Secret to Blackout Avoidance
There is a great tool for SWB prevention: I call it the ATRC test = ability to retain consciousness test. I thought I 'invented it' in early 2001, but it turns out a few other people have been using vaguely similar techniques.
WARNING: THIS IS VERY DANGEROUS AND MUST BE DONE WITH A BUDDY!!!!
Chances are that the first few times you try this you will almost certainly black out (on dry land) and crash on any nearby objects (possibly injuring yourself -- it happened to a guy here), so you must have a buddy ready to catch you when you fall!!!
Crouch down (buddy beside you), exhale fully, then RAPIDLY stand up while inhaling RAPIDLY. Continue inhaling to the max, then begin packing your lungs as fast as humanly possible. Count your packs, and pick a number that puts you within a few packs of totally full, and when repeating the test in the coming days and months, always use the same number of packs for consistency.
Once you have finished packing, remain standing (if possible), for about 15 seconds. Then, assuming you were able to remain standing, SLOWLY (!!!) exhale, SLOWLY!, through pursued lips (if you exhale rapidly you'll get a pounding headache).
If you are packing and start feeling light-headed, you may have to crouch down to avoid a blackout.
If your body is in a state which favors retention of consciousness, you should be able to do the test and remain standing, without the slightest bit of light-headedness.
A 'pass' is defined as performing the test and being able to remain standing. A 'B-type failure' is defined as having to bend over to stay conscious, but with no shaking or loss of motor control (B stands for 'blackout' type failure). An 'S-type failure' implies bending over and losing motor control and having a samba.
Here is the scale I use:
10 / 10 = pass with no light-headedness
9 / 10 = pass with slight light-headedness
8 / 10 = pass, significant light-headedness but no danger of having to bend over
7 / 10 = barely pass, vision & hearing fading, almost had to bend over
6 / 10 = finished packing fully, waited several seconds, then had to bend over
5 / 10 = finished packing fully, immediately had to bend over
4 / 10 = half way through packing, had to bend over
3 / 10 = didn't even start packing, had to bend over
2 / 10 = could barely even stand up without fainting
1 or less, fainted from just standing up
This test is the most remarkably accurate way to predict what will happen to you during a hypoxic (borderline) dive. If you fail (6/10 or less), then you shouldn't be getting in the water; you'll be risking your life, because you could blackout from a conservative dive, without warning.
Of course, even if you get 10/10, it doesn't mean that you can dive alone or push it, it just gives you a relative indication that you are in better shape than on days when you scored less than 10.
You'll find that adequate sleep, hydration & electrolyte balance are the most important factors to pass the test.
I have used the test almost daily for one and a half years, observing how I pass and fail based on what I eat, how I exercise etc., and I have developed special routines that put me in a 9/10 or 10/10. I have tried doing deep dives after failing the test, and during those dives I either BO'd, samba'd or had tunnel vision upon surfacing. It has been very accurate for me.
I usually do the test in the morning before going to the dive site, then again before putting my suit on.
Please remember that you must have a buddy watching you or else you could seriously injure yourself! Even with a buddy, do the test away from objects that might hurt you if you fall.
This test measures a huge number of physiological parameters, including adrenal gland function, blood pressure, hydration, cerebral hypoxia tolerance, high energy phosphate stores, nervous system excitability, etc. It is difficult to analyze them all; but the bottom line is that if you fail the test, you're in bad shape for diving.
Eric Fattah
BC, Canada