Understanding pulse oximeters & their usefulness

dsm · Post by **dsm** » Mon Oct 31, 2005 5:10 am

In a recent thread in support of 'our' Lori, the topic came up re getting a pulse oximeter to check one's blood oxygen saturation.

The thing that has occurred to me is just what should we as xPAPers consider useful in regard to blood oxygen saturation.

There are a lot of units coming to market that are comparatively inexpensive and these give instant readouts of b/o sat + heart rate but for us xPAPers, is this of any use ?, don't we want a nights recorded b/o sat info so when we wake up we can read it ?

If so (I am sure it is so) then just what type of oximeter is the type we should be looking at.

I see that ResMed have a $199 attachment to the S7 & S8 range that can further attach an oximeter & record the info on the data card or whatever.

Does anyone know what type of oximeter attaches to a Spirit or Vantage or Puritan Bennett or any other popular xPAP ?.

CPAP.com offers this b/o finger meter but what use would we be able to put it to ?
https://www.cpap.com/productpage/nonin- ... meter.html

Then I have seen surplus hospital stock such as ...

http://cgi.ebay.com/Datascope-Accustat- ... dZViewItem

My question is, which type of oximeter is going to be useful to us xPAPers - why & how ? - am hoping we have the usual expert knowledge on this interesting topic.

Cheers

DSM
(enquiring minds need to know )

WAFlowers · Post by **WAFlowers** » Mon Oct 31, 2005 11:29 am

It seems to me that what would be needed for an overnight study is a recording pulse oximeter unless you have a ResMed S7 or S8 and their attacment.

I know the PB doesn't have that option, and I don't think others do either.

dsm · Post by **dsm** » Mon Oct 31, 2005 7:58 pm

Bill,

I agree. So we can eliminate 'finger 'pulse oximeters.

That takes us into the realm of very expensive new gear capable of recording or to look at an eBay hospital/clinic throwout (I may try to get one).

What it seems to me though is that it is not practical for John Doe cpapper to be able to get an oximeter to use at home.

I will look into just what plugs into the spirit & the probe it supports. That could be interesting but is looking expensive.

The other question that intrigues me re b/o probes, is how a finger attachment can assess b/o sat ? Anyone got any thoughts or knowledge on this ?

Cheers

DSM

PS here is the reslink attachment for the ResMed rang - very costly for John Doe cpaper
https://www.cpap.com/productpage/resmed ... ystem.html

Sleepless on LI · Post by **Sleepless on LI** » Mon Oct 31, 2005 8:51 pm

DSM,

Thanks for bringing this up at a time when it's very pertinent in my life. I am going to be speaking with my DME in the next day, hopefully tomorrow, or two. I will ask him just what is available out there for people like us who like to do it ourselves, if there is anything other than what you mentioned for the S7 and 8.

Barb asked a really good question today that I'd like to run by your brain, as technical as it is. She asked me what would have caused my oxygen level to drop to 84% and create a reason for therapy if my AI and HI were 0 and 4 respectively during the study. Wouldn't one of those indices, at least, have had to have been significant in order to bring down my level to an 84% mark? If I had only an HI of 4, why would I have moderate desats? That doesn't really go together, does it? Mild apnea, but moderate desats? Any ideas on this one?

dsm · Post by **dsm** » Mon Oct 31, 2005 8:56 pm

Lori,

I will look into that - interestingly I am exploring the hypopnea index & what it means esp if the AI is negligable (I am a hypopnea person according to my charts).

I expect to get a oximeter of some sort.

Also I found this info on how the oximeter probes work ...

>>
These measurements are updated with each heartbeat. The probe emits an infrared light from one side of the finger and captures the residual light that passes thought the finger on the other side. The probe transmits this data to the monitor, which calculates the oxygen saturation of the blood. Used for patients with respiratory problems, and is required by law whenever a patient is under anesthesia. Note that these pulse oximeters measure Functional oxygen saturation, which is oxygenated hemoglobin expressed as a percentage of the hemoglobin that is capable of transporting oxygen.
<<

Cheers

DSM

Guest · Post by **Guest** » Mon Oct 31, 2005 9:05 pm

Sleepless on LI wrote:DSM,

Barb asked a really good question today that I'd like to run by your brain, as technical as it is. She asked me what would have caused my oxygen level to drop to 84% and create a reason for therapy if my AI and HI were 0 and 4 respectively during the study. Wouldn't one of those indices, at least, have had to have been significant in order to bring down my level to an 84% mark? If I had only an HI of 4, why would I have moderate desats? That doesn't really go together, does it? Mild apnea, but moderate desats? Any ideas on this one?

Might want to research hypoventilation, UARS, nocturnal asthma if you desaturate only by night.

However, wearing a pulse oximeter while awake should reveal if you also desaturate by day. If so then pulmonary conditions not exclusive to sleep should be considered as well.

Sleepless on LI · Post by **Sleepless on LI** » Mon Oct 31, 2005 9:07 pm

Thanks for that info, DSM. I will let you know what I find out, if anything, when I get to the DME's. Hopefully we will find out something to help us all.

dsm · Post by **dsm** » Tue Nov 01, 2005 1:27 am

Lori,

From what I gather many docs would be quite concerned at 84% b/o sat.

I saw one report where the doctor said he got worried if a patient gets below 92%. But apparently some severe Apnia sufferers can get down below 50% & this same report said thats when malfunction of body parts can start to occur.

I can't quite see how such a low AI could cause a low b/o sat reading. But I am a real novice in analysing this info.

Am still search sorces for info on b/o sat.

Cheers

Doug

Sleepless on LI · Post by **Sleepless on LI** » Tue Nov 01, 2005 5:44 am

dsm wrote:I can't quite see how such a low AI could cause a low b/o sat reading. But I am a real novice in analysing this info.

That's my concern. Doesn't make much sense...

john5757 · Post by **john5757** » Tue Nov 01, 2005 10:32 am

dsm wrote:Lori,

From what I gather many docs would be quite concerned at 84% b/o sat.

I saw one report where the doctor said he got worried if a patient gets below 92%. But apparently some severe Apnia sufferers can get down below 50% & this same report said thats when malfunction of body parts can start to occur.

I can't quite see how such a low AI could cause a low b/o sat reading. But I am a real novice in analysing this info.

Am still search sorces for info on b/o sat.

Cheers

Doug

DSM,

I have the ResLink but without the oxygen sensor attachment. One possible advantage of using this attachment is that it can measure minute Ventilation as it currently does for me and the flattening curve migh give more clues in why some may have a low AHI and have desats only during night.

Sleepless on LI · Post by **Sleepless on LI** » Tue Nov 01, 2005 1:43 pm

Well, I visited with my DME today to get my overnight pulse oximeter. Will be using it tonight. He did a baseline reading which read my level as 99%. But he said it can change when sleeping due to sleeping patterns, the fact that you're in the laying down position, and how the blood reacts. But he agreed that I probably shouldn't have been placed on CPAP to begin with and should probably have just been given oxygen because a 4 HI does not give need to be on CPAP therapy.

He asked if I had had any heart problems in the past, which I did ending in 2001 with the second of two cardiac ablations. I had supraventricular arrhythmia and tachycardia, which was cured. But he said that could be a sign that perhaps the heart is not pumping up to where it should be and that I need oxygenation at night.

I did ask about the machines that could do both and he didn't even know about the S7 and 8, so there goes any help he could offer in the dept.

Sorry I can't give you more info, but he didn't have any regarding anything he knows about that can do this. DOESN'T mean there isn't any, but...

LoneRider · Post by **LoneRider** » Tue Nov 01, 2005 2:00 pm

With all said this is interesting. I can remember several years ago, working on a project that use a simple clip on finger pulsoximeter, IIRC, all it did is constantly send the O2 and pulse informator over RS232, I believe it even scavanged power from the serial port for the LEDs. With one of those it would not be too hard to create a simple windows application to record over night.

The pulsoximeter used a my sleep studies was even simpler, it simply had a LED emiiter and received at different points along the plastic, they taped it on my finger and all was good. I would imagine it would be very simular.

The problem with actually making an over night pulsox recorder would not be the difficultly or the cost of parts, it *could* be the cost getting the device through the regulatory maze. Don't know if it would be classes as a Class I medical device or not??? I guess if you get the "Can not be used to determine any medical treatment" waver past them, it might not be. But I would think that anything that could be used to determine medical treatment would have to be validated. I will have to ask a friend who is an expert in the field of medical regulatory sutffs.

cheers,
Tom

Sleepless on LI · Post by **Sleepless on LI** » Tue Nov 01, 2005 2:29 pm

Tom, you and others like yourself, blow me away. How you could even begin to think of how to make a working pulsox, let alone one that works with Windows, makes me feel like the stupidest person on earth, which I know I'm not. Where do people like you come from? Did you always have a scientific analytical mind or did you learn through books?

I guess this is what makes the world go round. Everyone has the things that they're good at and enjoy doing. We put them all together and we have a little bit of everything we need. But things like this are so out of my comprehension to even entertain.

BP · Post by BP » Tue Nov 01, 2005 2:55 pm

dsm wrote:I can't quite see how such a low AI could cause a low b/o sat reading. But I am a real novice in analysing this info.

Could it be the duration and not the index itself. If I have one apnea event but it lasts 3 minutes you could conceivably desat to 50%. Just a thought, I have no direct experience with this but have done some basic online research.

As far as an oximeter, I have looked around quite a bit, and this one seems to be the cheapest that will do the job, although it is not cheap.

http://www.nonin.com/products/3100.asp

Nonin, is one of the leaders in this technology, if not the leader. To get access to all the features you need the software as well, another $700 I think.

Cheers,
BP

Sleepless on LI · Post by **Sleepless on LI** » Tue Nov 01, 2005 3:00 pm

BP wrote:Nonin, is one of the leaders in this technology, if not the leader. To get access to all the features you need the software as well, another $700 I think.

Cheers,
BP

Ouch. Just another $700 for the software? As Ralph Kramden used to say, a mere bag of shells.

My son also asked me, when they gave me the pulsox today, if it was a Nonin. That's what they use in the hopt. he works in.

My DME gave me a Respironics one. Now wouldn't you think they could make it to work with our Encore Pro software? The DME said, no.

Good thought about the event lasting a long time, enough to cause a desat. I said I was going to look at my graphs from my study and see if I could correlate the two. I forgot, so I'm off to do that now. Thanks for indirectly reminding me.

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