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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 sh

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?

mturmon 6y ago
I purchased a relatively cheap one from Amazon a couple of months ago. Less than $50, I believe. I tried some simple stuff when it arrived. I believe I was able to get it to swing within the 94-99% range by holding my breath and by deliberate, deep breathing, over the span of just a minute or two. It definitely was not pegged at 99%. The changes were surprisingly fast. My wife was able to get the same response. If it matters, I'm at about 500 feet above sea level (not high-altitude at all).
- deleted 6y ago
  [deleted]
- DangerousPie 6y ago
  How long did you hold your breath for?
  - mturmon 6y ago
    Perhaps 30 seconds? It was uncomfortable but not a big strain. I see someone nearby saying 2-3 minutes. For me, it was not that long!
    - mancerayder 6y ago
      I bought one a few days ago (weird coincidence), from Amazon for around $35 at the advice of a friend. Skeptical also, my 97% level upped to 98-99 with deep breathing, and then I held my breath as long as I could possibly do it and it dropped to about 93-94. That's obviously not a confirmation that it's calibrated or trustworthy, but at least it shows a relative measure that seems real in both directions of oxygen saturdation. Surely if I have a drop due to illness I should notice, even if the number isn't exact.
- michaelrpeskin 6y ago
  1) don't know how much I trust the stuff from Amazon - see my earlier comment above about working at a pulse oximiter company and all the calibration tests we did. 2) while being an intern and sitting alone in my cube, I had dozen of test meters just sitting there and when I got bored I'd do the same thing and try to get it as low as I could by holding my breath and then snap back up. Our office is at 5000 feet so 95% is normal for healthy folks, I could get down to 85 or so and then hyperventilate back to 97% or so pretty quickly.
deadmutex 6y ago
Did you purchase it in the USA? If so, you can check if it has been cleared as a Class II Medical Device from the FDA.
VectorLock 6y ago
Hold your breath. I've done that with a fingertip pulse oximeter I have.
- peripitea 6y ago
  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).
  - jimworm 6y ago
    If you weren't doing this already, try holding your breath after exhaling to reduce the amount of oxygen stored in your lungs, then the wait wouldn't be as long - 2-3 minutes is a good breath hold!
    - peripitea 6y ago
      In my experience this isn't that much better from a discomfort perspective, because (I would guess -- not an expert on physiology) the lower available oxygen in the lungs also leads to a more rapid increase in blood CO2. It might be a bit better depending on your particular body though, so yes it's worth trying both out. Actually I just tried it and yeah for me at least the full-lungs version is obviously longer but takes less discomfort for my SpO2 to start to drop (like well before contractions start), whereas on exhale I get more discomfort (around 15s before contractions) before a similar drop.
spaetzleesser 6y ago
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.
bdcravens 6y ago
I have CF, so I regularly check my o2 sat levels. I actually used mine the same day as I had a checkup; I recall it being spot on. (Homedics model from Walgreens I think)
literallycancer 6y ago
Hold your breath until in starts going down.
OJFord 6y ago
To test it's accuracy or just to see if it ever shifts from 99% (or random fluctuations)? For the latter you you'd just use inorganic material of varying thickness/opaqueness.
renewiltord 6y ago
Held my breath till I nearly passed out. Watched the indicator tick down. You'll start seeing stars and the meter should be matching you. It is hard to do so normally so I forced the air out and then pinched my nose shut with my fingers to prevent accidentally breathing in.
- amiga_500 6y ago
  Holding your breath until you really want to gasp in will surely see the level drop, certainly before you start to go dizzy.

mturmon 6y ago

I purchased a relatively cheap one from Amazon a couple of months ago. Less than $50, I believe. I tried some simple stuff when it arrived. I believe I was able to get it to swing within the 94-99% range by holding my breath and by deliberate, deep breathing, over the span of just a minute or two. It definitely was not pegged at 99%. The changes were surprisingly fast. My wife was able to get the same response. If it matters, I'm at about 500 feet above sea level (not high-altitude at all).

deleted 6y ago
[deleted]
DangerousPie 6y ago
How long did you hold your breath for?
- mturmon 6y ago
  Perhaps 30 seconds? It was uncomfortable but not a big strain. I see someone nearby saying 2-3 minutes. For me, it was not that long!
  - mancerayder 6y ago
    I bought one a few days ago (weird coincidence), from Amazon for around $35 at the advice of a friend. Skeptical also, my 97% level upped to 98-99 with deep breathing, and then I held my breath as long as I could possibly do it and it dropped to about 93-94. That's obviously not a confirmation that it's calibrated or trustworthy, but at least it shows a relative measure that seems real in both directions of oxygen saturdation. Surely if I have a drop due to illness I should notice, even if the number isn't exact.
michaelrpeskin 6y ago
1) don't know how much I trust the stuff from Amazon - see my earlier comment above about working at a pulse oximiter company and all the calibration tests we did. 2) while being an intern and sitting alone in my cube, I had dozen of test meters just sitting there and when I got bored I'd do the same thing and try to get it as low as I could by holding my breath and then snap back up. Our office is at 5000 feet so 95% is normal for healthy folks, I could get down to 85 or so and then hyperventilate back to 97% or so pretty quickly.

deadmutex 6y ago

Did you purchase it in the USA? If so, you can check if it has been cleared as a Class II Medical Device from the FDA.

VectorLock 6y ago

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

peripitea 6y ago
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).
- jimworm 6y ago
  If you weren't doing this already, try holding your breath after exhaling to reduce the amount of oxygen stored in your lungs, then the wait wouldn't be as long - 2-3 minutes is a good breath hold!
  - peripitea 6y ago
    In my experience this isn't that much better from a discomfort perspective, because (I would guess -- not an expert on physiology) the lower available oxygen in the lungs also leads to a more rapid increase in blood CO2. It might be a bit better depending on your particular body though, so yes it's worth trying both out. Actually I just tried it and yeah for me at least the full-lungs version is obviously longer but takes less discomfort for my SpO2 to start to drop (like well before contractions start), whereas on exhale I get more discomfort (around 15s before contractions) before a similar drop.

spaetzleesser 6y ago

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.

bdcravens 6y ago

I have CF, so I regularly check my o2 sat levels. I actually used mine the same day as I had a checkup; I recall it being spot on. (Homedics model from Walgreens I think)

literallycancer 6y ago

Hold your breath until in starts going down.

OJFord 6y ago

To test it's accuracy or just to see if it ever shifts from 99% (or random fluctuations)? For the latter you you'd just use inorganic material of varying thickness/opaqueness.

renewiltord 6y ago

Held my breath till I nearly passed out. Watched the indicator tick down. You'll start seeing stars and the meter should be matching you. It is hard to do so normally so I forced the air out and then pinched my nose shut with my fingers to prevent accidentally breathing in.

amiga_500 6y ago
Holding your breath until you really want to gasp in will surely see the level drop, certainly before you start to go dizzy.