IVAPS vs Vauto BPAP - Tidal Volume Question

[cmpman1974]

Many here have made comments I have a pretty large Tidal  Volume most nights.  It averages 650-750 mL typically based on months and months of data (median level actually). 

When I had my Vauto BPAP - ResMed Air Curve 10, reports showed Tidal Volumes again around 700-800 mL.  What would make a doc move to IVAPS with that level of Tidal Volume?  My numbers really haven't changed on IVAPS. I'm still at the 650-750 mL level consistently.  From all I've read, desired target Tidal Volume is 8-10 mL per Kg of Ideal Body Weight.  In my case, that figure is 560 to 750 mL per breath so obviously I easily meet this.  The thing I've despised about IVAPS is the pattern of breathing and the severe strain I feel on my back / scapula muscles each morning after sleep.  

I found this very informative presentation on Non-Invasive Ventilation, specifically for COPD and OHS.

https://calthoracic.org/wp-content/uploa...-Final.pdf

Based on the last few pages, it seems my settings are counter-intuitive for the goals of an OHS patient.  It says rise time should be extended.  My sleep specialist set it lowest possible at 150 milliseconds.  It says give patient a decent amount of time for the Ti min to allow them to take in a breath as it's harder for OHS patients.  My specialist set it as low as possible at 0.3 sec.  

Lastly, what's the point of treatment w/o concrete goals to hit.  In this case, shouldn't nighttime O2 levels and awakening PACO2/PAO2 be monitored a few times to ensure the new treatment is doing something worthwhile.  AHI seems like a less critical metric based on this stuff.  That said, my ABG test doesn't meet the official parameters for OHS to start as I had a PACO2 of 43, not >45, normal PAO2, etc.  However, I have many other markers that make it borderline so I could buy into the issue.  These include serum Bicarbonate levels often in the 27-32 range, restrictive patterns identified on spirometry (high 60% range), obesity, etc.

Info keeps showing IPAP/EPAP adjustments are required to try to meet a minimum O2 nadir.  Again, HOW when never noted?  It seems supplemental O2 is a tricky proposition with OHS as too much can be harmful and elevate CO2 retention further.  Things need to be carefully reviewed it appears. I was thinking it was a slam dunk if low O2 is proven, but it may be more complicated with an OHS patient.

I can suffer a bit to achieve a goal, but suffering from sore muscles to achieve nothing and feel worse than I did on a BPAP VAuto frankly irritates me.  I hate shooting in the dark with no true data.  Maybe I'm completely missing something as what IVAPS accomplishes and hope someone smarter can clarify. If I had Tidal Volume of 450 mL on VAuto then it would make more sense to me as the IVAPS mode would assure a higher Tidal Volume.   Maybe it's a timing issue of desaturations?  My AHI was around 3-5 on Vauto and now more around <1 on IVAPS.  It has not in any way equated to any physical improvements or general improvement in tiredness.  It seems 95th% pressure levels are around 15.8 (IPAP) / 10.0 EPAP.   So at the end of the day, I'm not far off from my old 16/8 pressure on Vauto, which was a bit lower than titration studies always recommended.  17/9 was also my tipping point to tolerating the high pressures.  No amount of pressure used in titrations brought O2 up where it should be.  One polysomnogram result recommended a 24/14 pressure, but still the O2 levels were low and AHI/RERAs high. I never understood what made the tech choose this level because it didn't seem to look better result-wise.

It's an interesting dilemma.  I hope this stuff may be of help for others too struggling for answers. On a side note, I hate the term Pickwickian Syndrome and the cartoon character always shown. Doctors even make jokes about it.

[Sleeprider]

Cmpman, I had a really good tenderloin and enough wine that I'm reserving this for tomorrow. Hope you understand, but there are some good ideas here, and I want to give it some clear thought. Meanwhile, hope you sleep well, or have a sense of humor.

[cmpman1974]

Cmpman, I had a really good tenderloin and enough wine that I'm reserving this for tomorrow.  Hope you understand, but there are some good ideas here, and I want to give it some clear thought.  Meanwhile, hope you sleep well, or have a sense of humor.

No problem. : Glad you enjoyed your dinner.  With all the great answers you offer people, you certainly deserve a break.  I look forward to your response when ready.  

I watched a 20 min video from a respiratory therapist teaching when to increase IPAP / EPAP for ventilation and oxygenation problems.  It was helpful.  What I took from it is I'm working in the dark as the physicians have no true ongoing data to support next moves outside AHI and usage time.  In an acute setting, these professionals focus on ABGs.  With a low number of apneas/hypopneas, the easy assumption is oxygenation is good.  If not doing an ABG later to re-check PACO2, again....nothing to work off of.  Not checking O2 stats at night with a pulse-oximeter...again nothing to work off of.    I hope them asking me how I feel day to day isn't the only gauge. lol.   It's akin to throwing a dart at a dartboard wearing a blindfold in a way, right?

My current max PS is 10.0.  The question is has that lowered PACO2 levels at all or does it need to go higher?  O2 is too low if these O2 rings are accurate at all.  So that may mean IPAP needs increasing or an oxygen bleed.  Without facts, all seems like a waste of effort.  

Based on OSCAR, 95% of the time my PS is 6.0 or lower and EPAP fixed at 10.0 and that controls AHI.  However, does that control CO2 levels?  Control O2 levels?

The attached report from quite a while ago was representative of a rather typical night on my VAuto.  91% high leak rate and never heard from the DME or docs to address.  Hard to comprehend.  I'm thankful I'm getting that aspect under control much better. How on earth does this not raise red flags for the DME? 7+ hrs of use and AHI under 3 - check, check, good to go. It makes me wonder out of a scale of 1 to 100, just how useful was BPAP therapy that evening?

[cmpman1974]

One more thing for you Sleeprider (or others)

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4069417/

EXCELLENT study here that states AVAPS is a novelty more than anything and not justified most times. I take 98% of my breaths spontaneously so even more questionable.

https://thorax.bmj.com/content/thoraxjnl...9.full.pdf

Another:

https://onlinelibrary.wiley.com/doi/full...resp.13458

Final one showing docs could do much more but won't because not enough money to be worth the effort. An example is trying to get the oximeter on a ResMed machine.

https://www.atsjournals.org/doi/full/10....101-033CME

As I keep saying, without before and after facts, nothing to truly assess.

[Sleeprider]

At this point, your doctor is relying on PACO2/PAO2 tests, that I presume are taken during the day, after you have recovered from your nocturnal desaturation. These test show marginal PACO2 and acceptable PAO2 results, which is not surprising. I think the ultimate solution to this qualifying problem would be to pull samples during a sleep test incorporating your use of PAP therapy with oximetry, and a blood test to be pulled upon waking in the morning, before you are able to recover to your normal daytime blood gas levels. The fact you desaturate to very low levels as measured by oximetry is really not in question, but CMS has written the National Coverage Determination to be highly biased to arterial blood gas results https://www.cms.gov/medicare-coverage-da...?NCDId=169 Since you do not display hypoxemia during the day and only require nocturnal supplemental oxygen, I see no other way to obtain this evidence. A properly designed sleep test in a facility with the capability to withdraw arterial blood samples would seem to be the best way to document both qualifying oximetry based desaturation, and blood samples demonstrating this impact.

I'm pretty sure I have consistently question your need for the backup rate in ST or iVAPS, and would have preferred seeing you on Vauto. One thing the AVAPS or iVAPS will do beyond a backup rate is to enforce a respiratory volume. You never appeared to have a volume problem, but your persistent desaturation as measured by oximetry has remained a concern that would normally be addressed with supplemental oxygen. We have observed no correlation between higher PS and PEEP and improvement of night time oxygen, but the over-ventilation indicated by your tidal volume may contribute to the lower PACO2 results..

[cmpman1974]

Sleeprider, yesterday was my first night I used a CheckmeO2 Max which Jeff recommended here.  I had much better luck with this device and it recorded a full night session easily.  I would choose this over the O2 rings any day.

Interestingly, the stats were better than my other device, but far from optimal.  I would've pulled it into an OSCAR chart, but for some reason my BPAP ST-A machine has the wrong date on the machine.  The DME didn't bother to make sure the proper date and time were in the machine at time of set-up.  Pretty crazy!  I am resolving the issue soon, but in the meantime attached are the summary O2 charts.  There are a few desaturation events still of concern, but zero association to any apneas/hypopneas.  At the time they occurred, breathing was stabilized, tidal volumes consistent, no significant mask leaks, flow rate on the machine consistent, mask pressure at a solid 15. So the question is are these real or device error?  

At the end of the day, a mean O2 of 91-92% still kind of sucks and the amount of time under 90% again isn't too good. . I think with all my co-morbidities trying to get a 95-96% mean O2 is kind of a pipe dream, but who knows. I don't know if that would equate to feeling better.  My biggest concern is all time spent under 90%.  

I looked back through historical blood CO2 levels for years as our provider has an online system that can do that.  It is glaringly obvious I had the issue forever and none of my physicians were aware enough to see if it can be addressed IF it can be. Of course they said to lose weight which is absolutely key.  It's so hard to accomplish goals when you're so tired you can barely function and yawning hundreds of times.  It's a vicious circle sadly. My serum bicarbonate levels were as high as 34-35 on many tests and almost always 29-31.  I rarely had a 24-25 mixed in, but I'd say those were perhaps 5% of the time. 

As to your comment about docs monitoring ABGs.  Ummm...no way.  The only time ABGs were looked at when I was undergoing intense chemotherapy treatment and extremely ill years ago.  No one ever thought to look at this until a year ago when the sleep doc requested it.  However that same sleep doctor wasn't aware pulmonary testing was a requirement to get a ST-A machine so who knows.  In retrospect, it was glaringly obvious ABGs should've been performed ages ago and it should've been an ongoing assessment as to efficacy of my BPAP treatment.  I probably have taken years off my life due to this.  U of M published an article stating CO2 retention is a higher predictor of mortality / severe illness than being a chronic smoker.  That says a lot.  I have felt 'poisoned' for ages in a way and now it kind of makes more sense.  

Another 'excellent' night of sleep according to OSCAR.  It did not feel like it.

[Crimson Nape]

If you started your oximeter near the reported CPAP start time, you can rename the oximetry filename to 20230318004630 and it will be able to be inserted into your daily data.  I actually would copy the original file and then rename the copy before inserting it.

- Red

[cmpman1974]

If you started your oximeter near the reported CPAP start time, you can rename the oximetry filename to 20230318004630 and it will be able to be inserted into your daily data.  I actually would copy the original file and then rename the copy before inserting it.

- Red

Yes I did...literally within 1-2 min.   Thanks!

[cmpman1974]

I took one last look at my last four polysomnograms.  Up until 2022, I was always on BPAP S (Air Curve 10 VAuto) treatment.  I never knew what the VAuto mode was, but I know I was never on it in the 10 years I had the machine.

It just seems like I was a pretty hopeless case over the years.  The doc jumped from BPAP S elevating pressures all the way to 24/14 to ASV (though NO Central apneas ever or CSR) to BPAP ST (complete failure with 120+ min under 88 SPO2) to most recently AVAPS.   I take some blame for my inability to tolerate the highest pressure levels.  I had to push back several times to lower it to a more tolerable level.  If I knew I was going hypoxic more often as a result, I would have been more incentivized to try to suffer more to improve that. I was solely looking at AHI and thinking to myself it's still controlled alright with the lower pressure I went back to.

How in any case can you justify approving a final pressure / treatment mode when your mean O2 and nadir O2 levels are extremely low?  If IVAPS was around all these years and was the solution to elevate O2 / eliminate CO2, why did I go 5+ years w/o?   From a titration aspect, IVAPS provided decent results at crazy high levels (EPAP: 10.0; PS min: 10.0; PS max: 20.0).  I seem to be amazingly tough to oxygenate with a machine.   Ironically, I looked back at my 2018 sleep study which showed a final titration level of BPAP S at 21/11.  It still resulted in low SPO2 stats and I just noticed the doc made a note indicating I should have a follow-up pulse-ox study overnight to determine if supplemental O2 was needed. I have a good memory and have no recollection that was ever followed through on. 

i guess I just never had any grasp how bad things were all these years from a vital statistics aspect.  I walked away from most follow-up consults believing I was titrated well and no major issues existed outside of the need to lose weight.  Wow was I so wrong.  I had many nights with high leaks for 50-90% of the entire night.  Not once did I ever get told about the low oxygenation with BPAP or high CO2 retention in 8+ years.  Looking back, it was clear as day presented with the evidence.  I have always been extremely fatigued and BPAP never improved me to where I needed to be.   It kind of makes me sick knowing how long I went with hypoxia and continue to.  I assume in some cases some people can't be optimized due to underlying issues.  Maybe I'm one of them.  Patients should clearly be told how severe the issue is and be informed even their machines are not getting them to where they need to be.  I  am a very complicated case with a complex medical history. 

I still find it perplexing about the continual transitions from BPAP S to ASV to BPAP ST, etc. Go figure insurance immediately turned down an ASV after going through the polysomnogram. : In my case, I was so convinced AHI was they key to treatment success.  I foolishly was chasing the wrong metric again due to not being educated enough.  Lot to learn. I just read past threads about the AirCurve 10 VAuto. Makes me wonder why I wasn't on VAuto mode instead of S mode. That seems like it may have been easier to tolerate if it titrated up as needed instead of the big pressures 100% of the time. 98%+ of my breaths are spontaneous so a ST mode seems pointless. My respiratory rate has been in the 13-15 range for 10+ years with S mode.

[cmpman1974]

Sleeprider, this should tell the story pretty well.  Last night on the advice of a non-sleep specialist doc, I went back on my VAuto BPAP on S mode (16/8) to see if it helped at all with the bad muscle / back rib pain I've been getting since on ST-A therapy.  This was the same machine I was on for years before ST-A.  As you can see here, I had a decent night.  AHI was well controlled  It is becoming glaringly obvious my issue is much bigger than straight apnea  I incorporated the oximetry data and pulse rate correctly this time finally! 

AHI of 0.58, very few events.....nadir O2 of 81%.  Mean O2 of 89%.  Spent 5+ HRS under 90% O2 level.  No wonder I woke up groggy as can be.  Low level of leaks, low number of events, not a huge amount of movement, etc.  I am fighting a losing battle when oximetry isn't monitored my the doctor.  It's a fake perception I'm doing well. This issue makes it so tricky to determine successful therapy.  Median tidal volume and Minute Ventilation certainly seem acceptable on the BPAP S, but apparently not with these poor SPO2 stats. PS is already at 8 here to expel CO2.  It makes me wonder if I need insane tidal volumes to compensate. If I do, my body will never handle those pressures so it's a no-win.  I really don't know where to go from here outside of aggressively asking for an overnight oximetry medical-grade test to confirm my suspicions.  We all know it'll show similar based on all the polysomnograms and other indicators.  

I guess I'd need to zoom in on the periods of low oxygenation to see if tital volumes were dropping concurrently.  I don't believe so from quick glance so I'm not sure how ST-A would remedy this.  If Vt is in the right range and no apneas/hypopneas are occurring, why would the ST-A machine feel the need to raise pressures to expel more CO2?  The final statistics are very similar between the ST-A and VAuto on S mode based on this single night of sleep. it is obvious from past data over 98% of my breaths are spontaneous.   With my current settings the best the ST-A could do is offer 2 units more of PS over my VAuto.