Is the S9 event data questionable at best?

PSG data is questionable at best because it's a single night, in an unusual setting, potentially in a different sleep position, etc. You might not get REM sleep or "normal" sleep for the patient even if he REMs. Even if it's technically correct, the sample size is too small, and there is a significant sample bias vs. data taken at home. Even if you claim the measurement is very accurate, you're not measuring the patient's REAL health problems in a real environment.

S9 event data has a different set of technical concerns, but the data is evaluating the patient's real sleeping conditions over many nights.

You have to understand the value of both kinds of data.

In particular, if you ARE having apnea problems, the S9 will probably show it. If the S9 says you're good, you probably are. If it shows a really high AHI, you probably do have real problems. If it shows a moderate AHI, you probably need to look in more detail and try to see if it looks like events while awake, or events that are short enough and minor enough that it doesn't matter that much.

That's my point Arch. I have matched apneas scored by my S9 with O2 desats enough to trust the data, and the machine to take care of me while I'm asleep.

archangle wrote:

robysue wrote:

sol wrote:The machine is fooled, cannot tell if you,re asleep or wake. Even if you,re asleep there is no way of knowing if its a true apnea or not, an apnea have to be accompanied with oxygen desat

On a PSG, an OA or CA does NOT require an O2 desat. It does require that you are asleep (according to the EEG) when the OA or CA occurs,

There's a little difference in the criteria different groups use, but my understanding is the usual definition requires an x% O2 desat or a y% EEG change. Plus a x% decrease in airflow.

Nope. For scoring an apnea on a PSG they are only looking for a 90% drop in airflow volume that lasts at least 10 seconds and occurs during SLEEP. Not everybody with OSA experiences the O2 desats.

For hypopneas, the situation is more complicated:

The AASM Recommended Standard (Rule 4A, that Medicare insists on using) requires at least a 30% reduction in airflow for at least 10 seconds AND a corresponding O2 desaturation of at least 4% for in order for a hypopnea to be scored. Such a hypopnea does NOT require an EEG arousal

The AASM Alternative Standard (Rule 4B) requires at least a 50% reduction in airflow for at least 10 seconds AND one or both of the following conditions, a EEG arousal OR a corresponding O2 desaturation of at least 3%, in order for a hypopnea to be scored.

See http://www.journalsleep.org/ViewAbstract.aspx?pid=27368 for a scholarly paper that discusses the affect that scoring the same PSG under differing rules for hypopneas can make on diagnosing a patient.

For some of us, the problems caused by our untreated OSA stem from the repeated arousals and their physiological affects on our bodies rather than the affects of O2 desats.

brucifer wrote:Whether you want to outright admit it or not, the data is fuzzy. You mentioned the false positives yourself. A rose by any other name is still a rose. What I am attempting to do in this thread is understand WHY the machine generated the data that it did. I'm looking for LOGICAL explanations, not faith-based reasoning. I'm a trained scientist, so that's how I think.

If you choose to trust the machine within what you perceive to be its limitations, that's your choice. However, I'm still learning about this machine, so please pardon me if I feel the need to press forward and ask tough questions. You're certainly welcome to ignore my posts if my questions and comments bother you.

I'm an engineer so I can understand where you're coming from. You want exactitude. It's not there. The data is no more fuzzy than are weather descriptions. I'm sure you accept weather explanations and predictions as being scientifically reliable, but not exact.

Having the CPAP on for 90 minutes while you were awake is not normal usage, hence the CPAP is not designed to filter out data during such a time period. As others have said the CPAP is not capable of distinguishing between being awake and being asleep. The machine accurately recorded your breathing pattern, and when that pattern fit the criteria for an event, it recorded it as an event. The lesson to take away from this is that your machine will occasionally record an event during your awake time prior to dropping off to sleep, or just after awakening. Those events do skew the overall results to a minor degree. Consider it noise in the overall collection of data.

What you will discover in time is that the number of events can, and will, vary widely and wildly from night to night, but not so much week to week, and will stay fairly steady month to month. The long term trend over several weeks, at a minimum, is what you want to focus on. In that case a few "false" positives will not materially distort reality. I've had event numbers go from something like 0 to 10 to 5 to 1 to 18 over consecutive nights.

I'm sure you will find, after many days of data, that you can distinguish your sleep period from your awake period just by looking at the flow graph. I can. It's almost uncanny how my breathing changes when I drop off to sleep. You can then adjust your event numbers to account for them. That is, you can adjust your data outside of the Resscan or Sleepyhead, but not within those programs. IMO, any such adjustment would be too minor to be meaningful enough to justify the effort to do it.

robysue wrote:Nope. For scoring an apnea on a PSG they are only looking for a 90% drop in airflow volume that lasts at least 10 seconds and occurs during SLEEP. Not everybody with OSA experiences the O2 desats.

It seems not everyone agrees on the definitions, even among the medical techs themselves.

Maybe we need another thread on this, but I found this:

http://www.esst.org/adds/ICSD.pdf

THE INTERNATIONAL CLASSIFICATION OF SLEEP DISORDERS, REVISED Diagnostic and Coding Manual
Produced by the American Academy of Sleep Medicine
Copyright © 1990, 1997, 2001

Diagnostic Criteria: Obstructive Sleep Apnea Syndrome (780.53-0)
...
D. Polysomnographic monitoring demonstrates:
1. More than five obstructive apneas, greater than 10 seconds in duration,
per hour of sleep and one or more of the following:
a. Frequent arousals from sleep associated with the apneas
b. Bradytachycardia
c. Arterial oxygen desaturation in association with the apneic episodes

I read this as diagnosing OSA requires arousal, heartrate change or O2 desat.

I guess that you could say that scoring an "obstructive apnea" occurs even if you don't have O2 desat, arousal, or heartrate change. However, they don't diagnose OSA unless you have the O2 desat, arousal, or heartrate change.

I appreciate the answers that you all have shared. Thank you.

At square one, I still find it intriguing and somewhat peculiar that my awake event data recorded over a 90-minute period while I was laying awake looked very similar to the data that I recorded this past week while asleep. Of course, I would need to conduct a much more thorough quasi-experimental study in order to determine within a reasonable degree of confidence that my observation was more than just a coincidence. Hmmmmm...it's something to consider doing in the future.

Anyway, this has been an insightful discussion. Again, thanks for your responses.