Oximeter CMS-50 and plethysmographic wave

Hello everyone,

I'm new in this site, so please forgive me if my questions are not clear.

I want to use the plethysmographic signal (the pulse wave) for research, so I have some questions that I think you can help me with:

• I was intended to purchase a CMS-50 oximeter. I need to save the pulse wave, should I need the CMS-50H? The CMS-50EW will do it? The CMS-60 also work?
• I need to use the pulse wave in real-time. There is a way to save this signal outside the PO2 software? (I mean, for example read the file where the signal is writing to, and use it in Matlab or similar)
• If I read the file with SleepyHead, can I output the data in a more readable file?

Thank you! please tell me if anything is confusing.

lbugnon wrote:I was intended to purchase a CMS-50 oximeter. I need to save the pulse wave, should I need the CMS-50H? The CMS-50EW will do it? The CMS-60 also work?

I have a CMS-50F new (blue) model. Hopefully this information helps you select or reject this particular device.

lbugnon wrote:I need to use the pulse wave in real-time.

This is not possible AFAIK because the finger probe uses the same physical port as the USB serial port emulation for data download and monitoring. It may be possible to make a splitter to have both features at the same time but I have not tried this.

lbugnon wrote:There is a way to save this signal outside the PO2 software? (I mean, for example read the file where the signal is writing to, and use it in Matlab or similar).

The CMS-50F new (blue) model has a recording capability where the recorded data can be downloaded from the oximeter by a SpO2 Assistant application and is automatically exported into a simple CSV data file format for SpO2 and Pulse measurements, and with a separate readable txt header file. The files are downloaded in bulk, not real-time.

lbugnon wrote:If I read the file with SleepyHead, can I output the data in a more readable file?

SleepyHead doesn't support the CMS-50F new (blue) model. I looked at the code and could make it work but the integrated functionality didn't seem to offer anything better than just using the SpO2 Assistant 2.50 supplied with the device.

SleepWrangler,

Thank you very much for your info! As I'm not specifically in apnea research, I was concerned only for the file format. As you say the file can be exported in CVS, there should be no problem to read the data.

I'm wondering, the stored data is only the PO2% and heart rate, or it also stores the pulse wave?

I'll need a model that allow real-time, I read that CMS-50H would do it, but as you say, I don't know if I can export the data without close the session.

The CMS-50F old style does allow realtime data transfer from the unit to the output USB port.
You would have to do some code development in order to effect the data hook up.
There are data port sniffers that can help in the process but I am not familiar with which one might be of use.

The new, blue face, model won't work for what you want to do but the earlier one will.
Contact Cooper Medical

customerservice@coopermedicalsupplies.com
To see if they still have any.

Best of luck with your project.

lbugnon wrote:Thank you very much for your info! As I'm not specifically in apnea research, I was concerned only for the file format. As you say the file can be exported in CVS, there should be no problem to read the data.

I'm wondering, the stored data is only the PO2% and heart rate, or it also stores the pulse wave?

user_1_1_20140416071108.txt

name=user
sex=0
age=0
Nationality=
weight=0.00 kg
height=0.00 cm
comment=
PIType=1
startTime=2014-04-16 05:18:58
length=4940

user_1_1_20140416071108.csv

SPO2,PULSE
96, 52
96, 52
96, 52
96, 52
96, 52
96, 52
96, 52
96, 52
96, 52
96, 52
...

lbugnon wrote:I'll need a model that allow real-time, I read that CMS-50H would do it, but as you say, I don't know if I can export the data without close the session.

All I can offer is that the SpO2 Assistant v2.50 has the ability to render a "real time" data stream. I assume this means at least one device has the ability to stream data out the USB port in a streaming mode. Possibly the fingertip mounted devices /w USB port have this feature.

I have no clue how "real time" the data would be. USB has all kinds of buffering, latency, jitter, and drift depending on how the application implemented the USB and application protocol stacks. The wrist mounted CMS-50F monitoring device draws a pretty little pulse wave graph on it's display but who knows really how much is real data vs a pulse template applied to a low frequency sampling algorithm.

Don't know how much error your application can tolerate. These are really simple devices. Maybe look at http://hackaday.com/?s=oximeter to see how others have implemented the sensor.

From what I understand a plethysmographic reading is the volume of blood being moved. The data file generated by my (old style CMS-50F) oximeter records the oxygen concentration, and heart rate, but DOES NOT contain the plethysmographic waveform or data.

-Bill

lbugnon wrote:I want to use the plethysmographic signal (the pulse wave) for research...

IIWY I would pick up a used Nellcor N595 (run ~350 - 400 bucks):

http://www.ebay.com/sch/i.html?_trksid= ... &_from=R40

and hook up to Pin 14 (see page 92):

http://www.meql.com/Manuals/Nellcor-N59 ... Manual.pdf

That will give you a 0 - 1.0 DCV output that you calibrate in your acquisition software to 0 - 255 (although since the pleth wave really does have a true numeric value, you could probably calibrate it to anything you want).

CMS50D+ and above record plethysomogram with live (cable attached) recordings, but when not using the devices recording ability to it's own internal storage.

It streams via the serial port a 5 byte protocol which includes Plethysomogram samples at 50Hz, it's rather easy to intercept with a good Serial port library.
(For reference, 19200 baud, odd parity)

SleepyHead displays this in realtime as it records in Live oximetry record mode. (I've just completely rewritten SleepyHeads oximetry components, it's even better now)
It doesn't export to CSV, mainly because I never saw a use for that yet - I can knock together an oximetry session export feature rather easily if that helps anyone.

If you need any more information, let me know.

Edit: Would a unix style script/program that dumps a byte stream of just the 8bit plethy data to a pipe be what your looking for?

/Mark

jedimark wrote:CMS50D+ and above record plethysomogram...

OK, but CMS*** notes that signal to be

Pulse Intensity
Range Continuous bar-graph display, the higher display indicate the stronger pulse.

Do we know if Pulse Intensity is simply graphic representation of the plethysmographic waveform, or does it account for other factors (artifact, etc.) as well?

Or do we really care?