Fixed v variable pressure

pratzert wrote: ↑

Wed Aug 18, 2021 11:39 am

He explained exactly what you said.... it takes time for the machine to adjust and therefore, may miss handling events as needed, due to the lagging response time.

Yeah, well....auto mode can still work well as long as someone sets the minimum optimally or close enough to where the machine might want to go.
It won't work so great to have the minimum set to 4 and someone needs 16 to hold the airway open...but set the minimum to 10 or 12 then it is close enough to adjust quickly enough in most situations.
What they can't do (and people seem to expect auto mode to do) is quickly increase the pressure to blow past the collapse of the tissues and they can't do that during the actual apnea event. If someone is using fixed mode and the airway collapses...that collapse is going to happen then as well because fixed mode can't try to prevent the next collapse.

Pros and cons to both...and either can work well as long as people understand how they work and the limitations and don't go expecting the machine to do something it can't do. Both modes can work well when optimally set. Just a matter of figuring out optimal settings. Isn't all that difficult. Just have to understand how and why the machine works...either mode.

pratzert wrote: ↑

Wed Aug 18, 2021 11:39 am

He explained exactly what you said.... it takes time for the machine to adjust and therefore, may miss handling events as needed, due to the lagging response time.

Ultimately, he made me understand whyy he wanted my machine adjusted to a set pressure.

I would only switch to the auto setting if I wanted to self-titrate.

Here's the problem with that (for many people).

Say you (like Pugsy) need about 7 or 8 for most of the night, but when you're in REM you need 16.

You can run the machine in straight mode, at 16, to try and catch everything, or you can run it in auto with a min of 8, and let it raise pressure for the relatively small amount of the night when you need 16.

She'd much rather have the lower pressure for most of the night, since 16 is somewhat less pleasant than 8.

My philosophy is to set the minimum high enough to prevent *most* of the events outright, and then let the auto mode handle the exceptions. (which is basically what Pugsy said).

Hi Palerider and Pugsy.

Yes, I agree that "if" you set machine to APAP mode, it should be set at your known minimum, ( or close to it) pressure so it doesn't have so far to reach higher pressure if needed.

I wouldn't set it at the minimum machine setting, unless self-titrating just to see how low the required pressure may be most of the night.

It's something you can always play with to try to hone in on the sweet spot.

I don't know what the insurance companies do now-a-days, but weren't they big on sending a patient home with an APAP machine to get them titrated instead of paying for a full blown sleep study at a center?

I wonder what setting they used on those machines?

pratzert wrote: ↑

Wed Aug 18, 2021 1:05 pm

I don't know what the insurance companies do now-a-days, but weren't they big on sending a patient home with an APAP machine to get them titrated instead of paying for a full blown sleep study at a center?

I wonder what setting they used on those machines?

They are even bigger on it now...using apaps...usually start with factory default settings and adjust minimum as needed depending on the results.
Heck...for some people something at or close to the factory defaults works out great.
If I didn't have REM muddying up things I wouldn't be surprised if the factory defaults would work well for me.

I can tell you this though...I am NOT ever going to use fixed pressure high enough to deal with my REM events.
To me it is just plain stupid...and horribly uncomfortable...to use 16 all night long to deal with events that only happen in REM and on a good night I am lucky to maybe get 20% of the night in REM. Given how poor my sleep quality (pain issues) is...I doubt I get all that much REM anyway. Not everyone sees such a big difference like I do though and those people probably do well with fixed pressures. Some people never need any real pressure change.

Just another one of the many things regarding cpap and sleep apnea that has a big YMMV sticker on it.
The only absolute...."there are no absolutes".

Re-enforcing what palerider and Pugsy said.

I like to keep my minimum pressure sufficiently high to address most of my apneas and so it doesn't have too far to go when I'm in REM sleep, where my Apnea is at its worse.

The following Graph demonstrates this exactly.

You can clearly see a pattern consistent with REM by an increase in my Respiration Rate and Flow Limitations. (1:00, 3:00, 4:30, and 6:00 ). During this time my device responds as it should and prevents what is sure to be Hypopneas and Apneas.


If I were in straight CPAP what pressure should I use?

With fixed pressure, leaving it at 12.0 cm, it would not address my needs during REM sleep, or the occasional closing of the airway for reasons unknown (7:30).

Or should I set it to straight 15cm, well beyond what my needs are 80% of the night, and still occasionally needing a little more pressure.

Fixed pressure, for many people is a compromise.