Nitrous oxide....

[GoBlue!]

In another thread, the practice of EMS administering an oxygen/nitrous oxide mixture to patients in pain was brought up. This was NOT suggested for diving injuries, just to be clear.

The question arose whether or not a oxygen/nitrous mixture could slow offgassing/DCI treatment. The argument was made that since nitrous oxide is an inert gas, like nitrogen, the two mixes (oxygen/nitrogen vs. oxygen/nitrous, both in 1:1 ratios) would have the same physiological effects with regard to offgassing. (original post)

I'm not sure I agree. It seems that 100% oxygen vs. a oxygen/nitrous mixture would have a similar (maximal) tissue-to-blood nitrogen gradient, and therefore would theoretically promote offgassing at similar rates.

1. Is this the case?
2. Any special properties of nitrous oxide that we should be considering, specifically?

<Disclaimer on>NOTE: I'm not at all suggesting the use of nitrous oxide mixtures for DCI treatment. This is a thought experiment only!<Disclaimer off >

Jim

 

[Wreckie]

Simple answer is that one of the contra indications to giving an injured person entonox is if they have been diving recently. The nitrogen in the mixture will combine with that coming out of solution in your body and make the bend worse.

The gas acts like a very rapid form of narcosis.

Mike

 

[J1M1]

cant see how it would effectively treat dci because of the nitrogen in it. Your loading nitrogen while your breathing it and trying to get rid of it as well. Pure O2 has no nitrogen so your offgassing at the most effective rate possible..JD

 

[Dr Deco]

Hello Blue:

Nitrous Oxide

This gas would not be a good choice for promotion of off gassing since it is a very rapidly diffusing molecule. There have been experiments performed to demonstrate the present of Subclinical bubbles in rats following a decompression by switching to nitrous oxide. This gas would rapidly enter the tissues and “pump up" the gas small gas bubbles. When these grew, the rats would display signs of DCS.

Clearly, this situation would not be a salutary one for a diver. :11:

Dr Deco :doctor:

Readers, please note the next class in Decompression Physiology :1book:
http://wrigley.usc.edu/hyperbaric/advdeco.htm

 

[fdog]

Not to mention that it sure doesn't seem to work very well. Every patient we've given it to has screamed just as loudly after it was administered. After the nitrous has failed, a whack of Demerol and they stop feeling pain.

We've given up on it. Sure sounded good when it first appeared.

All the best, James

 

[GoBlue!]

Dr. Deco- Thanks. That's exactly the explanation I was looking for. Makes sense that such a rapidly diffusable gas could "pump up" the gas bubbles....that's a reason that makes sense to me. Others were saying that the DCI could be worsened because of the "nitrogen" content of nitrous oxide, which I didn't buy into at all. That's like saying that CO2 would be good for offgassing, since there's "O2" but no "N." That sure doesn't make sense now, does it?? Molecules can't just be split up into individual letters.

Wreckie- See comment above. Nitrogen gas is not a component of nitrous oxide. There is an atom of nitrogen, yes, but NO2 is not converted into N2 somehow (at least that I'm aware of).

jaydee- I was not suggesting NO2 be used to TREAT DCI. I was wondering, at the molecular level of offgassing, how a NO2/O2 mix would be different than any other gas mix that does not contain nitrogen gas. Dr. Deco answered the question quite clearly.

Jim

 

[lamont]

is this an example of the isobaric counter-diffusion phenominon, similar to gas-switching from nitrogen-mix to helium-mix?

 

[vjongene]

Wreckie- See comment above. Nitrogen gas is not a component of nitrous oxide. There is an atom of nitrogen, yes, but NO2 is not converted into N2 somehow (at least that I'm aware of).

Jim

Small correction: nitrous oxide (laughing gas) is N2O, not NO2 (nitrogen dioxide). NO2 is a major air pollutant.

 

[sharpenu]

We here use Nitronox. It is N2O2, mixed with O2, to be exact. It is not very good as a sedative, but does work well as an analgesic. I like to use it in certain cases because:

1- Fast acting
2- wears off quickly
3- can't OD because it is self administered. The pt will be unable to continue administration long before they OD.

Other pain meds we have at our disposal can limit the Dr's choices later. That is what make Nitronox a good choice in certain situations.

Use would be contraindicated in the bent diver, not because diving is a contraindication, but because any altered mental state or neurological deficit is a contraindication to analgesic or sedative use in the EMS setting.

 

[will_tekkie]

interesting