Why not just crank it to max?

[max6166]

I am sure this is not a good idea, and am just asking this question in order to better understand OSA.

What are the reasons for using a conservative pressure setting, versus setting it significantly higher than the minimal setting required to prevent apneas?

In other words, my script calls for 8, but why not just set my pressure to 12, or even 16, and leave a lot of headroom?

The main reasons I can think of are compliance and comfort, since the higher pressures are less comfortable, but I am sure there are others.

Again, I am not advocating people do this. I only ask out of curiousity.

- Max

[leonardlake]

I use both Encore Pro and Encore Pro Analyzer to graph my AHI vs pressure. I find a minimum value for AI (.02) at a pressure of 8 and a minimum value of HI (.06) at 9.5. The minimum value for AHI ( .08 ) is at 9. For pressures above 11 my AI climbs steeply (7.00 at a pressure of 12). So I have set my auto pressure range from 8.5 to 10.5.

I am not sure what causes the large number of apneas at pressures greater than 11 but I have attributed it to an increase in centrals due to too high a pressure.

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CPAPopedia Keywords Contained In This Post (Click For Definition): Encore Pro, AHI, auto

[Snoredog]

leads to unstable sleep which eventually wakes you up. If you are going to be awake, why use the machine?

[kteague]

Max,

Those who use autotitrating machines do generally keep their maximum pressure a little above the their titrated pressure in order to meet any possible changing needs. A fixed pressure at a much higher rate is another story. That's untested territory so you don't know how your body might react. Yep, it could possibly prevent any obstructions, that is if the air didn't blow out leaks in the mask, out the mouth, or into the stomach - or cause centrals. More is not always better. Some on here have reported better data when they turned their pressure down. Ideally one using a fixed pressure machine could have data so they could know that their pressure is therapeutic.

You're right - comfort and compliance are factors to consider. It has crossed my mind to experiment and set the pressure high to to see what others experience then decided - nah, I'll accept their description and be glad for my 12.

[Guest]

Cause it doesn't work as well. I've done that. Cranked it way up. AHI all over the place. Woke up with a headache. Mask leaked. Bleh....

I thought maybe it was me, but when I reported in, the consensus was that there IS a perfect medium - and when you find that, you should stick to it. Not the highest setting, not the lowest setting. The setting that suits you perfectly - low AHI, comfortable restful sleep, waking refreshed, etc. etc.

Cheers,
B.

[lvwildcat]

Pressures that are set too high can actually cause central apneas.

[max6166]

Thanks for all the replies. I figured the situation was likely much more complicated than I had understood...

I can certainly see that leaks, discomfort, etc., would make a higher pressure undesirable, but I do find it strange that a higher pressure could lead to an increased AHI.

I don't really understand central apneas, but I would have thought it impossible for a higher pressure to increase the number of obstructive apneas. I do believe that this can happen; I just don't understand how.

I'll admit that I have been blindly fiddling around with my own pressure quite a bit, mainly out of desperation. I just have a basic M-series CPAP, fixed pressure, no auto, no card, etc. with a ComfortGel. My pressure is supposed to be 8.

CPAP therapy worked fantastically at first, then after about 2 months, I began to feel worse again. I started mouth-taping in case that was the problem. I also tried increasing my pressure to 9 and 10. I tried 12 and 13 briefly just to see what would happen.

For me, at least, there seems to be hardly any difference, no matter what I do. My sleep quality feels about exactly the same regardless of pressure, and I am just as tired in the morning.

My sleep is definitely better than it was before CPAP, but not nearly as good as it was when I first started therapy.

Anyway, that is what got me thinking that there must be more to it than "blowing open" the obstruction, since higher pressures weren't really making any difference.

Thanks,
Max

[Bearded_One]

Very technical description of the effects of CPAP at

http://nicuvet.com/nicuvet/Equine-Perin ... es%202.htm

Sample:

"CARDIOVASCULAR STABILITY: High CPAP can have a detrimental effect on the cardiovascular system, compressing right sided vessels, decreasing cardiac return which will result in decreased cardiac output. This may result in acidosis, tachycardia, decreased arterial blood pressure, etc. The amount of CPAP that is excessive and will produce this affect depends on the lung compliance. If the lung compliance is low, less intra-airway pressure will be transmitted to the plural space and cardiac compromise will be less. Hypovolemia will exacerbate the negative effect of high CPAP. Excessive CPAP may be detected by the development of acidosis, decreased dynamic lung compliance and increased CO2 retention. A trial of lower CPAP or increased IV fluids will resolved the problem, however it should be recalled that too low a CPAP will also cause acidosis."

[-SWS]

Very technical description of the effects of CPAP at

http://nicuvet.com/nicuvet/Equine-Perin ... es%202.htm

Sample:

"CARDIOVASCULAR STABILITY: High CPAP can have a detrimental effect on the cardiovascular system, compressing right sided vessels, decreasing cardiac return which will result in decreased cardiac output. This may result in acidosis, tachycardia, decreased arterial blood pressure, etc. The amount of CPAP that is excessive and will produce this affect depends on the lung compliance. If the lung compliance is low, less intra-airway pressure will be transmitted to the plural space and cardiac compromise will be less. Hypovolemia will exacerbate the negative effect of high CPAP. Excessive CPAP may be detected by the development of acidosis, decreased dynamic lung compliance and increased CO2 retention. A trial of lower CPAP or increased IV fluids will resolved the problem, however it should be recalled that too low a CPAP will also cause acidosis."

Bearded One, thanks for that interesting link!

I noticed that article was written by a veterinarian regarding the application of CPAP on foals. The respiratory concepts are clearly relevant to this thread. However I didn't realize that vets used CPAP on foals until I read that article.

And of course, I find myself wondering if horses complain about their DME suppliers nearly as often as we do...

[zorrro13]

[quote="max6166"]

My sleep is definitely better than it was before CPAP, but not nearly as good as it was when I first started therapy.

Anyway, that is what got me thinking that there must be more to it than "blowing open" the obstruction, since higher pressures weren't really making any difference.

Thanks,
Max