Therapy using Lumis 150 ST

[SingleH]

Hi StuartC,

I saw your last post with the 3 attached charts, I noted you mentioned you are only using a fixed EPAP of 5, but the screenshots show a range of 5-15, is that due to the bug in Oscar you previously mentioned in that Oscar doesnt accurately reflect the EPAP figures from the Lumis machine?

Given that your figures are very good on this low EPAP level I guess you never really experimented that much with the Auto EPAP feature?

[StuartC]

Screenshots that show EPAP of 5-15 are a bug.  To fix it, you have to enable Auto EPAP, then set both min and max EPAP to 5 and then disable Auto EPAP again.

I can't use Auto EPAP because it requires a PS range of at least 8.  My PS range is 2, i.e. 5 to 7.  

At EPAP = 5, PS = 5, I get O2 levels of about 96% with Mv just over 6 L and spontaneous trigger above 90% (the non-spontaneous trigger is mostly as I wake).  The PS of 7 gets applied (mostly) during REM when my RR drops, causing my Mv to drop and so my O2 to drop.  Even then PS is really only increased when Mv drops below about 5, which is where I have my target set.  No, as far as I know, this is not a typical way to set up iVAPS (works really well for me though and is based on a common strategy in industrial process control).

I can and have used max PS on 8 on occasion and have done okay.  I have also tried max PS of 9 and that caused my respiration to be suppressed leading to a low percentage of spontaneous trigger.  My assumption is that the machine over-ventilates me causing CAs, which it then controls with extended periods of mandated trigger.

So maybe I could set min PS = 0 and max PS = 8 but I need the machine to maintain a PS (of about 5?) for most of the night to achieve that Mv of 6 that provides good oxygen saturation.  In other words, I need to increase my Target Mv from 5 to 6 to tell the machine that is needed.  Around Christmas time I progressively increased Target Mv, without making any other change.  I spent more time each night with PS at 7 and my spontaneous trigger percentage decreased.  So I gave up, reversed my Target MV back to what I had it and am sleeping well as is.

[SingleH]

Thanks for the explanation StuartC. 


The restriction on having a minimum of 8 PS range is somewhat annoying. Regarding your test using your machine with an PS range of 0-9. I guess having the mn PS of 0 as a baseline could potentially reduce the change of overventilation, as your min IPAP will then be 5 and as I understand the machine will return to the lowest setting after obstructions have been cleared. I never actually looked when I had the unit for a trial but can the machine be set to Min PS of 0?

When you mention mandated trigger, do you mean iBR kicks in in response to your CA's.

On that point given the limited reporting of Oscar for the Lumis, how are you able to see what are CA's and secondly there is no way to assess your flow limit figures as those are not reported either right? One can only assume the machine is doing its best to handle them as required.

[StuartC]

Annoying is one word for having a minimum PS range of 8.  It is "only"  5 on an ASV and even that can be a nuisance, though mainly when you are trying to get it to do what it is not supposed to.

Yes, you can set min PS to 0, mut PS max cannot be less than 8 when that is so.  Zero PS will underventilate leading to hypercapnia for me.  Before iVAPS, I was using CPAP with pressure = 9 and EPR of 3 (effectively EPAP = 6 and PS = 3) and that was happening even in NREM.  

Yes, mandated trigger is iBR kicking in.  I have TPR set to 15, which means my background backup rate is 10.  So IPAP gets triggered automatically 6 seconds after my previous spontaneous inspiration.  Then, over the next (I think) five breaths, it speeds up until it triggers every 4 seconds.  To break that cycle, I have to spontaneously trigger IPAP in less time than that.  If PS is too high, I just don't do that.   

It is not an OSCAR limitation on the reporting of events, that comes from the machine.  Because EPAP is fixed, the machine has no need to differentiate OAs from CAs.  But on top of that, there should be no CAs because, by definition, an event is only an event if you do not breathe for 10 seconds.  As I described above, mandated trigger occurs in less time than that (provided TPR is set higher than 9) so, as long as your airway is clear, a CA should not be possible.  Because of that my default assumption is that UAs are obstructive and extended mandatory trigger (low spont. trigger percentage) is likely to be central.  I may be wrong about that, of course.

No, I do not assume that the machine is doing its best to handle flow limitations.  It is completely ignoring them because they have a computing overhead to calculate them and they have no purpose when EPAP is fixed.  If I want to know what my flow limitations are, I have to zoom in on my breathing chart and look at the individual waves myself.  

However, I honestly don't care what flow limitations I have.  On the CPAP, they were related to periodic breathing but that was resolved with EPR = 3 and it has not reappeared as PS has increased.  Another suggestion that flow limitations themselves are not that important is the V-Com, which appears to increase them and yet therapy improves for some with reduced CAs and less aerophagia.  Again, I certainly could be wrong about that.

[SingleH]

A lot of useful info in your post and it sounds like you have really grasped the functionality of this machine well.

A max PS of 8 would work as thats what seems to work best for him in terms of flow limits and somewhat normalizing his breathing waveform.

Interesting comments about your thoughts on Spont Trigger being low as a possible sign of CA's. When we trialed the Lumis the spont Trigger figure was around 97%+. Assuming the CA figures in the Vauto is accurate and his CA's averaging between 0.5-7 per night I guess that might work out at something like 3% assisted breaths. Maths has never been my strong point so my primitive assumption may be way off!

Also "annoyingly" Resmed seem to have a designed their product range in such as way that every product seems to be missing a feature thats found on another product, such as Spont cycle and Spont trigger on the Lumis, but only Spont cycle on the Vauto, or no Auto Epap on the Aircurve 10 ST-A or Easy Breathe only on CPAP or Bipap S modes.

Where are you at now in terms of your spont cycle and trigger figures? As I understand it having good patient-machine synchronicity is also of some importance.

I have a V-com here sitting in a bag and was going to test that, but I just cant not help but think its somehow fudging the figures by interfering with airflow.

[StuartC]

ResMed differentiate between sleep apnea machines and ventilators.  CPAP, VAuto, Lumis 100 S and ASV are all aimed at sleep apnea; they are essentially dealing with spontaneous breathing.  The Lumis and AirCurve ST and ST-A machines all have timed backup, which makes them ventilators.

Yes, the some clinical guides do describe the ability to turn on a fixed backup rate of 10 in S mode but I have yet to find anyone who has seen it in the settings on a VAuto.  The ASV has a backup rate of, I think, 7.  However, these appear to me to be protective measures against suppression of respiration through over ventilation.  I don't think they are an intended part of the therapeutic algorithm.  When there is no backup rate, there is no need for Spont. Trigger percentage in the sleep report as it is automatically 100%.  

I was under the impression that Easy-Breathe was available in VAuto mode, but you would know, not me.

My Spont. Trigger is generally in the low 90's and Spont. Cycle in the high 90's.  I have somewhat fudged my Spont. Cycle though.  Ti Max should be set to 30 / RR.  My median RR is 14 to 15 but my range is from 17-ish down to my background backup rate of 10.  Of course, I am still awake or waking for a lot of the time when my spontaneous RR is about 10 so, "for comfort", I have Ti max set to 3.0 s.  Technically that is probably too long but it seems to work okay for me.

V-Com introduces an extra pressure drop in the line that increases and decreases with flow.  The effect should be to slow inspiration, which would likely extend rise time.  That might be useful, especially if Easy-Breathe is off (or unavailable) where the max setting for rise time is 900 ms.  With Easy-Breathe in use on my CPAP, rise time was just about 1.5 s, from memory.  I do have Rise Time set to 900 ms, which I was also told I could do "for comfort" providing I do not have an obstructive lung condition such as COPD.  I am not certain of the truth of that statement but lower Rise Times reduced my Spont. Trigger, and that was enough for me to set it to the max setting.  What is important is that Ti min needs to be longer than Rise Time.

The place where I think the V-Com should probably not be used is with an ASV or in iVAPS.  They both work by automatically adjusting PS (and therefore IPAP) to achieve a target volume.  It seems counterproductive to me to introduce an element that works against the desired control action.  But that is my thinking.

[SingleH]

Thanks for all the info StuartC! Lots of food for thought one again!

I checked and the Vauto has Easy Breathe only on S-mode only, not Auto, which once enabled removes rise time. Backup rate is also availble in S mode only, not Vauto mode, and fixed at 10 BPM or Off.

I do recall you mentioning your long Timax and you had previously suggested that in my original post for my Dad, for whevever reason about 2.5 to 3.0 seconds is what he needs also to get his spont cycle in the 90's.

I have a V-com at home so may try that also, but I still remain sceptical, I imagine anything altering airflow would still disturb the sensitivity of the Vauto or any other device in terms of its ability to detect or respond to apneas.