Therapy using Lumis 150 ST

[StuartC]

I am going start this post about last night's sleep by saying that I actually woke up this morning.  For the first time since I do not know when, maybe even since before the Sarcoidosis diagnosis, I feel unusually alive and even somewhat energetic.  It may not last through the whole day or happen on days to come, and I may still have several of the challenges that I have been struggling with but, so far, today is amazing.

Which is my way of apologising for going Maverick last night.  I increased PS min from 4 to 6.  I also set Patient Target Rate (RR) to 13.  I did, at least, stay close to the suggested volumes and set Va = 4.7 L/min, which calculates to MV = 6.2 L/min, Vt = 480 ml and Vt/kg = 7.0 ml/kg IBW.

I have attached the chart and it is quite different. 

There is still quite a bit of regulated breathing rate but I did have 55% spontaneous triggers.  Perhaps most important is that the pressure did not spend the whole night at PS max. Looking at the machine driven respiration, there does seem to be some link between it and the pressure control topping out.

At this point my inclination is to:

• increase PS min to 7 <EDIT: I originally wrote 12, which would be the IPAP min, not the PS min> to increase Vt in NREM.  I am wary of going higher that that because (1) I think it might not be necessary and (2) the occurrences aerophagia in the past were linked to IPAP pressures of 13.
  
• Increase PS max to give the Va controller room to operate without being limited, because there does seem to be some correlation between regulated breathing rate and pressure at IPAP max.  But any increase to be only 1 cmH20 every few nights. <EDIT: I should probably do this first and wait until this settles before increasing PS min>
  
• Keep assessing the Va setting.  I think the associated tidal volume should remain below the median that I achieve with PS min and I think that difference should be more than 20 ml, but probably not more than 50 ml.
  

 
Oh, I have added last night's OSCAR data into the DropBox folder, in the DATALOG folder, and have replaced all the files in the SETTINGS folder with what appear to be new ones based on their timestamps.

Thanks

[Geer1]

There was lots of data to look through, I saw the CO2 graph but missed that they were switching back and forth between CPAP an AVAPS multiple times, thanks for pointing that out in highlighted version.

One thing to note is that CPAP used during the titration was likely fixed pressure CPAP without flex as that is usually the case and if they did use flex I would expected that to have been stated. Fixed pressure CPAP makes it harder to breath out and Bilevel with PSmin of 4+ gives you significant ventilatory assistance in comparison. This ventilatory assistance will keep your CO2 levels lower in the same way increasing from EPR of 3 with CPAP to PS of 5 in S mode made the oxygen desaturations go away.

The depression in respiratory rate is due to your CO2 levels being too low so high CO2 does not appear to be anywhere near an issue right now. Titrating ventilation down until your breathing stabilizes would find the upper limit of target ventilation that maintains CO2 levels just above apneic threshold. Titrating the Resmed way starting low and working up to prevent desaturations would find a lower limit of ventilation that stabilizes oxygen at which you probably would have decent CO2. If you used both methods you would end up with a range and the ideal value would be somewhere in that range.

As per your CPAP and S mode data your spontaneous TV is around/below 450. If you look at AVAPS data you will see the better data occurred with TV of 500 ml and when you forced extra ventilation on yourself to reach 600 ml it just results in maxed PS and depressed respiratory drive while your body tries to bring MV down against the machines wishes. Imo your target TV should be 450 to 500 at most. Target MV should be 6 lpm at the most as 6.3 lpm has given borderline results in the couple trials done. Your respiration rate is the interesting part and sometimes spontaneous respiration rate appears to be 14ish and at other times only 10-11 but it is hard to know how much of that is due to the influences of settings being used. I am curious what your spontaneous respiration rates were in S mode with 5 PS as that is probably what should be targeted. Dead space appears to be 120 ml (not sure if that is for all Resmed calculations or if it is based on your height but regardless is what it is in your case). Using this you can calculate targets and I think you should try Va of 4.3 with RR of 13 (450 TV, 5.85 MV) or Va of 4.5 with RR of 12 (495 TV, 5.94 MV) depending on which RR you think is best to try and target.

What is kind of curious is that rather than your body correcting itself when respiratory depression occurs sometimes your body just lets the machine continue to drive respiration. The best example of this is April 16th data where your spontaneous effort drove breathing most of the night but in second part of night you got stuck on max PS at backup rate because your body didn't know how to get itself out of that situation I guess. Using a higher PSmax will makes this occurrence more likely whereas further limiting PSmax would force your spontaneous breathing to kick back in. PSmax is meant to treat central apnea and periods of respiratory depression but in your case your respiratory depression seems mild enough it is mostly treated at 5 PS and the majority of respiratory depression we are seeing is being induced by high ventilation settings. Once you get your ventilation settings in line I doubt you will need the high PSmax but for now I would leave as is to see how the machine reacts with a decreased MV target. 

PSmin of 6 might be warranted but I wouldn't go higher than right now. PSmin will mostly act to drive CO2 levels when we get you breathing spontaneously and since PS 5 on S mode stabilized oxygen I would assume 6 is already more than adequate. I assume fine tuning this adjustment will have to be based on how you feel since you can't measure CO2 at home. Not much point playing with that until results are more consistent since you rarely spend time at PSmin anyways right now (including last night).

[StuartC]

Thank you.  I certainly would not have considered the use or non-use of C-Flex during the sleep stud.  That said, I never felt better using CPAP with EPR, or even on S mode they way I have felt today.

One of my thoughts was to have volume targets a bit lower then my spontaneous volumes, so if I am to not change PS min, reducing Va sounds reasonable.

I have been reticent to increase PS max before now because of how the pressure was running continuously at 14 (IPAP max) and would likely have gone higher if I had allowed it.  I am more willing to consider increasing it after last night when the median pressure was < 13 because a limited controller cannot do a whole job, especially if it is tightly coupled to iBR.  But waiting to see the effect of volume changes and reviewing again after a couple of nights works too.

Spontaneous RR has been 13, both on CPAP and S mode.

I have a possible theory about the night of the 16th.  In the first period of sleep, I was wearing an Evora Full mask.  In the second period, I was wearing a Vitera.  Rubicon pointed out that low CO2 (over ventilation) mcould contribute to non-spontaneous breathing, so I have been wondering if the Vitera might be more effective at diffusing CO2 than the Evora Full?  Can't be sure but it is a thought.  Even if true, it is neither good nor bad about each mask - it depends on each person.  I like the Evora because it does not leak but perhaps the Vitera could ultimately let me use lower pressure settings.  If I get sent for another sleep study any time, perhaps I can get them to work out which is better for me.

As you say, without the ability to measure CO2, all I can go on is how I feel.  I do not have the words to tell you what a beautiful "sunny" day today has been compared to 13+ years of "fog".

[Rubicon]

As you say, without the ability to measure CO2, all I can go on is how I feel.  I do not have the words to tell you what a beautiful "sunny" day today has been compared to 13+ years of "fog".

Well then I guess you accomplished more than me!

If you look at the previous images posted, the oscillation appears and disappears simply by changing the time selection!  That's essentially the same time period.  In one the periodicity bites you in the butt, and in the other it's gone!

But before anyone dismisses this phenomenon as an Oscar "bug", it's appearance is predictable--  it's associated with machine breaths when rate is constant:



Since the machine has taken over control of breathing, CO2 is not the driving force behind respiration during these periods.  It's lower than it should be, but is it the root of all evil?  Since MV is WNL, it's probably non-toxic, but increasing spontaneous breaths during NREM has been a goal so continuing towards that "target" especially given your recent result (tho one day doesn't necessarily make it a success, will try to figure that out later) suggests we're on the right track.  We are not interested in methods, we are interested in results.

That said, MV is actually lower than trend during machine takeover (which is odd because VA and pCO2 have a direct inverse relationship). I shall take that on for my chore for the day while you guys do more Dial Wingin'.

BTW do you have the CPAP folder from 3 Mar 2022?  With the oximetry data?  Do have oximetry data on any other days?  Can you pull the pulse data in after the fact?

[StuartC]

Given that the oscillations happen during controlled (steady) respiration, I was wondering if it could be some sort of resonance?

Another abbreviation I am missing = WNL? And only "probably" non-toxic? I actually had a chuckle at that.

I have created a second DropBox folder with O2ring data in it from 26 March onwards, when I started using the Lumis. Link and some instructions have been sent by pm.

[Rubicon]

That said, MV is actually lower than trend during machine takeover (which is odd because VA and pCO2 have a direct inverse relationship). 

And what makes that even more confusing is that control machine breaths can be as little as 50% efficient compared to spontaneous breathing because of ventilation/perfusion (V/Q) mismatch!

We really need some capnography.

Speaking of which, did we figure out why yet?  I think we're due for another review.  Based on the PFT results (yes it is interesting forgot to mention that) one starts to stray away for diaphragmatic paralysis and consider a whole different path (as previously noted, metabolic alkalosis). Transcutaneous CO2 vs ETCO2 (discuss later).

So IIWM I'd get the CO2 thing clear.  All these goals are based on 4 month old data that may not be valid any more.

[Rubicon]

It has been a long time since I did this but, on a chemical plant where oscillating outputs happen, I would start by reducing the proportional gain - especially on a flow loop or a low-volume, fast-acting pressure loop.  

And if we had a V60, we could use PAV (Proportional Assist Ventilation) and do exactly that!

Also if we had 6K hanging around.

And could pose as "Health Care Professionals".

No prob, there's more than one way to skin a feedback loop!

[Rubicon]

Given that the oscillations happen during controlled (steady) respiration, I was wondering if it could be some sort of resonance?

Another abbreviation I am missing = WNL?  And only "probably" non-toxic?  I actually had a chuckle at that.

"Within Normal Limits".

Yeah, "probably" is about as far as one could go, because in a normal person (and you seem to be getter normaler and normaler, so that CO2 I'm really thinking needs to be put under the magnifying glass) one shouldn't be doing "controlled ventilation".

As the definition of "resonance" changes upon one's discipline, I'm going to reply with a resounding "absolutely!".

But as it appears to be physiologically predictable, there's something underfoot.  Whether or not it proves to be clinically relevant or just a novelty...

[Rubicon]

Let's use this one instead to provide additional context:

[Rubicon]

Do you have any other CO2 data besides this one?