Maybe dumb question about varying stats

[ZzzCatcher]

Every morning, I have a peek at the quick info my Dreamstation APAP provides - you know, the hours of sleep, AHI, 90% pressure, mask fit, periodic breathing. My question is specifically about AHI and 90% pressure.

One morning, it might show be (these numbers are for description, not exactly accurate) an AHI of 1 with 90% pressure of 13. The next day it may be an AHI of 3 with 90% pressure of 9. I'm curious why the machine "allows" that kind of variation. As in, when it's looking like my AHI will be 3, why doesn't the machine boost pressure to 13 like it did the prior night?

This question is for my relatively-noob educational purposes, so if you're familiar with Reddit's "Explain like I'm 5", I'd appreciate it.

[LSAT]

Every morning, I have a peek at the quick info my Dreamstation APAP provides - you know, the hours of sleep, AHI, 90% pressure, mask fit, periodic breathing. My question is specifically about AHI and 90% pressure.

One morning, it might show be (these numbers are for description, not exactly accurate) an AHI of 1 with 90% pressure of 13. The next day it may be an AHI of 3 with 90% pressure of 9. I'm curious why the machine "allows" that kind of variation. As in, when it's looking like my AHI will be 3, why doesn't the machine boost pressure to 13 like it did the prior night?

This question is for my relatively-noob educational purposes, so if you're familiar with Reddit's "Explain like I'm 5", I'd appreciate it.

.

pugsy is very good at explaining this, but the 90% means.."at or below". Your pressure was at, or below 9 for 90% of the time.

[Pugsy]

We don't sleep the same each night so pressure needs can vary each night and some of those apnea events the machine won't respond to anyway.
So just looking on the LCD screen doesn't give much but a general overview of the big picture.

For example....if your AHI is 3 one night but the breakdown is 2 Clear Airway/Central and 1 OA or hyponea...the machine won't increase the pressure to try to prevent ClearAirway events because you can't fix centrals with more pressure unless you are using a really special machine and unless a person has a truckload of centrals creating a problem we just ignore the centrals.

The machine in auto adjusting mode has a specific algorithm that drives the pressure based on what the machine senses and your sleep and breathing varies from night to night anyway.

The data on the LCD screen...extremely limited and you can't really deduce much from that data except in very general terms.
You can't see event category breakdown into each type of event on the LCD screen and category is really important.

You need to be using available software to really see what the machine is doing and even then sometimes we don't always understand why it does or doesn't do something.
Do you know about the available software?
https://sleep.tnet.com/equipment

Here's a thread with some examples of what can be seen.
viewtopic/t103468/Need-help-with-screen-shots.html

The 90% pressure thing...it just means AT OR BELOW for 90% of the time and it can and will vary a lot and means nothing. It's easily skewed so on a short term basis I don't put a lot of stock in it for any evaluation. Now long term...like 6 months average...yeah it can be useful.

[Pugsy]

but you cant FIX centrals
an ASV will TREAT them by continuing the respiration in/out air when the central has caused you to stop trying to breathe

ASV machine prevent centrals by breathing for you or giving you that burst of pressure when you don't breathe on your own.
So whether you call it treating or fixing...the end result is no centrals and nice well oxygenated breathing.
To me treating is fixing...I am comfortable with using the words that way.

[ZzzCatcher]

Thanks for the info, Pugsy. I've got Sleepyhead for real stats (though I don't use it super frequently), and was just curious about all the variation in the quick 'n dirty Dreamstation info. Appreciate the explanation!

[rick blaine]

Hi, Zzzcatcher,

Here's the "explain it like I'm 5" version.

These numbers are useless without you knowing what they represent.

AHI is the average number of events per hour.

Average.

You could sleep for seven hours and have seven apneas - and that would be an AHI of 1.

You could sleep seven hours and have no apneas in the first six of those hours - and then seven in the last hour. And you'd still have an AHI of 1.

Average means 'for the sake of talking about it, we go for a more general statement.' It lets you compare treatment with no treatment, for example. You can say, 'before treatment, his AHI was 35. Now it's under 4," and that would let people know the treatment is working.

But it usually doesn't help (unless you're a specialist) to drill down smaller than that.

As for pressure, the 90 pc pressure is the pressure the machine was at - or below - for 90 per cent of the time.

If your sleep session was only 100 minutes, and the 90 pc pressure was 14, that means that for 90 of those minutes, the pressure was at 14, or less than 14.

Those 90 minutes could have been: 10 minutes at 14 cm, 10 minutes at 12, 60 minutes at 10 cm, and 10 minutes at 8 cm.

AND it doesn't necessarily mean that during those 10 minutes when it was above 14, then that was when the opening of blockages occurred. That was when the heavy lifting was done.

Some of the clearing might have taken place at 12 or 10 (cm).

The thing to remember is: the machine's SD card and its memory only record the throat closures it didn't manage to shift.

So all the times it succeeded in keeping your airway open - at whatever pressure - they don't show up in the charts.

Saying 'the 90 pc pressure was ... ' is a way of summarizing, knowing that with an auto-adjusting machine, the pressure will vary.

There isn't the kind of direct comparison you may be thinking of. Ie, the 90 pc pressure is less so therefore the AHI should be less.

People aren't like that. (Well, most people aren't.) Your sleep pattern can and will vary from night to night - within broad parameters.

But it's not like you're buying lengths of lumber or boxes of eggs.

And as for "when [it's] looking like my AHI will be 3, why doesn't the machine boost pressure to 13"? - the machine doesn't work like that.

The machine's algorithms look at a moving four-minute window, and they decide what to do on the basis of that. The pressure-changing algorithms don't look back over the last few hours - or even remember what happened last night.

The machine deals with what it 'sees' in those four minutes and - following the rules built into the machine's micro-chips - it adjusts.

And btw, it adjusts in small steps. In my machine, +1.5 cm at a time. Then it waits to see what that increase does. If it helps, fine. If it doesn't help, then up another 1.5 cm. Then see what that does ...

If you think about it, that is what you want. You don't want it going full tilt and jumping +5 cm all in one go, do you?

Will that do as a first try?

[ZzzCatcher]

Also super helpful! Thank you!

[LibtardsUnite!]

but you cant FIX centrals
an ASV will TREAT them by continuing the respiration in/out air when the central has caused you to stop trying to breathe

ASV machine prevent centrals by breathing for you or giving you that burst of pressure when you don't breathe on your own.
So whether you call it treating or fixing...the end result is no centrals and nice well oxygenated breathing.
To me treating is fixing...I am comfortable with using the words that way.

=======

nonsense

ASV does NOT PREVENT CENTRALS

it TREATS them by continuing the air flow when you stop breathing

there is no evidence that a burst of pressure will start your breathing during a central event

there ARE CENTRALS but they are TREATED so they dont cause problems

you can use words incorrectly if you wish
but that doesnt make them right

The posts on this thread by xxyzx are a perfect example of why we say IGNORE INFORMATION BY XXYZX, IT'S USUALLY WRONG AN D COULD BE DANGEROUS!!!

[palerider]

The next day it may be an AHI of 3 with 90% pressure of 9. I'm curious why the machine "allows" that kind of variation. As in, when it's looking like my AHI will be 3, why doesn't the machine boost pressure to 13 like it did the prior night?

This question is for my relatively-noob educational purposes, so if you're familiar with Reddit's "Explain like I'm 5", I'd appreciate it.

The machine can only do the best it can to accommodate the biggest variable in the equation...

YOU

While people like to think that things are all even and well defined in sleep, they're not, sleep varies a lot, depending on a whole host of circumstances...

[TASmart]

And you accuse me of picking at nits. What is the difference between preventing treating? There is no claim that ASV prevents/treats the cause of central/mixed apneas, only that it prevents or treats them from negative health impacts. But this is true nitpicking.