Inner Ear DCS

Pelagian

Hey All


One of our students has recently sustained an Inner Ear Bend on a non training dive with his buddy.

It was an air dive(OC) to about 150ft using a Sunto Vytec(RGBM) for decoing. He cleared his computer very gradually(shallow stops celared before reachin 50ft).

I am still just learning about Inner Ear DCS and most of the stuff I'm looking at is to do with Helium and Counterdiffusion.

Does anyone have any info/experience with this type of bend?


Cheers

Seb

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'Because... I was Inverted!'

ROB DAVIE

Dave? Simon?

jhaaja

In Finland we have had 2-3 cases in the past year and only 1 case came from a trimix dive. The others were air dives around 40-50m deep.

JH
Finland

magentaseas

Hi
A couple of years ago a fellow club member suffered an inner ear bend on an OC dive to about 35m.
The doctors couldnt say exactly why it happened or when it couldve happened on the dive (desent/ascent?). He was just unlucky. He lost his hearing in that ear and stopped diving incase it happened to the other ear.
It also took some time for him to get his balance back properly.
Cant remember the exact details off hand.

sharon

Dave Young

Seb,

Here is a link to a paper published in the Journal of Applied Physiology titled "Biophysical basis for inner ear decompression sickness" by Dave Doolette and Simon Mitchell: HTML link or PDF link (104Kb).

Hope this helps,

Dave Y.

Pelagian

That's the same depth range and gas.

Do you have any info on the dives or what the doctors came up with?

Cheers

Seb

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'Because... I was Inverted!'

jhaaja

I really don`t have any exact info. All I know that they made decompressions according to their plans. I can try to ask for more info. I am also interested in this issue. It seems that most of the DCI cases last year in Finland were inner-ear-DCI.

Pelagian

Thanks for the article Dave It's excellent.

Seb

__________________
'Because... I was Inverted!'

dteubner

This is my understanding of isobaric counterdiffusion.

People do gas switching to take advantage of the fact that helium is a 'faster' gas than nitrogen, that is, helium will leave tissues more quickly than nitrogen enters them so the total partial pressure of all gasses in the tissue will fall faster if you switch from a high helium content gas to a high nitrogen content gas than if you don't.

The problem is that gas switching can cause inner ear DCI - even without changing depth. Mitchell and Doulette have postulated that this is due to a phenomenon called isobaric counterdiffusion (ICD). ICD arrises when there are two separate gas sources for the tissue. It was first described in corneas of people in saturation breathing one gas mixture but exposed to a different one.

Inner ear DCI due to ICD occurs because the middle ear still contains a high ppHe while the blood contains a high ppN2. The helium diffuses from the middle ear across the oval window into the endolymph. WHat this means is that the ppHe in the endolymph cannot fall quickly enough because, as it diffuses into the blood, it is replaced from the middle ear via the oval window. Nitrogen, on the other hand enters the endolymph from the blood but doesn't diffuse well across the oval window. The net effect of this is that the PP of nitrogen in the endolymph rises but the ppHe doesn't fall. This means that the total pp of all gasses can exceed the m-value (or whatever you believe) and bubbles can form resulting in 'pure' inner ear DCS.

Simon and David's paper has a lot of maths to try to quantify this effect but, at the end, they recommend:-

Second, breathing-gas switches from helium-rich to nitrogen-rich mixtures will produce an oversaturation in the inner ear that increases with depth and decreasing inspired oxygen partial pressure. Such breathing-gas switches should be carefully scheduled either deep (with due consideration to nitrogen narcosis) or shallow to avoid the period of maximum supersaturation resulting from the decompression (Fig. 1). Switches should also be made during breathing of the largest inspired oxygen partial pressure that can be safely tolerated with due consideration to oxygen toxicity.

Inner ear DCI does not, of course, only occur with gas switching. It can occur on pretty much any dive. ISOLATED inner ear DCI is unusual but not all that rare. There may be an assosciation with PFO but the mechanism for this is not well understood (by me anyway).

We often look for reasons - Why did I get bent? Why an inner ear bend? A lot of the time there is no good reason except that the dice fell that way. At the end of the day, shit happens.

Dave T

Pelagian

Dave

Thanks for the summary, my interpretation of the paper was the same.

The problem here is that this case did not involve helium or deep diving.

I know there is unlikely to be a cut'n'dry answer , just trying to find out as much as we can to help the diver in question assess his options for continuing his diving.

We're arranging a consult with an ENT who is also a DIVe Doc to see if he can throw sone light on the subject(pun intended).

He has suggested that a roundwindow fistula or other barotrauma maybe the culrpit. He's not the only one who has suggested this.

Apparently differential diagnosis between IEDCS and IE barotrauma's is tricky as many symptoms are the same, and since recompression treatment has so far proven less effective on IEDCS than other types, the 'lets see if it gets better in the chamber' approach is also proving inconclusive.

I'll post what we find out.

Cheers

Seb

__________________
'Because... I was Inverted!'