Jul 17, 2012 at 1:51 pm #1292088
When the human body is transported to high elevations, ideally the respiration increases to the point of keeping up with the demand. The atmosphere gets thinner, and sometimes the blood oxygen saturation is diminished from (normal) nearly 100% down to 90% or 80%. Eventually, the subject blacks out.
Years ago, a miniature blood oxygen saturation meter cost was about $400, and it slipped onto a fingertip for the optical measurement. I believe that these were used on Mount Everest.
Just the other day in a store, I saw one for $40. Has anybody tried one of these?
Alternatively, we will just have to let the subject black out and then drag him down.
–B.G.–Jul 17, 2012 at 2:02 pm #1895472
Usually when my pulmonary edema sets in I'm vomiting and have a severe headache, so no tester needed for me.Jul 17, 2012 at 2:05 pm #1895473
"Usually when my pulmonary edema sets in I'm vomiting and have a severe headache, so no tester needed for me."
That's usually what happens to me when I get close to the altar……Jul 17, 2012 at 2:12 pm #1895476
I think we would all like to have a warning _before_ the point of pulmonary edema. For some strange reason, I don't vomit or get a severe headache. If I am pushing really hard, I will get tunnel vision. I thought an electronic gizmo would be neat, and it doesn't weigh much. It might be hard to calibrate to anything.
I have a test card for detecting mental impairment, but it requires one person to check the subject. The gizmo could be used by the subject himself.
–B.G.–Jul 17, 2012 at 2:19 pm #1895477
It seems that if you have a smartphone, you can use that to measure blood oxygen saturation levels. And from a quick google search and scan of articles, it seems they're quite accurate, or can be.Jul 17, 2012 at 2:24 pm #1895478
I don't carry any smartphone, and it would be much heavier than this little gizmo.
–B.G.–Jul 17, 2012 at 2:28 pm #1895479
"I don't carry any smartphone, and it would be much heavier than this little gizmo."
Ah, but many people do. So my comment was for those folks who might be interested who do carry smartphones – to know they wouldn't need a separate device.Jul 17, 2012 at 2:58 pm #1895493
@kgottshalkLocale: Colorado, USA
The hypoxia meter/pulse oximeter for $40 generally work well. I did home care nursing for several years and many of my oxygen dependent patients used them. They always correlated well with the more expensive one that I carried. Saturation (SpO2 <90% is considered to be hypoxic.
KarlJul 17, 2012 at 4:01 pm #1895504
Karl, that seems like good information.
Do you remember about how long it takes to get a measurement?
–B.G.–Jul 17, 2012 at 4:47 pm #1895509
@datsclarkLocale: San Francisco
I have a pulse oximeter that I bought for flight. I mostly keep in my flight bag, but it's fun to take on hikes to see what my ox levels are. I believe I have a NONIN from Turner, which i guess is approved for medical use.
I remember when I bought it being told to avoid cheap pulse-ox devices as they arne't accurate, but I'm certainly no expert on why or how they work. But I'm happy with with I got for ~60 bucks. It's really light weight, clips onto a finger, and shows the pulse and oxygen saturation in just a few seconds.Jul 17, 2012 at 6:25 pm #1895525
"The gizmo could be used by the subject himself."
After the other person checks him for mental impairment?Jul 17, 2012 at 6:27 pm #1895527
"It seems that if you have a smartphone, you can use that to measure blood oxygen saturation levels."
How does that work? I mean, I know phones are getting pretty darn smart, but measuring O2 sat?Jul 17, 2012 at 6:38 pm #1895532
If the subject refuses to use the gizmo, then that might be a sign of mental impairment. If the subject wants to use the gizmo, but can't remember how to work it, then that is a sure sign of mental impairment.
My mental test card requires the tester to be pretty clear, but it will find a subject that is slightly impaired.
I think when a policeman administers a field sobriety test to a suspected drunken driver, they use tests that look more for balance (ataxia) problems.
Blood is either fully saturated with oxygen, or else it is not. The oxygenated hemoglobin is one shade of bright red, and the poorly oxygenated hemoglobin is a much darker color. That is how the gizmo is supposed to work, by differentiating that color. What I don't know is how it develops a baseline reading. I would think that it is different from one subject to another.
Of course, it probably wouldn't work right on Tom, anyway, since olive oil flows in his veins.
–B.G.–Jul 17, 2012 at 6:48 pm #1895537
"How does that work? I mean, I know phones are getting pretty darn smart, but measuring O2 sat?"
I jumped the gun a bit, seems that the app isn't out yet, but it's been tested and it works, according to the article. It works by you holding your finger against the camera in most smartphones. The camera uses its 'flash' to illuminate your finger, and the app reads changes in your blood and records various things (there are already apps that read your heart rate this way, they work well).
Article that explains the app in development: http://www.wpi.edu/news/20112/kichonapp.htmlJul 17, 2012 at 6:57 pm #1895540
"It works by you holding your finger against the camera in most smartphones. The camera uses its 'flash' to illuminate your finger, and the app reads changes in your blood and records various things (there are already apps that read your heart rate this way, they work well)."
A phone that's smarter than me. Now that is depressing. :(Jul 17, 2012 at 8:39 pm #1895570
$40 is expensive, you can get them for $20.
Lots of old or sick people with decreased pulmonary function use them to let them know when they need to breathe oxygen.Jul 17, 2012 at 9:33 pm #1895578
"$40 is expensive, you can get them for $20."
Some of the cheaper ones have very inconsistent reviews.
When at high elevation, I've had some companions who looked a little sick, but they would not admit it. It would be nice to be able to put a number on it.
–B.G.–Jul 18, 2012 at 12:58 am #1895600
@stevec5088Locale: Central Calif
I think people can have a low O2 saturation, but still be ok at altitude. AMS is more complicated than just oxygen level in the blood.
There is a good report on the relationship between O2 saturation and Diamox use on a Kilimanjaro trip report by "Akichow" on WhitneyZone (link)
Bob G: I remember you from rec.backcountry. Please send me a PM or email.Jul 18, 2012 at 6:36 am #1895626
@acrosomeLocale: Back in the Front Range
The O2 saturation monitors work by shining a light through your finger, usually a laser. Fully oxygenated blood is one color, less than fully oxygenated blood is another color. The meter reads the absorption of the light in those wavelengths, compares them, and spits out a percentage. Since it is only making a RATIO of The two absorptions rather than caring about absolute absorption it doesn't matter how much is lost to fingers of different thicknesses- it works just as well on thick fingers as on thin ones. (And, actually, I think you can make them that use light reflectivity rather than absorption, too.)
But they don't work well through nail polish. Yeah, I'm looking at YOU, Dave. :)
Needless to say, I use them every day. And, an unacclimated person in Colorado Springs probably walks around just fine with an O2 Sat of 94%. It is hard to pick a cutoff for what is clinical hypoxia. By definition it is "clinical" when you have symptoms, not at some specific number. So, frankly, a mini mental status exam is probably more useful in the situation we're talking about. Of course, if someone was loopy and their sat is 98% then you've probably rules out hypoxia as a cause. Check their pack for empty bourbon bottles.
They are fun to play around with, though. And, notwithstanding what I just said, if I found someone with a sat of, say, 70% I would certainly take note…Jul 18, 2012 at 9:14 am #1895665
does anyone know how O2 saturation levels relate to anemia ?
in other words, do you get the same levels of readings whether or not you are anemic ?Jul 18, 2012 at 9:25 am #1895666
I've been looking at these for a while now as well. Does anyone know which one is the lightest?Jul 18, 2012 at 11:55 am #1895721
Dean, how does the meter get a ratio of two absorptions when it is taking only one measurement? I don't understand where the 100% sat baseline comes from.
I've never had AMS, but I've been around a number of climbers who had it, and pulmonary edema. I think it would be nice to have another tool to help make a diagnosis.
Meanwhile, the mental impairment test card works also. Too many times the subject will be laughing by the time he gets halfway through it and he is responding like a drunk. It might work better for the case of cerebral edema.
–B.G.–Jul 18, 2012 at 1:45 pm #1895743
@bzhayesLocale: So. California
What Dean is saying is that the meter reads the two different color frequencies and reports the ratio of the two. It does not matter how dense either one of the colors is by themselves since it takes the ratio of the two frequencies. The baseline (fully oxygenated blood) is assumed to be at one frequency the hypoxic (is that a word?) blood is assumed to be at another frequency. Since these are reported to be accurate meters, I would assume this is a valid assumption (this color frequency is the same for all people).Jul 18, 2012 at 2:05 pm #1895749
I think I understand the principle now. I'll run a measurement on a glass of orange juice and see if it gives me a decent answer. No, I can't do that since a glass of orange juice doesn't have a fingertip.
It seemed to me that if the meter were placed on a fingertip one way, that it might see and measure arterial blood (and get one kind of reading) and if it were placed another way, it might see and measure venous blood (and get a completely different reading).
–B.G.–Jul 18, 2012 at 2:47 pm #1895758
waste of money.
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