When will O2 truly help?

[Brandon Oto]

There's a fair amount of back-and-forth recently about the status of supplementary oxygen for a few high-profile conditions, such as stroke and cardiac arrest. It'll be nice to see how that eventually cashes out, but my personal interest is in the less-discussed fronts. A lot of prehospital providers -- particularly the poor BLS buggers who can't do much else -- tend to use O2 as a panacea, on the somewhat religious assumption that it'll help with almost any ailment.

But when will it actually help? I'm curious in two things --

1. For a given condition, in your PERSONAL EXPERIENCE, have you witnessed either ALLEVIATION OF SYMPTOMS or IMPROVED OUTCOMES following the administration of oxygen? This is obviously just anecdotal, but it's the best we're going to do in many cases.

2. For a given condition, have you seen any rigorous research that supports or denies either of the above?

I'm interested in this to better inform us all about the true indications for supplementary oxygen. It probably goes without saying that someone with dyspnea and trouble oxygenating will improve with high-concentration O2, but it is far from obvious whether the guy with the broken leg will hurt any less, the guy with appendicitis will live any longer, or the woman with nausea/vomiting will feel any better. "Throw on a cannula" may not be all that harmful but we'd probably all rather avoid unnecessary treatment when possible. So -- any thoughts? I'm interested in everything from AAA to Zebras.

I will say for my own small contribution that I've had mixed results giving patients with anxiety and similar psych states low-flow O2 by cannula; sometimes seems to help, sometimes not at all.

[HERBIE1]

Let's put it this way- a couple liters of O2 via a cannula cannot hurt. Like you mentioned, the placebo effect is certainly possible. I've told people who were anxious, nauseated, upset, weak, tired, etc that it will help them, and often times, it does. It's also a subjective thing- the person has to believe it, so your attitude, demeanor, and bed side manner is important as well. If the patient THINKS it will help, often times it will- especially if there's an anxiety component.

As for the clinical aspect- we never know- even ALS providers- what underlying issues they may have-ie their blood chemistry, metabolic issues, etc. Are they anemic but asymptomatic, and could benefit from the increased O2?

As an ALS provider, many times we establish an IV/saline lock- just in case, and it's never needed by us. Many times it's simply a convenience for the ER. If the patient perceives we are doing something to address their problem, it tends to put them at ease just a bit. That also means lower BP and heart rate, lower O2 consumption, and anxiety is lessened just a bit, so clinically it is relevant.

Edited November 12, 2009 by HERBIE1

[melclin]

Pain induced hypoxia is a good one. That being hypoxia that stems from a decreased minute volume due to pain on inspiration. Namely broken ribs, but I'm sure there's a plethora of conditions that would cause this trouble.

Especially for the BLS guys who might not necessarily have any pharmacological analgesia.

Seeing as you are looking for experience: When I had my appendix out I had a left over bubble of laprosocopy gas left over which was quite painful for a few days, particularly on inspiration. after a few moments I would start to feel increasingly short of breath which would make me breath harder which hurt, etc. It would come and go in "attacks". Whenever I'd have an "attack", they would whack a pulse ox on, and a nasal cannula and 5 mins later, no troubles.

I like the idea of this thread. As time goes on I think we are going to see more precautions and relative contraindications for certain Fi02s. We sit an learn at uni how archaic the "Everyone gets 8 through a hudson" idea is, then we sit down in prac classes and that's exactly what we get taught to do. It grinds my gears.

[Jwade]

Let's put it this way- a couple liters of O2 via a cannula cannot hurt. Like you mentioned, the placebo effect is certainly possible. I've told people who were anxious, nauseated, upset, weak, tired, etc that it will help them, and often times, it does. It's also a subjective thing- the person has to believe it, so your attitude, demeanor, and bed side manner is important as well. If the patient THINKS it will help, often times it will- especially if there's an anxiety component.

As for the clinical aspect- we never know- even ALS providers- what underlying issues they may have-ie their blood chemistry, metabolic issues, etc. Are they anemic but asymptomatic, and could benefit from the increased O2?

As an ALS provider, many times we establish an IV/saline lock- just in case, and it's never needed by us. Many times it's simply a convenience for the ER. If the patient perceives we are doing something to address their problem, it tends to put them at ease just a bit. That also means lower BP and heart rate, lower O2 consumption, and anxiety is lessened just a bit, so clinically it is relevant.

Herbie,

Can you please explain your rationale for the statement outlined in red please?

How is a person who is anemic going to benefit from inhaling O2? The basis of anemia is lack of red blood cells, hemoglobin is found inside the RBC, and as you know carries O2 everywhere, if you have a lack of RBC's and therefore a lack of hemoglobin carrying capacity, adding O2 is pointless. The O2 must have something to bind with to be effective.

Respectfully,

JW

[mobey]

Herbie,

Can you please explain your rationale for the statement outlined in red please?

How is a person who is anemic going to benefit from inhaling O2? The basis of anemia is lack of red blood cells, hemoglobin is found inside the RBC, and as you know carries O2 everywhere, if you have a lack of RBC's and therefore a lack of hemoglobin carrying capacity, adding O2 is pointless. The O2 must have something to bind with to be effective.

Respectfully,

JW

Not true, by increasing the partial pressure of oxygen (PO2), once the Hgb are fully saturated (oxyhemglobin) the oxygen will further saturate the blood plasma, leading to an overall higher Oxygen content in the blood.

O2 will dissolve in blood plasma.

Edited November 13, 2009 by mobey

[chbare]

Not true, by increasing the partial pressure of oxygen (PO2), once the Hgb are fully saturated (oxyhemglobin) the oxygen will further saturate the blood plasma, leading to an overall higher Oxygen content in the blood.

O2 will dissolve in blood plasma.

You are correct; however, we must keep this in perspective. I will will use the content of arterial oxygen formula to illustrate the point:

The CaO2 is calculated with the following:

CaO2 = (1.34 * Hemoglobin * SaO2) + (PaO2 * 0.003)

Let's say you have a Hb of 13, SaO2 of 96% and a PaO2 of 100 mm/Hg

CaO2 = (1,34 * 13 * 0.96) + (100 * 0.003)

16.7 + 0.3 = ~17 ml/O2/100 ml blood

So, you can see, even with a PaO2 of 100 mm/Hg, you are only adding 0.3 ml/O2/100 ml blood to your total CaO2

Let's say in the land of Oz we are able to have a 100% oxygen atmosphere and by an act of God we are able to increase the PaO2 to 760 mm/Hg

This would only come to 2.28.

This is why to have meaningful increases in oxygen via dissolved oxygen content, we typically look to hyperbaric therapy to significantly increase the partial pressure and thus dissolved pressure of oxygen in the body. Of course, such concentrations are rather toxic.

Take care,

chbare.

[tniuqs]

You are correct; however, we must keep this in perspective. I will will use the content of arterial oxygen formula to illustrate the point:

Take care,

chbare.

Thanks mobey and chbare ... I was starting to twitch when I read the first few posts.

[JPINFV]

Not true, by increasing the partial pressure of oxygen (PO2), once the Hgb are fully saturated (oxyhemglobin) the oxygen will further saturate the blood plasma, leading to an overall higher Oxygen content in the blood.

O2 will dissolve in blood plasma.

True, but it's like saying that a garden hose is going to help stop a forest fire. Sure, you're getting water on the fire, but the quantity just isn't there to be significant. Additionally, someone who is hypoxic due to low anemia is still going to show signs of hypoxia minus a low pulse ox reading. This is because a pulse ox measures the percent of red blood cells that are saturated, and not the oxygen carrying capacity of the blood.

[Jwade]

Not true, by increasing the partial pressure of oxygen (PO2), once the Hgb are fully saturated (oxyhemglobin) the oxygen will further saturate the blood plasma, leading to an overall higher Oxygen content in the blood.

O2 will dissolve in blood plasma.

Mobey,

YES, while technically what you said can " potentially" happen, there is NO way sticking someone on a NRB @ 15 liters will increase their PO2 enough to " Benefit the patient who is ANEMIC and already has a low HCT & HGB"

As someone else suggested, you would need at a minimum Hyperbaric chamber to help.....and you would still have to fix the anemia issue regardless.....So, I think your answer, while theoretically possible, real world application is not statistically significant.

Respectfully,

JW

[tniuqs]

Mobey,

YES, while technically what you said can " potentially" happen, there is NO way sticking someone on a NRB @ 15 liters will increase their PO2 enough to " Benefit the patient who is ANEMIC and already has a low HCT & HGB"

As someone else suggested, you would need at a minimum Hyperbaric chamber to help.....and you would still have to fix the anemia issue regardless.....So, I think your answer, while theoretically possible, real world application is not statistically significant.

Respectfully,

JW

Firstly a query just how does one evaluate PaO2 in the first place ? hint: there is no such critter as PO2 unless it is in a Math formula, may wish to goggle at PAO2 as well.

mobey is not just technically correct this exactly one of the reasons that one initiate's supplemental O2 in events of "anemic hypoxemia" please note the difference between hypoxia and hypoxemia as well.

Content and Capacity should be reviewed as well on can increase oxygen delivery to tissue using chbars equations by up to 2 volume % in fact at sea level with supplemental O2.

The Oxyhemoglobin dissociation curve illustrate affinity and shifts of the ODC something called "postage stamp effect" in regards to affinity of O2

http://en.wikipedia.org/wiki/Oxygen-haemoglobin_dissociation_curve#Factors_shifting_curve

This link to some Power Point Education look around you will find Oxygen therapy productions.

http://www.ccmtutorials.com/rs/oxygen/page06.htm

http://www.templejc.edu/dept/ems/Pages/PowerPoint.html

In regauds

to but it's like saying that a garden hose is going to help stop a forest fire.

Could you explain that particularly in regards to dang near every protocol guideline, for shock or blood loss, oxygen is first line drug in suspected cases of all "Anemic Hypoxemia"

cheers

Edited November 13, 2009 by tniuqs