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Comparing Oximeters - I should have known better...
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Moriarty Offline

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Machine: Respironics REMStar 50 Series Auto
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CPAP Pressure: 8.5-20 (average 9.4)
CPAP Software: SleepyHead

Other Comments: Image above is my CPAP machine...

Sex: Male
Location: Toowoomba - Qld - Australia

Post: #1
Ohmy Comparing Oximeters - I should have known better...
I have had a CMS50D (not the D+) for some time but decided last week that I would like to be able record over night so I ordered a CMS50F.

It arrived today and I wasted no time in comparing it to the 50D...

I knew from my work that no two instruments give exactly the same result when tested side by side but for some reason that concept escaped me when I allowed myself to be surprised by the facts that the SPO2 was consistently 4% lower on the 50F than on the 50D and that the Pulse rate varies by between nothing and 10Ppm...

The pulse rate on the 50F is more stable but generally lower than that displayed on the 50D...

So.... I will only be using the oximeters for relative measurements and not be able to regards either of them as accurate...

Like I said - I should have known...
01-31-2013 07:00 AM
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DocWils Offline

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Machine: Philips Remstar series 60
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Sex: Male
Location: Switzerland

Post: #2
RE: Comparing Oximeters - I should have known better...
In Oz, so I was told, you can bring in the device for calibration at your local medical supplier. Some hospitals do it also. I am certain there is a fee for it...

If neither of the oximeters show a drop below 85% you should be all right anyway - So long as you are recording above 90% you are in a safe zone no matter what. also, try another finger and see if that makes a difference - some machines have readers that are less sensitive and don't work well on the index and middle finger.
01-31-2013 08:09 AM
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Shastzi Offline

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Post: #3
RE: Comparing Oximeters - I should have known better...
I like to stay above 89% the ride is smoother up there.
=^.^=
01-31-2013 09:52 AM
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2Tim215 Offline

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Machine: S9 ResMed AutoSet
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Other Comments: OSA, Fibromyalgia, Rheumatoid Arthritis, Osteoarthritis, Gout, PTSD, & Meralgia paresthetica.

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Location: Finger Lakes Region, NY

Post: #4
RE: Comparing Oximeters - I should have known better...
I'm pretty sure the CMS 50D Plus is FDA approved and 24 hour data capable. As with any electronics you could have gotten a defected one. Maybe you can exchange it?

Tim
Finger Lakes Region, NY
01-31-2013 06:52 PM
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Moriarty Offline

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Joined: Jul 2012

Machine: Respironics REMStar 50 Series Auto
Mask Type: Nasal pillows
Mask Make & Model: Fisher & Pakel Pilairo Q
Humidifier: Respironics System One
CPAP Pressure: 8.5-20 (average 9.4)
CPAP Software: SleepyHead

Other Comments: Image above is my CPAP machine...

Sex: Male
Location: Toowoomba - Qld - Australia

Post: #5
RE: Comparing Oximeters - I should have known better...
(01-31-2013 06:52 PM)2Tim215 Wrote:  I'm pretty sure the CMS 50D Plus is FDA approved ...


I think that pretty well the whole CMS range is FDA approved but that approval does not guarantee absolute accuracy.

All electronic measuring equipment has a tolerance on its reading. In the case of all the CMS equipment the tolerance is +/-2% on both the pulse rate and the SPO2 readings...

What that means is that comparison of two devices could have readings that are up to 4% apart.

In addition to that I have found the 50D to be quite sensitive to how it is put on the finger - and to which finger it is placed on....

Add to the mix the fact that I have just discovered that I get an irregular heart beat at times that confuses the Pulse Rate software in the CMS and causes my BP Meter to give erratic results as well...

The GP is not too concerned about the ectopic beats but I am booked in for a 24 hr Holter test to see how big a deal it really is.
02-01-2013 06:19 AM
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archangle Offline
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Post: #6
RE: Comparing Oximeters - I should have known better...
(01-31-2013 08:09 AM)wilorg Wrote:  In Oz, so I was told, you can bring in the device for calibration at your local medical supplier. Some hospitals do it also. I am certain there is a fee for it...

If neither of the oximeters show a drop below 85% you should be all right anyway - So long as you are recording above 90% you are in a safe zone no matter what. also, try another finger and see if that makes a difference - some machines have readers that are less sensitive and don't work well on the index and middle finger.

There is apparently no way to calibrate these CMS oximeters. At least no way available to the end user. I'm sure anyone at a hospital or medical supplier would laugh at you.

Get the free SleepyHead software here.
Useful links.
Click here for information on the main alternative to CPAP.
If it's midnight and a DME tells you it's dark outside, go and check it yourself.
02-01-2013 07:16 AM
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DocWils Offline

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Machine: Philips Remstar series 60
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Sex: Male
Location: Switzerland

Post: #7
RE: Comparing Oximeters - I should have known better...
It is a firmware jig. I checked with our hospital here and they DO have the necessary means to do it on CMS devices, but only do it for recording devices, because of the built in interface. It is proprietary and apparently a bit of a pain. However, here in Switzerland, typically, they will not do it for the general public, only for in house devices. But hey, that is one of the lovely things I love about living here - the lack of availability of services and goods to the public. I went to four pharmacies today to try and find a 2 litre sterile glass bottle, to no avail - the hospital has plenty of them, but I can't get one because it is for personal use, not hospital use, and they control everything that goes in and out (no one steals scrubs here - they are all coded and signed out, so they HAVE to come back to the laundry or else - same with everything else).

An Aussie associate told me that some hospitals will do the adjust if needed, for a fee, but which ones he couldn't say. Either way, he said, and I agree, if the readings are not wildly out of whack, it makes little difference.

So, here's a hint - try the device on you third finger. Sit up straight with your legs slightly extended. Take a few deep breaths in through your nose and out through your mouth before you start it and then breath normally - you should read somewhere around 96-97% (if it doesn't try it on the other hand - sometimes calluses can throw off the sensor). If you read a point up or two points down, you know the range of the error. Now try it on your middle finger and your index finger to see if the sensor is strong enough to return data accurately on the two thicker fingers. If they do, then you have a baseline, If not, you know to use it on your third finger and know the correction factor. That was the way we did the check in school. And it was one of the punishments out Resident gave us as scut work if he didn't like you, to do that for all the devices on the ward.

To be honest, we never worried too much about a point or two of inaccuracy on these - the bp devices were and are far more important to be accurate.
(This post was last modified: 02-01-2013 08:27 PM by DocWils.)
02-01-2013 12:01 PM
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Moriarty Offline

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Posts: 270
Joined: Jul 2012

Machine: Respironics REMStar 50 Series Auto
Mask Type: Nasal pillows
Mask Make & Model: Fisher & Pakel Pilairo Q
Humidifier: Respironics System One
CPAP Pressure: 8.5-20 (average 9.4)
CPAP Software: SleepyHead

Other Comments: Image above is my CPAP machine...

Sex: Male
Location: Toowoomba - Qld - Australia

Post: #8
RE: Comparing Oximeters - I should have known better...
(02-01-2013 12:01 PM)wilorg Wrote:  So, here's a hint - try the device on you third finger. Sit up straight with your legs slightly extended. Take a few deep breaths in through your nose and out through your mouth before you start it and then breath normally - you should read somewhere around 96-97% (if it doesn't try it on the other hand - sometimes calluses can throw off the sensor). If you read a point up or two points down, you know the range of the error. Now try it on your middle finger and your index finger to see if the sensor is strong enough to return data accurately on the two thicker fingers. If they do, then you have a baseline, If not, you know to use it on your third finger and know the correction factor. That was the way we did the check in school. And it was one of the punishments out Resident gave us as scut work if he didn't like you to do that for all the devices on the ward.

To be honest, we never worried too much about a point or two of inaccuracy on these - the bp devices are and are far more important to be accurate.

Thanks for that Wilorg...
That is the kind of practical assistance that should be in a reference article somewhere on this site.
02-01-2013 08:24 PM
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DocWils Offline

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Posts: 1,271
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Machine: Philips Remstar series 60
Mask Type: Nasal pillows
Mask Make & Model: ResMed P10
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CPAP Pressure: 5-15
CPAP Software: SleepyHead

Other Comments:

Sex: Male
Location: Switzerland

Post: #9
RE: Comparing Oximeters - I should have known better...
One of the more interesting things that happens to me is that I get better oxygenation when I sleep than when I am awake - the reason being that using nasal pillows delivers air directly and overcomes the obstacles put in its way, like my rhinitis, but when awake, every in breath is limited by the collapse the my nasal walls and my deviated septum. So I get slightly less air than when sleeping with cpap - which explains partly why I wake up energised but get tired over the day and have eye focusing problems by early evening. If I didn't use an oxymeter I wouldn't have been able to track that down. If I were a mouth breather, that wouldn't be an issue, but alas, I am a nose breather.... bugger...
(This post was last modified: 02-01-2013 08:33 PM by DocWils.)
02-01-2013 08:32 PM
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2Tim215 Offline

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Machine: S9 ResMed AutoSet
Mask Type: Nasal pillows
Mask Make & Model: Swift FX Nasal Pillow - Medium
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CPAP Pressure: 6cm-12cm
CPAP Software: ResScan SleepyHead

Other Comments: OSA, Fibromyalgia, Rheumatoid Arthritis, Osteoarthritis, Gout, PTSD, & Meralgia paresthetica.

Sex: Male
Location: Finger Lakes Region, NY

Post: #10
RE: Comparing Oximeters - I should have known better...
I was curious about the accuracy of my CMS 50D Plus so compared it to my Blood pressure machine after a short work out. the ending pulse rate was only 1 beat off from the BP Machine which actually even hit the same ending pulse in a few seconds later. I believe they are pretty accurate. Mine has been very useful. And I believe they ALL have a slight -/+ variation as archangle posted about the CMS's. I think one thing to consider is once you have what YOU need, always use the same one so your comparisons are more accurate. I believe the CMS's only have a 3 year shelf life for some reason, maybe because of calibration issues? I'll have to check with my hospital and see if they have a calibrator. My wife works there so if they do it would be interesting to see where mine lands compared to one just calibrated. According to your OP you wanted the recording ability, so I would just stick with that one. One last note, usually one arm will vary compared to the other on most Blood Pressure machines, sometimes significantly. This may be part of the reason for the higher variation on the pulse, did you have one on each hand?

Tim
Finger Lakes Region, NY
(This post was last modified: 02-03-2013 09:21 PM by 2Tim215.)
02-03-2013 09:20 PM
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