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How Pulse Oximeters Work (2015)

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Re: How Pulse Oximeters Work (2015)

#41

Post by Darkphibre »

VectorLock wrote: post #35
deadmutex wrote: post #23

Earlier quoted context omitted.

IIRC, Fitbit has products on the market that has them. Works both on iOS and Android. https://www.wearable-technologies.com/2020/01/fitbit-adds-bl...

Wow they finally did it. After the hardware being there for _years_ they managed to get around to enabling the software. I already jettisoned them for Garmin after waiting so long.

Same frustrations here! Couldn't believe when I bought their smart device based on advertising that said they had the hardware to do it.... but it wasn't enabled.

Re: How Pulse Oximeters Work (2015)

#42

Post by spaetzleesser »

DangerousPie wrote: post #17

Does anybody have any suggestions for how to check whether a pulse oximeter actually works properly? I bought one online from a not particularly trustworthy shop. I have never seen it show any value other than 99%. How can I figure out whether it actually does anything and doesn't just show 99% no matter what?

I have a cheap one so I am not sure if the absolute values are correct. But they change very reliably and consistently. With breathing exercises I can take the value from the usual 95-97 to 99. When I hold my breath long enough I can take the value down to 75 or less.

There is a delay of 20-30 seconds between changing my breathing to the oximeter changing its value. I suppose this is how long it takes for the blood to get around in the body.

Re: How Pulse Oximeters Work (2015)

#43

Post by spaetzleesser »

amiga_500 wrote: post #33

Does anyone know the degradation in blood oxygen levels under moderate exercise for a person who is fairly health (not athlete but slim, does regular exercise)? I had covid, so bought one of these, and I'm now building my way back to being able to jog, after months of shortness of breath. I would like to be able to understand what level my blood oxygen %, for a normal, healthy person, would drop to when say jogging.

Mine doesn’t drop much during exercise.

Re: How Pulse Oximeters Work (2015)

#44

Post by dreamcompiler »

oehtXRwMkIs wrote: post #38

Fun fact about pulse oximeters: in California EMTs are regulated so strictly that it is illegal for them to use a pulse oximeter as it is deemed "invasive". So if anyone is experiencing a medical emergency that could successfully be delayed following the algorithm involving checking blood O2, they better hope the EMT is experienced/lucky enough to suspect low O2 or that there's a paramedic or nurse on board. It's def…

This is a very weird law. In NM, basic EMTs can use a pulse/ox, insert blind airways, inject narcan and epinephrine, administer nitroglycerine, attach an ECG monitor, and do half a dozen other things more invasive than a pulse/ox.

Re: How Pulse Oximeters Work (2015)

#46

Post by peripitea »

VectorLock wrote: post #36
DangerousPie wrote: post #17

Does anybody have any suggestions for how to check whether a pulse oximeter actually works properly? I bought one online from a not particularly trustworthy shop. I have never seen it show any value other than 99%. How can I figure out whether it actually does anything and doesn't just show 99% no matter what?

Hold your breath. I've done that with a fingertip pulse oximeter I have.

In my experience you need to hold your breath for a while (like 2-3 minutes) for blood O2 to start decreasing. Certainly doable (and safe as long as you're lying down away from water) but might take some practice getting used to the discomfort. You can hyperventilate a bit before to make it easier (though never do this in any other breath holding scenario).

Re: How Pulse Oximeters Work (2015)

#47

Post by seehafer »

oehtXRwMkIs wrote: post #38

Fun fact about pulse oximeters: in California EMTs are regulated so strictly that it is illegal for them to use a pulse oximeter as it is deemed "invasive". So if anyone is experiencing a medical emergency that could successfully be delayed following the algorithm involving checking blood O2, they better hope the EMT is experienced/lucky enough to suspect low O2 or that there's a paramedic or nurse on board. It's def…

Wonder where they got that definition of "invasive" because it surely wasn't in a medical textbook.

Re: How Pulse Oximeters Work (2015)

#48

Post by dmitrygr »

alister wrote: post #39
dmitrygr wrote: post #27

It is really grating that all the visualizations are wrong. Blue is shorter wavelength than red. Infrared is longer wavelength than red. Every single image is wrong. :(

The author explains his visualization as follows: One is a red light, which has a wavelength of approximately 650 nm. The other is an infrared light, which has a wavelength of 950 nm. (Throughout our description, we will show the infrared light in light blue. In reality, infrared light is invisible to the human eye.)

i mean this, for example: https://web.archive.org/web/20191230203925im_/https://www.ho...

Re: How Pulse Oximeters Work (2015)

#49

Post by tomjakubowski »

oehtXRwMkIs wrote: post #38

Fun fact about pulse oximeters: in California EMTs are regulated so strictly that it is illegal for them to use a pulse oximeter as it is deemed "invasive". So if anyone is experiencing a medical emergency that could successfully be delayed following the algorithm involving checking blood O2, they better hope the EMT is experienced/lucky enough to suspect low O2 or that there's a paramedic or nurse on board. It's def…

Citation please? Page two of LA County Health Services's "EMT Scope of Practice" document lists pulse oximetry as part of the basic diagnostic process for EMTs. This would seem curious if state regulations forbid that.

http://file.lacounty.gov/SDSInter/dhs/206315_802.pdf

Re: How Pulse Oximeters Work (2015)

#50

Post by pps43 »

supernova87a wrote: post #37
wlesieutre wrote: post #18

Speculated to be included in the Apple Watch S6 this fall. https://9to5mac.com/2020/03/08/apple-watch-blood-oxygen-satu... At the time they reported that there were mentions of it in an iOS 14 leak, but it wasn't clear if it would be a software update to existing watches (somehow able to detect it with existing heartrate hardware) or in a watch hardware revision. Since it wasn't mentioned in the watchOS news at WWDC,…

Does anyone know, in general, if a watch device already has a pulse measurement LED system, whether that can also serve as a pulse ox measurement? or are they different hardware requirements?

You need two LEDs (one visible, one IR) to measure oxygen level, but only one for pulse.
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