Pulse Oximeter

[Flojt]

Originally Posted by jome

Was this with or without packing?

I've only tried an oximeter a couple of times. I think it went into the 50s, but I don't think my saturation was actually that low, more likely the vasoconstriction just fooled the sensor, and they are inaccurate anyways under 70

The oximeters intended for medical use is set with sensors that works well to 60-70%.
But as Jome points out, due to the vasoconstriction, the measured sat in the fingers are "inaccurate".
I have seen 55% along with a heartbeat at 53, in a 5'10 STA, measured with fingerclip. Usually a sat in the 50% area is found during breatholds that last 7-8min.
The best and most accurate way to determinate the saturation is by blodgas analyzing.

But it's still intressting to use non invasive ways to measure the oxygen.

[Kimmo]

This is quite normal phenomenon. Pulse oximeters are not quite accurate in low oxygen levels. I just monitored one interesting pilot study where the test person made dry static packed and and without packing. Packed heart rates were something about 80/mins and without packs same person had heart rate bellow 40/mins. Interesting thing was to monitor this persons blood pressure which was for minutes 60/40 level while packed. These values vere monitored with the pulse oximeter as well as straight from inside of the wrist artery + transcutanic measuring.

- kimmo

[cebaztian]

What do you think I can expect from this one:
Finger Pulse Oximeter - Finger Oximeter FP300D at Favoriteplus.com

Sebastian

[trux]

Fingertip oximeters are not very well suitable for freedivers - they will show wildly incorrect values due to vasoconstriction once the diving response sets on (or due to vasodilatation after hyperventilation as recently discussed here, too)

[rbsub]

Does anybody know whether there exists a kind of pulse oximeter that can be connected to a computer via USB? That would be nice!

[ADR]

most of them can be linked live to a PC. even the really old ones usually have a serial port that can stream the data to a telnet session

[rbsub]

Thx for your answer. What I tought was of a small one like this one Seb mentioned.

Do you have an example of one (which is not too expensive)?

[ADR]

Quick search on eBay and here is one for you with a current bid of US$9.99 and a buy now price of US$150. This one has an RS232 port and for under $40 at most computer shops you can buy a USB convertor.

+ NELLCOR N-200 PULSE OXIMETER - eBay (item 360046377181 end time May-01-08 19:00:16 PDT)

You can get small portable units but still must have a proper sensor(earlobe) finger tip as explained is close to useless

Hope that helps

[cebaztian]

It seems like the fingertip oxies are not popular here.
I find them very useful for checking when OXY starts to fall and how fast it falls.
Seem to be fairly accurate down to 70% (depending price).

Vaso does not seem to be an issue for me.

Sebastian

[trux]

Originally Posted by cebaztian

It seems like the fingertip oxies are not popular here.
I find them very useful for checking when OXY starts to fall and how fast it falls.
Seem to be fairly accurate down to 70% (depending price).

Vaso does not seem to be an issue for me.

The problem is that when the value on a fingertip oximeter starts to fall, it does not indicate falling O2 saturation in your body. It only indicates vasoconstriction, and that tells absolutely nothing about your real O2 saturation. So yes, to some degree it is useful, because it shows you when the diving response really kicks in, but it is useless for diagnosing your O2 saturation.

[rbsub]

What about using an oximeter at your earlap?

[trux]

Yes, if you read posts at the beginning of this thread (or a few other threads about oximeters here on DB), you can see that it indeed works little bit better. The ear is close to the brain, and although there is certain vasoconstriction in skin everywhere anyway, it is less important than at the extremities. Eric Fattah uses a transcutaneous oximeter on his chest, which works better too, although also there the values are quite a bit off due to the vasoconstriction (or vasodilatation) in skin.

[wjohnson100]

Hi to all. I have extensive experience with using a fingertip pulse oximeter. I have found it to be very useful in figuring out the effectiveness of breathe up and relaxation techniques. If you use one you should expect the reading to stay steady for the first few minutes after you start your hold. The length of time that is depends on your lung capacity, effectiveness of your relaxation techniques, and which hold you are doing. For me the reading starts dropping at about 4:15 on my last hold and then drops 8-10% per minute after that, and all the way down to 73% at the end of a 7 minute hold, so it is tracking pretty well. All of these numbers vary widely from person to person, but you get the idea. It is not perfect but is just one more useful tool. They are very inexpensive and can be found at Amazon.com. Search under "Pulse Oximeter." Their only limitation that I am aware of is their range goes from 70%-99%. I know I can get my O2 saturation below 70%, so at that point the device may become unreliable.

One way you can tell if yours is still working during a hold is if it shows a pulse. Mine shows a wave form. If you cut blood off, the wave form goes flat. I tried it by squeezing my finger with it on. So even if you get periferal vasoconstriction, you will still get some pulse through your finger. If the wave form goes flat, then you know your reading is unreliable.

[Steinar]

What kind of Oximeter with earlobe sensor do you recomend?

I guess it`s a question about how much money you spend.

[wjohnson100]

I just use normal fingertip pulse oximeter and it gives me good results. I don't think you get much vasoconstriction on dry holds anyway. I have gotten good readings all the way down to 73% at 7 minutes. Much lower than that and it may be unreliable because they are not calibrated below 70% I think. It may also depend on the one you buy. You can see me using one if you go to YouTube YouTube - wjohnson100's Channel where I have two recent posts, one a 7:00 hold and another a heart rate reduction demonstration.