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January 15th 2014

14 Jan 2014 ="post-tag" > Written by  ="post-tag" >

Narcosis part deux
hydroxI wrote about inert gas narcosis a few days ago, giving an overview of how, when we dive below a certain depth, nitrogen can have a narcotic effect on your brain. Recreational divers that stay within the limits of their training and experience have nothing to worry about, at 30 metres narcosis is usually hardly felt by most people, and even at 40 metres you can learn to cope with its effects. But what about deeper diving; technical diving? I've undertaken countless technical dives to 55 metres, which is pretty much the limit of diving on air, and most of the time i've felt fine and in control. But occassionally I have been pretty narced. I've dived at Khao Sok National park in Thailand, diving to 55 metres to see an underwater forest and look for a school that sits at the bottom. I felt fine on each dive, but on reviewing the video footage me and my buddy took during one dive, it seems we spent the entire time singing incomprehensible songs to each other! The whole thing was pretty surreal, especially as the disturbed silt on the tree branches made it look like it was snowing!
Beyond 55 metres, technical divers need to breathe a different gas than air- trimix, which is a combination of nitrogen, oxygen and helium. Helium is added to the mix to reduce the percentage of oxygen and nitrogen that is being inhaled under increased ambient pressures. This lowers the partial pressure of those gases at a given depth compared with air and therefore reduces the effects of narcosis. The deeper you go, the more helium, and conversely less nitrogen and oxygen is required to be able to function. However, at some point helium also begins to have a narcotic effect on your brain, and beyond 150 metres you are susceptible to High Pressure Nervous Syndrome (HPNS). How badly HPNS affects you depends on your rate of compression, i.e. how fast you descend, the percentage of helium you're breathing, and how deep you go. Symptoms of HPNS include tremors, changes in the electrical signals in the brain, and somnolence (drowsiness). The deeper you go, the worse these symptoms will get until they can be life threatening (estimated to be around 360 metres for most people). But the boffins are always looking at ways to go further, and experiments with increasingly exotic breathing gases have allowed humans to go even deeper. Now, bear in mind that the deepest ever scuba dive by a real, living, breathing person in the ocean was 318 metres, and that more people have walked on the moon than dived deeper than 200 metres. Yet humans have sat in hyperbaric chambers and breathed hydreoliox, a mixture of hydrogen, helium and oxygen, and hydrox- hydrogen and oxygen, in order to push the boundaries, and limit the effects of HPNS. At 500 metres, hydreliox has been successfully used to reduce HPNS to a manageable level. But predictably, beyond this depth hydrogen becomes narcotic, and hydrogen narcosis kicks in. The deepest any human has ever dived was to 701 metres in a hyperbaric chamber using hydrox, undertaken by Theo Mavrostomos in 1990, technically making him the deepet human ever. I can only imagine how long it took him to get back to the surface! The next step is obviously to invent working gills in humans!
If you're not interested in breaking the record for the world's deepest scuba dive, but perhaps want to explore a wreck that sits at 70 metres, such as the Prince of Wales of HMS Repulse (both in the South China sea), you'll need to do some technical diving training. Guess what, we can do that at Big Blue. Big Blue tech can provide all the technical diving training you'll need, building up your comfort, introducing you to changing gases underwater and teaching you decompression procedures, so that you can stay down longer and go much deper than with recreational diving. If that sounds of interest to you, send an email to Big Blue Tech's manager, James Foleher here, or pop in to the tech shack to have a chat with the tech boys.

Bit of Korean?
Koh Tao has restaurants to suit all tastes, German, French, Mexican, Italian, Spanish, Japanese, Thai (obviously), but what about Korean? There are a couple of places that do Korean-style barbeques. Basically you get a hotplate that sits on top of a big bowl. You'll be given a plate of vegetables and a seperate plate of meat, then you get to retrace your ancestry all the way back to being a caveman as you have to cook your own food using fire! As the meat sizzles away on top, the fat drips down into a broth, which serves to thicken it. The broth boils the vegetables, so you end up with a bowl of delicious broth with veggies in it and a plate of cooked meat. There are surprisingly as many as four places that do this, one is in Jitson opposite Pi-Dangs, one is in Mae Hadd behind the petrol station on the main road (my favourite), one sits on the way to Chalock (called Golden 99), and one somewhere else that I have no idea where it is. It makes a nice change from the other types of food on offer around Koh Tao. How authentic it is is a little ambigueous, but I find myself sometimes eating there 3 times a week, so it must be pretty damn good!

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