Is it OK to turn off O2 in Rebreather Training?
- Thread starter doctormike
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OP
PREBRIEF
Instructor: At some point in this dive, I am going to turn off your O2.
Student (during dive): Hmmm. PO2 is dropping. Instructor must have turned off the O2. I'll turn it back on.
NO PREBRIEF
Student (during dive): Hmmm. PO2 is dropping. Wonder if the solenoid has failed? I hear it, but could it be obstructed? Did I accidentally switch to low setpoint? No, it's still at 1.3, and if I had I wouldn't hear the solenoid. OK, PO2 is down to 1.0, better add some O2 manually to maintain high setpoint. Hmmm... MAV does nothing. That means that either I rolled off the valve, there's a problem with the O2 feed, or I'm out of O2. SPG shows I still have 150 bar and stable, no bubbles, so no external leak. [checks tank valve, finds that it's off and opens it]. OK, let's try the MAV again. Now it works. Great, let's see if the solenoid can maintain high setpoint. Yup! So it was just the valve. If it wasn't the valve, then I would have had to bail out and figure out if there was a problem with the O2 feed after the dive, probably not fixable at depth. If it was just a disconnected MAV I could have reconnected it, but that wouldn't explain why the solenoid wasn't maintaining high setpoint. Cool! Glad that I was able to figure that out, I'll always remember this stuff.
Caveeagle
Contributor
So I am fairly new to CCR diving, but I am not new to failure mode analysis, and observing how adults learn and train for dangerous situations. Also, having recently experienced CCR training, I find this topic Intersting.
Perhaps when executed flawlessly (by the instructor & student) this could be successful, but I am forced to pass it through the filter of real world experience. Instructors and styles are not all uniform. Even among fully competent ones, there is a wide range of styles. Some are laid back , friendly, and seem to keep students at easy. Some seem to like a more high stress approach. I have seen the "drill sgt" approach. I have even seen the "sneaky b@stard" approach, where efforts are made to trip up a student. In one case, instructor swam up around students blind spots to turn off a SM tank valve, supposedly to simulate OOA during a gas switch.
My point is a drill can be made more or less stressful depending on the situation, timing and tone set by the instructor. And students can be at a huge disadvantage here. If you don't like how a class is going, or even if it feels potentially unsafe, you might need to man-up a lot to call him/her out.
It seems to me that a point is being overlooked. Letting a student know that the drill will (or could) happen on a particular dive, builds habit of actively watching your po2. If a student is NOT actively watching, then we should expect some (or more) random results from the test. A diver could be off in la-la land, thinking about lunch at the wing place.... and just happens to get lucky and notice the blinky red warning at .8. ...good result? I don't think so. Statistically speaking, how many times would you need to repeat this test before you came to any reliable confidence level. .. a lot.
Just my opinion, but demostation of a HABIT of active monitoring is far more useful.
Perhaps when executed flawlessly (by the instructor & student) this could be successful, but I am forced to pass it through the filter of real world experience. Instructors and styles are not all uniform. Even among fully competent ones, there is a wide range of styles. Some are laid back , friendly, and seem to keep students at easy. Some seem to like a more high stress approach. I have seen the "drill sgt" approach. I have even seen the "sneaky b@stard" approach, where efforts are made to trip up a student. In one case, instructor swam up around students blind spots to turn off a SM tank valve, supposedly to simulate OOA during a gas switch.
My point is a drill can be made more or less stressful depending on the situation, timing and tone set by the instructor. And students can be at a huge disadvantage here. If you don't like how a class is going, or even if it feels potentially unsafe, you might need to man-up a lot to call him/her out.
It seems to me that a point is being overlooked. Letting a student know that the drill will (or could) happen on a particular dive, builds habit of actively watching your po2. If a student is NOT actively watching, then we should expect some (or more) random results from the test. A diver could be off in la-la land, thinking about lunch at the wing place.... and just happens to get lucky and notice the blinky red warning at .8. ...good result? I don't think so. Statistically speaking, how many times would you need to repeat this test before you came to any reliable confidence level. .. a lot.
Just my opinion, but demostation of a HABIT of active monitoring is far more useful.
OP
Actually, the specific teaching technique that I am describing here is less stressful for the student than an instructor that turns off an OC gas supply. Think about it.
There are two outcomes. You see your PO2 dropping and you fix it and pass, or you don't and the instructor turns your O2 back on and you fail. In the second case, you probably weren't aware that the drill was even happening!
Much less stressful than switching to an OC reg and getting no gas. Probably less stressful than a loop recovery drill.
OP
If a student is not actively watching their PO2 all of the time, then they should not be diving a rebreather. You shouldn't have to be told that your instructor might turn off your O2 to build the habit of watching your PO2. This is MOD 1, day one.
ALWAYS know your PO2.
Preface: I am no scuba instructor but I do have some real world experience with performing drills ad nauseam. Being an ex-submarine sailor I can tell you with 100% certainty that knowing a drill (fire, flooding, loss of propulsion etc) keeps one in a heighten state of awareness. We knew drills were coming but we did not know what, where, when, or how severe they would be.
Perhaps the best of both worlds in the case of scuba drills could be the middle ground between telling them exactly what the failure will be or not briefing it at all. That middle ground being that you simply tell them there will be an equipment failure of some kind during the dive. The middle ground has the added side affect of keeping the student in a heighten state of awareness without them running through the exact steps required to solve the briefed "emergency".
Repeated drills also help build the crucial muscle memory needed to be able to react quickly, without much thought, and correctly if something does go wrong. It is that exact state of awareness that one would need to be in constantly to react to any given real world situation.
Perhaps the best of both worlds in the case of scuba drills could be the middle ground between telling them exactly what the failure will be or not briefing it at all. That middle ground being that you simply tell them there will be an equipment failure of some kind during the dive. The middle ground has the added side affect of keeping the student in a heighten state of awareness without them running through the exact steps required to solve the briefed "emergency".
Repeated drills also help build the crucial muscle memory needed to be able to react quickly, without much thought, and correctly if something does go wrong. It is that exact state of awareness that one would need to be in constantly to react to any given real world situation.
OP
OK, but think about this. A heightened state of awareness is not a good thing when you are training people to respond in the future to real world emergencies which are not announced ahead of time. You want the student to respond appropriately at ALL times, not just when they think that they are going to be tested.
Hospitals get announced visits from JCAHO all the time (the Joint Commission for Accreditation and Healthcare?). These are a HUGE deal, if they find problems with sterile technique, pre-surgical time outs, ID display, etc... the hospitals can get big fines or even shut down. The administration goes nuts during these visits, making sure that everybody is doing everything right.
So if you were having surgery, wouldn't you rather go to a hospital that did all that stuff the right way every day, rather than just when they had a pre-announced JCAHO visit?
Caveeagle
Contributor
What is the point of this comment? We are talking about training OC divers to be CCR divers. To take your comment at face value, we should just have an initial pass/fail test.. you sound as if solid po2 monitoring is. Pre-req to sign on for CCR training. How could you possible have this drilled into your head with only a background in OC diving?
OP
Not sure I understand. Didn't mean to upset you, sorry if I came off as snarky.
I was just responding to your comment that an advantage of letting the student know ahead of time that they were going to have a shutoff drill trains them to watch their PO2, otherwise they might be "off in la-la land, thinking about lunch at the wing place". If your CCR student is doing that, then forget about the O2 shutoff drill, they need to go back to day one of training to learn the most important thing - always know your PO2.
Does that make sense?
Your implication that a submariners training under heightened awareness somehow makes them unable to respond to real world emergencies is a little ignorant and short sighted to say the least. Drills are just that, simulated real world emergencies. We lived and operated under the constant threat of real world equipment failures in an environment not unlike (in most cases much more deadly) scuba diving that does not mean we were complacent when not drilling. There is/was that constant threat hanging over your shoulder, just like scuba diving.
That constant drilling made us infinitely more aware of our surroundings and equipment status. A skill that is very much needed while diving. It also made our reactions immediate and deliberate. No one wants to have some NUB (non useful body) milling about when the shyte hits the fan. I would rather not dive with someone with a wondering mind when my life and theirs could depend on that mental acuity.
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