Exploring better CPAP Settings

[don600]

Hi,

I've been a CPAP user about 70 days and have been trying to refine my settings. I use a Respironics Dreamstation and have experimented with higher starting pressures and reducing Aflex1 level. In general OA has rarely been a problem but H and CA are dominant. I'm enclosing a representative chart below (iincluding SpO2).

I'm just a beginner, but when I examine my charts I often see a pattern of: pressure increase, followed by increased ventilation rate, followed by a somewhat delayed increase in SpO2, folllowed by an H or CA. From what I read, this has the fingerprints of a treatment induced CA.  It looks like the overventilation that is dropping SpO2 is also increasing hypocapnia and suppressing respiratory drive. (In fact, I the main reason I  got the oximeter was so that I could get a better handle on whether my CA and H problem was actually causing clinically significant desaturations. In ten days of oximeter use, I've only seen one 3 sec desaturation to 86. Otherwise, 90 percent of the time my min SpO2 is 89 to 91. The chart below is representative.

Anyway, I am interested in seeing if there are experiments I can do to improve my CPAP settings. Obviously this a path that many clever people have preceded me on, and undoubtedly learned things along the way. Your advice would be appreciated.

BTW, my doctor, told me there is no SpO2 problem and I can discontinue taking it if I want. My AHI has been cut in half since my sleep study, so he is happy with my progress. I'm not being pressured by him to improve my numbers.

Thanks,
Don R. 

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[Sleeprider]

I agree SpO2 looks good, but your minimum pressure needs to be 7.0 or higher. These are nice low pressures, but with the slow and no-response of a Philips Dreamstation, you must optimize pressure to get it where it needs to be. Do not rely on the auto titration feature or your will end up with this level of events. To be honest, if I could put everyone on a minimum CPAP pressure of 8.0, I'd probably do it and go from there, rather than rely on these very low starting pressures. If you were using a Resmed, you could get away with it. Not with the Philips.

[don600]

Thanks for the quick response. Based on insights gained from this forum I have actually done some amateur experimentation with higher pressures, going from 5, to 6, to 7. I only did one day at 6, but did a 5 day stretch at 7. When I compared averages for 5 days at 7 with averages for a preceding 5 day period at 5, I observed:

1. No material change in OA (OA rate up 7%)
   
2. No material change in H (H rate up 5%)
   
3. Substantial increase in CA (CA rate up 184%)
   
4. Moderate increase in PB percent (Percent of time in PB up 29%)
   
5. A moderate increase in AHI (AHI up by 29%)
   

When I reverted to my original pressure of 5, I saw moderate decreases in CA rate and percent PB,  a rise in OA (3.4 to 5 events) and a moderate rise in H (28 to 32 events). My AHI improved by 6 %, which I consider to be noise. I'm not too worried about the OA and H because I am aware that some of the CAs that went away can convert to other events.I've enclosed the data and analysis in case this helps, but don't expect you to review it.

Despite this, I am open for retrying higher pressures with smarter settings, to see if it changes the answer. It is possible I inadvertently made choices that sabotaged the outcome.

I also notice that sometime I can awake early, check my AHI, and then liie in bed to see if I can return to sleep. I might spend 30 minutes just breathing slowly before I decide I can't sleep, and get up. I discover my AHI has gone from 4 to 8 during this period, due to my CPAP coding lots of CAs and Hs when I am not experiencing breathing difficulties. It's puzzling.

For now, the more I read about treatment-induced CA, the more I suspect this may be my problem. I got my oximeter because I wanted to try to figure out if my high H and CA numbers were clinically significant - I see no sign they are. Subsequent to my pressure experiment I reduced my Aflex to 1. I've also seen some mention of using a fixed pressure instead of auto-titration, but I don't know much about that.

Thanks for the advice.


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