Kinda Geeky - the story of the pulse oximeter
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wrote on 28 Jun 2022, 14:22 last edited by
Few people realize how recent of an innovation this is. When I started training, it was unheard of. By the time I entered private practice, 14 years later, it was the standard of care.
Pulse oximetry, combined with capnography (measuring exhaled CO2) made the practice of anesthesiology much, much safer.
https://pubs.asahq.org/anesthesiology/article/135/4/591/117099/Takuo-Aoyagi-Ph-D-American-Society-of
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wrote on 28 Jun 2022, 14:29 last edited by
Yeah, I'll get right on reading that.
But thank you for helping me recollect the proper name for what I've been referring to as the "fingerstick thingie".
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wrote on 28 Jun 2022, 16:21 last edited by
No sticking involved. It discerns light.
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wrote on 28 Jun 2022, 16:34 last edited by
Beer's Law or reflectance?
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wrote on 28 Jun 2022, 17:01 last edited by
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wrote on 28 Jun 2022, 17:17 last edited by
Oh, at 0:30 he says, "The oxygen saturation is effectively how much oxygen in your blood."
That's completely false. It is the percentage of hemoglobin that is carrying oxygen. If your hemoglobin is 7, and 100% saturated, you're carrying half the oxygen of someone with a 100% saturation with a hemoglobin of 14.
If you're anemic as hell, you won't do well, because you don't have the Hb.
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Oh, at 0:30 he says, "The oxygen saturation is effectively how much oxygen in your blood."
That's completely false. It is the percentage of hemoglobin that is carrying oxygen. If your hemoglobin is 7, and 100% saturated, you're carrying half the oxygen of someone with a 100% saturation with a hemoglobin of 14.
If you're anemic as hell, you won't do well, because you don't have the Hb.
wrote on 29 Jun 2022, 09:55 last edited by@George-K said in Kinda Geeky - the story of the pulse oximeter:
That's completely false. It is the percentage of hemoglobin that is carrying oxygen. If your hemoglobin is 7, and 100% saturated, you're carrying half the oxygen of someone with a 100% saturation with a hemoglobin of 14.
But the pulse oximeter would show the same 100% in both cases, right?
So, the total oxygen content in the blood stream would proportional to the hemoglobin value multiplied with the saturation, right?
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@George-K said in Kinda Geeky - the story of the pulse oximeter:
That's completely false. It is the percentage of hemoglobin that is carrying oxygen. If your hemoglobin is 7, and 100% saturated, you're carrying half the oxygen of someone with a 100% saturation with a hemoglobin of 14.
But the pulse oximeter would show the same 100% in both cases, right?
So, the total oxygen content in the blood stream would proportional to the hemoglobin value multiplied with the saturation, right?
wrote on 29 Jun 2022, 10:46 last edited by George K@Klaus said in Kinda Geeky - the story of the pulse oximeter:
@George-K said in Kinda Geeky - the story of the pulse oximeter:
That's completely false. It is the percentage of hemoglobin that is carrying oxygen. If your hemoglobin is 7, and 100% saturated, you're carrying half the oxygen of someone with a 100% saturation with a hemoglobin of 14.
But the pulse oximeter would show the same 100% in both cases, right?
So, the total oxygen content in the blood stream would proportional to the hemoglobin value multiplied with the saturation, right?
Yes.
Well, that plus a small amount of dissolved oxygen in the blood not bound to hemoglobin. Very small.
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@Klaus said in Kinda Geeky - the story of the pulse oximeter:
@George-K said in Kinda Geeky - the story of the pulse oximeter:
That's completely false. It is the percentage of hemoglobin that is carrying oxygen. If your hemoglobin is 7, and 100% saturated, you're carrying half the oxygen of someone with a 100% saturation with a hemoglobin of 14.
But the pulse oximeter would show the same 100% in both cases, right?
So, the total oxygen content in the blood stream would proportional to the hemoglobin value multiplied with the saturation, right?
Yes.
Well, that plus a small amount of dissolved oxygen in the blood not bound to hemoglobin. Very small.
wrote on 29 Jun 2022, 10:53 last edited by@George-K said in Kinda Geeky - the story of the pulse oximeter:
@Klaus said in Kinda Geeky - the story of the pulse oximeter:
@George-K said in Kinda Geeky - the story of the pulse oximeter:
That's completely false. It is the percentage of hemoglobin that is carrying oxygen. If your hemoglobin is 7, and 100% saturated, you're carrying half the oxygen of someone with a 100% saturation with a hemoglobin of 14.
But the pulse oximeter would show the same 100% in both cases, right?
So, the total oxygen content in the blood stream would proportional to the hemoglobin value multiplied with the saturation, right?
Yes.
Well, that plus a small amount of dissolved oxygen in the blood not bound to hemoglobin. Very small.
I wonder, though, how it is possible that both saturation and hemoglobin level can be measured by means of light reflection.
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@George-K said in Kinda Geeky - the story of the pulse oximeter:
@Klaus said in Kinda Geeky - the story of the pulse oximeter:
@George-K said in Kinda Geeky - the story of the pulse oximeter:
That's completely false. It is the percentage of hemoglobin that is carrying oxygen. If your hemoglobin is 7, and 100% saturated, you're carrying half the oxygen of someone with a 100% saturation with a hemoglobin of 14.
But the pulse oximeter would show the same 100% in both cases, right?
So, the total oxygen content in the blood stream would proportional to the hemoglobin value multiplied with the saturation, right?
Yes.
Well, that plus a small amount of dissolved oxygen in the blood not bound to hemoglobin. Very small.
I wonder, though, how it is possible that both saturation and hemoglobin level can be measured by means of light reflection.
wrote on 29 Jun 2022, 11:43 last edited by@Klaus said in Kinda Geeky - the story of the pulse oximeter:
@George-K said in Kinda Geeky - the story of the pulse oximeter:
@Klaus said in Kinda Geeky - the story of the pulse oximeter:
@George-K said in Kinda Geeky - the story of the pulse oximeter:
That's completely false. It is the percentage of hemoglobin that is carrying oxygen. If your hemoglobin is 7, and 100% saturated, you're carrying half the oxygen of someone with a 100% saturation with a hemoglobin of 14.
But the pulse oximeter would show the same 100% in both cases, right?
So, the total oxygen content in the blood stream would proportional to the hemoglobin value multiplied with the saturation, right?
Yes.
Well, that plus a small amount of dissolved oxygen in the blood not bound to hemoglobin. Very small.
I wonder, though, how it is possible that both saturation and hemoglobin level can be measured by means of light reflection.
Pulse oximeter doesn't measure hemoglobin. It measures the absorption of red and near infra-red light by oxyhemoglobin and deoxyhemoglbin. The ratio is the % saturation.
Looking around for how Ember measures Hb is not helpful.
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@Klaus said in Kinda Geeky - the story of the pulse oximeter:
@George-K said in Kinda Geeky - the story of the pulse oximeter:
@Klaus said in Kinda Geeky - the story of the pulse oximeter:
@George-K said in Kinda Geeky - the story of the pulse oximeter:
That's completely false. It is the percentage of hemoglobin that is carrying oxygen. If your hemoglobin is 7, and 100% saturated, you're carrying half the oxygen of someone with a 100% saturation with a hemoglobin of 14.
But the pulse oximeter would show the same 100% in both cases, right?
So, the total oxygen content in the blood stream would proportional to the hemoglobin value multiplied with the saturation, right?
Yes.
Well, that plus a small amount of dissolved oxygen in the blood not bound to hemoglobin. Very small.
I wonder, though, how it is possible that both saturation and hemoglobin level can be measured by means of light reflection.
Pulse oximeter doesn't measure hemoglobin. It measures the absorption of red and near infra-red light by oxyhemoglobin and deoxyhemoglbin. The ratio is the % saturation.
Looking around for how Ember measures Hb is not helpful.
wrote on 29 Jun 2022, 11:47 last edited by@George-K said in Kinda Geeky - the story of the pulse oximeter:
Looking around for how Ember measures Hb is not helpful.
They do have some information on how it works and link to various studies that supposedly illustrate that this actually works.
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@George-K said in Kinda Geeky - the story of the pulse oximeter:
Looking around for how Ember measures Hb is not helpful.
They do have some information on how it works and link to various studies that supposedly illustrate that this actually works.
wrote on 29 Jun 2022, 11:56 last edited by@Klaus said in Kinda Geeky - the story of the pulse oximeter:
@George-K said in Kinda Geeky - the story of the pulse oximeter:
Looking around for how Ember measures Hb is not helpful.
They do have some information on how it works
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@Klaus said in Kinda Geeky - the story of the pulse oximeter:
@George-K said in Kinda Geeky - the story of the pulse oximeter:
Looking around for how Ember measures Hb is not helpful.
They do have some information on how it works
wrote on 29 Jun 2022, 11:59 last edited by Klaus@George-K From what I understand, their key idea - compared to a normal pulse oximeter - is to use light at many different wavelengths, and supposedly by comparing how much light is reflected at each wavelength they can infer the hemoglobin level.
Also note that they are quite specific about the Bluetooth standard they are using. I'm glad that they don't use the outdated BT 3.0 and opted for BT 4.0. In any case, that seems to be more relevant than pesky details about how this "works".
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@George-K From what I understand, their key idea - compared to a normal pulse oximeter - is to use light at many different wavelengths, and supposedly by comparing how much light is reflected at each wavelength they can infer the hemoglobin level.
Also note that they are quite specific about the Bluetooth standard they are using. I'm glad that they don't use the outdated BT 3.0 and opted for BT 4.0. In any case, that seems to be more relevant than pesky details about how this "works".
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wrote on 26 Sept 2022, 15:35 last edited by
I remember being a young nurse working on a 40 bed pediatric unit in a big general hospital, sitting on an equipment committee. It was during the 1980s & we’d borrowed one to try out. We had no cardiac monitors on our unit. 02 saturation monitors were really expensive back then. ?Were they Nelcor? Thousands of $$$$. I recall listening to adult medicine people questioning how useful they’d actually be on babies and kids who wiggled & squirmed with their pudgy fingers & toes. Anyway, our unit got 1. It was in continuous use. To me, it ranked up there on the pediatric innovation scale alongside the buretrol, IV pumps & BP machines (thermometers too, but I recall doing a lot of axilla & rectal temps on kids back then). But with O2 sat monitoring, for little ones on a general ward, it meant too we could continually monitor pulse rate .. & that meant loads when little ones were sleeping.
Later, I remember the 1990s, working in peds and neonatal ICUs, learning, seeing limitations of O2 sat monitoring with certain patients, certain situations, conditions, ….where when drawing blood gases, 02 saturation values were expected to differ .. like of course they did … we had our eyes and experience to tell us why …. Using our brains, we “looked at the patient before we looked at the monitor”. George, remember that expression?
like, my gosh, George, .. “Systemic Racism” in O2 Saturation Monitoring”? .. it’s a thing, ya know. So, tell me if/when when such a race-corrected O2 Sat Monitor will be invented & sold cheap on Amazon?
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I remember being a young nurse working on a 40 bed pediatric unit in a big general hospital, sitting on an equipment committee. It was during the 1980s & we’d borrowed one to try out. We had no cardiac monitors on our unit. 02 saturation monitors were really expensive back then. ?Were they Nelcor? Thousands of $$$$. I recall listening to adult medicine people questioning how useful they’d actually be on babies and kids who wiggled & squirmed with their pudgy fingers & toes. Anyway, our unit got 1. It was in continuous use. To me, it ranked up there on the pediatric innovation scale alongside the buretrol, IV pumps & BP machines (thermometers too, but I recall doing a lot of axilla & rectal temps on kids back then). But with O2 sat monitoring, for little ones on a general ward, it meant too we could continually monitor pulse rate .. & that meant loads when little ones were sleeping.
Later, I remember the 1990s, working in peds and neonatal ICUs, learning, seeing limitations of O2 sat monitoring with certain patients, certain situations, conditions, ….where when drawing blood gases, 02 saturation values were expected to differ .. like of course they did … we had our eyes and experience to tell us why …. Using our brains, we “looked at the patient before we looked at the monitor”. George, remember that expression?
like, my gosh, George, .. “Systemic Racism” in O2 Saturation Monitoring”? .. it’s a thing, ya know. So, tell me if/when when such a race-corrected O2 Sat Monitor will be invented & sold cheap on Amazon?
wrote on 26 Sept 2022, 15:53 last edited byLike maybe I’m biased, should acknowledge my race, privilege, or something, but how the heck would a race-corrected 02 sat monitor help in situations of sickle cell, shunting anatomy, the near dead popsicle toes, all that? Like WTF is it with this word “systemic racism” and supposedly educated people?
