP as far as I possibly can - and that is why I plan to use ST instead of S mode, in case it decreases suddenly or more than I might anticipate.  Along the way I might just test the difference between standard and intelligent backup rates because both are available to me in ST mode.

I will also use that time to pursue an appointment with a new respiratory specialist.

I do not intend to update this thread daily, perhaps not even regularly, while I am doing this.  I will instead gather the results in a spreadsheet to provide summary data / graphs at some point in the future.

[Sleeprider]

Sounds like a good plan. We can often learn more from fixed pressure like ST. As exciting as the ST-A iVAPS mode seems, it is very hard for people to get good consistent results. There just isn't much experience out in the wild to advise on how to optimize the settings.

[Geer1]

I am fairly certain IBR has nothing to do with ventilation target. You are looking too close at mediocre data and trying to draw conclusions from it. You also incorrectly came to the conclusion that zone 2 is spontaneous breathing.

Zone 1 appears to be IBR like you say but with an incorrectly reported RR (as you also noted), it is clear that the OSCAR RR chart needs to be interpreted with a grain of salt. There is only a single spontaneous breath if you want to call it that (probably a hiccup, arousal or something along those lines) and this stopped the IBR process. That breath started just after 1:34:42 and the next breath was initiated just after 1:34:49 which is 7 seconds later. That corresponds with an 8.57 RR which is why IBR kicked back in. IBR then increased the RR to bring it back up to target just as it is programmed to do.

Because the RR dropped MV dropped which raised PS which increased TV. IBR was increasing RR and higher PS was increasing TV which brought MV back up to target quickly so then PS started decreasing. RR met IBR target and breathing stabilized although it was still being machine driven indicating your body still felt CO2 levels were low.  

As mentioned I am ok with you using S mode (or ST mode) and think it will be adequate but unfortunately it still hasn't sunk in that your main issue is that you are targeting too high of ventilation and now your goal is to try and do the same in S mode by increasing PS to chase higher ventilation numbers. Imo you are chasing unicorn results based on just over 2 hrs of sleep in a sleep study that used a different machine that targets breathing in a noticeably different way than this one does. A titration study that noted 10 BR was required to avoid spontaneous RR but the one thing that has never been taken into account is what your RR was (not reported so can't determine what your MV was during actual study which is more important than TV especially with this machine). 600 TV @ 10 BR is only 6L MV. 600 TV at 12 or 13 RR is 7.2 to 7.8 MV which is obviously too high imo. 

You asked your contact to know what Resmed recommends. Their recommendation as per titration guide is start at 6 ml/kg ideal body weight TV and work up from there. That is an initial TV of 420 instead of the 600 you are currently aiming for. 600 has already proven to be too high of a target and only achievable by depressing your respiration rate with high PS. TV of 420 is probably too low imo, 450-500 seems closer.

If you want to rely on titration results you need to get a titration done with Resmed equipment so you know what to target. Otherwise you need to self titrate to the best of your capability because these machines are too different to compare. I haven't seen AVAPS detailed data but all other PR machines are noticeably less responsive than Resmed which is likely why they target a higher ventilation with it. As you can see from your data this Resmed machine is extremely responsive making corrections after every single breath. 

If you feel up for it humor me and try a target Va = 4.0 and target RR = 11. This corresponds with TV of 480 and MV of 5.3. It is impossible for the results of this test to give lower ventilation than switching to S mode because your PSmin of 6 is higher than PS of 5 in S mode. This would be a test to confirm that your breathing will act spontaneously (as we know it does in S mode) if ventilation targets are low enough. Then you can increase and fine tune until machine starts taking over regularly.

[StuartC]

Geer1, you misunderstand the goal that I have had all the way from the beginning (post 2) to today - to translate the settings that I got in my sleep study from a Philips machine to work with the ResMed Lumis machine. 

Today that goal changed because, between your reply above and the phone conversation that I had, I finally understand that they cannot be translated.  I also finally understand that the volume values on my sleep study say more about the machine used on the night than they do about me as an individual.  Silly me for thinking anything else.  And now that I know why to ignore those numbers, everything changes.

So, now I start over.

No, I am not "chasing higher pressures".  At this point my intent is simply to measure and document how my body responds to a range of pressures, ideally to eventually find a "Goldilocks" pressure that is neither too low nor too high.  That is one approach.

The alternative is to follow the process described in the ResMed Titration Guide.  Except, ignore the instruction to set the Target Patient Rate to "no less than 15 bpm" because that's way too high. And ignore the instruction in the Clinical Guide that the TPR should be set "at the patient's actual respiratory rate" because even that is still to high.  But other than that, "She'll be right."  Forgive me for being skeptical about the processes  that I see written in ResMed Guides.

Sure, I can try a low Va, low TPR approach.  With the sleep report objectives blown away, I may as well do as they say on Star Trek and go where I've not gone before.  At worst it delays the start of the characteristation process that I have in mind.  At best it does actually get iVAPS  working sooner, which is a bigger upside.