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

"The air we breathe is a mixture of 79% nitrogen, 20% oxygen and 1% other gases..."

21% Oxygen, 78% Nitrogen, and the rest others. If my ambient O2 level was less than 21%, I'd start opening some windows.

"A more severe form of decompression sickness is when the bubbles reach the joints: this causes severe pain. In extreme cases the diver will contract every muscle in their body, lying on the deck bent double - hence the bends. Immediate treatment is essential in these circumstances as delay can lead to permanent disability."

'Joint' or 'pain only' bends are usually the least serious, next to skin bends. Sufferers rarely 'contract every muscle' and the chances of recovery are usually very good.

"The most severe form is when the bubbles reach the heart, lungs or brain and this can lead to death. This form of decompression sickness is rare as these organs fortunately absorb nitrogen faster than other tissue and they also surrender it to the respiratory system faster. It only occurs when the diver has grossly exceeded their decompression limits."

Most sufferers are either prone to DCI (e.g. because of a PFO) and / or are subjected to a rapid ascent. It is, unfortunately, not rare. About half of those recreational SCUBA divers treated for DCS in the UK will have Type 2 DCS, i.e. affecting the central nervous system, heart, lungs.. Not to mention CAGE.

"The symptoms of decompression sickness can appear from mere seconds after surfacing to an hour later."

To hours later, not 'an hour' later.

"Oxygen can be administered on-site in an emergency but this should only be administered by trained personnel."

Don't treat divers like idiots. If they know the difference between O2 and Entonox, then they are more than capable of administering it (the O2, that is). O2 can do little harm in a suspected case of DCS.

"During this time, the casualty may be given oxygen to breathe that can aid in the dissipation of the nitrogen in their system."

If the patient is not receiving O2 therapy during hyperbaric treatment, then they are not being treated properly.

"However, it is permissible to re-enter the water to complete missed decompression stops if it is done before symptoms appear and this may be necessary if the diver is running low on air."

Absolutely Dangerous!!! Any divers reading this, please DONT DO IT! In water recompression is a foly. This is one of the things that puts the 'Die' into Diving.

"They can then spend 24 hours or more on the bottom, returning to the diving bell to eat and rest. This is known as saturation diving..."

They spend far less time (about 4 hours if memory serves me) actually working on the sea floor, rotating between sea working, bell back-up, and in chamber. They use the bell as a shuttle between the sea floor and the hyperbaric chamber (e.g. on the diving ship) where they eat, sleep, phone home, watch TV, etc. This daily cycle last for about 28 days.

"Note that commercial divers are usually trained engineers, photographers or surveyors, etc, whose work takes them under water."

More usually they are welders.

�21% Oxygen, 78% Nitrogen, and the rest others. If my ambient O2 level was less than 21%, I'd start opening some windows.� If your ambient O2 level was less than 21% but 19% or more, you would hardly notice the difference until you started doing some hard exercise. When you have read as many books on diving as I have, you will find that the proportion of Oxygen in air is often quoted differently. Oxygen can vary between 19% and 21%. One thing I have never seen though is Nitrogen quoted at anything less than 79%. �'Joint' or 'pain only' bends are usually the least serious, next to skin bends. Sufferers rarely 'contract every muscle' and the chances of recovery are usually very good.� That�s what I said. The previous two paragraphs talk about skin bends or the niggles. The next paragraph the states �A more serious form� that means more serious than skin bends, which they are. Recovery is usually good, providing decompression treatment is available as stated. No treatment can lead to permanent disability. Notice the use of the word �can� not �will� Extreme cases do cause muscle contraction. The use of the word extreme implies a degree of rarity. Most sufferers are either prone to DCI (e.g. because of a PFO) and / or are subjected to a rapid ascent. It is, unfortunately, not rare. About half of those recreational SCUBA divers treated for DCS in the UK will have Type 2 DCS, i.e. affecting the central nervous system, heart, lungs.. Not to mention CAGE. This is technical mumbo jumbo which the article set out to avoid. To hours later, not 'an hour' later. I meant what I said. If symptoms haven�t appeared after an hour on the surface, they are unlikely to appear at all. Unless the diver gets out of the water, lays down and goes to sleep, thus slowing down his circulation. Don't treat divers like idiots. If they know the difference between O2 and Entonox, then they are more than capable of administering it (the O2, that is). O2 can do little harm in a suspected case of DCS. I�m not treating diver like idiots, after all I was one for ten years. But neither are they trained Doctors. O2 administered incorrectly can do a lot of harm. That is why the BSAC run training course for the administration of Oxygen on-site. If the patient is not receiving O2 therapy during hyperbaric treatment, then they are not being treated properly. Not true. Every case is treated differently. There are many reason why Oxygen may not be given. In most cases, Oxygen will be used, but it up to the Doctor to decide. The difference between can and will. Absolutely Dangerous!!! Any divers reading this, please DON�T DO IT! In water recompression is a folly. This is one of the things that puts the 'Die' into Diving. Rubbish. I have done it myself many times and have not had DCS. Reentering the water before symptoms have appeared is not dangerous providing the time lapse between the last scheduled stop and getting back into the water is no longer than a minute. We are talking in water decompression, not re-compression. Reentering the water after symptoms have appeared is dangerous, however, recent investigations suggest that even this might be exceptable in an emergency. As a newbie you probably haven�t yet got round to reading about Peer Review. As an edited article, this went through Peer Review where a lot of people read it, some commented on it, some made suggestions for changes which where made and it was finally excepted. Have a look at the following and you will see what I mean: http://www.bbc.co.uk/dna/h2g2/brunel/F96338?thread=202431 Stuart

"One thing I have never seen though is Nitrogen quoted at anything less than 79%."

I wouldn't have commented on this minor point if the rest of your text wasn't so inaccurate. However, as it is, I think you should read some more books.

"This is technical mumbo jumbo which the article set out to avoid."

OK, let me put it this way. Your original statement "It only occurs when the diver has grossly exceeded their decompression limits." is false.

"There are many reason why Oxygen may not be given."

Really? I don't think so. But then, what would I know? I'm only a Senior Staff Nurse at a large Hyperbaric Unit. O2 is part of the treatment for DCS - period.

Original:

"Re-entry decompression is when the diver re-enters the water and goes down to a depth that relieves the symptoms"

Now:

"Reentering the water before symptoms have appeared is not dangerous...Reentering the water after symptoms have appeared is dangerous"

Then you agree that your original statement is dangerous?

"As a newbie you probably haven’t yet got round to reading about Peer Review. As an edited article, this went through Peer Review where a lot of people read it, some commented on it, some made suggestions for changes which where made and it was finally excepted."

Well, there are peers... and there are peers.

One of the interesting points about publishing on the web (and by that I mean scientific papers as well as your article) is that it bypasses the conventional route of traditional peer review by selected experts before publication in a relevant journal.

This has the disadvantage of allowing in-experts to distribute inaccurate pieces of work (like your one) but also allows for more widespread criticism of the paper (or article).

With that in mind, I have read your article and I have made my comments. My suggestion for change is that you delete the reference to our unit's website (www.hyperchamber.com) - and please don't associate it with any more inaccurate articles in future.

I do not intend to continue this conversation.






(Any opinions expressed are those of the author, and are not necessarily those of Grampian University Hospitals NHS Trust.)

Just on the off chance that anonymous researcher does read this I will answer your points.

"It only occurs when the diver has grossly exceeded their decompression limits." is false.

This statement is to subjective to say outright that it is false and therfore I stand by it.

The heart and lungs absorb and release Nitrogen at a faster rate, so bubbles forming in those organs are rare. Normally bubbles that do reach the heart and lungs or got there via the blood stream either because there a lot of them or because of a delay in seeking treatment.

Being a senior Staff Nurse you will know that pure Oxygen is a lung irritant. By saying the Oxygen is administered as a matter of routine you are pre-empting a decision that is made by a Doctor. Perhaps ‘may’ might of been the wrong word to use, ‘can’ might have been more appropriate, but not will.

"Reentering the water before symptoms have appeared is not dangerous...Reentering the water after symptoms have appeared is dangerous"

Then you agree that your original statement is dangerous?

Not at all. The original statement says the same thing, in different words perhaps, but the message is there.

"Re-entry decompression is when the diver re-enters the water and goes down to a depth that relieves the symptoms" This sentence then goes on to warn of the dangers if symptoms have appeared.

The sentence advocating re-entry specifically mentions the lack of symptoms. Pretty much the same as my comments above. The article does say that re-entry decompression should otherwise not be contemplated.

You comments are all of a very minor nature, due perhaps to the lack of technical details which is the way it is designed to be. There is nothing that is grossly inaccurate. Just a matter of subjective interpretation and an overeagerness to pick fault based on your professional knowledge.

Well, there are peers... and there are peers.

Yes there are. h2g2 is specifically aimed at the non-technical. If I wanted reviewed by medical experts, I wouldn’t have published it on h2g2. It was reviewed by my peers, not yours, mine. Its not that it bypasses convential peer review, it just uses a different group of peers for a particular purpose. After reading this article, there are a lot of people that have a better understanding of Decompression Sickness that they would not otherwise have had.

If you want the link removed you will have to contact the Editors yourself. Once the article has been Edited, I have no control over it.

And while you are at it, you might like to look at my article on Hypoxia, Carbon Monoxide Poisoning and Drowning A817850, that has the same link.

Stuart

In the (possibly vain) hope of concluding this time-consuming endeavour, I shall try once again to explain the problems with your article. There are minor and major points.

(Minor) Your explanation of the composition of air is incorrect. Yes, levels vary, but the standard (and simplest) way to explain the composition of air is to state the standard values in dry air.

(Major) You state that if a diver experiences mild symptoms they may be more pre-disposed to DCS (correct) and should therefore reduce their bottom times. Although you later mention that they should be kept under observation, you do not make this clear. Many people try to ignore even obvious symptoms for fear of it interfering with their diving. I have seen it happen all too often. Some divers will even refuse to believe that the reason they can't walk is because they have DCS. Believe me, if enough people read your article, someone will take your statement to mean "even if you get a bend you can carry on diving". I'm sure that isn't what you mean, but people often change things in their minds to extremes in order to hear what they want to hear. Anyone giving advice on a medical subject like DCS needs to err on the side of extreme caution and explain things very clearly.

(Minor) You mention that being fat is a pre-disposing factor in DCS. Although there is some evidence to support this claim, I am not aware of any study that proves it to be a major factor. There are far greater risks, which you fail to mention.

(Minor) Your explanation of the different forms of DCS, and their severity is confusing. You start by talking about 'niggles' then mention 'pins and needles' and 'staggers' - both very serious symptoms. But then you go immediately on to talk of joint symptoms as a "more severe form" of DCS. This may be read as "joint symptoms are more severe than pins and needles or loss of balance". Also, your description of joint symptoms is extreme - most cases are relatively minor. If the DCS is bad enough to cause the severity of symptoms you describe, then it is likely that the patient will also have a neurological problem too, and it is this which is more likely to lead to permanent problems.

(Minor) You then mention the most severe form of DCS (Type 2) affecting the "heart, lungs or brain". You state that it is rare. "heart and lungs" yes, "brain" (and the rest of the Central Nervous System) no - Type 2 DCS is as common, if not more so, as Type 1.

(Major) Your claim that this form of DCS "only occurs when the diver has grossly exceeded their decompression limits" is profoundly incorrect. Perhaps you are confusing Arterial Gas Embolism with Decompression Sickness? Even so, there are other reasons for this to occur.

(Major) The time limit of "to an hour" for the onset of symptoms is incorrect. Yes, most people will experience symptoms within this first hour. However, there are a significant number (10-15%) who may experience symptoms after this (and perhaps even several hours after surfacing). After reading your article, people would be forgiven for thinking that if symptoms appear more than an hour following a dive, then it is not DCS. As before, you are providing potentially dangerous advice.

(Major) Stating that oxygen should only be administered to a diver with suspected DCS by “trained personnel” may discourage its use. I have asked some BSAC divers what they would do. They are confident that even the most basic qualified diver should have the necessary knowledge to be able to administer O2. You are right when you later say that “O2 administered incorrectly can do a lot of harm.” However, not administering it is likely to do far more harm. If it’s there, it gets given – period.

(Minor) You state that “Initially the pressure in the chamber will be increased to a 'depth' depending on the severity of the symptoms. Once the casualty is stabilised decompression starts.” I cannot speak for other Hyperbaric Units, but this is not what we do. Treatment is based on established profiles. Perhaps it would have better not to include such a generalisation in your article?

(Minor) Saying that “the casualty may be given oxygen to breathe” is misleading. The casualty WILL be given oxygen to breathe. You mention in a later post that I am pre-empting a Doctor’s decision and that there is a risk of lung irritation. Pulmonary oxygen toxicity takes several hours at normal pressure to develop, and is still rare during hyperbaric exposure. O2 is most definitely a must-have in the treatment of DCS.

(Minor) Despite claiming that you aimed to avoid “technical mumbo jumbo” you mention the use of digitalis, steroids and plasma. These are certainly not routinely used in the UK. Why mention such things in an article that is meant to be simple?

(Major) Your explanation of in water decompression may have been fine, except for the fact that you actually state “Re-entry decompression is when the diver re-enters the water and goes down to a depth that relieves the symptoms and then continues with the missed decompression stops.” Note particularly, “…goes down to a depth that relieves the symptoms…” This implies that if you have symptoms, going back down is OK. Again, this may not be what you mean – but it is what some people will take it to mean.

There are many good sources of information available, in print and on the internet, about decompression sickness. Your article does nothing to improve the health and safety of divers. You must realise that, whether intended or not, by providing information on a medical subject you are influencing the decisions that people may make in an emergency. You are ill qualified to provide such advice, so it would be better for all if you stayed clear of such topics.

You are right, it is a time consuming endeavour. All your comments are either trivial, subjective, or in one case, complete misunderstanding of what was said plus a total failure to appreciate the audience for which the article was aimed at.

It wasn’t intended to be read by the medical profession or divers for that matter, but by people who had heard of decompression sickness and were curious to know more. In that respect it fulfils its aim. That is what h2g2 is about. Anyone wanting to know more can follow the link.

In my ten years as an active diver, five as a diving supervisor, I only ever came across DCS twice. Both cases where very minor which cleared up with the need for hyper-baric treatment. Therefore, from my perceptive, and I imagine that of most divers, the more serious forms of DCS are rare. From your perspective where you probably only see divers that have DCS, it would seem more common. You don’t see the hundreds of thousands of diver that dive every year without getting DCS. I myself have, through an error on my part, exceeded decompression limits but did not get DCS. Consequently, it is reasonable to say that to get the more sever forms of DCS, you must have done something silly, like ignore decompression tables, misread them or misunderstand them.

Stating that people with minor symptoms should be kept under observation seems quite clear enough to me. What is not clear? That suspected DCS victims should be kept under observation.

The mere mention that oxygen can be used for the treatment of DCS is sufficient at this level. It was never meant to be the definitive article on DCS and its treatment. That is made clear in the article.

You concede that administering oxygen incorrectly can be dangerous. That is why getting hold of medicinal oxygen is not easy, it normally requires a doctors prescription. Therefore, if there is oxygen available, there is likely to be someone trained available to administer it. Not just the first individual that lays his hands on the thing.

“Re-entry decompression is when the diver re-enters the water and goes down to a depth that relieves the symptoms and then continues with the missed decompression stops.”

This implies nothing. It is simply a description of what re-entry decompression means. It neither condones nor condemns the practice. If you read the rest of the paragraph it goes on to mention things like not recommended, rarely successful and it takes a long time. The sentence that advocates re-entry mentions quite clearly that it can be done before symptoms appear I cant be held responsible for what some people will take it to mean if they cannot understand plain English and take sentences out of context.

Your statement that I am ill qualified without knowing what my qualifications are show a degree of arrogance that is difficult to reason with. Come down of your high-hours and read the article in its correct context. My qualifications did qualify me to give advice to divers on the subject of DCS and no diver I supervised ever got DCS. Mainly because when I was talking to divers I went into far greater detail than the article does. It was not meant to improve the health and safety of divers. It was designed to inform the layman with little or no knowledge of diving of one small aspect of it. To that end it succeeds. I shall continue to submit articles to h2g2 on the subject of diving medicine as and when I see fit with or without your approval.

Stuart
Joint Services Diving Supervisor (Retd)

”It wasn’t intended to be read by the medical profession or divers for that matter, but by people who had heard of decompression sickness and were curious to know more. In that respect it fulfils its aim. That is what h2g2 is about. Anyone wanting to know more can follow the link.”

So it is OK for your article to be factually incorrect on several points, confusing and misleading? I have detailed these points in my previous post. I have tried to be as clear as possible in order that you could understand. Why are you having such a hard time realising that you cannot write on a medical topic without ensuring that you are factually correct, clear and un-ambiguous? Divers WILL read your article, and as I have already clearly explained some may go away with the wrong information – with potentially serious consequences.

Your article contains some useful and accurate information on some aspects of diving. However, the points you address on DCS are poorly covered. I notice that a few (thankfully a few) people have given you positive feedback. They are not the sort of people I feel should be made aware that your article is misleading. The people I aim to help are divers – of which I see you have also given direct advice on DCS. This concerns me.

“In my ten years as an active diver, five as a diving supervisor”

I have been an active driver for 15 years – it does not make me a car mechanic. You claim to have been a diver for 10 years – why does that make you qualified to write an article on DCS?

“I only ever came across DCS twice. Both cases where very minor which cleared up with the need for hyper-baric treatment. Therefore, from my perceptive, and I imagine that of most divers, the more serious forms of DCS are rare. From your perspective where you probably only see divers that have DCS, it would seem more common. You don’t see the hundreds of thousands of diver that dive every year without getting DCS. I myself have, through an error on my part, exceeded decompression limits but did not get DCS.”

Two of our four medical consultants are divers. Several members of our nursing staff are divers. My girlfriend used to be a diver. Many of our friends are divers. And, of course, many of our Unit’s patients are divers. I know the score – I state on our Unit’s website that diving is a relatively safe activity. However, education is part of my remit – and misinformation is what you are providing. Can you not understand that your article is misleading? I know that no-one likes to be debunked or shamed in public, nut unfortunately you continue to persist in claiming that your article is acceptable. It is not. It has the potential to cause or contribute towards harm. I have detailed the reasons why already.

“Consequently, it is reasonable to say that to get the more sever forms of DCS, you must have done something silly, like ignore decompression tables, misread them or misunderstand them.”

YOU ARE WRONG!!! Read the research, study the past cases, do your homework! There are numerous cases of ‘undeserved’ DCS, many of which are very serious cases. You admit yourself that you have hardly ever seen DCS, so why do you persist in claiming that you are qualified to advise people on DCS? This is a subject that you have insufficient knowledge of to make such sweeping statements.

”Stating that people with minor symptoms should be kept under observation seems quite clear enough to me. What is not clear? That suspected DCS victims should be kept under observation.”

I have explained this. YOU do not make it clear. YOUR original text is NOT clear. I have already explained why you have not made it clear.

”The mere mention that oxygen can be used for the treatment of DCS is sufficient at this level. It was never meant to be the definitive article on DCS and its treatment. That is made clear in the article.”

Again, it is YOUR original text over complicates the matter. You say that O2 can only be given by “trained personnel”, that it is “pre-empting” a Doctor’s decision to give it otherwise, that it is a “lung irritant” and is “dangerous if administered incorrectly”.

I say: if O2 is there, give it!

That is all that needs to be said. Check out some of the web resources provided by health care professionals who actually have some experience in treating DCS.

You also make note of experimental drugs in DCS treatment like digitalis and steroids. This is surely way beyond the scope of your article.

”You concede that administering oxygen incorrectly can be dangerous. That is why getting hold of medicinal oxygen is not easy, it normally requires a doctors prescription. Therefore, if there is oxygen available, there is likely to be someone trained available to administer it. Not just the first individual that lays his hands on the thing.”

Of course I concede that it can be dangerous. However, I can assure you that no health care professional worth their salt (and for that matter, no experienced diver) would advise anything other than the following: IN ANY SUSPECTED CASE OF DCS – ADMINISTER HIGH CONCENTRATION OXYGEN.

You are going way off track talking about this subject. Oxygen prescription refers to its use in a non-emergency situation. Any suspected case of DCS is an emergency. It can by obtained easily - and can be used for any suspected DCS case BY ANYONE.

“Re-entry decompression is when the diver re-enters the water and goes down to a depth that relieves the symptoms and then continues with the missed decompression stops.”

”This implies nothing. It is simply a description of what re-entry decompression means. It neither condones nor condemns the practice. If you read the rest of the paragraph it goes on to mention things like not recommended, rarely successful and it takes a long time. The sentence that advocates re-entry mentions quite clearly that it can be done before symptoms appear”

Listen man, I have ran this paragraph past a few divers and experienced hyperbaric staff. They all say the same thing – you seem to be advocating in water re-compression. It doesn’t matter that it is not what you are trying to saying. The fact is that YOU give the wrong impression.

“I cant be held responsible for what some people will take it to mean if they cannot understand plain English and take sentences out of context.”

I think that sums up your attitude quite well.

”Your statement that I am ill qualified without knowing what my qualifications are show a degree of arrogance that is difficult to reason with. Come down of your high-hours and read the article in its correct context. My qualifications did qualify me to give advice to divers on the subject of DCS and no diver I supervised ever got DCS.”

I’m truly sorry that you feel it difficult to reason with criticism. You state that you have rarely had to deal with actual cases of DCS, yet you claim that you are qualified to give advice on DCS. As you correctly suggest, I have dealt with many more cases of DCS. I do not claim to be humble in my pursuit of factual information. So no, I will not come off my high horse!

“Mainly because when I was talking to divers I went into far greater detail than the article does. It was not meant to improve the health and safety of divers. It was designed to inform the layman with little or no knowledge of diving of one small aspect of it. To that end it succeeds. I shall continue to submit articles to h2g2 on the subject of diving medicine as and when I see fit with or without your approval.”

As I said, there are many better resources than yours. You need not re-apply!

Your form of ‘education’ is at the rear-end of science (of which medicine is a part). Unfortunately, the ‘BBC’ logo may confer some degree of credence to your article. Fortunately, despite this, most people will never encounter your article.

“Stuart
Joint Services Diving Supervisor (Retd)”

Stuart Walker
Senior Staff Nurse (Not Retd)
Hyperbaric Medicine Unit / Intensive Therapy Unit
Aberdeen Royal Infirmary

www.hyperchamber.com

Email: [email protected]