Re controversy over changing pressure

It only makes sense that the actual readings obtained in a sleep lab would be more accurate than those recorded by an xPAP machine at home. In addition to the more extensive nature of the readings, the equipment is much more advanced.

On the other hand, the actual sleep one achieves in a sleep lab can hardly be considered representative of the sleep a user enjoys at home. So you wind up with accurate readings of a night that misrepresents normal sleep.

At best all measuring devices can only provide a guide to determining the most helpful therapy. Personally, I plan on taking advantage of all the information I can get my hands on.

I really want this therapy to work.

Susan

Let’s use Tilly’s analogy of the weight scale and simplify it even further. Let’s use a couple of rulers … one has delineations of centimeters and the other has delineations of millimeters. Ok ok , metric units will only confuse us American patients so let’s use delineations of inches and ¼ inches such that the inch ruler represents xPAP software and the ¼ inch ruler represents sleep lab equipment.

Now the sleep lab ruler has a better precision than the software ruler. The accuracy however depends. With the sleep lab ruler, you can only afford maybe one or two measurements and with the software ruler we can take many many more measurements.

So now our sleep apnea characteristics (AHI?) are variable (this is key to the understanding of which is more accurate) from person to person as well as for each person from night to night. Knowing that this variability exists means that in order to get the most accurate picture of our AHI, we need to take as many measurements as possible (known as a significant sample of observations from the probability distribution function -- I would think a normal bell-curve distribution) and then take the average … a basic procedure of the scientific method. It is clear to me that the software ruler (although less precise) is more accurate because it can provide the most significant number of sample observations ... unless of course one is independently wealthy and can afford their own personal sleep lab equipped bedroom.

Accuracy vs precision …


SUMMARY:
Sleep lab equipment is definitely more precise than software alone.
Due to variability of measured observation (AHI), then in general, the one that provides the most measurements is most accurate.

DreamStalker wrote:Now the sleep lab ruler has a better precision than the software ruler.

Its not that simple.

Sleep labs measure numerous different dimensions/attributes of sleep (which is why a sleep study is called a Polysomnogram), whereas the flow generators measure a much smaller number of dimensions/attributes, so there are significant scope differences as well as precision differences.

In respect of AHIs your other comments are generally valid, but AHI is only one measure of sleep "performance" and while it has general validity in the treatment of OSA, it is not necessarily of much relevance in terms of the treatment of other SBD conditions, or other sleep related ailments, which may co-exist with OSA.

This is one of the continuing concerns of clinicians with respect to any "self medication" approach. Patients may treat their obvious symptoms and completely fail to treat other symptoms which are not so obvious but could be indicators of more serious issues.

Taking control of your own treatment also means taking responsibility for all that implies, which is often not well understood by patients (even otherwise generally well informed ones.)

On the other hand, clinicians as a group do "stuff up" more than they are ever likely to admit, so there is also a good case for patients taking an active role in managing their treatment.

The issue is really one of finding the right balance for each patient..

Cheers,

Bill

billbolton wrote:

DreamStalker wrote:Now the sleep lab ruler has a better precision than the software ruler.

Its not that simple.

Sleep labs measure numerous different dimensions/attributes of sleep (which is why a sleep study is called a Polysomnogram), whereas the flow generators measure a much smaller number of dimensions/attributes, so there are significant scope differences as well as precision differences.

In respect of AHIs your other comments are generally valid, but AHI is only one measure of sleep "performance" and while it has general validity in the treatment of OSA, it is not necessarily of much relevance in terms of the treatment of other SBD conditions, or other sleep related ailments, which may co-exist with OSA.

This is one of the continuing concerns of clinicians with respect to any "self medication" approach. Patients may treat their obvious symptoms and completely fail to treat other symptoms which are not so obvious but could be indicators of more serious issues.

Taking control of your own treatment also means taking responsibility for all that implies, which is often not well understood by patients (even otherwise generally well informed ones.)

On the other hand, clinicians as a group do "stuff up" more than they are ever likely to admit, so there is also a good case for patients taking an active role in managing their treatment.

The issue is really one of finding the right balance for each patient..

Cheers,

Bill

Yes I know it is not that simple ... I stated from the begining it was an anology to simplify (and should have said also to clarify) the previous ongoing discussion of this thread as to which method is more "accurate" with regard to monitoring and titrating someone who has already been diagnosed as having OSA.

I agree SDB is a much more complicated condition but again, what is the purpose of us patients using the software? It is not and should not be used to self-diagnose SDB. We are using it to "tweak" our setup to our changing body and different mask interfaces with respect to AHI ... and in some cases also to correct a bad sleep lab titration (at least that is how I use my software).

So I think we are in agreement ... the sleep lab ruler is actually more like what you engineers call a "scale" with different delineations for measuring different parameters and the software ruler is only one part of that scale with coarser delineations (ie. software is only a subset of the sleep lab equipment - aka scope).

The point I was attempting to make with my post is that the specific parameter (AHI) which we as patients try to "tweak" our setup for is represented more by a probability distribution function rather than an absolute value. Consequently, having more measurents or observations will lead to a more narrow uncertainty with respect to the accuracy of our tweaking. Software provides us "patients" (not sleep lab clinicians) more observation measurements in a more cost effective way.

I totally agree with the rest of your comments regarding clinician concerns and patient responsibility.

In addition, we are (usually) using the data capable machine only AFTER we have had the polysomnogram(s). While it is useful to me to see the sleep study, including the sleep stages and spontaneous arousals not helped by titration, etc., the main reason was so that the doctor could give a diagnosis of OSA and get me treated via cpap. The polysomnogram is a one shot deal, while the data from the machine (monosomnogram?) is an ongoing measure to help me track and improve the success of the treatment originally determined by the poly data.

I had numerous spontaneous arousals not taken care of via titration. There was a note in my report about this, but no recommendation about what to do about it. No one has paid it any heed but me. Now, having a way to track this would be very useful if I could do it every night and try to figure out if there was any external reason they were occurring.

Another possibility is that my (mis)titration at 5 cm H2O did not take care of them, but the more appropriate self-titration via machine data at 9 cm H20 may be handling those, too if they were caused by "subclinical hypopneas," UARSlike phenomena or something similar. But perhaps not, because some days I'm still tired despite a very low AHI and no leaks. Not near as tired as before, though.

When I get enough time, I'm hoping to figure out if the SleepTracker watch can be used to find out more about the arousals.

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CPAPopedia Keywords Contained In This Post (Click For Definition): Titration, CPAP, AHI, Polysomnogram

RosemaryB wrote:The polysomnogram is a one shot deal

For PAP treatment it should be a two shot deal, one to establish a formal diagnosis and then a second one following the diagnosis to establish the appropriate treatment parameters and effectiveness.

Cheers,

Bill

billbolton wrote:

RosemaryB wrote:The polysomnogram is a one shot deal

For PAP treatment it should be a two shot deal, one to establish a formal diagnosis and then a second one following the diagnosis to establish the appropriate treatment parameters and effectiveness.

Cheers,

Bill

billbolton wrote:

RosemaryB wrote:The polysomnogram is a one shot deal

For PAP treatment it should be a two shot deal, one to establish a formal diagnosis and then a second one following the diagnosis to establish the appropriate treatment parameters and effectiveness.

Cheers,

Bill

echo wrote:That's funny that most centers now actually use APAPs for the titration itself.

It's even funnier that MY sleep doc said that "APAPs are not accurate", yet they use APAPs during the titration. Go figure. My take on that it that they ahve a hard time determining central's from obstructive events and for some reason "they respond too slowly" (i'm still not sure about either one though).

_________________

Got any evidence to show most centers are using APAPs for titrations?

I rely on my SpO2 readings as I have found my own subjective judgment can apparently be quite wrong.

This past week I slept without cpap because I was sure I was feeling good & didn't need it. I was using my nasonex each night & felt my breathing was fine.

Last night I was smart enough to strap on my SpO2 probe & evaluate my night. I woke feeling a bit sluggish but was sure I had had a good night's sleep. Later that night I looked at the night's SpO2 data & it told a quite different story, perhaps one of the worst nights for desats I have ever recorded. What an awakening.

Guess who is now right back on his regular cpap.

DSM