Earned, Un-earned or Predisposed?

[DandyDon]

But tables are inherently conservative unless you dive a perfect square profile at a depth exactly divisible by 10 e.g. 80 feet or 100 feet.

Drop down one extra foot to 101 for 30 seconds and it makes very little difference on the computer,but following tables by the book that has just become a 110 foot dive,which will significantly reduce NDL.

True, unless you carry the waterproof card and adjust on the swim, or the Wheel - which is too much for me. My implication is that aggressive is an inappropriate adjective. You can dial in more conservatism on some models, but leaving the water in the green is my primary objective - along with drink and pee a lot.

 

[Divedoggie]

I am pretty sure that was my issue as well.

There is one other part of that description that piqued my interest, although it did not appear to have been a factor, and that was the rapid ascent in the rescue scenario described.

I once played a rescue victim during a scenario in which the diver was supposed to bring an unconscious diver to the surface. This was being done at nearby Rock Lake, where I could settle down in a weedy area and appear to be unconscious. As I lay there with my eyes closed, I felt the rescuer get on my back and lift my inflator hose. Then I heard the rush of air as he pushed the button for all he was worth.

I knew what was going to happen next, so I immediately began a full force exhale that lasted all the (very brief) time it took to get me to the surface, where I broke through like the submarine in Hunt for Red October. It was scary, frankly. The instructor conducting the class and I later discussed the need for an emphasis on safe ascent rates in the pre-dive briefing in the future. (The student had done it correctly in the pool, but...)

A lot of people don't realize that, according to Boyle's Law, air expands more during an ascent at altitude than at sea level. I calculate that at Santa Rosa, air expands more than 10% more going from 34 feet to the surface than it does at sea level.

That is scary! We all definitely need to over emphasize safe ascent rates. Maybe I can tape a slate to the back of my head with a stern reminder written on it!

On the health issue: I was thinking the symptoms are similar to a marathon runner "hitting the wall." They collapse, can't move extremities and lose bladder and bowel control. After receiving fluids with electrolytes and oxygen, they recover quickly.
If we Instructors become overzealous we are subjecting our bodies to all kinds of stress. Pressure and tempurature changes, excess Nitrogen, dehydration, physical work, responsibility, any emotional baggage, lack of sleep, etc. Kind of like a bizarro marathon!