16% CO level per life pack 15

[ERDoc]

Sysmet, are you confusing pCO2 with CO levels? You can get your CO level from venous blood, it doesn't have to be an ABG. It's a little weird that in 20 minutes the CO level dropped from 16 to 10%. What is the half life of CO on room air, 100% O2 and in a dive chamber? Where was the pt found?

[croaker260]

I think there's a fairly poor correlation between the RAD-57 cooximetry and SpCO on ABG, so this may have been a false positive. The troube is, when you see that sort of number, you have to assume that something real is happening until you get a clean ABG.

AaOX4, and in no distress, at an SpO2 of 84% doesn't quite jive, even if the patient had pre-existing pulmonary disease. So, at the very least, it's probably false-high. Any chance that you can follow up with the ER and see what they got on ABG?

Actually, the technology used in the RAD-57 and the off shoot variants (for in hospital use) is fairly reliable and well studied.

THe probablem with inaccurate readings, especially false highs, is typically operator error (though cigar smokers can have baseline readings up to 20% ).

The problem is that many many people don't read the instructions, and don't watch for the "spoofs" that will throw it off, like high light environments against a bright background during the zero process. We had a HUGE problem with this with the local FDs when this came out. ANother common mistake is failure to zero it for each separate patient. We had this problem at a house fire with multiple patients, many false "high readings" on that one. .

THe clinical research I have read shows a variable of 2% each way (above or below, if I recall correctly...its been a while)

Sysmet, are you confusing pCO2 with CO levels? You can get your CO level from venous blood, it doesn't have to be an ABG. It's a little weird that in 20 minutes the CO level dropped from 16 to 10%. What is the half life of CO on room air, 100% O2 and in a dive chamber? Where was the pt found?

IIRC, there have been case reports of relatively high CO readings mitigated with high flow O2 in about an hour, with out hyperbaric therapy.

Note to all: I am not a chemist nor a physicist, but IIRC, the fluid dynamic of CO is far more viscous than O2 and nitrogen, therefore you can have "bubbles" (probably a poor term to use. ) of CO that does not disperse evenly over a given area. It is true that it is heavier than air, so it will seep where gravity generally takes it, but it will not disperse evenly. This is why it is sometimes hard to "detect" CO with atmospheric monitors that the FD uses. If you dont find the "bubble" you wont get a reading.

Edited March 27, 2012 by croaker260

[systemet]

Sysmet, are you confusing pCO2 with CO levels?

No, at least, I don't think so. Perhaps I'm making the assumption that any carboxyhemoglobin is unable to participate in oxygen transport, when instead the non-CO bound sites can still deliver oxygen, even if the p50 is left-shifted.

You can get your CO level from venous blood, it doesn't have to be an ABG.

I wasn't aware of this, but it does makes perfect sense that the SpCO is going to be the same in both venous and arterial circulations.

It's a little weird that in 20 minutes the CO level dropped from 16 to 10%.

I think there's an equipment problem here. I have it hard to believe a patient with a true SpCO of 16% is in no distress, but I'd love to hear if there's a flaw in my reasoning.

[chbare]

Carbon has an atomic mass of about 12, Oxygen of about 16 and Nitrogen of about 14.

CO will have a molar mass of about 28 grams/mole and a density of about 1.25 grams/liter (28/22.4) at STP if we model it as an ideal gas ( which it is not ).

N2 will also approximate CO in molar mass and density.

O2 has a much higher molar mass of 32 grams/mole and a higher density of about 1.43 grams/litre.

Air has a molar mass of about 28.8 grams/mole and a density of approximately 1.28 grams/litre.

Air is more dense than CO and should in theory effuse slower than CO if we use Graham's law. I am not sure on comparing viscosity, but inertial forces typically dominate when bulk amounts of gas move, so I would expect rather high Reynolds numbers along with turbulent flow patters where viscosity does not play a significant role. Perhaps CO experiences strong intermolecular forces, and if I recall, there is a dipole moment on the CO molecule, so intermolecular forces probably play a role. However, I want to say air has a slightly higher viscosity than CO?

Anyway, just some additional information.

[chbare]

Edit: I was attempting to make a lucid point above, perhaps it's best to disregard the post as it does come off a bit confusing and pretentious; however, that wasn't my intention.

[systemet]

Actually, the technology used in the RAD-57 and the off shoot variants (for in hospital use) is fairly reliable and well studied.

THe probablem with inaccurate readings, especially false highs, is typically operator error (though cigar smokers can have baseline readings up to 20% ).

This paper was discussed a little in a few EMS forums:

http://www.ncbi.nlm.nih.gov/pubmed/20605259

There's a couple of instances where the RAD-57 failed spectacularly, for example patients with:

%COHb (RAD-57) %COHb (Lab)

0 15

0 17

0 20

0 35

24 5

13 0

I've cherry-picked the outliers, but this is from a pretty small cohort (n = 121). The study reports a sensitivity of 48% for %COHb > 15%. On the other hand, despite the outliers above, it's still very specific, at least in this cohort. So maybe this weakens my argument --- as it when the RAD-57 reads high it tends to be right. It's just that a low reading doesn't mean anything more than a clean ECG for ruling out NSTEMI on a patient with horrible anginal symptoms.

The problem is that many many people don't read the instructions, and don't watch for the "spoofs" that will throw it off, like high light environments against a bright background during the zero process. We had a HUGE problem with this with the local FDs when this came out. ANother common mistake is failure to zero it for each separate patient. We had this problem at a house fire with multiple patients, many false "high readings" on that one. .

This seems like good advice.

THe clinical research I have read shows a variable of 2% each way (above or below, if I recall correctly...its been a while)

In the study cited above the mean difference is 1.4 %COHb units, but the standard deviation of the difference is 7.3%, or put another way, 1 in 3 of the subjects had a difference in their readings of either > +8.7 COHb, or < -5.9% COHb. So the variable is actually pretty huge.

IIRC, there have been case reports of relatively high CO readings mitigated with high flow O2 in about an hour, with out hyperbaric therapy.

I found an article that quote a t1/2 as being about 80 minutes for 100% normobaric O2, although they note that a range of values from around 30-120 minutes have been reported in othe studies.

So I guess it depends on what you'd consider "mitigated". If the half-life's about 2 hours, in the first hour you'll see about a 30% reduction in the %COHb.

Note to all: I am not a chemist nor a physicist, but IIRC, the fluid dynamic of CO is far more viscous than O2 and nitrogen, therefore you can have "bubbles" (probably a poor term to use. ) of CO that does not disperse evenly over a given area. It is true that it is heavier than air, so it will seep where gravity generally takes it, but it will not disperse evenly. This is why it is sometimes hard to "detect" CO with atmospheric monitors that the FD uses. If you dont find the "bubble" you wont get a reading.

Without really understanding the physics, I took a look here: http://www.lmnoeng.com/Flow/GasViscosity.htm and the values seem pretty close, for viscosity. It seems like there's a slightly lighter density for CO, so it might tend to settle downwards, but I think this would offset a lot by random motion.

But I can understand that it could be easy to have regions within a structure where the CO might be higher, and regions where it might be lower, and that if you test in one, it might give you a false sense of security.

Edit: I was attempting to make a lucid point above, perhaps it's best to disregard the post as it does come off a bit confusing and pretentious; however, that wasn't my intention.

Me too.