Panic!!!

[boulderjohn]

Perhaps my criticism is misplaced. The courses I taught under the NAUI banner were designed for a particular sub-set of the diving community.

Here is another bit from history.

NAUI had a set of standards that students needed to meet, but they allowed instructors to add to that set of standards. This was common for classes taught in universities, because the courses had way more time than was needed to become a basic scuba diver. NAUI focused its efforts on university instruction for a very practical reason. Its financing system was based on what founder Al Tillman had learned when he directed the taxpayer supported program through Los Angeles County. They were a non-profit that survived by donations in lieu of taxes. For example, Skin Diver magazine supported them for their first years. Bill High loaned them $200,000 (IIRC) one year to help make ends meet. Focusing on university classes seemed ideal because the instructor got paid by the school using the tuition the students paid that would have gone to another physical education class if not for scuba--so it was essentially free to the student, and the instructors were paid by someone else. In the long run it turned out to be a bad idea, because it very much limited its potential student pool.

 

[Mantaray95616]

Assuming you are diving within no decompression limits, then there is a chance (but only a chance) that you will get decompression sickness. That is not a desirable, but it is much more desirable than drowning. It is also far more desirable than a lung overexpansion injury, which is what will almost certainly happen if you hold your breath.

I will put these two together to explain a big difference in modern (for the last few decades, really) instruction and instruction back in your day.

Today nearly all agencies use a variation of mastery learning, which does not use the traditional idea of failing. In traditional learning, students are taught for a specified period of time and then given a grade compared to a standard. It could be a failing grade. In mastery learning, students are taught for however long it takes for them to meet the standard. In theory, no student ever fails, but that does not mean they all pass. They may decide that they are having enough trouble that they don't want to continue. Some students will meet standards very quickly. Some will take much longer. It doesn't matter. They get the same certification.

Hey, if you look back on my posts, the original courses , before NAUI was created, were based on students mastering skills at their own pace and then being tested. Maybe failing is the wrong word; but if a student is unable to complete a necessary skill before the course ends (they can make as many attempts as they like) they cannot be certified. They are still welcome to re-enroll in later courses. What's so different between our two methologies?

In the two specific cases I brought up it was a matter of judgement. In my opinion neither of them would ever be comfortable in an underwater environment and I acted accordingly and with regret.

 

[Mantaray95616]

Hey, if you look back on my posts, the original courses , before NAUI was created, were based on students mastering skills at their own pace and then being tested. Maybe failing is the wrong word; but if a student is unable to complete a necessary skill before the course ends (they can make as many attempts as they like) they cannot be certified. They are still welcome to re-enroll in later courses. What's so different between our two methologies?

In the two specific cases I brought up it was a matter of judgement. In my opinion neither of them would ever be comfortable in an underwater environment and I acted accordingly and with regret.

I haven't yet got theknack of selectong quotes.

I have two comments regarding bouyant and free ascents.

At the depths you would be normally diving, fully emptying your lungs is unnecessary and can make the ascent more stessfull. Maintain an open airway and let change in ambient pressure do its work of expelling excess air. Does anybody know why the navy recommends completely emptying the lungs.? I can only quess that it is because of the extreme depths and a pressure differential on leaving the sub.

The second is regarding the Royal Navy's use of oxygen. Pure oxygen was used by the navy's frogmen in rebreather sets (no bubbles) to avoid detection.

Pure oxygen becomes TOXIC at a depth of 33 Ft. A pure air mixture becomes toxic when the partial pressure of oxyen reaches 14.7 psi (165 ft). This is one of the reasons mixed gas diving evolved. The human body can tolerate a certain amount of toxicity.

 

[Goonzodiver]

Assuming you are diving within no decompression limits, then there is a chance (but only a chance) that you will get decompression sickness. That is not a desirable, but it is much more desirable than drowning. It is also far more desirable than a lung overexpansion injury, which is what will almost certainly happen if you hold your breath.

I never talked about holding your breath during the ascent, which would be suicidal (if you have breathed compressed air at depth).
I talked about mastery of breathing and self-control, but I would also say aquaticity, which freedivers normally have, something that was recognized by Marcante and which instead does not have much value in modern courses, as far as I know.
For Marcante it was essential that a true diver master both worlds (with and without scuba) and as far as I'm concerned I think he was right, especially if you are a scuba diver who occasionally doesn't use a BCD, another skill I mentioned (the "old school" ... ).
It is clear that an uncontrolled ascent is better than dying by drowning, but an ascent managed calmly (with the awareness of being able to manage the situation even if you are unable to breathe for about two minutes, during which you not only have to ascend but you have also to do something else first, such as possibly freeing yourself from some entanglement) is better than an uncontrolled ascent.
And I repeat: freedivers are not necessarily those who hold their breath, they are those who do not use breathing apparatus, by definition, as exemplified in the videos I linked.
As you can see, freedivers can expel air if they want, I didn't think there were difficulties or misunderstandings on this point...

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[Goonzodiver]

Why are you so negative on this topic? Do you feel that training for emergencies is silly?

What? Absolutely not.

 

[Goonzodiver]

The second is regarding the Royal Navy's use of oxygen. Pure oxygen was used by the navy's frogmen in rebreather sets (no bubbles) to avoid detection.

Pure oxygen becomes TOXIC at a depth of 33 Ft. A pure air mixture becomes toxic when the partial pressure of oxyen reaches 14.7 psi (165 ft). This is one of the reasons mixed gas diving evolved. The human body can tolerate a certain amount of toxicity.

Pure oxygen in rebreathers was first used in submarine escapes by the British (Davies apparatus), German( "tauchretter"), US and Italian (A.R.O.) navies, so not only the Royal Navy.
It was with Hans Hass in the early '40s that oxygen rebreathers began to be popular for diving.

Momsen lung - Wikipedia

en.wikipedia.org

In figure an early oxygen rebreather used by US Navy, the Momsen Lung.

PS
Oxygen toxicity also depends on exposure time as well as pressure.

 

[Goonzodiver]

I haven't yet got theknack of selectong quotes.

I have two comments regarding bouyant and free ascents.

At the depths you would be normally diving, fully emptying your lungs is unnecessary and can make the ascent more stessfull. Maintain an open airway and let change in ambient pressure do its work of expelling excess air. Does anybody know why the navy recommends completely emptying the lungs.? I can only quess that it is because of the extreme depths and a pressure differential on leaving the sub.

Going from one bar, present in the submarine, to several bars, the lungs would instantly be compressed by a factor that depends on the depth at which the escape occurs, so it is better that the compression moves the lung tissue as little as possible, which therefore must be, let's say, at their residual volume, otherwise there is the risk of instant traumatic lung squeeze.
Moreover, if you have an oxygen rebreather (like submariners had) you cannot expel air so easily and if you did it would be risky because at a certain point of the emergency ascent, in a very stressful situation, you could allow water to enter the airways, and possibly reaching the CO2 elimination substances of the scrubber, which would practically become caustic soda.
Not to mention the not small probability of losing consciousness during the ascent from the submarine. If you have open airways it is certain that you will drown, because there is no voluntary gesture that closes the airways to water when needed. Having the breathing circuit isolated from the water there is the possibility that you can regain consciousness within a few minutes of reaching the surface (where you are breathing pure oxygen at 1bar from rebreather), or at least you can be rescued.
[In essence, it seems to me that surfacing from a submarine is not like making an emergency ascent with a broken scuba.]

 

[happy-diver]

Oxygen toxicity also depends on exposure time as well as pressure.

and the number of pre oxygen breaths you exhale into the apparatus before adding oxygen

 

[Mantaray95616]

Going from one bar, present in the submarine, to several bars, the lungs would instantly be compressed by a factor that depends on the depth at which the escape occurs, so it is better that the compression moves the lung tissue as little as possible, which therefore must be, let's say, at their residual volume, otherwise there is the risk of instant traumatic lung squeeze.
Moreover, if you have an oxygen rebreather (like submariners had) you cannot expel air so easily and if you did it would be risky because at a certain point of the emergency ascent, in a very stressful situation, you could allow water to enter the airways, and possibly reaching the CO2 elimination substances of the scrubber, which would practically become caustic soda.
Not to mention the not small probability of losing consciousness during the ascent from the submarine. If you have open airways it is certain that you will drown, because there is no voluntary gesture that closes the airways to water when needed. Having the breathing circuit isolated from the water there is the possibility that you can regain consciousness within a few minutes of reaching the surface (where you are breathing pure oxygen at 1bar from rebreather), or at least you can be rescued.
[In essence, it seems to me that surfacing from a submarine is not like making an emergency ascent with a broken scuba.]

Thank you for the explanation. I didn't consider implosion as a factor but knew that at 300 ft., on exit, there would be an immediate10 fold increase in ambient pressure.

As you said, it lt's like comparing apples and oranges.

I may have read about it years ago, but I had forgotten about the role of oxygen rebreathers in submarine escape. The relatively short ascent time would mitigate the effects of breathing pure oxygen.

Anyway it is is not an issue for scuba divers. At the beginning of a free ascent they are already breathing air at ambient pressure

 

[Mantaray95616]

Are we still on topic? It's so easy to get sidetracked.

What has submarine escape procedures have to do with either scuba or freediving? - Nothing although interesting.

Why should CESA and bouyant ascent training be specifically linked to Panic!!. Just like any other underwater skill, it is taught to avoid panic.

On the back and forth arguments between free divers and scuba divers: Both share the same environment and have many things in common but breathing protocols are different and cannot be interchanged. Scuba divers have compressed air in their lungs at depth and as they surface the ambient pressure drops and the volume of air in their lungs increases causing their lungs to expands to a point where the lungs will rupture unless the excess air is released.

A normal (non-competitive) free diver will normally hyperventilate at the surface to reduce the partial pressure of CO2 in their lungs (the buildup of CO2 in the lungs is what triggers the urge to breath not the lack of oxygen), execute the dive and because the lungs compress on descent on the way back to the suface the lungs can only re-expand to there original sze . Hence no chance of rupture. Free divers however do. from time to time, release some air from their lungs as a comfort measure or, on nearing the surface, to clear their snorkel before breaking surface. The main risk to a free diver on ascending is Hypoxia also known as Shallow Water Blackout. By hyperventalating and artificially reducing the partial pressure of CO2, a state of oxygen deficiency can go unnoticed resulting in blackout.

Scuba diving and Free diving are not mutually exclusive. The free diver doesn't require any scuba skills but nothing stops them doing both. However, I firmly believe that a scuba diver should acquire some free diving skills.

One other major difference is related to buoyancy. As a free diver descends there is an increase in negative bouyancy due to the contraction of the lungs and thus accelerating their rate of decent. Scuba divers can experience somewhat the same thing by breathing out fully.

Just so that you know where I am coming from; when I lived in the Bahamas, I spent more time freediving while spearfishing than on scuba dives. You have to train to be a good free diver. It took quite a long time to develop procedures, lung capacity and the stamina that eventually allowed me to stalk Nassau grouper and other fish with a Hawaiian sling at depths sometimes n excess of 60ft. In other words I think I know what I am talking about