Things Scuba Instructors teach that are either bad or just wrong.

[L13]

A negligible increase of O2 exposure vs. non-negligible decrease in tissue tension.

As an example, NDL at 30 m on air (GF x/80) is 15 mins, CNS of 4%. Adjusting GFs to give 15 mins when on EAN34, one would surface at a GF of 59, CNS of 9%. That's a long way from an O2 exposure of 100%, and even the relevance of "100%" is debated.

He is concerned with "The long term effect of oxygen on the lungs, called pulmonary oxygen toxicity." We are talking about a man who has probably been diving longer than most people on this board. He states that when he was young he exposed his lungs to ludicrous (by today's standards) amounts of O2 for long periods of time. N2 has only an acute risk. O2 has an acute and a chronic risk. He suspects that he has already pushed the limits for the chronic risk and is being careful. The chronic risk is poorly understood, and his actual exposure is probably not adequately documented. I don't blame him for being careful of the risk that may be significantly higher for him.

I, on the other hand, am much more concerned with DCS (and CNS) than he is, given my history of exposure. I suspect the vast majority of us have not put in 10's of hours at PO2 >> 2.0, so we should probably be more concerned about DCS (and CNS). He may or may not be right about the greater risk, but he is being overly cautious about both, so he is being safe.

 

[boulderjohn]

I just remembered an interesting example of an instructor/agency teaching something wrong. I am going to be vague as Hell so that no one recognizes who I am talking about.

The first day of class, we were handed a textbook and told to read it by the next day. The instructor proceeded to lecture us on key materials from the first half of the book we would be reading that night. In one instance, he told us emphatically how a certain skill needed to be done, no matter what other fools may say.

The next morning, as class began, I brought up the fact that the textbook said the exact opposite of what he had told us in class. He looked at me as if I was absolutely nuts, and then he sat down and looked at the textbook. And he looked at it some more. And he looked at it some more. Eventually he looked up and agreed that the textbook did indeed say the opposite of what he had said. He told us to ignore the textbook and do what he had said.

Here's the problem: our instructor wrote the textbook.

So was he wrong when he wrote the textbook, or was he wrong when he told us to ignore the textbook?

 

[Bob DBF]

So was he wrong when he wrote the textbook, or was he wrong when he told us to ignore the textbook?

Probably both.

 

[wetb4igetinthewater]

I just remembered an interesting example of an instructor/agency teaching something wrong. I am going to be vague as Hell so that no one recognizes who I am talking about.

The first day of class, we were handed a textbook and told to read it by the next day. The instructor proceeded to lecture us on key materials from the first half of the book we would be reading that night. In one instance, he told us emphatically how a certain skill needed to be done, no matter what other fools may say.

The next morning, as class began, I brought up the fact that the textbook said the exact opposite of what he had told us in class. He looked at me as if I was absolutely nuts, and then he sat down and looked at the textbook. And he looked at it some more. And he looked at it some more. Eventually he looked up and agreed that the textbook did indeed say the opposite of what he had said. He told us to ignore the textbook and do what he had said.

Here's the problem: our instructor wrote the textbook.

So was he wrong when he wrote the textbook, or was he wrong when he told us to ignore the textbook?

Now that is freaking hilarious!

 

[kinoons]

You are mixing up two different kinds of toxicity. The long term effect of oxygen on the lungs is called pulmonary oxygen toxicity. It is not talked about so much in recreational diving any more because, as you suggest, it really isn't an issue.

The reason for the MODs of nitrox in both recreational and technical diving is different. We are not concerned as much (hardly at all) with the long term effect on the lungs. We are worried about suddenly going into convulsions, which has an important short term effect, not only on the lungs, but on the whole body. Although it is hard to predict how long it can take, a diver who was breathing 36% nitrox on a dive to a wreck that was between 150-170 feet deep took about 20 minutes before he toxed and died.

No I didn’t mix them up - I specifically said that those who dive at deep depths run the risk of acute oxygen toxicity. It was literally the first part of the article that I quoted.

Then I discussed the risk for folks who are at 2-3 ATM. That’s recreational type diving.

Then I said that for long term toxicology there isn’t any very good evidence that a high risk is present, but that I would be open to that possibility.

Although I do appericate the additional insight into deep diving and oxygen toxicity as that is a subject that I am not very fluent in as a recreational diver and a non-dive medicine clinician.

 

[BoltSnap]

he is being safe

Actually, "he is trying to be safer."

 

[BoltSnap]

So was he wrong when he wrote the textbook, or was he wrong when he told us to ignore the textbook?

No, you were wrong to take the course with him

 

[Wibble]

Here's the problem: our instructor wrote the textbook.

So was he wrong when he wrote the textbook, or was he wrong when he told us to ignore the textbook?

Oops!

Seems more of a symptom of poor technical editing and review. Hopefully most courses will have the material technically edited (checking the content is valid) and proof edited (checking that the words make sense -- typohs, grammargh, wording order correct it is, formating). Those are very different processes requiring different skills.

 

[boulderjohn]

Oops!

Seems more of a symptom of poor technical editing and review. Hopefully most courses will have the material technically edited (checking the content is valid) and proof edited (checking that the words make sense -- typohs, grammargh, wording order correct it is, formating). Those are very different processes requiring different skills.

A lot of course material is not easily checked facts. Quite a bit can be the opinion of the author or agency about how something is best done. There can be disagreements. In this case, it was all about how to handle a certain kind of emergency situation, and that is a matter of opinion.

 

[Wibble]

A lot of course material is not easily checked facts. Quite a bit can be the opinion of the author or agency about hos something is best done. There can be disagreements. In this case, it was all about how to handle a certain kind of emergency situation, and that is a matter of opinion.

Wot, team bailout? Only need everyone to carry enough for one and a bit persons to surface alive...

Yeah, right!

(Of course it becomes an issue for big boy full-on deep hypoxic dives, but not your run-of-the-mill normoxic dives -- MOD1, MOD2 and a bit beyond)