Central Apnea question

[vsheline]

Actually, I think ResMed's Forced Oscillation Technique (FOT) is quite accurate, unless unintentional leak is too high (more than 24 Liters per minute) or is varying quickly.

24L is the amount of leaks that can happen before the therapy is negatively impacted, meaning when it starts to affect CM h2o pressure.

Understood. I was just being more conservative than the author of the ResMed white paper. The ResMed white paper says the algorithm to distinguish between Central versus Obstructive apnea is accurate up to about 30 L/minute unintentional Leak, but I am not sure how much attention ResMed paid to the case that Leak may be varying quickly.

Apneas occurring while unintentional Leak is greater than 30 L/minute are classified by ResMed as Unknown type rather than Central or Obstructive.

I upped my pressure from 8 to 10 just to see what would happen, lo and behold all my CA events in sleepyhead turned to Hypopneas and it was more in line with my sleep study data.

I think the results of your testing pressures of 8 and 10 may show that if obstructive apneas are not eliminated by an adequate treatment pressure, the Central Apnea Detection algorithm may mistake obstructive apneas as being central apneas if the airway is still partly open.

So it is especially important to use an adequately high Pressure setting to properly treat obstructive apneas when using fixed-pressure CPAP mode compared to APAP mode. In APAP mode, Flow Limitation and Snore will likely cause the pressure to be raised and eliminate obstructive apneas which occur when the airway is still slightly open, but in CPAP mode it appears that these may be misreported as Central Apneas.

In your test, changing your pressure from 8 to 10 seemed to convert apneas into hypopneas. Increasing the pressure will not convert true central apneas into hypopneas. Only obstructive apneas will be converted to hypopneas by increasing the pressure.

At a pressure of 8 there was Flow occurring during these apneas but the Flow must have been only 10% or less, compared to the average Flow during the most recent 3 minute period. A 90% or greater reduction in Flow is ResMed's definition of an apnea. At a pressure of 8, it appears that obstructive apneas were occurring when the airway was not yet completely closed off, and because the airway was still (partly) open, these apneas were scored as clear airway apneas.

I suggest that 8 (and perhaps 10 also) may be too low of a pressure to completely treat your obstructive apneas and hypopneas.

My Doctor said it's best not to worry about the "type" of event because the Cpap machine can just guess with an algorithm.

So, counting all events (including clear airway events), I suppose your AHI was low enough at a Pressure of 8 that your doctor decided to keep the pressure at 8.

Were there problems which occurred at 10 which made you lower the pressure back to 8 instead of consulting your doctor and raising the pressure higher to eliminate the hypopneas?

You may want to consult your doctor again about this.

Take care,
--- Vaughn

[SnuffySleeper]

I just got done my second sleep study, which I think will result in my pressure increasing by a large amount, or he is going to put me on apap. So yeah, 8 might not be doing it for me even though my ahi is a daily 1.8 to 2.0.

I just went back down to 8 as I didn't want to explain to my doctor on the follow up visit why I didn't follow his prescription, as he checks my sd card each visit...lol

My doctor is more hands on, and wants to see me every 6 months which is not the norm from reading other people's experiences.

[zonk]

Both S9 Autoset and S9 Elite detect CSA but enhanced algorithm is only available in the S9 AutoSet
The enhanced Autoset algorithm clever little thing, knows when to raise pressure in response to snoring and flow limitation (FL) which are sign of air airway collapse (not open airway). By doing that, pressure stay low as possible to deal with FL and not raising pressure unnecessary to induce CSA ... one action solved two problems like the two birds in one stone story

Edit: S9 Autoset enhanced algorithm is not available in S9 Escape Auto and previous autoset devices such as S8 Autoset
Great leap forward in the treatment of OSA

[vsheline]

My doctor is more hands on, and wants to see me every 6 months which is not the norm from reading other people's experiences.

Sounds like a good doctor.

Hit him up for an APAP prescription. ;-)

[zonk]

My doctor is more hands on, and wants to see me every 6 months which is not the norm from reading other people's experiences.

Sounds like a good doctor.

Hit him up for an APAP prescription.

I,m intrigued, what hands on doctor suppose to do more than checking the numbers on the report card?

[SnuffySleeper]

My doctor is more hands on, and wants to see me every 6 months which is not the norm from reading other people's experiences.

Sounds like a good doctor.

Hit him up for an APAP prescription.

I,m intrigued, what hands on doctor suppose to do more than checking the numbers on the report card?

He's an ENT as well. But this will only be my 4th month on cpap so I'll let you know, what the visits are like after 6 months.

I suspect he'll just want to know how things are going and give me another survey to file out. I don't mind at all, he gives me free nasonex samples every time I come in, so that's worth the trip alone

I am definitely going to try and get an apap prescription, but doctors in Ontario don't prescribe them easily.

[Sleepster]

No the sleepyhead data was from my s9 at home, and we compared it with my sleep study data.

Oh, so what happened is that you had hypopneas during your sleep study and CA events with your S9 on different nights.

CPAP machines measure flow rate (in liters per minute, say) and pressure (in cm H2O). They can do some pretty amazing things with those two measurements, like sending pressure pulses to determine if your airway is open or closed, but they cannot do most of the stuff that's done with the measurements taken during a sleep study.

[SnuffySleeper]

No the sleepyhead data was from my s9 at home, and we compared it with my sleep study data.

Oh, so what happened is that you had hypopneas during your sleep study and CA events with your S9 on different nights.

Well, pretty much my S9/Sleepyhead was reporting all CA events and nothing else. Which got me worried. 1st Sleep Study reported almost all hypopneas that my Doctor gave to me, so I wanted to figure out why. I think vsheline is close that my Hyponeas aren't being treated totally with the low pressure and reporting them as CA events.

My second sleep study will confirm this, I'll know for sure wednesday when I go in for my follow up appointment.

[Sleepster]

Well, pretty much my S9/Sleepyhead was reporting all CA events and nothing else. Which got me worried. 1st Sleep Study reported almost all hypopneas that my Doctor gave to me, so I wanted to figure out why.

Almost all hyponeas while the CPAP machine was connected, correct? At that time it's likely the tech was adjusting the pressure, so he may have had it too low. Plus, that would have been your first night on CPAP and your body will react differently than it will once you spend a few nights with it and get adapted. I had a AHI of 15 my first night at home, but within 3 nights it was down below 5 and it stayed there.

I think vsheline is close that my Hyponeas aren't being treated totally with the low pressure and reporting them as CA events.

You have the S9 Elite, not the S9 Autoset. Your machine doesn't respond to events. It just applies a steady pressure of 8 cm.

My second sleep study will confirm this, I'll know for sure wednesday when I go in for my follow up appointment.

Why are you having a second sleep study?

[SnuffySleeper]

No, the hypopneas were from the first sleep study that got me diagnosed with OSA. So no cpap. The CA events were after 2 months (mainly CA events for 2 months straight) after being on Cpap that I showed to my doctor on my thrid doctor visit. After THAT visit he booked my second sleep study to adjust the pressure WITH cpap and am about to go to the follow up visit to get the results from the second sleep study.

The CA's being reported by the S9 are actually hypopneas that the theory is the pressure is too low and not treating them fully so the s9 is reporting them as CA events.

The Autoset and Elite both detect CA events and report them. You are thinking of the algorithm that responds to CA events and increases the pressure, which the elite would not have because it doesn't adjust the pressure. Doesn't matter though as I was always talking about the algorithm that reports CA's not the one that adjusts the pressure.