Triggers of Dive Accidents

[Freezerbrn]

Hi there, the common saying used to be to "be back on the boat with 500 psi". Of course, we didn't really know what pressure we should start ascending at to achieve that unless we asked or figured it out. Starting your ascent at 500 psi, as you're saying above, is giving you even less reserve if you're deep enough to plan a safety stop. Starting your ascent at 500 psi would be fine on a shallow dive, but you might want to consider beginning your ascent much earlier on deeper dives in case you or your buddy have issues and need more air. You can search "rock bottom" or look at Lamont's signature to figure out how to calculate what your turn pressure and reserve should be depending on the type of dive you're doing and apply it to your own type of diving. My buddy and I usually start ascending from deep dives once the first one hits1000 psi. If we have to get back to an ascent line before that, we will usually start heading to the line at around 1300 - 1500 psi, depending on how far it is. We will then do a deep stop about half way and a slow ascent plus an extended safety stop.

You should plan to do a safety stop for deeper dives. You may want to look into the research on deep stops as well for deeper dives.

Keep reading, keep learning. Most of us probably dive differently than when we first started. I know that I've become more conservative as I go along and with all the info I read on this board and others.

Looking back on my post I think I gave the wrong impression. I didn't mean to imply that someone should use 500 psi as a turn around point or to start an ascent. The theme of the OP was regarding triggers of dive accidents (OOA). Excluding overhead environments, entanglements, catastrophic equipment failures, medical emergency etc, it leaves monitoring air consumption. By this rational, my comment (head up if you realized you were at 500 psi) was based on loosing track or how much air was used and suddenly noticing. Air permitting do a SS and buddy breath with your buddies Octo. It's rare IMO that you and your buddy have the same SAC so it would be possible to do the SS while sharing air. I made that comment because it happened to my buddy and I during OW class. She go below 500 psi and the DI had us go up and do a SS. Did we need too. No, max depth was 45 feet 40 mins dive time. Did I know I could skip it, nope. Just did what I was instructed. I would blow the SS if we didn't have the air to do it. (Based on your comment) Should I infer that the SS for OW divers with a max of 60 fsw is not really needed then it's possibly over stressed in the OW class.

I know that the assumption is that new divers don't know how to orally inflate their BC's or were taught it and this may be true, but our DI always had us do it on the surface.



My turn around psi is 1500-1200 psi. Thank you for the info and recommendations. I spend a lot of time reading SB and learning as much as I can.

 

[danvolker]

It would work in that application, but so would a lot of easy to use electronics these days.


.

Thal,
Speaking of all the new electronics which will alert for low air supply....
Here is a picture for you....diving on a chater boat with 15 divers, many new....at about 40 minutes into a 55 foot deep dive, most beginning to ascend....you are suddenly aware of a symphony of computer alarms, notifications, and bells and electronic sounds surrounding you....the natural noises of the ocean now replaced with the "Dance of the DEMA Show"....
With all the alarming going on, which ones are suggesting a slower ascent, which ones are suggesting that the NDL will arrive in 5 minutes, which ones are suggesting a diver is low on air, and which ones are proclaiming a tank half full to be empty?

At least with the honking first stage, you had no doubt it was low on air....and the mechanical failure / false warning far less likely than the computer alarming with nonsense the owner does not want it alarming on....

Regards,
DanV

P.s.
I do remember Pat's regulator honk being disconcerting.... I think some people would try hard tp prevent the low on air from happening, so this honking did not scream this out to the world.
Fortunately, Pat Frain was rarely low on air.

 

[Peter Guy]

I just want to re-emphasize the issues here and attempt to make a distinction between the new(ish) diver and the experienced one regarding safety stops and being low on air.

While I wish I had the time and committment from all of my Open Water students to faithfully practice their various skills once every couple of weeks after they have been certified, the REALITY is that I will be lucky to have 10% of them even do a dive once every 6 months after being certified (and taking the trip that prompted the class). I'm sorry Thal, Dan, Bob, et al, but I'm just not that good enough of an inspiration as an instructor to get them to do this -- dive AND practice their diving skills.

Thus, MY HOPE is that they learn, and retain, enough to be safe throughout their dive AND THAT IF/WHEN they screw up they get to the surface as quickly as safely possible (and that is actually pretty darn quick). I don't want them screwing around, getting possibly panicked, waiting for that last hard breath (been there, done that -- and I wish J-valves were still in use) -- I just want them ON THE SURFACE while being able to breathe normally all the way up. AND once on the surface, they have a sufficient supply of air to inflate their BC/Wing so that they STAY ON THE SURFACE.

In the PNW, we've had way too many deaths "due to drowning" which, in reality, were due to being OOA for in each of the three (at least) cases the victim was able to get to the surface. But, sadly, they had no air left and couldn't power inflate their BCs and orally inflating (and/or dumping their weights) left them in the panic resulting from being OOA.

Yes, Dan V and Thal have the skills necessary to run out of air at 100 FSW and then calmly doing a free ascent AND then calmly finding their inflator hose, press the right button and calmly inflate their wings. Unfortunately, the students I seem to have trained (and those I have seen) just don't have those skills -- perhaps because I'm a rotten instructor or, just perhaps, because, well, you may be able to determine other reasons.

In any event, for THE VAST MAJORITY OF BASIC OPEN WATER DIVERS, if they are low on air, the safest place is ON THE SURFACE -- and the sooner the better. At least that is what this poor, inexperienced, lowly PADI instructor believes.

 

[MXGratefulDiver]

Actually Peter, I agree with everything you just said. You can't make people practice ... you can only emphasize to them why you think they should.

Ultimately it's the diver's responsibility to decide whether or not that's what they want to do ...

... Bob (Grateful Diver)

 

[danvolker]

I just want to re-emphasize the issues here and attempt to make a distinction between the new(ish) diver and the experienced one regarding safety stops and being low on air.......

Thus, MY HOPE is that they learn, and retain, enough to be safe throughout their dive AND THAT IF/WHEN they screw up they get to the surface as quickly as safely possible (and that is actually pretty darn quick). I don't want them screwing around, getting possibly panicked, waiting for that last hard breath (been there, done that -- and I wish J-valves were still in use) -- I just want them ON THE SURFACE while being able to breathe normally all the way up. AND once on the surface, they have a sufficient supply of air to inflate their BC/Wing so that they STAY ON THE SURFACE.
......snip....

In any event, for THE VAST MAJORITY OF BASIC OPEN WATER DIVERS, if they are low on air, the safest place is ON THE SURFACE -- and the sooner the better. At least that is what this poor, inexperienced, lowly PADI instructor believes.

Peter,
I have no doubt you are an excellent instructor, from the degree that you clearly care about optimal training ideas for students....
I think we are getting closer to a consensus....if new divers came up with more air, there would be less Deaths. I would be far more emphatic about the new diver having the ABSOLUTE REFLEX trained into them, to check spg constantly, and to begin surfacing from the 60 foot (max 60 for new divers) dive at 1000 psi......than I am about the CESA being ingrained....I still think a CESA is great to "hard wire" into a diver, but it is eclipsed by the constant checking/perfect awareness of tank pressure gauge reading and mental calculations about what this means for them.

Regards,
DanV

 

[Ken Kurtis]

What do those DAN papers say about DCS morbidity?

I'll repeat what I posted earlier from Karl Huggins, Director of the Catalina Hyperbaric Chamber and a noted expert in the field: Decompression sickness (bends/DCS) rarely kills anyone.

AGE (embolism) is definitely life-threatening and frequently results from an OOA incident that produces a rapid ascent (doesn't have to be panicked . . . but frequently is) where either the diver holds their breath on ascent or doesn't exhale properly/enough on the way up.

AGE often kills. DCS rarely kills.

Draw whatever conclusions you want from that.

- Ken

 

[spoolin01]

Spoolin,
The idea of a safety stop is to reduce risks....If a new diver is "planning" a dive, they should be planning to come up with around 1000 psi, AND planning on doing a safety stop.....they will have plenty of air to come up slowly, and plenty of air to do the stop.

And...plenty of air to inflate their BC on the surface and chill till boat pickup...

So when a new diver blows the plan, and at 60 feet down, realizes they are at 500 psi, the safest thing they can do ( after making a very unsafe lapse in attention to spg) is to collect buddy and make a nice controlled slow swim upward to the surface...Once on the surface, they can inflate the BC, and still gain some offgas benefit floating on the surface ( still in the water).

If the new diver feels threatened by missing the safety stop at 15 feet, I would rather they suck O2 on the boat for 10 minutes.....It will be negative reinforcement ( peerwise and boat-wise) for inattention to the spg on the dive, and it will add the safety measure ( or more) of the safety stop. Remember, this is NOT a required deco stop.
The next time they dive, with the big scene of having to suck O2 on the boat, they may well be more likely to watch the guage, and begain ascent at 1000 psi.


Also,
Different fitness levels of divers will have different needs regarding the safety stop. Let's say you are a novice diver who is also an elite level triathlete( and you do NOT have a PFO) , and your buddy is 60 pounds overweight, and has not run further than the bathroom or kitchen in 10 years....You just did a 60 foot dive for 45 minutes.... a nice slow ascent for you ( without safety stop on this No Deco Dive), should give you a larger margin for safety than your buddy doing the same ascent and holding at 15 feet for 3 minutes...
Your buddy, if he trully wants safety, may require 3 minutes at 25 feet, and 3 minutes at 10 feet...and he could benefit by beginning to do cardio training to enhance perfusion (bloodflow) throughout his/her body...For someone to pontificate about how they want more safety, and completely ignore the huge safety margin of good physical conditioning, is just a little disfunctional.
You could say that the very non-fit new diver, may find it desirable, to have a contingency for the day they ignore their spg and have to come up with no time or air for safety stop---the contingency would be having their own oxygen tank on the boat, and using it on the boat, if this occurs...

REgards,
DanV

Yes, reducing risks is the point of this discussion! Yet you are either being perplexingly single-minded about the least-pressing risk: not having (gobs of)surplus air when atmospheric air availability is a virtual certainty, or you have access to knowledge of the physiological risks (safety stop is optional, O2 on the boat is superior to in-water off-gassing - the humiliation of the diver being just a bonus I'm assuming) that is so certain that you're able to advise any other diver that planning for rare and inconsequential contingencies, or minor convenience, should absolutely take precedence. No question, insane not to... Yet just a post or two earlier you gave thanks to a painstaking elaboration about the individuality and noteable unpredictability of DCS, as well as mentioning it yourself.

Why is it not the better plan to give yourself as much opportunity for off-gassing? Frequent assertions are made here about the risk of not getting your ass right to the surface, yet no credible risks have been articulated. Absent some certainty about how to view nuances of DCS risk, how are you making your assessment?

 

[wmw999]

I'm another new diver and really appreciate this thread. The panic that would come with OOA would be overwhelming for most newish divers (probably like me), particularly if they aren't that current, or haven't really thought about how they would respond to given emergencies. Maybe an emergency scenario checklist could be part of a "plan your dive" packet given to students at certification (not that there is one -- but an easy reference card that you get with certification might be nice). What you're thought about is less scary than what you're surprised by. Awareness? Well, when you're having fun it's easy to run through air I'm sure; it's easy to run through altitude on a skydive, and there you even have the earth getting bigger. You have to emphasize checking, and what to do if you've failed. A tank monitor as a requirement for new divers sounds like a great idea, particularly when a newbie might be diving with a buddy who isn't a DM, but whose gas consumption is a lot better. If it could be integrated with the tank somehow rather than with the regulator that'd be better -- the dive shop asks about credentials and gives you the appropriate tank. Of course, there might be other reasons why that's not a good idea, but the only way to have good ones is to have more bad ones ; I'm good at that.

Rather than having instructors encouraging students to get AOW right away (yeah, it happened to me, too), it'd be great if instructors and/or shops would instead offer the suggestion to go on easy dives possible locally, just to get some practice. Maybe shops could offer buddy boards (like the one here) with students from other classes. Where there is somewhere reasonable and local, that'd work. Obviously not everywhere. But if you make it easy for people to do the right thing, they might actually do it.

Dang I'm wordy. But I've done some accident analysis in skydiving (I've been jumping 35+ years), so this is really interesting to me. There are significant parallels.

Thanks for the thread

WP

 

[lamont]

In any event, for THE VAST MAJORITY OF BASIC OPEN WATER DIVERS, if they are low on air, the safest place is ON THE SURFACE -- and the sooner the better. At least that is what this poor, inexperienced, lowly PADI instructor believes.

+1...

 

[spoolin01]

I just want to re-emphasize the issues here and attempt to make a distinction between the new(ish) diver and the experienced one regarding safety stops and being low on air.

Thus, MY HOPE is that they learn, and retain, enough to be safe throughout their dive AND THAT IF/WHEN they screw up they get to the surface as quickly as safely possible (and that is actually pretty darn quick). I don't want them screwing around, getting possibly panicked, waiting for that last hard breath (been there, done that -- and I wish J-valves were still in use)

Do you think over-emphasis on getting right to the surface 'pretty darn quick', when there's little risk of being out of air, could be having a perverse effect psychologically? When I free dive, focussing on the approaching surface induces distress - it's better to look out and calm myself about the inevitability of surfacing, not to anticipate it. Could a safety stop of some sort be a useful pause to gather your wits and plan for the surfacing? Provided you've determined you can either continue to breathe bottled air, or free ascend, whatever your comfort level.

In the PNW, we've had way too many deaths "due to drowning" which, in reality, were due to being OOA for in each of the three (at least) cases the victim was able to get to the surface. But, sadly, they had no air left and couldn't power inflate their BCs and orally inflating (and/or dumping their weights) left them in the panic resulting from being OOA.

These are all the more tragic for the massive fail they are. But surely they are nevertheless perverse anecdotes.

I'll repeat what I posted earlier from Karl Huggins, Director of the Catalina Hyperbaric Chamber and a noted expert in the field: Decompression sickness (bends/DCS) rarely kills anyone.

AGE (embolism) is definitely life-threatening and frequently results from an OOA incident that produces a rapid ascent (doesn't have to be panicked . . . but frequently is) where either the diver holds their breath on ascent or doesn't exhale properly/enough on the way up.

AGE often kills. DCS rarely kills.

Draw whatever conclusions you want from that.

- Ken

I'm sure you would agree that there's a lot more to be known about those fatalities before the causes are sufficiently understood. As just one of the simplest considerations, I'm betting that once you experience AGE, DCS damage is no longer of interest to anyone. At any rate the thread has digressed from the useful discussion you began of the possible role of gas management training and OA coping skills in reducing AGE deaths, to whether certain rules of thumb regarding fairly benign scenarios are advisable, or overly pedantic.

The conclusion I was more interested in was the damage from DCS, not just fatality. You're in a better position than I to have an idea of what kind of traffic those chambers get - are they sitting idle, deaths being as rare as they are? Is that piece of the safety picture worth bringing into the discussion?

I'd still like to know the answer to the question, which group of divers fares better health-wise over the course of their diving careers, those who push the limits of reserve gas planning or those who push the limits of absorbed gas management?