Anyone tried the CMS-P yet? Or bought from Contec?

late4work wrote:... the difference is that the CMS-P probe plugs directly into your USB port. Your notebook computer, PC or whatever is the METER.

I see! That is a good idea, if you are willing to connect to a computer every night and start it up. So really this product is only a sensor, hardware wise. Considering the price of that sensor in China, this should have been under $25

After the initial novelty wears off, I figure that I'll only use it when I suspect I might be having a problem, or once a month - whichever comes first .
Even though using the smartcard on the CPAP is less hassle, I don't think I'll be reading that data all that often as time goes by either...

However, for someone who intends to use the oximeter on a regular basis, a dedicated recording/display unit like the CMS-60D is certainly going to be more convenient to use .

The CMS-P sensor must have a USB interface chip, but otherwise I suspect it is the same as the finger sensors for the other units - which look the same.
However, I think all of them have an embedded microcontroller which controls the interleaving of the LED's, compares the attenuation of the of the two light wavelengths received by the photocell, and formats the data that gets streamed to the monitoring/recording device.

Still, at labor rates in China, we could argue that all of these devices are overpriced

late4work wrote:The CMS-P sensor must have a USB interface chip, but otherwise I suspect it is the same as the finger sensors for the other units - which look the same.
However, I think all of them have an embedded microcontroller which controls the interleaving of the LED's, compares the attenuation of the of the two light wavelengths received by the photocell, and formats the data that gets streamed to the monitoring/recording device.

late4work, Yes, it definitely has the USB interface. But it is possible all it has is a multiplexed a/d converter, and then everything can be done at the pc, including the modulating of the leds.

On the other hand, if you know that the sw on the pc is same as the ones used with their other meters, then they must have literally everything on that finger sensor. Even though the latter may seem like a bit more hardware, it might indeed be cheaper for them to do that way, since they already have a recording finger tip meter model (one piece). Just remove the memory, add usb interface -- you have a new model with identical software; the least amount of engineering. Since the memory needed for storing one night's data may cost only pennies these days, all those meters, except for the color screen sub unit, cost about the same to manufacture. It is simply a marketing scheme; that is assuming they have done the architecture/engineering of both the hardware and software correctly in a modular way.

I decided to get a pulse oximeter and found this thread in the course of Googling. Based upon late4work's post I bought the CMS-P, also on eBay from medonline888, and I concur with everything he said about it.

feeling_better wrote:

late4work wrote:The CMS-P sensor must have a USB interface chip, but otherwise I suspect it is the same as the finger sensors for the other units - which look the same.
However, I think all of them have an embedded microcontroller which controls the interleaving of the LED's, compares the attenuation of the of the two light wavelengths received by the photocell, and formats the data that gets streamed to the monitoring/recording device.

late4work, Yes, it definitely has the USB interface. But it is possible all it has is a multiplexed a/d converter, and then everything can be done at the pc, including the modulating of the leds.

On the other hand, if you know that the sw on the pc is same as the ones used with their other meters, then they must have literally everything on that finger sensor. Even though the latter may seem like a bit more hardware, it might indeed be cheaper for them to do that way, since they already have a recording finger tip meter model (one piece). Just remove the memory, add usb interface -- you have a new model with identical software; the least amount of engineering. Since the memory needed for storing one night's data may cost only pennies these days, all those meters, except for the color screen sub unit, cost about the same to manufacture. It is simply a marketing scheme; that is assuming they have done the architecture/engineering of both the hardware and software correctly in a modular way.

I realize that this is getting a bit off topic here but I do believe all the pulse & oxygen calculations are being done inside the sensor itself and that the computer is being used merely for displaying & recording information. I base this conclusion on the fact that if you plug the sensor in, put it on your finger and wait a few seconds, and THEN start the program, you immediately get data. If you've got the program running already, then connect the sensor and put your finger in it, it takes a few seconds for data to appear.

In other words, it takes the sensor a few seconds to figure things out and start sending data over USB. If the program itself was responsible for this, the delay in data being displayed would be present whether the sensor was connected already or not.

Finally, having the computer handle the low-level logic would introduce a great deal of latency in the data, which is clearly not present because I've felt my pulse (two fingers on neck) and watched the graph of my heart beating and they are 100% perfectly in sync. Through my experiences with photography (low shutter speed=blur) and music (guitar delay pedals, a few milliseconds makes a big difference) I know that I can tell the difference between 0ms and 200ms or more.

Also: people should be aware that these kinds of oxygen sensors don't actually tell you how much oxygen is in your blood. All they tell you is how oxygenated the hemoglobin molecules in your blood are. This may sound like splitting hairs, but you could be really low on hemoglobins (due to some health issue unrelated to CPAP) and the oxygen meter could still say 99% because what small amount of heboglobins you have are loaded with oxygen, but if there aren't enough of them flowing through your blood, your body is still deprived. This is not really of concern for CPAPrs but still something to be aware of.

late4work wrote:Review of PC based recording Pulse-Oximeter
Finger sensor:

I have experienced some soreness in the area right behind my fingernail after wearing the sensor for an entire night. I can't quite figure out why this is happening. If anyone has an explanation or suggestion, I'd welcome your input.

I "suffered" the same problem of soreness - it left a 5mm diameter area that took a few days to go back to normal, after the first time I used the sensor overnight.

The problem is either a pressure point OR thermal heating from the sensor - I would put my money on it being THERMAL.

My "guess" is because the sensor uses 5 Volts from the USB port for power - it may have a voltage regulator that drops the voltage down to 3.3 volts, and so [1.7 Volts] X [current used] is dumped as heat. You cannot feel this just wearing the sensor for a half hour or so, but when the hand is under the blankets overnight it certainly leaves its mark on the finger.

The next time I used the sensor for an overnight study, I placed a "Band Aid" wrapped around the finger, one side just near the nail bed, the other side near the first knuckle. The absorbent pad of the "Band Aid" was positioned near the nail of the finger. The LEDS in the sensor could still shine through my fingernail, but at the place where the sensor had made a "hot spot" the finger was protected by the absorbent pad. This gave enough "thermal insulation" that wearing the sensor overnight did not produce any soreness at all !

The "Band Aid" also restricted movement of the knuckle - and so gave less movement glitches.

Although I used a "Band Aid" I guess anything handy could be used, just a piece of paper wrapped around the finger (as positioned above) may be all that is required to keep the heat away from the skin surface.

With the above "thermal protection" I find the CMS-P sensor comfortable to wear for long periods without causing any issues.

N.B. I have used the term "Band Aid" - because that is what they are commonly known of here in New Zealand. If the term is unfamiliar to you, here are some pictures of what I placed on my finger:

http://en.wikipedia.org/wiki/Adhesive_bandage

I just remove the BAND AID from the finger the morning after - with NO further problems.

The CMS-P is still currently sold (circa August 2011) - so the above technique may be useful for other users.

Regards, Geoff.