[CPAP] Disappointing Auto CPAP Results

[benjaminthurston]

I recently purchased a PR DreamStation Auto CPAP, primarily because I'm curious about the auto-titration feature. After 10 or so days in Auto mode, my AHI ranged from a low of 4.2 to a high of 12.

I previously used a PR System One BiPAP, with settings of 11 and 17, per a sleep study years ago. I recently discovered that I could use SleepyHead to view statistics from my BiPAP, and found that my AHI on BiPAP was often <1.0, although with some strange spikes to almost 29 around Christmastime.

Curious about the somewhat disappointing results from Auto CPAP, I changed my new DreamStation from Auto to CPAP, with a fixed pressure of 15 cm, and saw an AHI of 1.8. 

My expectation was that the Auto CPAP would adjust to yield comparable results to what I experienced on BiPAP, but with better comfort due to not increasing the pressure beyond what's required. What I found instead, as detailed above, is that my AHI is considerably higher in Auto CPAP than in fixed CPAP. Can anyone explain why this is? I can post SleepyHead screenshots of both systems, if that's useful. Thanks!

[Crimson Nape]

Hi benjaminthurston -

You will need 4 or more posts before you're able to display your results.  In the meantime, review the links at the bottom of this post.  When you're ready provide the link address to Imgur or Photobucket and I'll be glad to help. Try to pick a daily graph that is representative of your old results and one that best describes your newer one showing  the higher AHI.

[Sleeprider]

The Dreamstation auto CPAP would not produce satisfactory results based on default settings of 4-20 pressure. It is just too slow to reach pressures you need for proper therapy based on your prior BiPAP settings of 17/11. A starting pressure of 11 and maximum pressure of 20 might be satisfactory, but auto CPAP is very different from bilevel with a pressure support of 6 cm.

I still use my PRS1 BiPAP Auto 760. Great machine, and I suspect you may find your bilevel more comfortable and effective than CPAP. It will help to know what kind of events were flagged by the CPAP and what pressures you were using.

[Gideon]

Post your screenshots, that way we can see what is happening.
Please pay attention to the section on organizing them.
My signature should guide you.

[benjaminthurston]

Well, as noted by Crimson Nape, I can't post screenshots yet. If I could they would show, for example, the DreamStation Auto mode adjusting to a maximum of around 13 cm, while still allowing 6.9 AHI, or up to 11.5 AHI on another night. Of course, in CPAP mode the AHI is better (e.g., 1.7 AHI), because I used a fixed pressure of 15 cm. I guess my real question is, "Is the Auto algorithm trying to control to some AHI, and if so, what?" Or perhaps another question; "What's its value, if it still allows an AHI toward the upper range of "Mild OSA" while a somewhat higher fixed pressure gets me into the Normal range (<5 AHI)?"

[Sleeprider]

A couple more posts, and images won't be a problem. I would still recommend using links to images hosted elsewhere, or you will be deleting things to post new ones every time. Tutorials on organizing and linking images are in my signature.

What was the pressure range on your APAP with those results?

[benjaminthurston]

Sleeprider,

The APAP was set for 8 cm min. and 20 cm. max., and typically showed a 90% pressure of 12 cm to 13 cm.

I'm not sure I understood your comment about "using links to images hosted elsewhere", but I think you're talking about uploading to Imgur, and pasting the link into the post--right?

[Sleeprider]

Philips auto CPAP machines are somewhat slow to increase pressure to respond to pending obstructive events, and they tend to try to reduce pressure back towards the minimum. This means it must be within 2-cm of your optimum (90%) therapy pressure to have any hope of being effective. In contrast, the Resmed Autoset machines can increase pressure rapidly and stay at an effective pressure. Basically, your setting would have worked with the Resmed, but for the Philips in Auto mode, I would suggest a pressure of 13.5 to 18 in auto mode, based on your results in CPAP mode.

Most of us host images on Imgur, and then use the posting option on that site to use BBcode to post to this forum, after clicking on the huge thumbnail. That process is covered with screenshots in the second link in my signature. That produces an image like this:

[benjaminthurston]

Sleeprider,

Perhaps that's why the ResMed Autoset device seems to cost nearly twice what the the PR DreamStation Auto CPAP costs!

I do understand about uploading to Ingur and using BBcode to post. I tried to do that with my original post, but didn't have the requisite four posts behind me.

I'll give the DreamStation Auto a try using something like the settings you suggested, but it seems more likely that I'll just go back to the PR System 1 BiPAP, toy with the settings a bit, and keep the DreamStation for a backup.

Thanks for all your help!

[benjaminthurston]

Now that I'm off probation and have presumably figured out how to link to images uploaded to Imgur, I have one more question for the OSA gurus. As I mentioned earlier, my ResMed System 1 BiPAP Pro set at 11/17 cm often gives me AHIs <1, as shown in the second screenshot. However, on one notable night last December, my AHI jumped up almost to 29. I don't recall anything special going on that night, although the fact that I had to get up three times for pitstops should have been a clue that something was going on.

Anyway, does anyone have any insight into what might have caused this?