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Questions about sleep study results

This area is for discussion of Sleep Studies used in the evaluation of Sleep Apnea.

Questions about sleep study results

Postby sskat » Sat Dec 18, 2010 1:04 am

Hi everyone,
My name is Heather, and I've just completed a sleep study for apnea. I have not yet been contacted by my doctor to discuss the results of the test, but the technician shared some information with me from the report. I was wondering if I could get a little help understanding this information, it would be greatly appreciated as I was not able to do much research prior to the study ... a doctor's visit for fatigue resulted in a sleep study the following night.

Here are some of the results I was given:

The sleep efficiency was 70.7% and normal sleep onset time of 25 minutes. REM sleep latency, 172 minutes, was normal.
The overall respiratory disturbance index (RDI) was 20.4 per hour, RDI during rem sleep was 22 per hour. The Apea-Hypopnea index (AHI) was 18. There were 110 total events with 15 obstructive apneas, 8 mixed apneas, 32 central apneas, 42 hypopneas, 13 RERAs. Mean duration of events was 11.8 seconds, with a maximum of 23.5. The baseline oxygen saturation was 96%; the minimum during the study was 87%. Prolonged cardiac rhythm monitoring was unremarkable.

Diagnosis: Moderate obstructive sleep apnea syndrome with mild oxygen desaturations.

There are other stats I can provide if needed.

My questions are as follows:

I was diagnosed with obstructive sleep apnea, although it seems as though I had more central apneas than obstructive. Can someone explain this, and should I be concerned about the central apneas (in my very brief readings on the topic before the study, I seem to recall reading that central apneas can be related to other health problems?). Although I have not seen the report from the second night with the CPAP machine, the technician did tell me that there were no apnea events with the pressure at 9.

What does "baseline oxygen saturation" mean? Is that an average?

What is an RERA index?

And finally, could someone please explain these stats?

Average SaO2 during REM: 96
Average SaO2 during NREM: 96

<90% <80% <70% <60%
Minutes of sleep w/SaO2, REM .1 0 0 0
Minutes of sleep w/SaO2, NREM . 3 0 0 0

Thanks in advance for any help you can provide!
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Postby CrohnieToo » Sat Dec 18, 2010 12:28 pm

Baseline 02 saturation was the 02 measurement taken prior to your sleep study, prior to going to bed at the lab.

RERA index is the Respiratory Effort Related Arousals. This would include Apneas, Hypopneas and Hypopnea "wannabes" which could also be called UARS (Upper Airway Resistance Syndrome). It wouldn't include central apneas since there is no attempt to breathe due to the brain not telling the body to breathe.

REM is Rapid Eye Movement sleep. Your average 02 saturation during REM was 96% which is good. NREM is Non-REM sleep which is where we spend most of our sleep time.

The last I'm not sure of.
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Postby Aloicious » Fri Dec 31, 2010 3:26 am

Just to clarify and add a little to what was already said,

a RERA (respiratory effort related arousal) actually does not include an apnea or hypopnea, it only includes the 'wannabes'...a RERA is when you have a flattening of the nasal pressure waveform, or increasing respiratory effort that leads to an arousal (an 'arousal' is a change in your EEG waveform and possibly a change in muscle tone/tension). basically when a doc is looking at RERAs they're looking at possible respiratory problems that can't be defined as a clear cut apnea or hypopnea (for example, no desaturation in your blood O2) but still are causing interruption of your sleep (arousals). like UARS which was already mentioned. when they mention the 'index' they're simply referring to the averaged number of RERAs you experienced per hour during your study.

a baseline oxygen saturation is typically a 'normal' oxygen saturation, its kindof used like a yardstick to measure O2 variations against.

the numbers at the end of your post mean this:
your average O2 saturations while you were in REM (combined) was 96%, your average O2 saturations while you were in NREM (non-REM, also combined) was also 96% both of these are good.

and lastly, that actually should look like a table but in forums its hard to post those. it says that while you were in REM, your oxygen saturation (SaO2) was below 90% for 0.1 minutes, with zero minutes below 80%(and subsequently 70% and 60%)...and while you were in NREM (non-REM), your O2 levels were below 90% for 0.3 minutes, with zero minutes below 80% (also 70%,60%) these numbers are for the entire course of your study, so if this info is from your CPAP night study, then it includes ALL the pressures they tried, both the successful and less-successful pressures. but either way these are good numbers.

central apnea can indeed be a sign of other medical problems, but aren't always, it would be worth talking to the doc about when you next meet with them, or give them a call or something. but if the tech told you that you were controlled with NO respiratory events at a pressure of 9, to me that sounds pretty good. a good portion of the diagnosed population tend to end up with a pressure of between 8-12, so your results sound good and normal to me.
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Postby Linda » Thu Jan 06, 2011 12:36 am

The explanations for baseline oxygen saturations were spot on. I would only add that the reason they check your "normal" blood oxygen levels before you get into sleep, is that "normal" is a little different for everyone. For most people, as I understand it, daytime blood oxygen saturations are in the upper 90 percent range. But for some people, that daytime saturation level might be lower. That could be in part from longtime untreated sleep apnea, or it could be from other things like longtime smoking. They want to see how the saturation levels change during sleep.

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