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it is unexpected, intelligent, satirical humour basically.....perhaps just British thing.
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My quarantine is officially over, so I could go and get food for myself - and see how I am doing with "actual physical things" at the same time.
I take my SpO2 / PR meter with me just so I can attach numbers to my "empirical feelings".
So off I go: the plan is a quick ten mile trip to make sure the car is charged - parked up for two weeks, it's going to need some charge for sure - then ASDA; Fuel the car; Tesco. (ASDA does stuff Tesco doesn't and vice versa).
Park at ASDA: gloves, face mask, list, O2 Sats at 93% (pretty good at the moment, and getting better but a long way off the 98 ~ 99% you lot are probably still working with). Took me a while, and I had to have a sit down breather for a few minutes after I'd used the self scan for two carrier bags and pack of toilet rolls, but I did it! That's the most physical activity I've had other than vomiting for two weeks!
Back to the car, everything in the boot, return trolley, bin gloves.
Sit down, check SpO2 sats: 75%. ![Elephant | [mastadon]](https://codeproject.global.ssl.fastly.net/script/Forums/Images/elephant.gif) - that's why I'm so exhausted.
Forget fuel, forget Tesco: Time to go home, I'll try that one tomorrow.
That was over an hour ago, and my sats are back up to 87%, and rising slowly. Still a bit light headed and my back hurts, but other than that, I'm fine. This is going to take a while.
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
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Mate, you're going to have to take things way easy and in small and slow steps - just think of it as prep for old age .. oh, wait 
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You're a cruel man ... 
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
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I suppose he speaks from experience
M.D.V. 
If something has a solution... Why do we have to worry about?. If it has no solution... For what reason do we have to worry about?
Help me to understand what I'm saying, and I'll explain it better to you
Rating helpful answers is nice, but saying thanks can be even nicer.
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Interesting that you're working with an external blood O2 monitor. I was just doing some online browsing (within the last 20 minutes prior to your post) as to how one can justify that they can possibly work.
Here's my reasoning: The device is working on the optical density reading from of a beam of light sent through your finger (or into and reflected back). It measures the amount of hemoglobin present vs. deoxyhemoglobin (the bluer stuff when the oxygen is used up - usually holding CO2. This certainly can be measured and compared to other reading on the same finger on the same person.
HOWEVER, it take no account of the optical density of the person's skin, thickness of that skin, and their blood-count. We haven't even entered into scattering as each person's body's a bit different. In other words, it really cannot work unless it is specifically set up (standardized) for a particular user by comparison with their actual blood and a proper oxygen saturation
analysis. It is certainly using infrared as were it using anything in the visible spectrum than those with very dark skin would be unmeasurable. The references had some mention of certain drugs and physical ailments that can interfere, as well.
Now I'm not saying it's quite useless - you do have relative readings for yourself and that can be of some value (as you just experienced via exhaustion and recovery). If this all sounds like I'm over-suspicious of it's utility, consider that of the several MD's I've visited (when live visits were a thing), they use these devices for the purpose of taking one's pulse. Period.
Still - they made their money selling them to every physician's office and hospital and now have cut the price and are marketing them for exercise junkies.
Just be aware of it's intrinsic limitations - the readings are relative. If you correlate them with your own perceived physical condition you can very likely use them.
I guess I ought to sign off on this as Sciencesplainer
| Ravings en masse^ |
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| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
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That's why I bought one - not for "absolute values", though I'm pretty sure the "medical grade" ones all paramedics carry and are the first thing they attach are accurate, mine code £29 from Amazon. So I'm expecting relative values, not absolutes.
The idea is to confirm I've pushed a bit too hard (or will shortly) and give me a better "feeling" for how much I'm improving on a daily basis. I'm anal retentive like that ...
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
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OriginalGriff wrote: I'm anal retentive
You keep it where? 
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I had a USB-C fitted ... 
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
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I hope it was not too painful
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Might sound like a Sciencesplainer myself but I looked a bit into the subject last year when I needed to buy one for a friend. You can find the TL;DR on Wikipedia[^].
Quote: HOWEVER, it take no account of the optical density of the person's skin, thickness of that skin, and their blood-count. We haven't even entered into scattering as each person's body's a bit different. In other words, it really cannot work unless it is specifically set up (standardized) for a particular user
Quoting from the same source: "By subtracting the minimum transmitted light from the transmitted light in each wavelength, the effects of other tissues are corrected for, generating a continuous signal for pulsatile arterial blood."
A coda triggered also by Griff's post: went on Amazon to look at the oxymeter I bought in 2018 for 35$.... it is now 90$... man, some people a making a killing from this killer pandemic!
Mircea
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Went to your Wikipedia article: It talked about normalization - and that brought a question to my mind: normalization is essentially putting all items on a fixed scale (for example, 0 to 1 is very common, by subtracting the minimum and then dividing the values by the maximum in the range).
Anyway - normalized with respect to what it has - which is (as I had noted in my OP) that you can use it to compare you to various states of yourself and not much more.
Further down the page, in the limitations section, this was born out.
Quote: The metabolism of oxygen can be readily measured by monitoring expired CO2, but saturation figures give no information about blood oxygen content. Most of the oxygen in the blood is carried by hemoglobin; in severe anemia, the blood contains less hemoglobin, which despite being saturated cannot carry as much oxygen.
So - it compares you to you. In actuality, since it does not have a zero value, it cannot even really normalize. How does it know how low you can go? Essentially, this is why none of the medical professionals I've seen use it for any purpose beyond pulse. You'd need a blood-count to know how much hemoglobin is potentially available.
As for the interesting concept of price: The reason I happened to have been looking at this before Griff's post is this item on NewEgg's email offers for the day.[^] Others are on the page, as well, more in line with you original $34 price point. I've seen what you're referring to: a $25 webcam offered for $100 - $200.
| Ravings en masse^ |
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| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
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Some people are just criminals, robbing the gullible: go to FleaBay, search for "HDMI cable", and put the sort order to "most expensive first". Were you really expecting people to pay that much?
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
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Geez!
All this science - I don’t understand.
This is just my job ( five days a week)!
If you can't laugh at yourself - ask me and I will do it for you.
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I use an SpO2 and SmO2 sensor in my training and the physics behind Near Infrared Spectroscopy (NIRS) Sensors is well understood. If you want to read about it check out Moxy's explanation. It's a bit brief but they had a virtual conference a couple of weeks ago where Roger at Moxy went deep into the details of it all. I'm still waiting for the on-demand videos to be posted but if you're at all interested I'll post them when they appear.
One interesting bit is they absolutely do take into account differences in skin, adipose layer etc and use ray tracing to model the path of the light to form a lookup table that can be used to interpret the light scattering. A simple and clever solution that also handles whether the skin or wet or dry (we get sweaty during tests!) while providing the ability to sample multiple times a second.
cheers
Chris Maunder
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I spent literally several years doing spectroscopy via transmitted light. Things you must absolutely have for absolute values: blanks. Blank are essentially unredacted samples of the materials with which you compare your experimental results. You use a sample of a known concentration to check it's absorbance (a value linear with concentration). You also have a sample, the 'blank' which has all of he background media (in which the samples were dissolved, for example) so you know their contribution to the spectrum. The result is that you can analyze the spectroscopic results independent of artifacts. It was common, in many instruments, to have duel beams, one with the sample and one with the medium: per-selecting out the background.
A good example: when I did infrared spectroscopy I had not only the absorption of the sample but also the contribution from the water in the air. One had a spectrum, in the same apparatus/container with no sample. This yielded, of course, the spectrum of the air. This could then be subtracted from the original with the result that the spectrum was now just that of the sample.
So - what do you get when you have a single beam instrument on a variable medium? You can make measurement and compare them to one another. You can then get relative values. You can (a lookup table) then have a mechanism to measure the state of that particular system. If you had concurrent actual blood work to analyze and label each reading you can even give them absolute values (which you do not have, otherwise). Without that, your real reading scale has as it's limits "exhausted" and "rested". That can be useful - but it all works only for a single user because it is a single system and a single lookup table. Using that table for someone else's finger won't work . . .
. . . they need their own table. Hence, that is why the MD's realized it's not useful for blood oxygen levels. They measure you once, when you come by. How accurate a reading can they get with a single value?
So - you can certainly use it to check yourself out. Your mental lookup table that maps it's readings to how you feel and what you've been doing can give you some information. It's a device that must be personalized (general case).
A single-beam one-shot measurement of a sample in an environment that is itself only characterized in the most general sense will only yield the most general (and of limited accuracy) data.
Fat? Thin? Black? White? Healthy? Anemic? Living at high altitude? How does it know - and if you could tell it yourself, how much of the preceding do you actually know?
| Ravings en masse^ |
|---|
| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
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W∴ Balboos, GHB wrote: I spent literally several years doing spectroscopy via transmitted light
Awesome. We need to meet up, get drunk, and you can talk me through it start to finish. That would be awesome.
With O2 sensors on a person it's always been remarked that it's the relative numbers that matter. Even shifting the sensor half a cm totally changes the readings during a workout, so good luck getting consistent absolute values between workouts.
For me it's the trends over time in a workout (is my SmO2 recovering each interval, have I hit my utilisation limit? HAve I opened up my capillaries enough to start the workout?) and for SpO2 I'd be assuming that the sensors will give you a good enough answer to "Am I oxygenated or should I call the hospital" that they are worth the time.
cheers
Chris Maunder
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Chris Maunder wrote: Awesome. We need to meet up, get drunk, and you can talk me through it start to finish. That would be awesome.
If that seems exciting, consider that in graduate school I separated Uranium isotopes using a pulsed CO2 laser in a tube 30 cm long - about 10x enrichment factor than the current state of the art.
There's also "induced surface ensembles on transition metal surfaces" - computer modeled (Monty-Carlo) and then proven experimentally.
Basically, perhaps you meant "very drunk".
I've never been a bar-drinking type of guy. More like opening a bottle of single malt or getting some six-packs of good IPA in a comfy spot in someone's home - even kitchen tables are good. Wine is too effective at putting me to sleep, but I'll admit that a five liter box can take you a long way into the evening.
But back to the subject at hand. I'm glad you brought in that it is a relative measurement - and selfishly, it's to confirm I wasn't just blowing smoke out my ass on the way spectroscopy works. Tools are good for what they can do and as long as you know their limits they're perfectly fine.
| Ravings en masse^ |
|---|
| "The difference between genius and stupidity is that genius has its limits." - Albert Einstein | | "If you are searching for perfection in others, then you seek disappointment. If you seek perfection in yourself, then you will find failure." - Balboos HaGadol Mar 2010 |
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W∴ Balboos, GHB wrote: More like opening a bottle of single malt or getting some six-packs of good IPA in a comfy spot in someone's home - even kitchen tables are good
Me too, absolutely.
cheers
Chris Maunder
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Well done Paul - for your efforts you can have a go on my MV when ewe is better 
"We can't stop here - this is bat country" - Hunter S Thompson - RIP
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I will not hold you to that!
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
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You are welcome mush
"We can't stop here - this is bat country" - Hunter S Thompson - RIP
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OriginalGriff wrote: This is going to take a while.
Yup.
I didn't hear you complain about being confused anymore. Just take it slow and avoid people who have the common flu; you don't want that right now.
Bastard Programmer from Hell 
If you can't read my code, try converting it here[^]
"If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.
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I'm not confused anymore, provided I don't try to think too hard. That uses extra oxygen, so it's as bad - or worse - than physical exercise. Apparently, overall for the brain it's a total of 1 ~ 2% extra, which is trivial, but in local cortical regions it's 5 ~ 10%, and that's enough to tip me into deficit in places.
So heavy thinking, real concentration, is right out as it almost immediately becomes counter productive ... 
"I have no idea what I did, but I'm taking full credit for it." - ThisOldTony
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As bad as it sounds, it's still a step up from last week. Hope your taste is at least improving a bit.
Lots of relaxation, lots of protein. Buy an extra steak. You have to recover, after all 
Bastard Programmer from Hell
If you can't read my code, try converting it here[^]
"If you just follow the bacon Eddy, wherever it leads you, then you won't have to think about politics." -- Some Bell.
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