DIR UK Donegal

[And]

Originally Posted by Clare Gledhill

For the fantastic video shot by John Kendall see here....you'll see me at the rear and occasionally Bob "don't stop me now" Cooper - who was seeking to be a solo diver....

He does that. He probably needed the toilet. I think he bowled over three french cave divers racing to get out at Trou Madame.

Andy

[Rick Huggins]

Originally Posted by And

He does that. He probably needed the toilet. I think he bowled over three french cave divers racing to get out at Trou Madame.

Andy

Yeah, then left his fins up there for me to get!!

[Adrian Kelland]

Originally Posted by And

He does that. He probably needed the toilet. I think he bowled over three french cave divers racing to get out at Trou Madame.

Andy

No P valve? - Ah worse case scenario

[Padowan]

Nice report Clare - very jealous, I've been wanting to get out there for ages!

One question, you state at one point:

Originally Posted by Clare

We jumped in eventually (well sort of fell in my case) and made our way to the shot. I could already feel the effect of breathing hypoxic gas and signalled to John to drop down to 6 metres a.s.a.p. where life became more comfortable

Does this mean you were breating hypoxic (generally thought of as <16% O2 in my book) back gas on the way in? Or by hypoxic do you just mean less than 21% O2?

[Clare Gledhill]

Originally Posted by Padowan

Nice report Clare - very jealous, I've been wanting to get out there for ages!

One question, you state at one point:

Does this mean you were breating hypoxic (generally thought of as <16% O2 in my book) back gas on the way in? Or by hypoxic do you just mean less than 21% O2?

15/55 Simon - not that bad until you have to work a bit

[Padowan]

Aah OK, no worries. I tend to generalise my meaning of hypoxic and think of mixes with very low FO2s.

[Tease mode ON] Working hard on Hypoxic mixes is no worries when you have a little computer pumping in all the O2 you need! [Tease OFF]

[Lou]

Simon - Isn't 15/55 a mix with a low FO2 then? What would you count as something with a very low FO2? Isn't it hypoxic by any definition of the word?

[Padowan]

Originally Posted by Lou

Simon - Isn't 15/55 a mix with a low FO2 then? What would you count as something with a very low FO2? Isn't it hypoxic by any definition of the word?

Yes 15% O2 is low and by definition anything less than 21% is hypoxic in gas terms, but it's not so low that you'll pass out after a few breaths under normal conditions, which is generally where I am thinking about when referring to hypoxic gasses (ones that you can't breathe on the surface). Generally 14-15% at the surface is considered the minimum you should be breathing under dive conditions (low workload, but not so low as just sitting relaxed), this is a PPO2 of 0.14-0.15 bar.

Consider this though - aeroplanes are pressurised to approximately 9psi, vs surface pressure of 14.7psi, equate this to bar and a plane is at 0.61bar absolute, with 21% air in the cabin, this gives an in-cabin PPO2 of 0.128bar, so approximately 0.13bar or the equivalent of breathing 13% O2 on the surface. People don't pass out when walking up and down the aisles, but it does partly explain how easy some people find it is to sleep on a plane!

So in answer to the original question, I start "thinking" hypoxic with gasses of about 12% O2 and below. Having done hypoxic trials on a rebreather in a relaxed state, I did not start feeling like I was about to pass out until the PPO2 dropped to well below 0.1bar (>10% sirface O2 equivalent)

[Lou]

Cheers Simon - that's clear now.

Lou

[Madfish]

Does John Kendall do wedding videos too - how cool would they be? Thanks again Clare for a really enjoyable read (again) and glad you had a great trip. You do seem to pack the experiences in! Trip Tart.....what about a new signature 'Clare Gledhill - not bent, just twisted!'
And please take more care - don't want you joining the dodgy knee club

Dianne