Any others with CompSAS using CPAP/APAP?

[of_the_west]

Hi all,

In short: I'm a newbie to CPAP and have just started on therapy this week. That said, I'm a quick study and I've been reading a lot, but I have some questions about my condition and initial experiences using the ResMed AirSense 10 AutoSet.

Some background: My home sleep study indicated an AHI of 23.2 over two nights. 21.4 ODI, 1.2% snore index. In total over the two nights I had 171 apneas and 190 hypopneas, and of the apneas, the vast majority were central (137). My CAI was 8.8 (or 38% of my events). Lowest SpO2 was 79%, though I didn't have any significant hypoxia: mean SpO2 was 90.9% with a 93% waking baseline. I've historically had a low SpO2. That said, I had a significant number of cyclic airflow limitations that didn't register as obstructive hypopneas, so my sleep study AHI was likely a significant underestimation of my disordered breathing at sleep.

This week I started on therapy with the AirSense 10 AutoSet. Current settings are 5-15, no ramp, full-time EPR at 3, and EPAP at 4.0. I'm using the Philips Dreamwear nasal mask/cushion with no leaks.

Since I started therapy (I'm only 3 days in), my OSA index has gone down to 0.25, Hypopnea index to 0.43. But the CAI is 16.3 average, and 20.5 most recently. Average pressure delivered by the machine over the night has been 5.69 with a max of 8.32. I live at an altitude of 5400 feet and my body just seems to be hypersensitive to the low CO2 levels at altitude. Now that I'm on CPAP, that seems to be bearing out as the central apneas haven't subsided and in fact have increased as compared to my sleep study. I realize it may be to soon to come to any conclusions and that it may take some time for my central apneas to go away as I get used to CPAP, or they may never go away and I might have to move to ASV therapy.

My issues & questions:

1) Even at the low pressures my machine seems to be settling on combined with the EPR at 3, I feel like I can't exhale - it feels like I'm exhaling through a pinhole or almost having to force my exhalation. I realize some of this might be that I have to get used to the sensations of CPAP, but it's really disconcerting as I often feel like I'm suffocating. I know this is a common newbie feeling, but I'm wondering if something else could be going on? My nasal mask seems to fit with no leaks, but I don't know if it could be sized incorrectly?

2) I'm doing my best to be 'compliant' and get used to the therapy, but since my central apneas are so prevalent I'm waking up constantly with the feeling that I'm suffocating. As a result I have had an awful week of sleep and I've been walking around like a zombie. Also, often I feel acutely air starved, and I'm not sure if that's a direct effect of the central apneas, or if it's because the machine pressure is too low, or both. My understanding with the AirSense AutoSet machines is that they deliver the minimum air needed to keep your airway open and eliminate OSAs, but I'm wondering if the pressure at which the machine is auto-titrating is too low? That said, my OSAs and hypopneas are almost completely gone...

3) I'm curious if there are others here that have had a high incidence of CSAs with CPAP/APAP who successfully moved to ASV therapy? If so, I'd love to hear about your experience. My understanding is that it will be a tough fight with insurance to get ASV authorized, but that ASV has been fantastically successful for people living at altitude with complex sleep apnea.

4) Has anyone who lives at altitude experienced a marked improvement in their condition by going down in elevation or to sea level? I moved to elevation just over two years ago, and that's when my partner started suspecting I had sleep apnea. We're not sure if I had it when living at sea level, but I definitely didn't sleep this poorly or have any reason to think I had sleep apnea. I'm wondering if I could see an improvement by moving back to a lower elevation given that the vast majority of my apnea events seem to be central apneas.

Thanks in advance for your wealth of experience and compassion.

[Pugsy]

Current settings are 5-15, no ramp, full-time EPR at 3, and EPAP at 4.0.

1) Even at the low pressures my machine seems to be settling on combined with the EPR at 3, I feel like I can't exhale

EPR of 3 is useless if your starting pressure is 4 or 5 because the machine can't ever drop below 4 cm no matter what the EPR is set at.
At the most when you first start the machine you are getting 4 exhale and 5 inhale which is just a 1 cm reduction.

Most people will feel air starved at those settings starting out. You really need to have 7 cm starting point if you want to use 3 EPR so that the machine can drop the full 3 cm. Try it and see if it is more comfortable. Change the 5 starting pressure to 7 and see how it feels.

[JDS74]

I switched from an auto BiPap machine to an ASV machine about 3 years ago and have had a significant increase in my feeling of well being. I don't have any experience in the difference at altitude except in air travel. It is my understanding that cabin pressure in aircraft approximates that at about 5,000 feet. When traveling by air, I have great difficulty in keeping my SpO2 levels above 88% and can do so only by continuously hyperventilating. For a five hour flight, that really sucks (pun intended.)

You didn't mention the altitude that you moved to. That would be helpful.

With the rate of occurrence of CSA events, it looks as if an ASV machine is the way to go.
However, make sure that you don't have some other underlying medical condition that is contributing. For example, Cheyne-Stokes respirations can occur along with CSA events and are a concern for cardiac issues. I would recommend a chat with your sleep doctor to make sure that nothing else is going on and then move to see if an ASV machine would be appropriate.

Here is a link to a small study on the effects of moderate altitude on sleep apnea and in particular the increase in central apneas.
https://www.researchgate.net/profile/Ja ... ion_detail

It is reported that upon successful treatment of obstructive apnea, central apneas emerge and so it could be that in your case both of these effects are present.

I did not have any issue in my insurance coverage regarding the switch. My doctor wrote a scrip for me which I filled and submitted to the insurance company along with a sleep study from the Mayo clinic showing complex sleep apnea and sample reports from the machine showing significant central apneas and they just issued a check. In my case, the purchase was direct from an online DME with the request for reimbursement afterwards.

I would recommend that you discuss this possible change with your insurance company to find out what criteria they need for coverage and/or do they reimburse from a direct purchase rather from a local DME. Some companies are fine with that, others are not.

[magni]

4) Has anyone who lives at altitude experienced a marked improvement in their condition by going down in elevation or to sea level? I moved to elevation just over two years ago, and that's when my partner started suspecting I had sleep apnea. We're not sure if I had it when living at sea level, but I definitely didn't sleep this poorly or have any reason to think I had sleep apnea. I'm wondering if I could see an improvement by moving back to a lower elevation given that the vast majority of my apnea events seem to be central apneas.

Thanks in advance for your wealth of experience and compassion.

I don't have a wealth of experience, having only been on CPAP for about a month. But I'm using the same machine you are, and if anything have the same issue, but worse - and I live at 7300' (Black Forest, CO). I've been getting around 50-60 AHI, almost entirely centrals (although obstructive/etc seem like good numbers). I'd be more terrified about it if it weren't for the fact that (after decades of never seeing a doctor) I had my heart and various checked during an episode of various issues that turned out to be acute hypothyroidism (TSH==198). I had problems with severe fatigue, couldn't breath (or think) well, and had some blood numbers that made it look like my kidneys were failing, but all of that seems to have been secondary to the thyroid issue. My doctor doesn't seem as worried about the number of centrals as I was after (for example) reading the wikipedia page on CSR, so maybe they think it's related to the hypothyroidism, which is on its way to being resolved but not quite there yet.

What's interesting is that, out of all my nights of huge centrals, I had one of almost none. It took me a while to remember what was different about the preceding day, and it was that I spent nearly all of it in Denver, 2000' lower. Since then, I've spent a couple of full days in Colorado Springs at 6000', and those days both resulted in nights of 30ish AHI instead of my usual. I have trouble believing that there's such a fine threshold effect, but who knows. I grew up in a suburb of Denver, so maybe I'm attuned to 5280'? Note that each of these nights was in my usual bed, usual routine, nothing out of the ordinary except where I spent most of my waking hours (normally I work from home at 7300').

I haven't mentioned the altitude theory to my doctor yet, but have an upcoming appointment after yet another TSH blood test (sigh).

[of_the_west]

What's interesting is that, out of all my nights of huge centrals, I had one of almost none. It took me a while to remember what was different about the preceding day, and it was that I spent nearly all of it in Denver, 2000' lower. Since then, I've spent a couple of full days in Colorado Springs at 6000', and those days both resulted in nights of 30ish AHI instead of my usual. I have trouble believing that there's such a fine threshold effect, but who knows.

As I understand it the 'fine threshold' response to altitude can in fact be a huge factor. The key is CO2, mainly that at altitude there's less of it, just as there's fewer molecules of any gas at altitude. And because CO2 plays such a huge role in respiration, going up in altitude can really screw with that autonomic feedback mechanism resulting in an exponential uptick in CSAs. See: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3227706/ It would follow that going down in elevation could result in less CSAs because there's more CO2 available to our bodies, thus helping us to regulate breathing in a more normal fashion. For my part, I didn't exhibit sleep apnea at sea level -- my sleep apnea presented after two years of living at 5400 feet here in Colorado.

[of_the_west]

After a few more nights of APAP usage here at altitude with the ResMed Airsense 10 Autoset to manage my prevalence of central apneas, I found out and learned some interesting things that might help someone else in the future:

• Turning off EPR altogether helped tremendously in managing my CSAs. I went from an average CAI of 15 down to 1-3 in a single night after turning off EPR. The opposite was true: turning EPR on (at the "3" setting) resulted in a subsequent, significant uptick in CSA events.
• Similarly, turning off the Ramp feature helped to reduce the CSAs that occur at early-onset sleep (that time when we have a nervous system communications delay)
• Raising the minimum pressure from 5 to 6 (for me) helped me to overcome a feeling of air starvation while at the same time reduced my CSAs. The theory on this is that the higher pressure overcomes the feeling of air starvation, but it also allows some CO2 to pool up in the mask which in turn helps my brain to regulate my respiratory rate and thus reduce CSAs.
• My doctor switched me out of APAP/Autoset mode into CPAP mode at a constant pressure. Again the theory here is that it reduces the variability in pressure that can affect CO2 levels and my body's response to those CO2 levels. As my doctor put it, the goal is to find a balance between a pressure that delivers the minimum necessary to overcome any OSAs and a feeling of air starvation with higher pressures that might cause CO2 washout in the mask - which in turn would cause my body to go into a high loop gain situation and start having lots of CSA events.

The end result for me has been that I hyperventilate less in response to low CO2 levels (hyperventilation is typical of the high loop gain associated with CSAs), I've overcome my OSAs completely (which were minimal to start), and my CSAs and hypopneas are now minimal - I went from an AHI of 23.2 to 1.9-2.5 in just a few days.

Of course, mileage may vary (as always) depending on the individual. Some people just don't respond to CPAP therapy for managing CSAs at altitude-- often CPAP can make the CSAs worse. Thankfully in my case it looks like after a week of usage that CPAP might work in lieu of the more complex and expensive ASV therapy.

[magni]

After a few more nights of APAP usage here at altitude with the ResMed Airsense 10 Autoset to manage my prevalence of central apneas, I found out and learned some interesting things that might help someone else in the future:
<snip>

Fascinating - I'll try these (the ones that I can) tonight. I do apparently have an ASV machine coming.

My most recent trip down to Denver once again dropped my night-of AHI down to ~3, only to see it come back to >50 the next night.