Pulse Oximeters

[lethal dose]

I've always been told that too much o2 on a copd'Er knocks out their hypoxic drive... thus resulting in an affected spo2 level... no? I'm curious, but that's how we practice.

[Decon]

I've always been told that too much o2 on a copd'Er knocks out their hypoxic drive... thus resulting in an affected spo2 level... no? I'm curious, but that's how we practice.

Another one of those theory based ideas burnt into everyones brains without any scientific proof.

Is it possible, yes. Is it likely, nope.

[FL2011]

From Harrisons:

OXYGEN Supplemental O2 should be supplied to keep arterial saturations
90%. Hypoxic respiratory drive plays a small role in patients
with COPD. Studies have demonstrated that in patients with both acute
and chronic hypercarbia, the administration of supplemental O2 does
not reduce minute ventilation. It does, in some patients, result in modest
increases in arterial PCO , chiefly by altering ventilation-perfusion 2
relationships within the lung. This should not deter practitioners from
providing the oxygen needed to correct hypoxemia.

UpToDate also has a good article on this topic: Use of oxygen in patients with hypercapnia They cited a few studies, one of which was where ARF pts were given 5L O2 and even though there was a slight decrease in minute ventilation that it couldn't account for the total increase in PaCO2, and even though ventilatory drive decreased it was still higher than in controls implying it was still being augmented by other factors.

Pulled the physio text back out, O2 really has no direct effect on central ventilatory regulation, basically only on peripheral chemoreceptors.

[lethal dose]

Very interesting. I'm gonna have to keep reading, fellas. This has really got me wondering.

[MIKE G]

+1 to the COPD debunking. Conversion to hypoxic drive is not as common as most once thought and even then giving them O2 in the short term is not going to be a major concern in reality.

As to use in the field, I do not use it as a snapshot but as a trend just as all other vitals should be used. I can stick the pulse ox on a patient and confirm that a palpable pulse matches the pulse ox reading then I have pretty good confidence that I can trust at least the pulse reading. This can be helpful when treating multiple patients as I just have to glance and I can get a pulse. As for the SaO2 reading I watch it as a trend and consideration and not a compass. If it is high when I first put it on and perform a treatment and it goes down I am going to have one more piece of information when reevaluating my treatment same in reverse if it is low when I stick it on and I perform my assessment and treatment and it improves then I have one more bit of feedback on my patient. Remember, treat the patient and not the monitor. Capnography, particularly waveform is very useful but is not inexpensive or super portable which makes it difficult for fielding in wide use.

I would love to have a PDA sized device that could give me 12 lead, SaO2, ETCO2, ABGs, and half a dozen other things that was visible under night vision, did 10 second processing, trending, cost under $1k, was water and shockproof, and I got a free sample ;-) but that aint happenin. I will take every little bit of information I can on my patients but understand that I will not be blinded by a single piece of information. If my patient looks like shit and the SaO2 is 100% I am not going to pat them on the shoulder and finish my paperwork.

Just my thoughts,

[lethal dose]

Well put, mike. I'm gonna have to read up. I work at a small community hospital... maybe we're still in the old skool. Thanks for the insight, gentlemen.

[Danny Boy]

Yeah..... er....... what Mike said.

[gan1hck]

+1 to the COPD debunking. Conversion to hypoxic drive is not as common as most once thought and even then giving them O2 in the short term is not going to be a major concern in reality.

As to use in the field, I do not use it as a snapshot but as a trend just as all other vitals should be used. I can stick the pulse ox on a patient and confirm that a palpable pulse matches the pulse ox reading then I have pretty good confidence that I can trust at least the pulse reading. This can be helpful when treating multiple patients as I just have to glance and I can get a pulse. As for the SaO2 reading I watch it as a trend and consideration and not a compass. If it is high when I first put it on and perform a treatment and it goes down I am going to have one more piece of information when reevaluating my treatment same in reverse if it is low when I stick it on and I perform my assessment and treatment and it improves then I have one more bit of feedback on my patient. Remember, treat the patient and not the monitor. Capnography, particularly waveform is very useful but is not inexpensive or super portable which makes it difficult for fielding in wide use.

I would love to have a PDA sized device that could give me 12 lead, SaO2, ETCO2, ABGs, and half a dozen other things that was visible under night vision, did 10 second processing, trending, cost under $1k, was water and shockproof, and I got a free sample ;-) but that aint happenin. I will take every little bit of information I can on my patients but understand that I will not be blinded by a single piece of information. If my patient looks like shit and the SaO2 is 100% I am not going to pat them on the shoulder and finish my paperwork.

Just my thoughts,

perhaps the pulse is helpful....but as for the SAO2 number in the field....I don't know....

CO exposure....hypotension...dirt...etc....always make the number suspect..at least to me..

if it's low, and you're giving a face mask by NRB....what else is there to do...

if it's a 100...and the guy looks like doo doo...are you not going to intubate....?

I just think that field care..(along with in house care) has become too technology dependent.

[Iraq Ninja]

Our PO has been missing from our med bag for a few months, and I will have to buy one on my own to get another one (original was a gift from an other unit), so this discussion has been interesting.

Honestly, I have been avoiding the issue but Mike G makes some good points.

[MIKE G]

perhaps the pulse is helpful....but as for the SAO2 number in the field....I don't know....

CO exposure....hypotension...dirt...etc....always make the number suspect..at least to me..

if it's low, and you're giving a face mask by NRB....what else is there to do...

if it's a 100...and the guy looks like doo doo...are you not going to intubate....?

I just think that field care..(along with in house care) has become too technology dependent.

I hear ya on the tech dependency, my response isnt to throw out the tools we have but to educate providers to not be dependent or use them as compasses. Part of that is understanding the limitations you mentioned as well as learning effective assessment techniques without the technology.

I do remember an AAR at SOMA a few years ago from a SOF provider. Said he had a situation with multiple patients with respiratory issues after some sort of engagement. He had multiple Onyx pulse ox units and use them on his patients. He was limited as to the amount of O2 he had and used the feed back from the pulse ox to titrate the O2 to where the patient's SaO2 was in a comfortable range for him but also to where it would last for the expected flight. He reported that if he dropped below a certain threshold of Lpm that the SaO2 dropped significantly so he found a balancing point. Who remembers how to do O2 calcs?


Not my case but something to think about.