The Martini Rule

We've really had a lovely run of flat seas and nice temperatures and today was no exception. There was a seal playing around and I felt a little apprehensive as there was a seal attack in the harbour area over the weekend, and the existing concerns around rabies. Luckily this seal seemed friendly and not particularly interested in us.

I've had some comments after the previous blog and thought that maybe I should share some more pictures. Don't worry, I will return to posting pics of Hout Bay and our swims soon, but please allow me to indulge once or twice more.

Above is some more pictures of the Helicopter Underwater Escape Training. You can see in the first picture how it is tilting, in the second picture you can see one of the divers, and the guy with a yellow hardhat - which indicates that he cannot swim to the divers. I think that might also be why he is sitting at a big open door, whereas there is the smaller 'windows' in front and behind him. The people on the other side are already being submerged. And then the last pic - we've just made it out of the chopper.

You might be wondering about the name of the blog post - the Martini Rule...well this is from Diver Medic training I used to teach on. In the oil and gas industry (and I suppose broader), the divers fulfil a very important job under water sometimes at great depths. They do welding, they fix things, they inspect etc.

One specific group of diver, called saturation divers works at depths where they need to decompress in a diving chamber, and typically one (if not all) of these divers are trained in advanced first aid - called Diver Medics. The demands and/or environment in which they will need to render first aid, is fairly unique though.

Coming out of the diving chamber

Keeping it simple and sharing my long forgotten understanding. The diving chamber holds an internal pressure that is higher than the ambient or atmospheric pressure. In the commercial diving and oil industry the diving chambers can be used as a temporary environment for divers that are working shifts at great depths- to eat, rest etc. They are only decompressed once, which enables them to work at greater depths for longer. Obviously these guys are pretty used to the depths, but for someone like me going into the diving chamber once it hit about 50 meters I feel 'tipsy' and this speaks to the The Martini Rule. Which states that the impact of the depths are similar to having a Martini (I would say a very strong one) on an empty stomach. And as you go deeper the number of Martini's increase :-)

The effect (nitrogen narcosis) has to do with a gas law known as Henry's law - where oxygen and nitrogen (and other gases) in the body has an increased solubility at the higher pressures. Stated slightly differently - the amount of dissolved gas in a liquid (blood) is directly proportional to its partially pressure above the liquid, and this phenomenon seems to be specifically linked to nerve membranes and transmissions. Also, nitrogen is far more soluble than the other gases.

Divers that are exposed to the depths and used to the Deco or diving chamber, can develop a tolerance and they can cope with the change in pressure. However, to their great delight their party trick is to give you some paper and a pen and they ask you to draw a geometric shape for example a triangle. It becomes more and more difficult, this is because one's manual dexterity and ability to perform basic motor skills are impaired as the nitrogen levels in your body is changing. And since you are feeling tipsy and even confused, it feels weird. Now imagine having to put up an IV line or give an injection...my next blog in the series of taking over the Hout Bay Swimriser blog for a week, will be about the frog and the surfer. Stay tuned.