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[Equipment] CMS50F Pulse Oximeter
#1
Looking to purchase this Oximeter as it seems to be one that Sleephead will support.   If anyone has and or is familiar with the CMS50F Oximeter as to what the sample rate when it is recording for up to 24 hours.   Just curious how often it is recording data as in the number of samples / second or is it the number of samples / minute.  

Also curious as to how quickly do the oxygen saturation number drop vs. time.      I recently had a sleep clinic test and when I requested a copy of all the results it was not the copy of the graphs like we see in the Sleepyhead software but just a very short Drs. report stating some AHI (74) result and that my O2 dropped to 65%  So I am not sure how long of my sleep study was this low or if it took all night to get that low??.     So I was just curious if any one has monitored their Pulse and Oxygen number and then held their breath to see how fast the oxygen level drops.
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#2
I believe the CMS50F samples every 6 seconds. The F model will only record one session and will overwrite the previous recorded data if you stop it and start again. So don't stop it if you get up for a bathroom break during the night. Also, if you accidentally thump the finger probe it may show up as a quick spike in your data, so don't worry when you see them.
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Useful Links -or- When All Else Fails:
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#3
The manual for the 50F is pretty sketchy, I cannot find the sampling rate, but it is sufficient to determine a HR at whatever your BPM is and it looks like it checks the SPO2 every second or 2. ITs faster than you body reacts or changes. I have not tried a breath holding experiment at all, I will give it a shot when I get a chance. It does seem that there is a lot of jitter in the readings, not sure if its my blood flow or the sensor.
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#4
If the cpap is doing it's job, the o2 should be ok now.
my 50f seems to sample at a per second rate. The o2 level in your finger has a lag time to what is real time events. It takes some seconds for that blood to get to your finger tip. you will also see this in the sleepyhead charts, where the desat happens after the event. I've used it a few times for peace of mind. Even though, I consider the ebay $50 well spent.

I found the machine sd card didn't log some real desats and it also logged hyponemia events where I didn't desat. I'm not dropping under 90% and only have a couple of real desat periods a night now
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#5
Hi c2workout,
WELCOME! to the forum.!
Good luck to you with your CPAP therapy, hang in there for more answers to your questions.
trish6hundred
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#6
We just rolled out the SleepO2 an Android App which works with Contec CMS50K wearable Oximeter.

You can search in Google Play for the App. The App also integrates with Fitbit.
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#7
I have that unit, but don't know the sampling rate. Both heart and primary docs say it is more than adequate though.

As to the sleep study, contact your doctor's office and tell them that you want the RAW data not just the summary report of your sleep study for your records. It should be a series of graphs.
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#8
There is a comma separated data file created that MS Excel reads. Four columns DATE, TIME, SPO2, and PULSE. The file contains an entry for every second of the recording. While this does not directly answer the question of sensor sample rate, it is suggestive. I looked at one minute of data for Pulse 4,5,1,8,11,15,2,14; for SPO2 - 3,8,2,5,4,38. The string of numbers are the length of time a value persisted consecutively before changing. So for pulse, the value at the start of the minute persisted for 4 seconds, the new value lasted 5 seconds then 1 second, etc.

I don't know whether there is any "sub second" sampling that results in the reported values. Hope this helps
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#9
My data suggests that the sample rate is once a second.

.
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