lower pressure better numbers

[sleepyhead63]

When I did my sleep study my doctor recommended my pressure set at 14, but lately I been experimenting with my set pressure and found the more I lowered my pressure the better my numbers where.I went all the down to 12.8 and finally got under 5 for ahi, so I was wondering if I went down alittle more would do better? How is it durning my sleep study my pressure was set so much higher?

[goose]

I don't have a direct answer to your question -- but here was my experience.

I titrated at 5cm......can't breathe at 5, so set to 7 which was ok (barely), but AHI wouldn't go below 11.....

Set machine to 10 based on my sleep test and titration test reports and summaries (basically an educated guess). AHI 2.8 average from July to October.

Getting greedy and trying to lower my numbers a bit, I set it at 11...AHI 3.8

Then I set in APAP mode with a range 9-11 and my average pressure was 9.9 (pretty close to 10 ). It also showed in the details that my AHI was always better at 10 than it was at 11......

So yes, a lower pressure number can cause a better AHI!!!

Hope this makes sense and helps a bit....
cheers
goose

[Guest]

I had my APAP set to 12 max. From software, I noted that occasionally an apnea happened at 12. Moved the max setting to 13. After a week, HI's had increased with higher setting. Apnea incidents were about the same so I lowered it back down to a high of 12.

So, yes, higher can produce hypopneas.

[ozij]

Sleepyhead,
Are you using the machine in its automatic mode, or in CPAP mode?

If it's in cpap mode, then the answer is yes - with the pressure too high for our needs, some of us respond with what is called "pressure induce central apneas" - we stop breathing because our brain reacts with "this much pressure in the lungs means there's no need to draw a breath" and then is jolted into action by a drop in oxygen - a drop which would not have happened if the brain wasn't confused by that extra pressure. Lowering the pressure solves this problem.

If its in auto mode, that may still be true, but you may be experiencing the benefit of a narrower range. Some of us have hypopneas in response to the pressure changes, so it wouldn't be too much pressure, but too many changes giving you bad results. Solving this problem means checking carefully where on the scale you do best.

If you're in auto mode, what is the bottom of you range now?

O.

[DreamStalker]

Could be several reasons.

Could be you are having central apnea at higher pressure.

Could be that you are having fewer leaks at lower pressure.

Could be changes in sleep position or medications or even diet.

[sleepyhead63]

I am using it in cpap mode. What exactly is central apneas? How come my doctor did not pick up on me possibly having central apneas?

[ozij]

A "central apenea" is an apnea (breathing stop) caused by your central nervous system, and not by an obstruction. We use it as shorthand for those situtations where your airway is open, but you're not breathing. Too much pressure can cause that.

As DreamDtalker said, it could be those other things as well.

If they are pressure induced apneas, they may simply not have appeared in the sleep study - that is if you're using the machine as they set it up for you.

A Resmed machine on automatic mode will never raise the pressure above 10 when it encounters an apnea, and that is its way of avoiding pressure induced apneas. It will raise the pressure if it encounters snores and flow limitations.

Respironics and PB have different ways - each its own - to handle this possibility, and they do raise the pressure above 10 in a auto mode.

http://www.talkaboutsleep.com/sleep-dis ... chat.htm#6

6. Why does AutoSet Spirit (and AutoSet T™) have the A10 algorithm?

ResMedSimon answers: The A10 algorithm increases pressure in response to Flow Limitation, Snore, and Apnea up to 10cm H2O. Above 10cm H2O, pressure response to Flow Limitation and Snore continues, but there is no response to Apnea. AutoSet Spirit and AutoSet T do not differentiate between obstructive and central apneas. Increasing pressures above 10cm H2O in response to apnea can lead to "runaway" central apneas.

Yes, you may do better when you go further down - the only way to know that it to try - do it slowly and carefully.

You may also want to try a automatic setup with the bottom at 10 - that way the machine will raise your pressure as needed for snores and flow limitations (which are considered apnea precursors) but won't keep you on an atificial hight and won't raise the pressure for apneas.

O.

[socknitster]

I doubt you were having centrals at the higher pressure, those are usually reserved for pretty high pressures (above 15, I am guessing.)

I think everyone's pressure needa are like a bell curve. You optimize your therapy when you find the pressure that is the top of the curve. They are supposed to do that at the sleep study, but we all know that sleep study conditions are less than ideal. If you go down the curve on either direction, either higher or lower pressure, you are going to find more events happening.

I got to experience finding this out for myself twice. First when I was diagnosed last June and the second time after my tonsilectomy when my pressure needs decreased dramatically. I did it all on my own, with my bipap auto, no psg necessary.

If you don't have an auto, you can try changing the pressure once a week by a cm or half cm in either direction, keeping good charts to record pressure vs. ahi. That is what I would do.

Never use only one night of data. Use at least three days or a week is even better.

And use sense, of course. But you can't hurt yourself and you have already discovered you are doing better at your own prescribed pressure.

There have been studies done where a patient found their own perfect pressure by experimentation and how they felt alone--no data. And they were successful. You can do it one better.

Jen

[sleepyhead63]

Thank you all for your input, I think I will try auto mode tonight and set the bottom to 10 like ozij recommended and see how it works.

One thing about my sleep study, it was a disaster the first half they tested me then about 4:00 am they woke me up and hooked me up to cpap. the mask was ancient, and a full face mask which even today I can't find one that works. I remember having the mask on for about an hour and could not take it anymore and told the tech I was going home. He told me I had to stay longer to complete the study but I told him I am done,going home. My sleep study was only 6 hours and I think I actually slept half of that.

[billbolton]

I doubt you were having centrals at the higher pressure, those are usually reserved for pretty high pressures (above 15, I am guessing.)

Some users can start experiencing central apneas when the flow rate gets even only slightly above their optimal rate, whatever that is (low or high), so central apneas are by no means limited to higher flow rates.

I think everyone's pressure needa are like a bell curve.

Some users needs are, some aren't. It depends on the specifics of the underlying root cause of the SDB presentation for each user.

But you can't hurt yourself

As a generalisation that's mostly correct, but for some users it may not be.

Again it depends on the specific underlying root cause of the SDB presentation. For some users even a small change in pressure can have significant unintended impacts, while for others large changes have little impact.

Cheers,

Bill

[track]

Some of us have hypopneas in response to the pressure changes

I wonder why that would be. Why would a higher pressure cause more hypos or is there such a thing as a "central hypoapnea".

[ozij]

A change in pressure means either up, or down.

O.

[track]

"A change in pressure means either up, or down."

I know. No question that a lower pressure can increase hypos but why can a higher pressure increase hypos too?

[ozij]

Its a reaction to the change, not the pressure as such. My guess is that its a kind of startle reflex - your body (lungs, brain) senses the change and breathes shallowly till it figures what's going on.

O.

[track]

Interesting...I didn't know that. I have found that taking the pressure up does not always lower the Hypos...even if it's in cpap mode. There seems to be a sweet spot and anything above or below that point can be higher.