Provocative talk yesterday at NSS-CDS: Toss out the rule of thirds?

[Tom_Ivan]

This is a stupid discussion. No one is hitting their thirds then spontaneously loosing their remaining gas.

... Unless you were diving a single tank and got extremely unlucky!

 

[CG43]

I was a test subject for a psychological stress response test at UF back in my college days, when I was in psychology. I was in crazy good shape, they threw everything at me and my heart rate and respiratory response never fluctuated. The psychologist came in and told me they had to toss my test. To quote Rudyard Kipling: "If you can keep your head when all about you Are losing theirs and blaming it on you...."

Okay, then I'll give you a stress factor of 1.1.
Other divers unfortunately have much higher values; here, for example, you can read up to 7.0 or 10.
Without getting into an argument about the accuracy of these values, there seem to be very large differences in how divers react to critical situations.

You talk about "good shape." What does that mean to you?
Running a marathon in under 3 hours or holding your breath for a long time ?
Is your unusual stress reaction innate, or do you have special training or tricks?

I really mean this and not ironically: If you know or do something that keeps you calm and that hasn't already been written to death, share it with us.

 

[rddvet]

Sorry, I am not a technical diver. How can one increase their RMV to that degree over any period of time?

Under extreme exertion and/or psychological stress, I have not been able to increase my RMV over a sustained period to more than 2-3 times my average RMV.

Thanks

Have a major malfunction at a very far distance from the entrance of a cave and see what happens. Most issues can be managed by your training. But often in these scenarios its not one issue, its one issue that cascades into a group of issues.
Someone's passing through a tighter siltier part of the cave and knock a reg loose releasing a ton of gas. It blows out the passage and visibility is near zero while you have to manage the emergency on your own because your buddy can't see what's happening. In the meantime your buddy backs out of the passage to clear water. You then are fixing a problem alone, with no visibilty, not knowing where your buddy is and have to feel your way back to the clear water. You're either going to handle it like a champ or shi- your pants and start gulping air.
I was in a smaller clay passage once and someone blew it out ahead of me and the only logical path was forward through it. I stayed calm and was able to be in contact with my buddy, but even being calm my consumption shot up. Swimming for 3 minutes in touch contact with someone you can't see feels like an hour.

 

[scubadada]

Hi @rddvet

I have no problem regarding the possible extreme stress and the effect that might have on gas consumption. Simply, what is the magnitude of the increase, 2-3 times or 6-10 times one's normal average?

EDIT: To get an idea of maximal breathing rates, I went back to the ANSTI simulator regulator testing. In condition 1, the RMV is 1.32 cu ft/min and said to be an aggressive rate for a single diver. Condition 2 has an RMV of 2.65 cu ft/min and is said to be the rate for a single diver at an extremely high workload or an aggressive rate for 2 divers. My average RMV for the last >2000 dives is 0.36 cu ft/min. Condition 1 would be 3.7 times that and condition 2 would be 7.4 times that. Based on my own RMV under high workload, I don't think I would be able to breathe at the rate of condition 1 for more than a very brief period.

@rsingler is very knowledgeable regarding respiratory physiology and diving. Perhaps he can help with the question regarding increased gas consumption while diving under stress. Thanks in advance.

 

[mr_v]

Have a major malfunction at a very far distance from the entrance of a cave and see what happens. Most issues can be managed by your training. But often in these scenarios its not one issue, its one issue that cascades into a group of issues.
Someone's passing through a tighter siltier part of the cave and knock a reg loose releasing a ton of gas. It blows out the passage and visibility is near zero while you have to manage the emergency on your own because your buddy can't see what's happening. In the meantime your buddy backs out of the passage to clear water. You then are fixing a problem alone, with no visibilty, not knowing where your buddy is and have to feel your way back to the clear water. You're either going to handle it like a champ or shi- your pants and start gulping air.
I was in a smaller clay passage once and someone blew it out ahead of me and the only logical path was forward through it. I stayed calm and was able to be in contact with my buddy, but even being calm my consumption shot up. Swimming for 3 minutes in touch contact with someone you can't see feels like an hour.

I recently dealt with a similar scenario. My first stage blew up in a tight passage. Bubbles everywhere. Silty bottom below. My buddy was a few feet behind but there was nothing he can do because it was impossible to get closer. So he was watching from the back hoping that I'd deal with the problem. All turned out well, and despite me being in control of the situation from the start, I noticed an elevated heart rate and an urge to "just leave this place." Took a few seconds to calm down and having something like 2x bailout required for the dive helped a lot. Actually, it was 2x of the NSS-CDS requirements so about 3x.

 

[jadairiii]

You talk about "good shape." What does that mean to you?
Running a marathon in under 3 hours or holding your breath for a long time ?
Is your unusual stress reaction innate, or do you have special training or tricks?

Moderately fast distance runner since high school, running 4 to 5 times a week, 3-10 milers depending on the mood, at a mid 6 min pace, during my college years. Knees are shot now, but 3 days a week in the pool, about 2 miles, long course in 50 mins, interval training. Today, at 64 I can still swim, within a 3000 meter workout set, 400 meters in a long course pool in 6:30. So I was not in bad shape in college (no Olympian) and not too shabby today, but feeling my age.

No special stress "training" but I was not a coddled child, I was raised from an early age on dealing with stress (always work the problem) and I've worked in stressful jobs most of my life, blue collar, white collar and no collar. Add to that I grew up "in the water", so I pretty comfortable, and I'm not claustrophobic.

And there in lies, IMO, the possible problem with "stress" in divers, many of the issues that aren't "diagnosed", like claustrophobia. I've been diving with a lot of divers, in observing them, that are claustrophobic but either dont admit it, or dont realize it or suppress it. I've seen a few "highly trained" cave divers loose their sh*t in silt outs, or very dark water. Same with wrecks, I can tell those divers that do dig going into a wreck.

 

[34109411]

Yesterday, at the annual NSS-CDS conference in Alachua, Stratis Kas gave a talk in which he questioned the supposed conservatism of the sacred rule of thirds. His argument is that with a two-diver team, if one diver is out of gas at the farthest point on thirds, there is no realistic hope of team survival. His research shows that RMV increases for both divers, but particularly for the out-of-gas diver, by a factor of as much as 6-10 times normal average.

His math showed that even a three-person team, with two sharing, wouldn't make it. On fourths, a four-person team, which included Edd Sorenson and Wes Skiles among the donors, had an acceptable margin.

He didn't offer a clear solution to the dilemma he posed. He suggested it likely that in a two-diver team, on traditional thirds, in the extreme scenario, the out-of-gas diver would have to be abandoned for anyone to survive. He acknowledged that the extreme scenario is also extremely unlikely.

Thoughts?

all depends how far you are in the cave... so is right in a certain way.

 

[Wibble]

Everyone loves to blame manifold failures on doubles. Cause that happens all the time. Don't you know that's why sidemount is SOOOOOO much better?

No; it's twiddling your knobs that's the issue. Sidemount has them in front of you where you get the full purchase and grip to turn them, not to mention that you can see the regs and hoses or even remove one cylinder.

Backmount is a PITA where you cannot fully hold the knobs and twist them with your arm bent inconveniently backwards over your shoulder (a lot of people close valves by rubbing their palm on the knobs).

And yes, I have had a jammed valve knob on a twinset/doubles which has clouded my opinion of twinsets.

Love the convenience of backmount, hate the drawbacks. They need constant practice to get the shutdowns working swiftly.

 

[rddvet]

Hi @rddvet

I have no problem regarding the possible extreme stress and the effect that might have on gas consumption. Simply, what is the magnitude of the increase, 2-3 times or 6-10 times one's normal average?

EDIT: To get an idea of maximal breathing rates, I went back to the ANSTI simulator regulator testing. In condition 1, the RMV is 1.32 cu ft/min and said to be an aggressive rate for a single diver. Condition 2 has an RMV of 2.65 cu ft/min and is said to be the rate for a single diver at an extremely high workload or an aggressive rate for 2 divers. My average RMV for the last >2000 dives is 0.36 cu ft/min. Condition 1 would be 3.7 times that and condition 2 would be 7.4 times that. Based on my own RMV under high workload, I don't think I would be able to breathe at the rate of condition 1 for more than a very brief period.

@rsingler is very knowledgeable regarding respiratory physiology and diving. Perhaps he can help with the question regarding increased gas consumption while diving under stress. Thanks in advance.

Unfortunately I think people always want a hard metric of data to hang their hat on but its not always realistic. They can do studies on divers doing heavy work or under heavy duress but how accurately does that translate to a real world experience? I think that data will never be found.

 

[rddvet]

I noticed an elevated heart rate and an urge to "just leave this place."

The "I just want to get the f--k out of here" mental demon can be very very real and probably one of the things that gets some people in alot of trouble. I think any technical diver who's experienced a big issue has experienced it.
I personally am one of those people who's personality is just to keep pushing on through while I figure something out rather than stopping, gathering my thoughts, and slowly solving the issue. Its a personality flaw that I had to work on in cave diving. But its also why cave diving is mentally relaxing for me, because I shut that bad part of my brain off. One of the few places I can.