Treating low grade CA with ASV

[tossinandturnin]

Hi all, I am hoping someone can shed some light on my case.

I was diagnosed with severe sleep apnea which was mostly linked to the 170 hypopneas while sleeping on my back. During my sleep test I had 30 OSA and only 3 CA events. I have been able to treat the OSA with CPAP/APAP low pressures of 7.0 or thereabouts. I have attached charts for a fairly typical night using APAP 6.8-9.6 and CPAP 7.2.

I still occasionally have one or two 30 second OSA events during the night, but in general increasing my pressure tends to make my results worse.  This is mainly due to treatment emergent (?) central events. In addition to this both my CA and OA tend to be worse with EPR enabled.

On paper I am considered "cured", but I am finding I am not getting restful sleep. I suspect I am getting aroused by the CA events. (I have recorded myself on camera and do see myself stirring, but it's difficult to determine what causes what).

During a CA event I often see the waxing/waning effect on the flow (see charts), I also occasionally see it during the night where there was no event triggered. Another effect I sometimes see is the flow rate gradually taper down over the period of an hour or so, then eventually 'hiccup' with an hypopnea back to normal levels.

Going through all the clinical guides, titration guides, forum posts etc my understanding is this would normally be treated with ASV if the CA AHI is above 5 (and LVEF>=45%).  I have a couple questions regarding this:

- Is it still a good idea to treat CA<5 with ASV anyway and its only a question of cost, or are there other reasons to avoid it?
- Even though my CA index is 1.5 or so, I suspect it may be disturbing my sleep, I am also seeing other flow "weakening" effects - is this a good reason to use ASV?
- I understand using EPR makes CA events worse, so it's odd that bilevel would be used to treat CA. My understanding is that the bilevel aspect of ASV may actually make the body want to stop breathing even more - but the backup rate aspect of it ASV overrides this instinct by forcing breaths. This sounds like making a problem worse then fixing it by force and becoming dependent on the ventilation... Is this a fair assessment?


I should add that I have a secondhand machine in ASV mode that I am trialling and am finding it acceptable to use, albeit the pressures a bit high and getting some leaks. These ASV charts are posted here: https://imgur.com/a/QoFH6fd

Some questions on ASV:

- When using ASV mode I have a high degree of leaks, but I don't really notice them or get much of a dry mouth. My EPAP pressure is lower with ASV than when using APAP/CPAP. Are leaks normally such an issue with ASV?
- I am also not clear why the IPAP pressure auto raises to the maximum and spends most of the time up that high when I apparently only have low grade CA - I would have thought it would stay at the minimum most of the night.
- Could using a vAuto with appropriate settings give better results with less potential side effects?

[Sleeprider]

ASV is capable of treating both obstructive and central apnea, as well as any periodic breathing as you show in your charts. This Resmed Clinical Titration Guide explains how it works beginning at page 28. https://www.resmed.com/us/dam/documents/...er_eng.pdf Many members here treat CA < 5/hour and even use this therapy for non-central events like UARS and of course therapy emergent CA like yours. While heart failure is a concern with ASV due to the SERVE-HF study, this wiki explains the even that risk has not been repeatable in subsequent studies. https://www.apneaboard.com/wiki/index.ph...nd_Summary

I see you have ASV available, and your current settings appear to be EPAP min 5.2, EPAP max max 7.0, PS min 0.4, PS max 5.4. Those are novel low pressure settings, and seem to be working pretty well. The reason for a minimum PS is to make therapy more comfortable and help improve spontaneous inspiration. The PS max should be high enough to treat any CA and periodic breathing. I have found with many individuals that if PS min is too low, therapy is not tolerated as well and more hypopnea events arise. Your chart suggest your EPAP range is effectively stopping obstructive events, I would increase PS min to 2.0 and PS max to 7.0. At some point you might try PS min 3.0 and PS max 8.0 and compare for comfort. You seem to do well with ASV and in my opinion should continue its use. Try to document the benefits of this therapy compared to CPAP and discuss it with your doctor. You may end up with a prescription.

[tossinandturnin]

Thanks for your feedback Sleeprider, I'll try your suggestion in a few days after I've collected some data for the current settings.

This is a chart for last night with slightly lower PS: https://i.imgur.com/mh7cMvI.png
It seems all my issues with CAs on CPAP have been replaced with hypopneas instead - but they don't seem as impactful. Your theory on a low min PS causing hypopneas may be correct, although I experienced just as many when using a PS 1.0-6.0. Perhaps it might just need some more acclimation.

The reason I am trying to keep the PS low is because otherwise it raises the IPAP to levels that I have shown on CPAP is unnecessary. It also causes me leaks and a bit of discomfort. With C|APAP I only need a EPAP+IPAP of 7 or so.

With ASV it seems to be eager to use the max PS all the time which means it's tricky to get it any lower than 10 to 12 or so. I can't really understand why it ramps up to the max IPAP a lot of the time given that in theory I should be having only a couple CAs through the night even at 0 PS.

This, and the fact EPR makes things worse, makes me think BIPAP is actually terrible for central events - it could just be that ASV has a workaround for all the problems it causes by using a backup rate.. it makes me a bit uneasy to have high IPAP with this theory. Maybe a vAuto with sensitive trigger will be a gentler solution ?

[Sleeprider]

Maybe this will help.  The Resmed ASV protocol wants you to increase EPAP for hypopnea, but assumes PS max will be high enough to compensate for central respiratory effort.

[SarcasticDave94]

Grumpy Dave asks if you might add OSCAR charts as an attachment instead of imgur. I find them easier to view. Thanks much.

Something else the grump is seeing is some Ramp action or what appears to be the Ramp increasing pressure chart pattern. Try to minimize that as best as you're able to. ASV therapy typically doesn't play well with Ramp.

[jcp519]

The reason I am trying to keep the PS low is because otherwise it raises the IPAP to levels that I have shown on CPAP is unnecessary. It also causes me leaks and a bit of discomfort. With C|APAP I only need a EPAP+IPAP of 7 or so.

With ASV it seems to be eager to use the max PS all the time which means it's tricky to get it any lower than 10 to 12 or so. I can't really understand why it ramps up to the max IPAP a lot of the time given that in theory I should be having only a couple CAs through the night even at 0 PS.

This, and the fact EPR makes things worse, makes me think BIPAP is actually terrible for central events - it could just be that ASV has a workaround for all the problems it causes by using a backup rate.. it makes me a bit uneasy to have high IPAP with this theory. Maybe a vAuto with sensitive trigger will be a gentler solution ?

If you have a CA or experience periodic breathing, you actually need more PS to maintain your minute vent. The ASV algorithm doesn't just increase PS when you have a CA, it increases it when your minute vent drops below that target threshold. You having a CA/periodic breathing on CPAP shows that you actually need that higher IPAP in that specific moment to stabilize your breathing.

An ASV will raise the IPAP to higher levels to force you to breath whenever it detects a drop in your minute vent. The ASV always wants to maintain the target minute vent from a 3 minute running period. So if it drops too much, no matter if you have a CA or not, it will increase PS until it detects your spontaneous breathing is enough to maintain your minute vent. I you set your PS too low, the ASV cannot effectively combat CA events and you will still experience some level of periodic breathing or even a central related hypopnea.

Bipap alone as it stands is worse for CA, but the variable PS of ASV forces your body to take a breath, thus preventing the CA. That higher IPAP is what keeps you from having a CA and thus an arousal disrupting your sleep. ASV is a bit of a brute force method, but it works very well to treat both OA and CA.

[tossinandturnin]

Ok thanks. I would attach images to the forum but was hitting issues with the 3 image limit.

I will try a higher min ps, it just means the max also needs to be increased to levels that are tough. 

This actually relates to why I am using ramp despite normally having it off. If you see the first ten minutes of my minute vent as I first get into bed it's quite high. This drives the ipap high and causes a viscous cycle of fighting and raising the pressure. The ramp turns all this off and you can see that by the time ramp is finished my breathing has reached more average levels - which sets a more reasonable target for the asv.

Am on holidays now, will adjust when I get back.

[SarcasticDave94]

You can choose to increase pressure settings fractionally, it doesn't need to be whole numbers only. Dave's fractional equals the ResMed pressures have steps of .2.

Enjoy the holiday

[jcp519]

I'd also try to make sure you're very calm and have a steady breath rate when you first put the mask on. I usually try to lie down for 10-20 mins and relax before I put on my mask and sleep. The higher pressure just takes time to get used to. Persistence is key!

[tossinandturnin]

I tried using a higher PS range of 1.8-6.8 and again of 1.0-6.0, but in both cases I found myself waking with a racing heart rate and having to restart the device to stop it fighting me. I had a very low AHI for the 1.8-6.8, but I also barely slept so that is likely a factor. My PR is on the chart for the 6th.

While I think a higher MinPS is probably helpful, the mandatory increase to MaxPS causes my pressures to sit in the 11cm range which is simply too high for me given my OSA is resolved with <7cm.

I modified the firmware to allow flexibility of the high MaxPS and used a range of 0.6-3.2 with static EPAP- this gave me a much smoother experience, lower and flatter minute vent - albeit with many more hypopneas. My heart rate still rose in a similar manner at 3am, but it didn't wake me. I don't see this issue with low pressure APAP/CPAP, and don't always see it with ASV.
I have had recent heart valve surgery so I am trying to avoid a racing heart.

I can resolve my OSA with ~7cm, which causes a few CA events. But I believe there are many more disturbances happening that are not flagged. It seems similar to this thread about CA feedback loops: https://www.apneaboard.com/forums/Thread...#pid354925 , which I believe is the cause of my lack of restful sleep. (but am also struggling through CBT-I as well).

My optimising strategy is to get a smooth 'minute vent' with minimal pressure and pressure changes as possible given that it causes CA. This means keeping EPAP as low as possible for OSA, and MaxPS as low as possible to prevent rises and fluctuations. The other option is to jack up MaxPS and just blast myself with a forced breath - but this doesn't seem like a great option given it seems to cause a pounding heart.

I will raise maxPS+0.2 each night and minPS+0.2 every second night until hypopneas resolve, if that gets too high I will start reducing EPAP instead as well.