An Obstructive Apnea that's not Obstructive? [graph]

Everything that I have learned and read over the years tells me that an Obstructive Apnea is always a full closure or partial blockage of the Upper Airway. That then creates a reduce breathing amount which in turn means less oxygen is entering into your body and the blood stream (oxygen deprivation) which makes OSA patients feel bad and leads to the side effects we see.

Looking over my graphs from last night it appears I had an Obstructive Apnea that didn't have any change in the flow limitation. I've highlighted between the red lines the 10 second Obstructive Apnea, you can see where the Minute Ventilation changes but when you look at the Flow Limitation there is none. Usually at this point with an Obstructive Apnea you would expect to see the Flow Limitation spike down because there's a blockage. There was no leak at this point but the pressure did increase to compensate for what it thought was an Obstructive Apnea.



Personally I would have recorded this either as a Central Apnea or an Unknown Apnea seeing there was no restriction / blockage in my upper airway.
I thought this was quite interesting to see whether the S9 managed to interpret it wrong or whether there can be other types of Obstructive Apneas that the S9 is able to detect for.

What are your thoughts?

Hi Dave... I posted this to Katie's Thread a few minutes ago:

A possible answer...

I have been going over this and perhaps the answer lies in the definition for from the Data Management Guide: " Flow Limitation is a measure of partial upper airway obstruction. This measure is based on the shape of the inspiratory flow–time curve. A flat shape suggests upper airway obstruction." The obstruction is not measured separately - it is based totally on the shape of your Insipation of your Flow Graph.

Therefore when your inspiration flow does not show flattening... there will be no Partial Obstruction and of course when there are no Inspirations during an Apnea Event... there will be no Flow Limitation. Since it is all relative to the Flow Graph there are no measurements and presumably as we have discovered... little accuracy by measurement of obstruction. It only records the shape of your Inspiration.

If your Inspirations on your Flow Graph are consistent and in the correct shape for an obstruction then it records correctly. Perhaps we begin having Centrals and during the time that we are having a Central... the obstruction takes place in the airway and it is recorded as Obstruction during the Apnea Event...

Nord

Thanks Nord, I'll take a look over my other graphs and see if there's a common trend here.

Removed - probably not useful to the topic at hand. Sorry.

This is from my thread, which essentially asks the same question:

Nord...this is starting to make sense to me now. What you're describing is a "mixed apnea". From Sleep Apnea--the Phantom of the Night, page 63:

"We frequently see another type of breathing pause during sleep. Usually these events begin with a central apnea, yet when the patient tries to initiate breathing there is an obstruction. No airflow results because the throat is now blocked. These apneas are referred to as mixed apneas because they include elements of a central apnea and an obstruction. New information suggests that the airway narrows slightly during central apnea. In a patient with an obstructive component this could cause obstruction as breathing resumes. Usually, treatment of obstructive sleep apnea eliminates these occurrences. Only rarely do mixed events begin with an obstruction and proceed to become a central event."

Can you tell, by looking at your graphs, if this might be the case?

KatieW wrote:... Can you tell, by looking at your graphs, if this might be the case? ...

Katie and Nord, I will jump in at this point to make an couple observations.

First, I *really* appreciate the work you are doing. I truly wish my VPAP Adapt SV unit provided this level of granularity. I may upgrade my ResScan software to see if the software enables better granularity of data. However, I suspect the advance of technology is what allows this level of granularity in the data.

Second, while the graphs might show soemthing such as mixed (or as it is now called Complex Sleep Apnea), you need to remember that the information provided by the S9 is only indicative of the condition. To use an analogy. Think of this as a windsock that indicates the wind direction and strength. IF the central apneas are severe enough to need to be addressed with some xPAP therapy, the full sleep study is needed to confirm the data and titrate to the proper pressures.

Here's an article that describes how Central Sleep Apnea can result from the application of CPAP therapy:

Central Sleep Apnea on Commencement of Continuous Positive Airway Pressure in Patients With a Primary Diagnosis of Obstructive Sleep Apnea-Hypopnea
http://www.ncbi.nlm.nih.gov/pmc/article ... .5.462.pdf

It concludes:

A significant minority of patients with a primary diagnosis of OSAH have either emergence or persistence of CSA on CPAP. Risk factors include male sex, history of cardiac disease, and CSA on baseline PSG.

With this stance, I am not just sticking up for the medical community on this. This is more an issue of accuracy of the data. Though the S9 provides an amazing leap forward in the data collected, it does NOT collect informaion about the sleep state. It does not have the years of data behind it to show the accuracy of the measurements it provides. In otherwords, while it acts as a pretty darn good windsock, it is just that.

Some questions that might need to be answered include:

• Are the apneas positional?
• Do the apneas occur during REM or NREM state?
• What is the O2 desaturation during these apneas?
• How does pressure increase impact the central apneas?

And so on. Those are some of the questions any doctor would want to know before embarking on BiPAP S/T or an ASV unit to address the ComplexSA.

Oh, and don't get me wrong. You can land a plane with just a wind sock. But with somethng as difficult to manage as central sleep apnea, it is VERY important to have very accurate results.

John, I've been hoping you would jump into this discussion.

Your analogy using a windsock is very helpful. I'm just trying to understand this windsock.

It's fun to learn, and maybe it's more of a learning exercise for me right now. I got good therapy on the S8, and am getting good therapy on the S9. The numbers are just numbers, I know.

Thanks John.

JohnBFisher wrote: Katie and Nord, I will jump in at this point to make an couple observations...

...while the graphs might show soemthing such as mixed... (con't)...the full sleep study is needed to confirm the data and titrate to the proper pressures.

Here's an article...

(con't)...it does NOT collect informaion about the sleep state. It does not have the years of data behind it to show the accuracy of the measurements it provides. In otherwords, while it acts as a pretty darn good windsock, it is just that.

Some questions that might need to be answered include:

• Are the apneas positional?
• Do the apneas occur during REM or NREM state?
• What is the O2 desaturation during these apneas?
• How does pressure increase impact the central apneas?

And so on. Those are some of the questions any doctor would want to know before embarking on BiPAP S/T or an ASV unit to address the ComplexSA.

Oh, and don't get me wrong. You can land a plane with just a wind sock. But with somethng as difficult to manage as central sleep apnea, it is VERY important to have very accurate results.

Thank you John...

Yes, hopefully everyone that reads this thread will NOT take any of this info as the last word in Medical Science... at least not my info. I am a Newbie and have been on the S9 for 5 days and my only other experience with CPAP is a loaner for some 3 weeks that only provided Compliance Info. For myself, and maybe I can speak for Dave and Katie, I/we are trying to understand what info the S9 gives to us and whether or not it is relevent to our symptoms and our therapy.

Since everyone has a unique experience, there are some sharing of graph irregularities and symptom anomolies such as this - then we can learn from it together. I think the warning from the "windsock" is to give the info learned - its due value as just what it is.

The warning, I think, is: "Don't go out on any limbs and don't change your treatment (except minor things) without good evidence (M.D. or Sleep Study)" I have to wait a couple of months for my next Sleep Study. At least now I'll be able to ask better questions.

That warning needs to be remembered, I'm sure. But after that warning, although the S9 provides a very deep level of "granularity", not all the graphs are that clear about what the machine is telling us. Hopefully further investigation by all those interested will help us to get closer to understanding... perhaps not. But with many individual minds and experiences working together... some better understanding will take place.

We may not be able to "land the plane" but we'll be able to ask better questions of the "tower" (they still have windsocks)... Please forgive the drawn out analogy... I thought it was a good one.

Nord

KatieW wrote:... Your analogy using a windsock is very helpful. I'm just trying to understand this windsock.

It's fun to learn, and maybe it's more of a learning exercise for me right now. I got good therapy on the S8, and am getting good therapy on the S9. The numbers are just numbers, I know. ...

Don't get me wrong. I *really, really, really* like the work I'm seeing. As dave21 noted in another thread:

dave21 wrote:... it's great looking and reviewing over the stats and understanding better at how to be treated by the CPAP technology when in a lot of our cases, nobody reviews our data anyway ...

Amen! I'm working on a write up of my last visit with my sleep specialist. He is excited and pleased that I use this data to help improve my sleep therapy. He got very frustrated with my DME (due to an incorrectly set pressure), but accepted that I can set my pressure and then be trusted to monitor both the xPAP data and pulse oximeter data.

KatieW, I know that you, dave21 and Nord realize the efficacy data is just a windsock. I remind other readers. It's all too easy to see something here in this forum and then take it as gospel and INSIST that if the machine says it, it must be the case. That's a quick way to get a sleep specialist to tune out our complaints. But hey! Lots of planes still land just using a windsock for guidance.

As Rested Gal notes, the following study did not even use efficacy data to allow the patients to titrate their own pressure:

Can Patients with Obstructive Sleep Apnea Titrate Their Own Continuous Positive Airway Pressure?
http://ajrccm.atsjournals.org/cgi/reprint/167/5/716

It concludes:

... Self-adjustment of CPAP at home will provide equal or superior efficacy in the treatment of obstructive sleep apnea (OSA) as compared with in-laboratory titration. ... Home self-titration of CPAP is as effective as in-laboratory manual titration in the management of patients with OSA.

Just imagine how much more skewed the results would be if they were instructed to learn about their machines, use the efficacy data and use this forum to guide their decisions!

Is it possible that the machine records a central as an obstructive because it doesn't 'know' what a central is?

T

Terminator wrote:... Is it possible that the machine records a central as an obstructive because it doesn't 'know' what a central is? ...

Well, the newer units check for a clear airway and assume if the airway is clear (no obstruction), then the airway is central. If it detects an obstruction, it will mark it as an obstruction. It is possible it is actually a mixed apnea (starts as a central but ends as an obstruction). But without the chest and abdominal bands it MAY not get it right. Until the algorithm is clinically proven, I doubt doctors will trust these numbers ... and for good reason. Until any researcher can test and prove the same results, then such claims are just that claims - not fact.

But is it possible? Sure. It's just not all that likely.

But as I keep saying, think of the efficacy data as a windsock, not full instrumentation. It's good enough to help you land and keep your therapy on course, but not accurate enough to replace a sleep study.

Would an older machine like mine be more likely to record a central as an obstructive?

T

Terminator wrote:... Would an older machine like mine be more likely to record a central as an obstructive? ...

Truthfully, it just records the event as an apnea. It does not try to claim that it is obsturctive or central. Your unit does not have a way to tell the difference between the two events. From the CPAP.com website:

SmartCard: Records 9 Months usage, Date/Time, Duration at pressure, snoring and apneic events information. Download the Smart Card to your computer with additional purchase of Respironics EncoreViewer Software 1.0 & Smart Card Reader.

That's what I thought... Thanks, John!

T

KatieW wrote:This is from my thread, which essentially asks the same question:

Nord...this is starting to make sense to me now. What you're describing is a "mixed apnea". From Sleep Apnea--the Phantom of the Night, page 63:

"We frequently see another type of breathing pause during sleep. Usually these events begin with a central apnea, yet when the patient tries to initiate breathing there is an obstruction. No airflow results because the throat is now blocked. These apneas are referred to as mixed apneas because they include elements of a central apnea and an obstruction. New information suggests that the airway narrows slightly during central apnea. In a patient with an obstructive component this could cause obstruction as breathing resumes. Usually, treatment of obstructive sleep apnea eliminates these occurrences. Only rarely do mixed events begin with an obstruction and proceed to become a central event."

Can you tell, by looking at your graphs, if this might be the case?

Katie,

What really attracted me to your post here were the below 2 snippets in your quote ( having found myself in a battle over this very point). The debate I was in got downright nasty.

It was in regard to forms of 'Mixed Sleep Apnea' and the two quotes from above say "These apneas are referred to as mixed apneas because they include elements of a central apnea and an obstruction" ... "Only rarely do mixed events begin with an obstruction and proceed to become a central event".

At the time I refer to, I described how the latter occurred. I was also interested to see that the book you quote from has a foreword of praise from the eminent Collin E Sullivan.

Very reassuring.

Cheers

DSM