h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Entry: Decompression Sickness - A805457
Author: Stuart - U199978

This is a follow up to the article on Nitrogen Narcosis.

The decompression examples given under the heading Prevention, were taken from tables that were current in 1986. There is no reason why they should have changed, but they might have. If anyone has more up-to-date information, I would be grateful to hear from them.

Stuart

DCS is also called "Caisson Disease". Hard hat workers building caissons (pier foundations) had to work in pressurized environments and would experience this when they left the work environment.

You mention chambers as being the treatment, which is true. However, I think it is worth mentioning that if you suspect you or your dive buddy has DCI/DCS, you should stop diving and immediately begin administering pure oxygen. Even if the symptoms are mild, you should still contact an organization like DAN or a doctor specializing in barotrauma to get professional medical advice. Catching it early on is better than catching it later on (or never).

With respect to flying after diving, the recommendations I've seen are a minimum of 6 hours and preferably 24 hours. Transport Canada has a good page about DCS at http://www.tc.gc.ca/civilaviation/cam/tp13312-2/section2/decompression.htm and they say that DCS has developed when doing non-deco diving within recreational limits and going to 10000' ASL within 12 hours of diving.

It might be worth adding s to the Royal Navy, NOAA and the Divers Alert Network.

Typo in the first sentence of the third paragraph under Effects: severe

It's definitely a good start!

Another good one Stuart As soon as any technicalities can be agreed upon, into The Guide with it

Hi Gordon,

I thought of including “Caisson Disease” in the article but decided against it as the article is primary to do with divers although I agree it does happen.

I must disagree with your comment on administering oxygen. In all my time as an active diver I have never been on a dive where oxygen has been available not have a ever been taught to use oxygen. This applied even when diving in way out places where the nearest decompression chamber was 2,000 miles away, although skilled medical help was only half an hour away. Administering pure oxygen can have its own problems and should really only be done under medical supervision. I have only ever known of oxygen being administered during decompression treatment in a chamber.

Here in the UK the first point of contact for decompression sickness is HMS Vernon, both military and civilian. They act as a clearing house for all decompression problems and keep a register of all decompression chambers in the UK and there state of readiness. Its no good driving fifty miles to a decompression chamber, only to find when you get there that there is already somebody in it.

The recommendations from Transport Canada probably tend to ere on the side of caution, as do most recommendations from organisations that could be held liable for the advice they give. My information was taken from a medical text book and you know what it is like trying to sue the medical profession.

I an not surprised that there have been cases of decompression sickness at 10,000 feet ASL in un-pressurised aircraft. Another 3,000 feet and RAF regulations would have required the use of oxygen just to be able to breath. The article did say to keep below 5000 feet in un-pressurised aircraft. Commercial aircraft usually maintain a cabin pressure of 6000 feet ASL even thought he aircraft may be flying at 32,000 feet. This should not be a problem.

I have looked at the Royal Navy site. As good as it is, there is nothing that has any relevance to this article. I have never heard of the other two organisations.

Thanks for the feedback

Stuart

Thanks for that Gosho. Getting the hang of this PR thing.

Best wishes

Stuart

It must be a difference between North American and British diving practices. Most of the dives I've done this year have had oxygen kits with people who know how to use them. In an emergency situation, I think anyone can administer oxygen. It's a first-response procedure.

The PADI Adventures in Diving manual says "First, give patients emergency oxygen in the highest concentration possible - as close to 100% as you can". The it says to contact emergency medical care immediately and arrange for transportation to a medical facility. This is consistent with DAN's recommendations on treatings DCI/DCS.

I re-read my original post and I wasn't as clear as I could have been. I meant to say that first you administer oxygen prior to transportation to emergency medical care.

There defiantly is a difference between North American and British diving practices. I was trained according the BSAC regulations. Never had anything to do with PADI, but I know there were differences between the two. We used to get PADI trained divers coming to us and the differences were quite noticeable. We have to put them through a quick conversion course to iron out the difference, some of which could lead to confusion which could be dangerous.

An example is the diving flag. The flag used in the UK is the International Code Flag Alpha. A blue and white flag which, when flown by itself from the masthead, is recognised throughout the world to mean "I have divers down, keep clear and at slow speed". Except in North America where they use a red flag with a white diagonal cross.

Regards

Stuart

Bringing this up to the surface of PR. Hoping it doesn't get the bends on the way.



For the record, this is another excellent clear and factual entry. It might be worth putting in a footnote either saying that there are differences in practice between the US and the UK, or saying that this is about practice in the UK, or specifying some of the differences.

N

Thanks for that Ben.

It does seem to be doing a decompression stop about half way down the page. Time to surface!

Stuart

Hi Stuart,

Another good entry on diving - good work!

Some comments:

I think this entry needs something about dive computers. Illness stopped my diving about eight years ago, and a lack of time and cash has prevented me from re-starting again, but I believe that most UK divers now use computers rather than tables. The recommendation is that the two divers abide by the most conservative computer.

The problem with tables is that you have to assume that your deepest depth is the depth for the whole dive, while dive computers can take depth variation into account and give more time to divers without jeapordising safety. Most divers with computers carry an waterproof table summary card in case of failure. There can be problems with divers on holiday pairing up with different buddies with different computer readings, though. The BS-AC tables of 1986 have definitely been superceded by now.

Gordon is right about administering pure oxygen to DCS sufferers, but only from trained personnel. I think that most diving clubs in the UK send people on Oxygen administration courses. If I recall correctly, it's because there's too much nitrogen in the body already, so it's a bad idea to introduce any more! I think it's also good for injuries in general.

See http://www.hyperchamber.com/decompression_illness/ for more info.

I think it's also worth comparing and contrasting DCS with "burst lung" (air embolism) which - from memory - has very similar symptoms but starts much sooner after surfacing. Is it worth mentiong that DCS symptoms do not always appear immediately after re-surfacing?

Another tip for avoiding DCS is to start the dive season slowly and build up to deeper depths (good practice for all kinds of reasons), and if you're doing two dives in a day, to start with the deeper one first and then do a shallow one (you'll still be demcompressing while underwater, but more slowly).

A more general point to make is that this article is for information only, and that divers ought to abide by the recommendations of their training / governing body in their country.

Off topic: I found that the difference between BSAC and Padi divers is (or was, several years ago) partly about rescue and safety training. By the time I did my first open water dive, I knew enough first aid and rescue drills to save my instructor's life should I need to. I don't think that Padi do (did) much in the way of safety or first aid until they get to instructor level. I was always told not to dive with Padis, as you couldn't count on them to save your life should they have to.

TTFN

Otto

Hi Otto,

Many thanks for you comments. A few modifications seem to be in order. I think I will change the paragraph about decompression tables. Not having current dave tables available and finding it extreamley difficult to get information out of the BSAC, it's probaly best just to mention that there many different tables.

Dive computers where avaialble when I was diving fifteen years ago, but they were very unreliable. I imagine technilogy has advanced since then and they are a lot more reliable now.

That URL you quoted is very good. I think I will put a link to that in the article. It expalns the problem in more technical detail for any who is interested in the technacalities.

Best wishes

Stuart

Thought I'd drop by and say despite the niggles, it is otherwise a great article. I've always been interested in diving (never done it though) and since that Radiohead song, I've always wondered what the bends actually was.

Now I do!

Hi Ford,

Glad you liked it. Don'tknow much about Radiohead though, bit after my time!

But as the man said, Education, Education, Education. You can never get to much of it.

Best wishes

Stuart

You're never too old!

There have been some studies published in the last year or two that indicate that reverse-profile diving isn't the evil it was once thought to be. If I recall correctly, the DAN newsletter had something about this a couple of issues back.

You're right that the entry is for information only. I put a simialr disclaimer on an entry about Ottawa International Airport that's pending because I discussed flying into the airport from a pilot's point of view.

WRT PADI vs the other training orgs, you're probably right that the open water divers don't come out with many first aid skills. However, I think they assume that open water divers will likely be diving with a DM and/or a rescue diver. PADI does have a rescue diver course somewhere between advanced open water and dive master. (I have yet to take it, but I will.)

Cheers!

I'll be short: Great Entry.

That's it,

HELL

Oh BTW, there are many typos in there, the Sub-Eds usually do a great job sorting them all out in most cases, but I'd suggest you to double check jargon and technical vocabulary, just in case.

HELL

I'll second those comments.

This was a nice entry without getting so technical that it would blow my mind.

(not that this takes much)



- Jimi X

Thanks Jimi, glad you liked it.



Stuart

Thanks Hell. I've run it through the spell checker again and picked out a few typos.

It seems that correcting one error, generates a few more. These grammer checkers are not as smart as they think they are.



Stuart