Triggers of Dive Accidents

[Diver0001]

I'M NOT SUGGESTING WE STOP TEACHING OOA OPTIONS.

I didn't think you were suggesting this. As I said to Peter I assumed it was a thought experiment and that's all good.

What I AM saying is that IF we didn't teach OOA options, would we put a better/greater emphasis on not running out of air. And would that make a difference?

Sure. If you're walking a tight-rope with no net, then the motivation to not fall is much higher. That's true. But the consequences if you do are severe. Risk consists of chance AND consequence. Perhaps by not teaching OOA procedures you can lower the chance somewhat but in exchange for more severe consequences.... As a thought experiment it's interesting, but in reality we should be concerned with the *total* risk exposure and not just one element of that.

I'm also asking if the fact that we teach OOA options unwittingly gives a singal to new divers that it's no big deal to run out of air because there are ways to "fix" that?

And I'm also suggesting that the data from DAN, showing 41% of 350 fatalities having OOA as the trigger should be a wake-up call that something might be amiss. If the number was 1% I don't think I'd be on my soapbox.

I agree with the wake-up call. For the students I think it would be helpful for them to hear the 41% statistic when you're talking to them about the need to arrive at the safety stop with a proper reserve and the need to keep a good watch on air supply. Naturally this is a risk you want them to be aware of and to mitigate. However; the OOA procedure *is*, in fact, a "fix". Yes, it shouldn't be taken lightly but a "fix" is necessary in some situations and you don't want to make them so afraid of it that when it does happen they freak out and increase their chances of failing. It's one of those cases where *what* you say is far less important than *how* you say it, I would think.

I would say "in addition to or instead of". There's still an underlying assumption in your statement that what we do now works, and while it should, the data seems (to me at least) to suggest differently.

Ok, well I'm not sure we know enough about the data to really speculate on what it's telling us. Maybe of that 41%, 80% of those ALSO included buddy separation. If that were the case, (I'm not saying it is, because I simply don't know... this is to illustrate the point) then you might conclude that there isn't much wrong with the OOA procedures but that we're not putting enough emphasis on buddy contact.

You see what I'm saying? Root causes of accidents are seldom apparent from a superficial reading of the statistics and while it's tempting to draw conclusions from the statistics, I think it's important to really dig into the details too.

R..

 

[spoolin01]

One thing the WKPP discovered/proved, was that individuals with very high VO2 max scores ( from elite level cardio sports) had much higher rates of perfusion ..as a result of peripherol adaptations to training....while in gassing could be said to be more rapid in these individuals, offgassing was far more rapid, and an entirely new set of tables was created ( George Irvine, Bill Mee, Jarrod Jablonski, Dr Bill Hamilton) to allow indivualized tables for highly fit divers doing extreme exposures...

You might consider that an enormous safety benefit could accrue to you and those you care about, if a priority is given to obtaining elite level cardiovascular fitness.
Not only would your ability to offgas be enhanced, but the recovery potential of an extremely fit diver will be higher than an unfit one--degree of inflamation response, and your ability to quickly recover from this. You could certainly relate this to the studies on recreational diver populations where you believe some tissue damage was evident.....there would be two entirely separate populations, with entirely different effects on their tissues.... However, based on the very large number of recreational divers in the 1960's, 70's and 80's that did not suffer a horrific, diving induced infirmity in their golden years, any correlation you find in autopsies is "functionally irrelevant"...if no health complications were known of, and no lifestyle modifications forced on them, then the enjoyment of the diving lifestyle is going to trump your tiny tissue anomalies.



I still think you should read the DIR link of the article on George and the WKPP decompression strategies. You should enjoy the level of science acheived, WHERE ideas were tested with hundreds of man hours, reshaped, made better, retested, and so on until the achievements of today....over 4 mile long penetrations at depths around 280 feet, with run times over 6 hours....decos from 12 to 17 hours where Navy tables would have you at multiple days, doing mass deco from your deco.....

The deep science for this can be discussed....I could get Bill Mee to answer some good questions by email, and I could post here....

Let me know.

Regards,
DanV

That's interesting stuff, and worth knowing. I've maintained better than average fitness all along though certainly not elite class, but at 56 the bar is not that high, and there comes a point where balancing exertion against wear seems prudent (certainly wish I'd appreciated that more all along...). I'll read the article, always interesting when someone takes a systematic approach to an issue.

Autopsies and casual population observations are on separate ends of the spectrum. As you point out it's not an obvious problem, and that provides a backstop, but better data (or expertise) is needed to understand the tissue observations in context.

On the topic of the diving population, do you think the 'conservatism' of the typical dive profile has changed over the time you refer to? Typical depths, times, ascent rates? I gather the training guidance has become more conservative, do you think that's produced a real shift in the profiles of the bulk of divers, or more those who dive more aggressively?

 

[danvolker]

That's interesting stuff, and worth knowing. I've maintained better than average fitness all along though certainly not elite class, but at 56 the bar is not that high, and there comes a point where balancing exertion against wear seems prudent (certainly wish I'd appreciated that more all along...). I'll read the article, always interesting when someone takes a systematic approach to an issue.

Autopsies and casual population observations are on separate ends of the spectrum. As you point out it's not an obvious problem, and that provides a backstop, but better data (or expertise) is needed to understand the tissue observations in context.

On the topic of the diving population, do you think the 'conservatism' of the typical dive profile has changed over the time you refer to? Typical depths, times, ascent rates? I gather the training guidance has become more conservative, do you think that's produced a real shift in the profiles of the bulk of divers, or more those who dive more aggressively?

Actually, I think the changes were to hide the infusion of more PFO's and many more individuals with substandard fitness...essentially, when you go from a niche sport catering to a small number of adventureres, to attempting to pull in the mass market, the fitness level MUST drop with this change.
More than likely, a study on an adjusted population would show little benefit to the portion of the population which did not suffer from PFO's, or from the battle against the "bulge".
I don't think the ascent rate change from 60 feet per minute to 30 feet per minute was a game changer for the percentage of the population without the fitness/health issues.
As Thal mentioned in one of his posts, the safety stop was a way to stop a 120 foot per minute ascent before it reached the surface...in that, it was quite effective, and the benefits to all fitness groups would be clear.

Back to your concerns...a HIGHLY FIT diver will offgas very effectively, and if you add Oxygen at 20 feet, you can dramatically effect the potential for inflamation which concerns you.

Regards,
DanV

 

[Thalassamania]

Oxygen at 20 ... can't be beat.

Green gas is good gas!

 

[The Chairman]

An unexpected OOA I just had.

I dive steel HP130s with opposing valves. I do this as they are also my side mount tanks, and it just works better. My routine when I dive on a boat is to dive them singly. After I am all kitted up, and before I stand, I take two breaths off of my reg while watching my SPG.

But this was a different day. It was ROUGH 7-9s and everyone was a bit stressed: especially the boat crew. I was being jostled all over the place. As I put my reg in my mouth and turned to splash, I heard the crew man say "You're ready now..." Two and a half breaths later, I had no more air. My DM had turned it off. My first response was to kick for the surface hard. Sure, I had sucked my BC dry as we were doing a "hot drop". As I hit the surface I reached for my valve... it wasn't there! Ah, but I had company on the surface, so I asked the guy nearest me to turn on my air.

How many times have I taught others what to do. Now mind you, I never felt panic. Sure, there was that atavistic jolt to my system that something was wrong, and with most of the peeps in my party still on the surface, it was a no brainer to join them. I don't remember breathing out on the way up... my mind was dealing with other issues. I was focused on only one thing: Air.

Mind you, all the training in the world can never substitute for the real thing. To think that we can train people to respond in a canned fashion is delusional. Task loading is off the chart when the ca ca hits the fan. The best way to deal with any OOA is prevention.

Yes, the DM and I talked a bit about valves and such. I suggested it would be better if he touches a diver's tank and he THINKS the air is off, he needs to have the diver breath and look at that SPG to be sure he has it right. I also showed him how my tank indicator is GREEN when it's on and RED when it's not.

 

[danvolker]

An unexpected OOA I just had.

I dive steel HP130s with opposing valves. I do this as they are also my side mount tanks, and it just works better. My routine when I dive on a boat is to dive them singly. After I am all kitted up, and before I stand, I take two breaths off of my reg while watching my SPG.

But this was a different day. It was ROUGH 7-9s and everyone was a bit stressed: especially the boat crew. I was being jostled all over the place. As I put my reg in my mouth and turned to splash, I heard the crew man say "You're ready now..." Two and a half breaths later, I had no more air. My DM had turned it off. My first response was to kick for the surface hard. Sure, I had sucked my BC dry as we were doing a "hot drop". As I hit the surface I reached for my valve... it wasn't there! Ah, but I had company on the surface, so I asked the guy nearest me to turn on my air.

How many times have I taught others what to do. Now mind you, I never felt panic. Sure, there was that atavistic jolt to my system that something was wrong, and with most of the peeps in my party still on the surface, it was a no brainer to join them. I don't remember breathing out on the way up... my mind was dealing with other issues. I was focused on only one thing: Air.

Mind you, all the training in the world can never substitute for the real thing. To think that we can train people to respond in a canned fashion is delusional. Task loading is off the chart when the ca ca hits the fan. The best way to deal with any OOA is prevention.

Yes, the DM and I talked a bit about valves and such. I suggested it would be better if he touches a diver's tank and he THINKS the air is off, he needs to have the diver breath and look at that SPG to be sure he has it right. I also showed him how my tank indicator is GREEN when it's on and RED when it's not.

Time to bring back "walking the plank" for the DM
DanV

 

[Ayisha]

From what I can relate to as a diver with less the 20 dives is that, there is a lot of multi-tasking with unfamiliar equipment, in an unnatural environment (for humans) in a position (horizontal) that human beings don't spend much time in. 1.Looking at gauges with lots of changing numbers, 2. Buoyancy control (inflate deflate), 3.Location/Navigation, 4. Buddy location, 5. The reason we are there looking at the sea life. For some (me included) it's a lot to take in and keep track of. I'm sure with time all of this becomes 2nd nature.

You bring up a good point about the issue of inexperienced divers struggling with all the unfamiliar things to them in diving, the equipment and the protocols, and yet will pursue deep dives, venture into an overhead environment or somehow go beyond their training. If all of the basic skills, equipment, buoyancy, navigation, controlled breathing, gas management, etc. are not second nature, then divers should dive over a shallow bottom until they are second nature. Many divers rush in on dives they are not physically or mentally ready for and this can greatly affect their gas consumption. Any issues on shallow dives will be magnified on deeper dives, and the diver can get into trouble faster. Being overweighted, playing with the inflate/deflate buttons, being nervous, working hard, etc. can consume a lot of gas and bring a diver to OOG faster than one might think.

BTW, regarding this statement: "Buoyancy control (inflate deflate)" not necessarily for you, but others who may be struggling with buoyancy. If you are correctly weighted, you should need to inflate/deflate very little other than for descending/ascending. If you are correctly weighted, it is easy to become neutral and stay neutral just by using your lungs if your depth is not changing drastically. Become overweighted, however, and you will have to compensate often and work harder (fin or flail, typically) to maintain position, using up your gas. The correct amount of weight you need can be verified on the safety stop with a lighter tank by noticing if you have a bladder full of air to little or no air in your BC. If your BC is full, you're very overweighted. If you can hold a 10 foot stop and make a slow, controlled ascent to the surface, you're correctly weighted. Hope that helps.

 

[Mr Carcharodon]

I can tell I am still a very fast off-gasser....

Regards,
DanV

How can you tell that you are?

 

[danvolker]

How can you tell that you are?

When doing serious deco dives, where the volume of offgassing is high, and I am using stop times from WKPP tables ( much shorter than traditional tables) , after surfacing and within 30 minutes I feel optimal--as if I could go for a bike ride.....One of George's points he would make, is that if your deco profile was poorly shaped, and you are still having issues with bubbles, then you will feel a general malaise....I also know from doing thousands of dives off of Palm Beach in the 140 or less depth range, with a 30 minute surface interval, I am pretty much able to treat the next dive as if it was my first....which is not to say I necessarily WILL do this, but more about what I can do if I have enough reason to. Doing the very deep deco dives where you have 100% oxygen with you is the only way you can really "experiment" with your stop times, so that if you don't offgas as fast as you had planned, you can fix the problem without significance....this is NOT something I am advocating, and I realize MANY, particularly Spoolin, will believe this is a foolish practice of risking long term injury. What I "know" now, about my personal off-gassing, is mostly from the thousands of tech dives in the 90's and up to around 2003, when I would be pushing the envelope, and where there are counterbalancing risks-----a long deco strategy adds risk to the dive by creating a huge delay in dealing with sudden changes in the constantly changing ocean environment...storms come up, a diver could get hurt, JAWS is getting more playful than we like, whatever..
The shorter deco times that are allowed by the WKPP approach, makes us more able to handle these sudden events, and with the fast offgassing physiology, the shorter deco stops will prevent you from having to do as much deco from your deco, and THIS is lowering the risk, physiologically speaking....

Regards,

DanV

 

[DBailey]

WHY are people running out of air, and what can we do about it???

- Ken

I lump this into Gas Management. I know there are many people on this board that preach up and down about Gas Planning. There are even some great articles on this board about how to plan your gas.

But...

After reading those guide, I can't remember any of them really explaining how often your air pressure should be checked underwater. Sure, veteran divers don't need to check their air very often because they know how they breathe. Newer divers don't have a firm grasp on that yet.

Give me a tank with a random amount of air in it. I can attach my gear and enter the water without any gas planning. No matter what the volume of air is in the tank, I can guarantee you that I will make it back to the exit point safely and with some air to spare. Why? I monitor my air while underwater.

If you monitor your air underwater, there is never a reason (short of unexpected equipment failure) that you should ever be surprised by the amount of air left or ever run out of air.

Even most of the text books (from all agencies) gloss over this fact. Sure they mention "check your pressure gauge", but they never go into the frequency of checks.

This is one thing that I try to beat into the heads of my students. If you are monitoring your air, then you should never run out. It is plain and simple. There should never be a point for a new diver that they look down and see "OMG, I am at 500 PSI". Somewhere along the way they should have noted that they were at 2000, 1500, and 1000.

I do teach gas planning, but I spend more time on gas monitoring. I teach they should check their air pressure after any significant event. Gear up - check air. Hit the water - check air. Having problems clearing your ears - check air. Reached our depth - check air. Look at shark - check air. Water in the mask - check air (after clearing). Had to dump some air from the BC - check air. Checked out the seahorse - check air. In class, I want them to check their air each time the successfully complete a skill.

If the student is properly geared and streamlined, it should take mere seconds to check the air pressure. Nothing is being missed on the dive by frequent pressure checks.

Back to the question, most people don't teach any kind of air monitoring. The students are taught that a certain signal from the instructor means report your air pressure, but they are not taught to self monitor their remaining air.