Question on finger Oximeters

I know that most instructions say to place the red light on the fingernail side of the finger, but I also have a finger oximeter that says place the red light on the opposite side (fleshy side).
So my question is, does it really make any difference which side I use (fleshy or nail side)?

(Of particular interest for women with painted and or artificial nails)

I have never seen a finger oximeter used with the light on the pad side.
Nail side is almost always preferred.
I always test my polish for light transmission.
Dark colors block the light.
Any product on your nail must be light enough to allow pulse-ox operation.
The instrument always trumps your manicure.
If it prevents operation--LOSE IT
One nail should be enough.

chunkyfrog wrote: ↑

Wed Oct 12, 2022 10:08 am

I have never seen a finger oximeter used with the light on the pad side.

IIRC, there are two types of pulse-ox systems, transmission and reflectance.
Wearable oximeters, such as watches and a few finger* oximeters are designed to be reflectance types and avoid the fingernail polish issues.

*see duckbill oximeters such as Wellue Oxyfit and Relion Delux.

Wondering1 wrote: ↑

Wed Oct 12, 2022 8:12 am

I know that most instructions say to place the red light on the fingernail side of the finger, but I also have a finger oximeter that says place the red light on the opposite side (fleshy side).
So my question is, does it really make any difference which side I use (fleshy or nail side)?

(Of particular interest for women with painted and or artificial nails)

Since they operate by looking through your finger, and comparing the difference in transmission between red and infrared light, it shouldn't matter which way you put the oximeter on your finger.

Easy enough to test, put it on one way, then turn it over and try it, compare the results.

palerider wrote: ↑

Wed Oct 12, 2022 12:28 pm

Since they operate by looking through your finger, and comparing the difference in transmission between red and infrared light, it shouldn't matter which way you put the oximeter on your finger.

Does the watch oximeter look through the wrist?

Tec5 wrote: ↑

Wed Oct 12, 2022 2:19 pm

palerider wrote: ↑

Wed Oct 12, 2022 12:28 pm

Since they operate by looking through your finger, and comparing the difference in transmission between red and infrared light, it shouldn't matter which way you put the oximeter on your finger.

Does the watch oximeter look through the wrist?

Not the subject at hand, if you want to know, go figure it out and report back.

palerider wrote: ↑

Wed Oct 12, 2022 12:28 pm

Easy enough to test, put it on one way, then turn it over and try it, compare the results.

Did I mention that I have two pulse-oximeters?
So did a quick test (comparing the nail side vs pad side toward the visible red light). There was no obvious difference which side was exposed to the red light.

But on further examination, I found that the position of the visible red light and what I assume to be the detector were different between the two ximeters.

In one case the red light and detector were same side of the finger (apparently the "light" travels through the finger from the nail to the pad.
In the other oximeter the "light" and the detector are on the same side (nail or pad) so the "light" travels across the surface of the nail or pad.

(with the later, there are no electronics at all on one side of the finger well, the advertising for this oximeter calls it a duckbill type)

Back in the melamine Age, I had a treadmill with a pulse oximeter
that clipped to the earlobe.