Emergency swimming ascent 33ft depth limitation?

[danvolker]

Interesting discussion. However, should someone new to diving be concerned about this? I mean, is it really a common problem? From these discussions, my sense is, no.

The way I see it, people really new to diving are the ones who are most likely to run out of air...and also very prone to getting far away from their buddy--due to low situational awareness...they get involved in something, and everything else stops existing to them. Suddenly the regulator breathes really hard, and in such a situation, having practiced an emergency swimming ascent before would be a good way to survive ....

 

[dumpsterDiver]

I think many of the opinions expressed in this thread are wrong. People talking about swimming up for 1 or 2 minutes with no air and then relating this to the times and physiology of free diving seem to fail to understand the very significant differences.

The two activities are not comparable at all. A free diver goes through a long rest before a dive, they slow their heart rate, relax their muscles, mentally prepare for the dive and then perform some deep breathing before the dive and then fill their lungs to capacity before the dive.

It is ludicrous to compare a well rested and prepared freediver to a scuba diver who is thrown into an emergency situation when he looses all air at depth. I am not talking about a diver who runs his tank low and needs to sip their air on ascent. I am talking about a true emergency where ALL air is lost. The diver may not realize about the problem until they exhale and have no air in their lungs.

If this occurs when the scuba diver has their heart rate up, the ability to function without breathing is drastically reduced! This fact is so intuitively obvious to me that I am amazed that people would continue to promote the idea the a CESA is going to be ok with a 2 minute ascent.

If you do not believe me, try jogging and then EXHALE and see how long you can hold your breath. I seriously doubt that many people can make even 20 seconds.

 

[danvolker]

I think many of the opinions expressed in this thread are wrong. People talking about swimming up for 1 or 2 minutes with no air and then relating this to the times and physiology of free diving seem to fail to understand the very significant differences.

The two activities are not comparable at all. A free diver goes through a long rest before a dive, they slow their heart rate, relax their muscles, mentally prepare for the dive and then perform some deep breathing before the dive and then fill their lungs to capacity before the dive.

It is ludicrous to compare a well rested and prepared freediver to a scuba diver who is thrown into an emergency situation when he looses all air at depth. I am not talking about a diver who runs his tank low and needs to sip their air on ascent. I am talking about a true emergency where ALL air is lost. The diver may not realize about the problem until they exhale and have no air in their lungs.

If this occurs when the scuba diver has their heart rate up, the ability to function without breathing is drastically reduced! This fact is so intuitively obvious to me that I am amazed that people would continue to promote the idea the a CESA is going to be ok with a 2 minute ascent.

If you do not believe me, try jogging and then EXHALE and see how long you can hold your breath. I seriously doubt that many people can make even 20 seconds.

I would agree with the 2 minute scuba diver free ascent... an OOA diver in this scenario should be surfacing in seconds, not 2 minutes. As most new divers have significant air in their BC, as soon as they swim up about 10 feet, they are beginning to cruise faster and faster, with no more swimming needed. If they had zero air in their BC, they would need to add some as the 2nd stage allowed, with 10 or 20 feet of ascent...if not, they would indeed have a challenge.... If memory serves though, I think this began with a dry suit diver's question about this, and with a dry suit, they would quickly be on the "up elevator"

 

[Thalassamania]

Deep ESAs are quite possible and in the old days were routine. When I qualified for my 150 card I had to do an ESA from that depth. It was not especially difficult. After course time was reduced in the 1980s there occurred a spate of training realated ESA accidents and lots of rules, regulations and procedures were instituted, based more (IMHO) on individuals opinions than on any consistent reality. These rules, regulations and procedures are still in place.

 

[danvolker]

Deep ESAs are quite possible and in the old days were routine. When I qualified for my 150 card I had to do an ESA from that depth. It was not especially difficult. After course time was reduced in the 1980s there occurred a spate of training realated ESA accidents and lots of rules, regulations and procedures were instituted, based more (IMHO) on individuals opinions than on any consistent reality. These rules, regulations and procedures are still in place.

Of course, back in those old days, all of us knew how to swim, or we would never have been certified. Some of the people who thrash around with useless fins, and go nowhere, really better have air in their BC...

Back in the 70's I routinely did 90 and 100 foot free ascents for fun and practice, and I did not get forced to use a bc back in those days ( by the charter boats). If you were nervous back then, you would drop your weightbelt...though I never needed to do that....

 

[wve]

Interesting discussion. However, should someone new to diving be concerned about this? I mean, is it really a common problem? From these discussions, my sense is, no.

Not really, but the questions are good because it makes you think again about what you think you already know.

It is possible to over-think something, but most people get in trouble from the opposite tendency.

 

[dumpsterDiver]

Of course, back in those old days, all of us knew how to swim, or we would never have been certified. Some of the people who thrash around with useless fins, and go nowhere, really better have air in their BC...

Back in the 70's I routinely did 90 and 100 foot free ascents for fun and practice, and I did not get forced to use a bc back in those days ( by the charter boats). If you were nervous back then, you would drop your weightbelt...though I never needed to do that....

I used to practice ditch and don of the scuba unit in over 60 feet of water. That has NOTHING to do with the ability to stay alive in a REAL 100 ft Emergency ascent. I can make an ascent from 50 or so no problem, but I worry that new divers are hearing that THEY can make a 10o ft ascent with no air, no problem.

 

[Bubble_Boy]

I don't know much on this subject. The only thing I can bring to this discussion is about the 33ft PADI limit. I have heard that it is extremely unlikely to get DCS from anywhere above that depth, maybe that's why those limits are set...

 

[Trace Malinowski]

Years ago, I had a full face mask failure in the days when we just wore a FFM without bailout for cold water diving. I made a "blow and go" ascent from 70 - 80 feet which was much easier than in training. Between my ascent speed and humming, I didn't experience that empty lungs feeling and the ascent actually felt pretty good. When teaching the skill in training, I often feel that humming becomes more difficult which also means that my lungs aren't as "relaxed" as they should be during the skill. This is my concern for myself and my students during the exercise. Should positive pressure somehow create gas trapping in the alveoli then serious barotrauma could occur.

As a freediving instructor, I've made many ascents from 100 - 200 feet and I'm sure that the misinformation in the manual as reported by the OP is directed at freediving. The increased partial pressure at depth in which a diver may remain conscious after long breath holds combined with a pressure drop in which tissues such as the lungs expand back to their near normal volume during ascent could result in an oxygen pressure drop below what is needed to sustain consciousness.

According to the US Navy, freediving breath hold times have a 60 second safety factor. After that it's a crap shoot. I've blacked out at 2:38 and have successfully held my breath many times over 5:30.

Blacking out during an emergency ascent on scuba is most likely going to be from AGE and not from SWBO.

 

[Zippsy]

I don't know much on this subject. The only thing I can bring to this discussion is about the 33ft PADI limit. I have heard that it is extremely unlikely to get DCS from anywhere above that depth, maybe that's why those limits are set...

There is no such thing as a PADI limit. You can also get DCS from ascending too fast from just about any depth, considering the nitrogen in your system. Finally, the bigger concern is lung overexpansion injury which is more likely to happen in those last 33 feet. Please re-read your OW manual.