DAN Recreational Diving Fatalities Workshop Proceedings - 2011

[felixtibs]

Going into my SDI training I was really fearless. I had no fear doing a CESA 5-6 times between the depth of 30'- 10'. I certainly didnt have any fear getting my AOW dehydrated with a 5mm suit in 54* water. Turns out i was just ignorant.

Then I started reading...

Diver Down
Cockroach in my Regulator
DCS findings

Thats when i realized DCS can hit anyone at anytime whether they obey the rules or not. And thats when i realized I spent 5K on training/equipment and now I really dont think I am cut our for the risk of endangering myself and my family. IMO, the education and profession is so non-chalant about the risks because many accept the risk factors as fact.

There is NO SUCH THING as just returning to the surface! its either drown or sit with that anxiety regarding "Am i going to go into DCS" while getting rushed to a hospital.

Its too bad, because if I wasnt such a spaz, I could really enjoy this sport.

 

[Thalassamania]

You seem to be a poster child for the problem I was identifying. A properly performed free ascent, if you are not engaged in decompression diving, is not likely to get you bent ... I've done, literally, hundreds, perhaps thousands, if you count all that I've done with students and I've never been bent.

 

[drrich2]

Felixtibs:

Thats when i realized DCS can hit anyone at anytime whether they obey the rules or not. And thats when i realized I spent 5K on training/equipment and now I really dont think I am cut our for the risk of endangering myself and my family.

There are probably seemingly endless reams of film footage and photos of horrible traumatic car accident victims, and yet most of us drive. Hopefully well and with due diligence, but we drive. Some people may cry that driving is necessary in their area/life-style, but even those people often take 'unnecessary' trips (e.g.: to the movies, to grab a pizza, etc...).

Is scuba diving any different?

Richard.

 

[Thalassamania]

I'm going to go out on a limb and suggest that the reason the scientific diving community enjoys the safety record that it does is (aside from good medical screening) because of the time spent working on free ascents and free diving. All of my students can comfortably and confidently hold their breath for 2 minutes (or more) and all have made, on the order of, 50 buoyant free ascents, first free diving and then later on scuba as part of learning, practicing and perfecting the doff and don exercise. If there is no cause for any medical concern and if any problem from equipment or less than careful monitoring of gas supply can be met with a calm and confident, properly executed, free ascent ... would that not go a long way in accounting for the scientific diving community's safety record?

How long is the recreational scuba diving world going to insist on jumping out of an airplane without a reserve chute and blaming the ensuing collision with the ground on running out of air?

 

[boulderjohn]

Thal will be no doubt shocked at the degree to which I agree with him. The lack of knowledge about how to perform a safe emergency ascent is appalling. Here is a current thread on the topic. If you read it, you will see that there is all sorts of advice offered on the topic of breathing off the BCD as an out of air emergency measure, and I am the only one who suggested that such a measure is unnecessary because a free ascent is so safe and easy. I think the following advice from a poster with tons of training and experience reflects common thinking, is what goes through the mind of OOA divers at depth, and is the reason for these embolisms:

In OOA with not help around you have 2 choices: Use whatever air you have in stage/hose & BC and bolt to the surface and deal with the consequences, or drown. ​

Most recreational instructors are poorly trained in how to conduct free ascent training, when that is combined with the fact that recreational divers receive little training (usually one tense, frightened, trial) in how to do a free ascent, that combination is, understandably, deadly. There were a lot of free ascent training incidents, and the result was that the agencies tightly controlled the way in which free ascent training was conducted.

I have long argued that CESA is improperly taught at the OW level and leads a poor understanding on the part of the students and especially to an "I could never do this in a real emergency" attitude. The instructional approach absolutely violates instructional theory and results in incorrect learning. I had long arguments about this with the leadership of my own agency regarding this several years ago, to no avail.

So we are left with a situation in which we are prevented from taking the single biggest step to increase diving safety, effective free ascent training, by agency blindness and the fact that free ascents have not been a central pillar of diver training since the 1060s and the current instructor cadre has not been trained to conduct such training, but rather has been systematically terrified to do so.

At least two agencies (BSAC and UTD) ban the instruction of CESA altogether, on the theory that you should never be without immediate access to a redundant air source, and if you found yourself in such a situation, you should be headed to the surface at once. When BSAC came up with that policy, I asked its director (or whatever title) what would happen if the diver found himself OOA without a redundant air source, despite that training, and he said that the diver would have to do a CESA--without any training. I never asked UTD, because I was a UTD student and knew the answer: never be more than a few feet from your buddy, and if you lose your buddy, go to the surface. Period.

A properly performed free ascent, if you are not engaged in decompression diving, is not likely to get you bent ... I've done, literally, hundreds, perhaps thousands, if you count all that I've done with students and I've never been bent.

The percentage of divers who get bent while diving within NDL's rounds off to zero, and it isn't nearly a close rounding. Look at any of the DAN fatality studies over the years and see how many of those cases were related to DCS--almost none. The real threat is embolism from that panicked ascent.

 

[boulderjohn]

I thought I would take a few minutes and detail what I think is wrong with SOME of the typical OW training in free ascents.

1. Divers are not taught (unless the instructor goes outside the curriculum) that the tank is not OOA at depth. The tank must have greater pressure within it than the ambient pressure at that depth, or the regulator cannot deliver air. If the diver ascends and the ambient pressure decreases, the regulator will be able to deliver air. The effect is more pronounced as the diver gets nearer and near to the surface.

2. In proper instruction, the instruction must mirror that assessment as much as possible for the student to succeed. Teaching students in a way that is different from the assessment may actually teach and ingrain incorrect skills and knowledge that can result in failure on the assessment. In scuba instruction, the actual real life emergency is the equivalent of the assessment. Here is how that works out in the pool instruction for CESA.

A. In a real emergency, the diver is ascending from depth and heading straight to the surface. The air inside the lungs is expanding rapidly upon ascent. A diver should be able to exhale from 100 feet all the way to the surface while ascending at a controlled rate because of this expansion.

In the pool training, the diver swims horizontally, with almost no ascent in most cases, and they therefore get no benefit from expanding air in the lungs. Divers struggle to exhale the entire way, and the big learning they get is "If I can't do this for 30 feet, how can I possibly do it from any deeper?"

B. As stated above, in a real situation, if a diver does indeed blow through all air too quickly, the diver should be able to get some air immediately by inhaling through the regulator. If the diver is approaching the surface, there should be a pretty good breath available. The proper thing to do in a real emergency, then, is to inhale.

In both the pool and the OW checkout dive, a student who inhales through the regulator just before reaching the surface has failed the exercise and must do it again. The student is thus given a failing grade for doing the right thing. The student learns that the air in the tank is not an option for them, even though it really is.

C. Depending upon the quality of one's regulator, in real life there is a warning before the diver goes OOA. As the pressure in the tank approaches ambient pressure, it becomes harder and harder to breathe. I have breathed stage tanks down to nearly empty at pretty good depths, and I know when the tank is getting low while I still have several breaths remaining, and I am using a very good regulator on those tanks. The effect is lesser in shallower water. If a diver feels something wrong with the regulator intake, realizes the situation, and heads to the surface, the diver should be able to make it all the way (given the ability of the regulator to deliver more air at shallower depths) without doing a CESA. (That is why "normal ascent" is still listed as the first choice in the Low on Air list of choices.)

There is a holdover relic from the days of older instruction and lesser regulators in the pool training. The instructor is supposed to shut off the student's valve to simulate a low air situation. The student is supposed to signal OOA upon feeling resistance in the regulator. With modern regulators and with the depth of pool training, that does not happen. There is no warning whatsoever--just a sudden loss of air. The exercise therefore teaches students that once they feel something wrong in the breathing, it's all over. Unless the instructor does what I do instead, the exercise teaches the wrong thing and is counterproductive. (I take the SPG in my hand and barely crack the valve until I see the needle bouncing. The student gets a more realistic feel of what it is like to be almost OOA.)
​

3. The panicked "I need to breathe" feeling a diver gets during the training is not caused by a lack of O₂, for which the body has nearly no signal. The feeling is caused by a buildup of CO₂. Divers are not taught, unless the instructor goes outside of the instructional materials, that they still have O₂ in their system, and even if they have absolutely nothing to breathe, they should still be able to make it to the surface with a safe ascent.

 

[Thalassamania]

Thal will be no doubt shocked at the degree to which I agree with him.

I am not shocked at all, I think we see similar roots to the problems but come to different conclusions about how to solve them.

The lack of knowledge about how to perform a safe emergency ascent is appalling. Here is a current thread on the topic. If you read it, you will see that there is all sorts of advice offered on the topic of breathing off the BCD as an out of air emergency measure, and I am the only one who suggested that such a measure is unnecessary because a free ascent is so safe and easy. I think the following advice from a poster with tons of training and experience reflects common thinking, is what goes through the mind of OOA divers at depth, and is the reason for these embolisms:

In OOA with not help around you have 2 choices: Use whatever air you have in stage/hose & BC and bolt to the surface and deal with the consequences, or drown.

​

​

A shining example of how thinking has, unfortunately, become quite uncommon.

​

I have long argued that CESA is improperly taught at the OW level and leads a poor understanding on the part of the students and especially to an "I could never do this in a real emergency" attitude. The instructional approach absolutely violates instructional theory and results in incorrect learning. I had long arguments about this with the leadership of my own agency regarding this several years ago, to no avail.

They made a bonehead move to begin with and it has now become gospel, no one (it seems, save you and I) is willing to remark the the Emperor is buck neked.

At least two agencies (BSAC and UTD) ban the instruction of CESA altogether, on the theory that you should never be without immediate access to a redundant air source,

I agree, in theory. that you should never be without immediate access to a redundant air source, but what have they done to assure that never occurs?

and if you found yourself in such a situation, you should be headed to the surface at once.
you should never be without immediate access to a redundant air source,

and how do you head to the surface? Why a CESA that you are not comfortable performing, of course.

When BSAC came up with that policy, I asked its director (or whatever title) what would happen if the diver found himself OOA without a redundant air source, despite that training, and he said that the diver would have to do a CESA--without any training. I never asked UTD, because I was a UTD student and knew the answer: never be more than a few feet from your buddy, and if you lose your buddy, go to the surface. Period.

is this a suitable location for the obligatory "farm animal stupid" remark?

The percentage of divers who get bent while diving within NDL's rounds off to zero, and it isn't nearly a close rounding. Look at any of the DAN fatality studies over the years and see how many of those cases were related to DCS--almost none. The real threat is embolism from that panicked ascent.

Now that you've pinpointed the issue, the question is, "how to solve it?"

I thought I would take a few minutes and detail what I think is wrong with SOME of the typical OW training in free ascents.

1. Divers are not taught (unless the instructor goes outside the curriculum) that the tank is not OOA at depth. The tank must have greater pressure within it than the ambient pressure at that depth, or the regulator cannot deliver air. If the diver ascends and the ambient pressure decreases, the regulator will be able to deliver air. The effect is more pronounced as the diver gets nearer and near to the surface.

I think that is commonly taught outside of PADI and is the reason for the recommendation to retain the regulator in the mouth during the ascent.

2. In proper instruction, the instruction must mirror that assessment as much as possible for the student to succeed. Teaching students in a way that is different from the assessment may actually teach and ingrain incorrect skills and knowledge that can result in failure on the assessment. In scuba instruction, the actual real life emergency is the equivalent of the assessment. Here is how that works out in the pool instruction for CESA.

A. In a real emergency, the diver is ascending from depth and heading straight to the surface. The air inside the lungs is expanding rapidly upon ascent. A diver should be able to exhale from 100 feet all the way to the surface while ascending at a controlled rate because of this expansion.

In the pool training, the diver swims horizontally, with almost no ascent in most cases, and they therefore get no benefit from expanding air in the lungs. Divers struggle to exhale the entire way, and the big learning they get is "If I can't do this for 30 feet, how can I possibly do it from any deeper?"

B. As stated above, in a real situation, if a diver does indeed blow through all air too quickly, the diver should be able to get some air immediately by inhaling through the regulator. If the diver is approaching the surface, there should be a pretty good breath available. The proper thing to do in a real emergency, then, is to inhale.

In both the pool and the OW checkout dive, a student who inhales through the regulator just before reaching the surface has failed the exercise and must do it again. The student is thus given a failing grade for doing the right thing. The student learns that the air in the tank is not an option for them, even though it really is.

C. Depending upon the quality of one's regulator, in real life there is a warning before the diver goes OOA. As the pressure in the tank approaches ambient pressure, it becomes harder and harder to breathe. I have breathed stage tanks down to nearly empty at pretty good depths, and I know when the tank is getting low while I still have several breaths remaining, and I am using a very good regulator on those tanks. The effect is lesser in shallower water. If a diver feels something wrong with the regulator intake, realizes the situation, and heads to the surface, the diver should be able to make it all the way (given the ability of the regulator to deliver more air at shallower depths) without doing a CESA. (That is why "normal ascent" is still listed as the first choice in the Low on Air list of choices.)

There is a holdover relic from the days of older instruction and lesser regulators in the pool training. The instructor is supposed to shut off the student's valve to simulate a low air situation. The student is supposed to signal OOA upon feeling resistance in the regulator. With modern regulators and with the depth of pool training, that does not happen. There is no warning whatsoever--just a sudden loss of air. The exercise therefore teaches students that once they feel something wrong in the breathing, it's all over. Unless the instructor does what I do instead, the exercise teaches the wrong thing and is counterproductive. (I take the SPG in my hand and barely crack the valve until I see the needle bouncing. The student gets a more realistic feel of what it is like to be almost OOA.)
​

You are right, I would add to that there are an insufficient number of repetitions of the CESA skill to either help the student to gain comfort with (not to mention "mastery" of) the skill.

3. The panicked "I need to breathe" feeling a diver gets during the training is not caused by a lack of O₂, for which the body has nearly no signal. The feeling is caused by a buildup of CO₂. Divers are not taught, unless the instructor goes outside of the instructional materials, that they still have O₂ in their system, and even if they have absolutely nothing to breathe, they should still be able to make it to the surface with a safe ascent.

Since virtually all free diving training has been dropped from the curriculum(s) students do not get this either.

So, what to do? Change the existing course within it's current time, lengthen the course, add a separately priced product?