Accuracy of CPAP AHI Readings

MMcG · Post by **MMcG** » Sun Sep 26, 2021 8:20 am

Hi,

I just started using a Devilbiss CPAP machine a couple of weeks ago. It has a "Smart Flex" function which reduces the pressure on exhalation. I started using this function a few days ago and I've noticed since that my AHI count has gone up to 6 from about 2.5 previously. Also my puff exhalation (% time) has doubled from 15 to 30. I wonder whether using Smart Flex has caused this although it sounds counter-intuitive for puff exhalation. Another related question. I'm wondering if the machine underestimates my AHI figure, because while I may wear the mask for six hours or more, I've only been getting about four hours sleep, as I wake frequently. Maybe the machine figures this out and divides the total number of episodes by the time asleep as opposed to time wearing the mask, but I just don't know. Any feedback would be greatly appreciated. Thanks in advance, Mike.

Pugsy · Post by **Pugsy** » Sun Sep 26, 2021 8:26 am

These machines don't have any way to know if we are asleep or not. They only measure air flow/breathing.
You are getting an AHI based on machine/mask use and it doesn't matter if asleep or awake.

MMcG · Post by **MMcG** » Sun Sep 26, 2021 8:54 am

Pugsy wrote: ↑
Sun Sep 26, 2021 8:26 am
These machines don't have any way to know if we are asleep or not. They only measure air flow/breathing.
You are getting an AHI based on machine/mask use and it doesn't matter if asleep or awake.

That's what I suspected. Then that means my true AHI using the CPAP machine is probably much higher, at least 50% more. My sleep lab test recorded 22.6 but my mean apnea duration was nearly 30 seconds, so not breathing for about ten minutes of every hour asleep! I keep waking every 90 minutes or so with the dry mouth and choking sensation I used to wake with in the mornings before being diagnosed. So I know I'm still getting apnea episodes but the CPAP machine keeps waking me up and then it takes ages to get back to sleep. It's a real struggle.

Pugsy · Post by **Pugsy** » Sun Sep 26, 2021 9:04 am

MMcG wrote: ↑
Sun Sep 26, 2021 8:54 am
the CPAP machine keeps waking me up and then it takes ages to get back to sleep.

Maybe it's the apneas the machine is trying to kill that are waking you up that are the real reason for the wake ups.

What are your settings? All of them?????

MMcG · Post by **MMcG** » Sun Sep 26, 2021 10:03 am

Pugsy wrote: ↑
Sun Sep 26, 2021 9:04 am

MMcG wrote: ↑
Sun Sep 26, 2021 8:54 am
the CPAP machine keeps waking me up and then it takes ages to get back to sleep.
Maybe it's the apneas the machine is trying to kill that are waking you up that are the real reason for the wake ups.

What are your settings? All of them?????

My pressure us set to auto pressure 5-12 by my consultant I I can't change that, but it will be reviewed fortnightly. I can adjust the ramp (starts at pressure setting 4) and smart flex settings myself. For the last few nights, I've set the ramp to 30 minutes. And the Smart Flex is set to always on (max level 3) with full "rounding" of 5 on both inhale and exhale). From the limited read-out data I can access via a smartphone app (very poor app), my 95% pressure is usually 9 or less.

Pugsy · Post by **Pugsy** » Sun Sep 26, 2021 10:13 am

MMcG wrote: ↑
Sun Sep 26, 2021 10:03 am
My pressure us set to auto pressure 5-12 by my consultant I I can't change that,

Well actually you can change it if you had a mind to.
It's easy.
https://www.apneaboard.com/adjust-cpap- ... tup-manual
Though please understand I am not advising changing anything because I really have zero data to evaluate beyond AHI numbers.

You are using a range of pressures and going by the smart code for results.
What you are lacking is the detailed data like what was the pressure when you had the flagged apnea events.

Exactly which model machine are you using?

Pugsy · Post by **Pugsy** » Sun Sep 26, 2021 10:15 am

would someone else please explain full data and why limited data (numbers alone) really don't help us much...along with SWJ flagged stuff affecting numbers.

I just can't do it today....hand not doing so great.

chunkyfrog · Post by **chunkyfrog** » Sun Sep 26, 2021 10:58 am

(Virtual kisses to Pugsy's ouchie)

Miss Emerita · Post by **Miss Emerita** » Sun Sep 26, 2021 11:57 am

Is your machine any of these:

DV54 Auto
DV64 CPAP
DV64 Auto.

If yes, then it is partially supported by the Oscar software (see link below). The software might allow you to see information that could be helpful in adjusting your settings.

It is possible -- though we don't know -- that your higher AHI is largely due to central apneas. These are cessations of breathing of 10 seconds of more that do not involve any obstruction in the airway. It is not uncommon to see these after the heavier breathing involved in a brief arousal. This is sometimes called sleep-wake junk.) Or sometimes you'll have some centrals during an extended period of straight-up wakefulness. (Awake breathing is much less regular than normal breathing during sleep.)

For some people, centrals also can show up with the introduction of pressure relief (like your flex). The boost to pressure as you inhale can tend to wash out enough CO2 to reduce your "breathe now" reflexes. (The same mechanism is sometimes involved in SWJ; heavier arousal breathing can reduce CO2.) You pause your breathing, CO2 levels rise again, and you recommence breathing.

Raising pressure will not fix central apnea. In addition, if you are having centrals and they're mostly while you're awake, or they're mostly SWJ, the problem is the arousals and wakefulness, not the centrals.

On the other hand, if the increase in your AHI is due to obstructive apnea events or hypopneas, raising your minimum pressure could be quite helpful. I'm not sure how flex works with your machine, but it may be lowering your exhale pressure below your set minimum pressure. If so, then compensating for flex by raising your minimum would make sense.

But without any idea of the breakdown of your AHI, it's impossible to say what's going on. I hope you can get some more insight by using Oscar.

Are you in the UK? I ask because if you are, I'll let Rick Blaine know. He's our UK PAP expert and might be able to help you navigate the system.

MMcG · Post by **MMcG** » Sun Sep 26, 2021 12:07 pm

Pugsy wrote: ↑
Sun Sep 26, 2021 10:13 am

MMcG wrote: ↑
Sun Sep 26, 2021 10:03 am
My pressure us set to auto pressure 5-12 by my consultant I I can't change that,
Well actually you can change it if you had a mind to.
It's easy.
https://www.apneaboard.com/adjust-cpap- ... tup-manual
Though please understand I am not advising changing anything because I really have zero data to evaluate beyond AHI numbers.

You are using a range of pressures and going by the smart code for results.
What you are lacking is the detailed data like what was the pressure when you had the flagged apnea events.

Exactly which model machine are you using?

I don't think I can change it. Firstly, it is a rental arrangement and the provider has locked access to those settings. But, secondly, even if I managed to unlock and change it, I would probably be in breach of my rental agreement and the provider and my consultant would know when they download the data fortnightly. And yes, you're right, I can't get that data, but my guess from the noise that the machine makes when it wakes me is that it is at or near the max setting (12). Sounds like the best I can do is take a look over the shoulder of the technician who downloads the data next time he arrives!

MMcG · Post by **MMcG** » Sun Sep 26, 2021 12:12 pm

MMcG wrote: ↑
Sun Sep 26, 2021 12:07 pm

Pugsy wrote: ↑
Sun Sep 26, 2021 10:13 am

MMcG wrote: ↑
Sun Sep 26, 2021 10:03 am
My pressure us set to auto pressure 5-12 by my consultant I I can't change that,
Well actually you can change it if you had a mind to.
It's easy.
https://www.apneaboard.com/adjust-cpap- ... tup-manual
Though please understand I am not advising changing anything because I really have zero data to evaluate beyond AHI numbers.

You are using a range of pressures and going by the smart code for results.
What you are lacking is the detailed data like what was the pressure when you had the flagged apnea events.

Exactly which model machine are you using?
I don't think I can change it. Firstly, it is a rental arrangement and the provider has locked access to those settings. But, secondly, even if I managed to unlock and change it, I would probably be in breach of my rental agreement and the provider and my consultant would know when they download the data fortnightly. And yes, you're right, I can't get that data, but my guess from the noise that the machine makes when it wakes me is that it is at or near the max setting (12). Sounds like the best I can do is take a look over the shoulder of the technician who downloads the data next time he arrives!

My machine is a Devilbiss Blue (in the US it would be sold as an IntelliPAP AutoAdjust CPAP with SmartFlex).

Pugsy · Post by **Pugsy** » Sun Sep 26, 2021 12:59 pm

Where are you located?

MMcG · Post by **MMcG** » Sun Sep 26, 2021 2:04 pm

Miss Emerita wrote: ↑
Sun Sep 26, 2021 11:57 am
Is your machine any of these:

DV54 Auto
DV64 CPAP
DV64 Auto.

If yes, then it is partially supported by the Oscar software (see link below). The software might allow you to see information that could be helpful in adjusting your settings.

It is possible -- though we don't know -- that your higher AHI is largely due to central apneas. These are cessations of breathing of 10 seconds of more that do not involve any obstruction in the airway. It is not uncommon to see these after the heavier breathing involved in a brief arousal. This is sometimes called sleep-wake junk.) Or sometimes you'll have some centrals during an extended period of straight-up wakefulness. (Awake breathing is much less regular than normal breathing during sleep.)

For some people, centrals also can show up with the introduction of pressure relief (like your flex). The boost to pressure as you inhale can tend to wash out enough CO2 to reduce your "breathe now" reflexes. (The same mechanism is sometimes involved in SWJ; heavier arousal breathing can reduce CO2.) You pause your breathing, CO2 levels rise again, and you recommence breathing.

Raising pressure will not fix central apnea. In addition, if you are having centrals and they're mostly while you're awake, or they're mostly SWJ, the problem is the arousals and wakefulness, not the centrals.

On the other hand, if the increase in your AHI is due to obstructive apnea events or hypopneas, raising your minimum pressure could be quite helpful. I'm not sure how flex works with your machine, but it may be lowering your exhale pressure below your set minimum pressure. If so, then compensating for flex by raising your minimum would make sense.

But without any idea of the breakdown of your AHI, it's impossible to say what's going on. I hope you can get some more insight by using Oscar.

Are you in the UK? I ask because if you are, I'll let Rick Blaine know. He's our UK PAP expert and might be able to help you navigate the system.

Thanks for all the considered advice. I'm new to this so a lot of it washes over me at the moment, but I'm determined to learn. I'm in Ireland, so, yes, the same machine I have is probably marketed in the UK under a similar label. My liaison technician is a very knowledge guy, but I reckon the more I inform myself, the more I'll get from speaking to him. BTW, even though I'm in my mid-60's, I have an engineering (structural) background, and am more tech savvy than most people of my age. Being half asleep most of the time hasn't helped though!

BlueDragon · Post by **BlueDragon** » Wed Sep 29, 2021 9:05 am

MMcG wrote: ↑
Sun Sep 26, 2021 12:12 pm
My machine is a Devilbiss Blue (in the US it would be sold as an IntelliPAP AutoAdjust CPAP with SmartFlex).

While the list of OSCAR-supported machines says that the DV6x series are "partly supported," that is an exaggeration; it is certainly not supported well.

However, we are currently beta testing full support for the DV6x series. See the first thread in the forum if you would like to help beta test OSCAR for your machine.

Or, if you would like me to look at your data and post some screenshots here, make a zip of your data card and upload it to my Dropbox folder. Please include your forum name in the zip file name so we know who the file is from.

BlueDragon · Post by **BlueDragon** » Sun Oct 17, 2021 4:20 pm

OSCAR 1.3.0 is available now and includes support for the DeVilbiss BLUE machines.

Accuracy of CPAP AHI Readings

Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings

Re: Accuracy of CPAP AHI Readings