Fixed vs auto pressure ?

[SaldusMiegas]

Saw my sleep doc today for the first followup appt after starting therapy 2 months ago.

My initial prescription based on a titration study was a constant number.

After a couple of weeks of high AHIs I turned on auto mode and based on the data and advice from members here I narrowed the range down to a span of about 4cm and continued on auto mode. Btw the high-ish AHI was the number predicted by the titration study, but I wanted to try for AHI below 5 which I think is the goal.

I am avoiding mentioning numbers because my question is philosophical and I use other threads for detail analysis and feedback on specific data.

Today the doc (PA) said auto mode is good for zeroing in to about 95% on the therapeutic pressure and next step is to peg a constant pressure at the therapeutic level. Then he said he would advise the DME to set the pressure (never acknowledged nor asked if I was messing with it).

So I asked if they always prefer constant and he said yes it helps eliminate incidents if you remain constant at the therapeutic level.

So I am left to wonder about a few things...

.. It makes sense to me that once you know the best setting then a constant pressure level would eliminate the incidents normally required to ratchet up to therapeutic level in auto mode and thereby reduce AHI.

.. I also have observed that determining this therapeutic level takes some experimenting. My initial titration study recc was 4 cm away from today's recc based on my going rogue and setting the machine on auto. If I hadn't done that we could be six months of 60-day tweaks to arrive at this number.

.. I'm not sure we have determined it yet because my AHI is still high-ish. But I'm willing to set to the level we (i.e. my trusted apnea board experts) and my Doc PA all agree is pretty close and see if the AHI outliers go away.

So bottom line question: is the constant pressure the way to go (if it can be determined) or is auto pressure preferable while accepting that incidents are required to arrive at the optimum pressure each night to make them go away?

Any thoughts?

Saldus Miegas

[PaytonA]

In my opinion, the answer to your question depends a lot on the patient's situation. If the person can comfortably sustain the constant pressure, especially if it is on the high side, then I think that the constant pressure may give one more protection from the odd event sneaking through. It may also be more comfortable for people who are very sensitive to changes in pressure.

Auto units are probably more beneficial for patients who have to deal with aerophagia or pressure induced central apneas. One can use a lower average pressure and still have the PAP respond to events and/or precursors to keep the events in check. There are probably some other pressure induced problems that I have not thought of that might make it more beneficial to use auto CPAP.

Just my thoughts.

Best Regards,

PaytonA

[big_dave]

It sounds like you're on the right track. I believe some people do best on fixed pressure, but others (like myself) do best using auto mode. The only way to find out is by trying both and seeing which works best.

[under pressure]

We don't sleep exactly the same night after night, so why use the same pressure every night?

The Auto if set properly can use a range to handle varying conditions such as weight changes, different sleep positions, varying alcohol intake, different stuffiness with seasonal allergies, other seasonal changes due to temp............there are all kinds of variables in our lives that make us sleep differently every night, an auto machine set with the proper range can handle many of these variables to give you an optimum therapy that a fixed pressure can't address.

[Mark Douglas]

We don't sleep exactly the same night after night, so why use the same pressure every night?

The Auto if set properly can use a range to handle varying conditions such as weight changes, different sleep positions, varying alcohol intake, different stuffiness with seasonal allergies, other seasonal changes due to temp............there are all kinds of variables in our lives that make us sleep differently every night, an auto machine set with the proper range can handle many of these variables to give you an optimum therapy that a fixed pressure can't address.

I quite agree.
While everyone is different I think it safe to say no one is absolutely the same day after day or even perhaps hour to hour. I am thinking about trying a fixed setting just so I can say I did however I am becoming consistent @ AHI of below 1 so I think I will wait until I can afford a pulse-oximeter before messing too much with P settings in the hunt for the illusive AHI of -1 :grin:
In view of glaucoma as a potential side effect of cpap therapy I would think maintaining as low a pressures as works for any one individual a worthy goal.

[zonk]

This debate is never ending
The doctor is pulling the wool over the eyes

[Mosquitobait]

So I asked if they always prefer constant and he said yes it helps eliminate incidents if you remain constant at the therapeutic level.

This is a doctor in a mindset. He's going to use the same hammer for everybody whether they like it or not probably because most of his patients don't question it. In my own case, the goal apparently was to maximize oxygen while minimizing events. In the mean time, I had bought a used machine and brought in my SD card. During titration, the oxygen levels at 8, 9, 10 and 11 were the same. My AHI was much lower (under 1) with my auto settings of 6-12 and no ramp. So, she set it to a range of 8-12. I found I had to add the minimum pressure of 6 and ramp up to 8 over 20 minutes. Going straight to 8 was making me almost dizzy.

Do you have heart problems? Do you have blood pressure issues? These are the two where it MAY be in your best interests to have a set pressure. One member indicated that a set pressure would reduce the changes in blood pressure she would experience during sleep. I would guess that this would come from her sleep study, but they didn't do blood pressure during my sleep study. How would you know if the blood pressure is changing? These are things to ponder. Some people simply feel better at a set pressure.

[3porpoise]

Hi SaldusMiegas,
Have you tried a couple nights side sleeping and a couple nights back sleeping to see what the difference is in AHIs and pressures required for each position?
Take Care,
3

[PollCat]

Having slept for the majority of years on a cpap at a constant pressure, I discovered that I slept much better on auto. I suspect that the only way to determine which is best for you is to try both ways.

[SaldusMiegas]

Thanks to everyone for your thoughts on this. I appreciate the perspectives I hadn't thought about.

The difference between sweet side sleeping and fitful back sleeping is one I can relate to since my AHI in the sleep study varied by sleeping position and it is probably a factor in events over the course of a night on any nights where I spend any time sleeping on my back.

The other medical factors don't directly apply to me (except BP which as you noted we don't normally measure while sleeping) but it's good to know there are other considerations beyond my little fish bowl that our docs have training and get the big bucks to think about.

Based on all the feedback I will go for a week or so with the recommended constant pressure of 14 and see how it compares with the previous couple of weeks of 10-14 auto. If it feels better and drives down the AHI then it stays, else I know why I am rejecting it. Either way is a win.

Gosh it sounds funny to myself to be discussing whether and how I will follow my doc's recommendations in this way. But on the other hand I have the live data to work with and the thoughtful advice from people with a lot of experience successfully treating sleep apnea to augment the one-time every few months consult with a doc who has a ten minute window to review, decide, and discuss it with me. So I'm not dismissing my doc but using you all as an additional resource who have a lot of ground truth to offer.

thanks again to all.

Saldus Miegas