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Shipwrecked & Comatose, drinking fresh mango juice
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<font color='#810541'>sort of a follow on from the Dr. Tim thread, but a serious question so I've started another thread.

We are told over and over that Entenox should not be administered to a bent diver, to any diver in an accident up to 48 hours after a dive (I carry a laminated card to that effect) but I didn't really know what the effect would be.

I did a little google search to find out what is in entenox, and the only link that seemed to have any information on the composition was this one

open this page then search for 'entenox'

So, if the composition is 50% Nitrous Oxide (NO2) and 50% Oxygen, how does that differ from a 75% Nitrox fill?  The advice is often given that a diver in trouble gets the highest available Nitrox mix if pure O2 isn't available.

Serious question - I know we have medical / scientific folk on board who can give me some more facts!

Andy
 

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To the best of my knowledge, it's because NO2 is absorbed more readily across the respiratory membranes than N2 and is more reactive once absorbed. Plus the sedative and anaesthetic effects of NO2 are definately not conducive to good management of a DCI casualty. If Mary's done any anaesthesiology thus far in her medical degree I'm sure she'll have more data on diffusion rates and such like

The more rapid absorption of nitrogen will (as I'm sure you already know) increase the size of existing bubbles and exacerbate the DCI
 

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I think it is the fact that NO2 means that yet ANOTHER gas is added to the bloodstream of a diver whose problem is that he's already got too much. So it'll aggravate the problem.

Nitrox only has Nitrogen and Oxygen, so isn't adding anything that isn't already there. And it's got less Nitrogen than air, so it'll help to get the stuff out of the diver quicker by letting less IN.
 

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Shipwrecked & Comatose, drinking fresh mango juice
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<font color='#810541'>I think I was mentally over simplifying NO2 as Nitrogen & Oxygen as opposed to a molecular level compound ...... I'm not a chemist by the way (like, it was hard to tell)
 

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Ginger, Irish, sometimes stroppy
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The NO2 is more readily absorbed into the bloodstream and so would potentially decrease the ability of the blood to remove other , less soluble gases such as Nitrogen.

The thing that I would be curious about and am not sure of is whether the NO2 is actually metabolised in any way or if it leaves the system intact, if it is metabolised then the products may make someone who is carrying around a lot of N2 worse.

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from a quick look NO2 does not seem to be metabolised but the following may be of interest

As nitrous oxide diffuses out of the body, it reduces the amount of oxygen within the airways, and there is a relative diffusion hypoxia. Because of this, it is sometimes recommended that after the procedure is finished, that the person be placed on 100% oxygen to help diminish this diffusion hypoxia. I find that it is not necessary to do that when using nitrous oxide for conscious sedation/analgesia for outpatient procedures in healthy patients.
 

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Just not enough dive time.
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Yes!
Put someone in a chamber with greasy hair and fill it with 02, bye.

Matt
 

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C'mon Darthmoll. You're on-line, but you're being strangly silent. Are you scared? At least I've got the balls to stand and argue my corner, with my real name! I think I know who "you" are, that's why you're running.

PETER KELLY
 
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