Hypopneas vs. Flow Limitations

There's nothing cut-and-dried about measuring the human body. There is a lot of science (i.e. hard work and money) behind what is understood about OSA and its treatment and the issues are far from settled. Don't make out like that's a bad thing, I'm certainly glad they understand this stuff a lot better now when I'm being treated than that did if I'd have been diagnosed 20 years ago. Heck, at one time they actually thought carving up the inside of your mouth and throat was the only way to treat apnea.

When a medical professional says something about "hypopnea this" or "flow limitation that" or "blah, blah, blah apnea" they have some specific definition in mind for those terms. If you really want to understand the implications of what they're saying, then you have to ask and make sure that you know the specifics of their working definitions. There is absolutely no magical way of guaranteeing that everyone means the same thing when they say the syllables Hy-Pop-Ne-A. You can't really have a meaningful technical conversation about this stuff unless you're sure you've pinned down the definitions.

Brent Hutto wrote: You can't really have a meaningful technical conversation about this stuff unless you're sure you've pinned down the definitions.

Your statement supports what “neversleeps” posted and I agree with both of you. That lack of clarity and the breath of involvement by different people is what making this discussion thread so interesting. For certain, if we can’t understand each manufacturer’s or even a fellow poster’s definition, and how they are using that information, we won’t have more than a random chance at getting much that is meaningful from these discussions. With that thought still oscillating in my head I see this process as a challenge and a concern.

rested gal wrote: "Must" reading for understanding IFL stuff are the excellent posts by -SWS:
Links to -SWS discussions

In those links, a good one to start with would be:
viewtopic.php?t=817

Great posting Rested!

I’ve been buried in reading through your list and fortunately there is no way to finish it today.

After going through the articles in ozij post, I found this article had some good information about oximeter use in relation to OSA:
Getting the Most Out of Nocturnal Pulse Oximetry

Clearly, nothing is simple in this stuff and more than likely there aren’t any hard tables that can be used in isolation. For certain the variety of articles I found show that oxygen saturation levels can be affected by a lot of factors, but one of articles referenced below indicates desaturation cycle data can be an indication of whether an OSA event is a cause in the desaturation:
Utility of Oxygen Saturation and Heart Rate Spectral Analysis Obtained From Pulse Oximetric Recordings in the Diagnosis of Sleep Apnea Syndrome*


As a side note, I’m finding xPAP therapy has nearly become a second job. For certain it has me studying as if I were going to stand for “orals” and creating tables and data references for a publication in the NEJM.

Brent,

Point well taken. A controversial definition is better than no definition. It begs the question, however, depending upon the criteria used at the local sleep lab: how many patients (who would benefit from CPAP therapy) end up not qualifying for a diagnosis of OSA because they don't meet the cutoff as it pertains to the questionable use of desat levels for hypopneas? In addition to the hypopnea debate, I was surprised to learn the type of oximeter used can also yield such different (potentially non-qualifying) results. I should know better, though. I want this to be an exact science and it simply isn't. Even with a universally accepted definition (e.g. apnea), the interpretation and (potentially non-qualifying) scoring of PSG results can vary substantially from tech to tech. Sometimes I lose sight of the fact that sleep science is still in its infancy.

Come to think of it, I could take my temperature with 3 different thermometers and get three different results too. But, while the precision of the instrument used and the accuracy of the human interpretation may vary (for thermometers as well as PSGs), at least the criteria for measurement is standard on a thermometer. I want that same assurance for all things OSA related! Oh well... I'll try to get over it... I also want world peace and new siding on my house. That hasn't happened yet either...

Brent Hutto wrote:If you really want to understand the implications of what they're saying, then you have to ask and make sure that you know the specifics of their working definitions. There is absolutely no magical way of guaranteeing that everyone means the same thing when they say the syllables Hy-Pop-Ne-A.

My emphasis.

Or more humourosly, as announced by the inimitable Humpty Dumpty:

"When I use word <snip> it means just what I choose it to mean -- neither more nor less"

Thanks, RG, for posting those pictures of PB\s working definition of flow limitations and hypopneas. I saved them for future reference....

O.

neversleeps wrote:Come to think of it, I could take my temperature with 3 different thermometers and get three different results too. But, while the precision of the instrument used and the accuracy of the human interpretation may vary (for thermometers as well as PSGs), at least the criteria for measurement is standard on a thermometer.

Some questions are easier to answer than others. Temperature is an easy one, apnea stuff is hard. There's a story (perhaps apocryphal) about Ted Williams as a hitting coach after he retired from playing. A rookie asked him what to do with a hard-breaking slider that just catches the lower outside corner of the strike zone. Ted's answer was "Son, you just watch that one go by...nobody said hitting was easy".

ozij,

I had actually thought of the Humpty Dumpty quote, too. Good one.

Thanks, all, for the interest and the great analyses and references. Yes, this is certainly a full time occupation, being a well informed hosehead! But worth it. Truth is, that is the RTs and the DMEs were half as knowledgeable as people on this super forum, well, that would be, well, never mind...

I often say, our first mistake is thinking that medicine is an exact science. But one step at a time, maybe we will get to more universal definitions, and requirements for a machines' definition of an event, and for diagnostic definition, and and and

Thanks for the directions. Now I have my reading cut out for me. I was told that the PB 420 S would give me the same Silverlining info as the 420 E. I think I'll double check it before my 2 month trial period runs up.

Regards to all,
Happy Easter, Happy Passover, Happy Spring!
AII

AII
When you installed SL3, it automatically installed a bunch of demo files. Some are for machines no longer pruduced, I believe. But you'll find one for the 420E as well. Play around with it, so you'll know if the price difference is worth it for you.

Your salutation bears repeating:

Happy Easter, Happy Passover, Happy Spring


                  

(Yes, they really look like that, and the temprature is about 17-20 degrees.....
Celsius, of course, Why, did anyone think otherwise? )
O.

bump