From Sep '99 Undercurrent
http://undercurrent.org
[Youre 100 feet down with two buddies. Both come to you out of
air. What do you do?
If youre as experienced and alert as one diver we know of, you
could pass your primary second stage to one buddy, give your
octopus to the second, then begin a slow ascent valving fresh air into your buoyancy compensator and breathing through your BCs oral inflator mouthpiece. Its a little tricky and takes some practice,
but it works. Yet none of the commercial training agencies
teaches BC breathing at any level.
In fact, since we first reported on this technique several years back, the industry seems to have closed ranks against it, even though its been successfully tested in a variety of predicaments.
Were hardly advocating breathing BC air as a standard
practice only as a last resort.
Even if you suck your tank dry, you Emergency Breathing from Your BC what the agencies refuse to tell you can get some air through your regulator as you ascend and the air in your tank expands. But once your tank is bone dry, youll still
have residual air in your BC (or at least in your inflator hose). If you added air with your power inflator, it will be pure and contain 21% oxygen. If you orally inflated your BC, it will still contain 16% oxygen.
Bear in mind that air in your BC will also expand as you rise. If
you put your BC mouthpiece in your mouth and keep trying to
inhale and exhale while you rise, you should be able to do without
air for at least 20 seconds. By then, air volume will have increased
enough to provide a breath.
Studies conducted by the late Al Pierce of the YMCA concluded that you can exhale back into your BC and keep rebreathing the same air 13 times or more without becoming overly hungry for fresh air. (After all, exhaled air is good enough for
artificial respiration.) With this technique, instead of free-ascending with no air, youll have some air as you rise, which will allow you to make a slower and safer ascent.
Even so, agencies refuse to teach this technique at any level.
The key objection voiced by SSI, PADI, and even DAN seems to be
the possibility of respiratory infection from bacteria inside the
BC, but your vest can be disinfected with solutions readily available in dive shops. Or you can use benzalko-nium
chloride, which is available at drug stores under the brand
name Zephiran chloride. Apparently the Coast Guard uses
Listerine.
Besides, why should you be concerned about a lung infection in an emergency? There are a helluva lot more cures for
respiratory infections than there are for drowning.
The second biggest objection made by training agencies is
that divers will need to master new skills and perhaps to over-learn some old ones. For instance, you must be able to clear
the ounce or so of water from your inflator hose mouthpiece without choking. Other skills required vary depending on whether your first stage is still supplying air. Additional objections include difficulties with buoyancy control, such as ascending too fast or the possibility of arriving on the surface with no lift in the BC.
Frank Toal of NAUI summed up the attitude of the certifying
agencies and manufacturers we contacted by stating that BC
breathing ...could be used as a last-ditch effort versus drowning,
but, because it is at best a very difficult technique, it is not taught
in any course as required training.
To gain confidence in your ability to act in an emergency,
practice this and all of the other BC breathing skills with your gear in shallow, calm water. Be sure to disinfect your BC first.
Clear your mouthpiece. Most current inflator hose mouthpieces have openings for easy purging, so the best method is to tilt the end of the mouthpiece down and blow a little air in so the water runs out of the holes. This will take only a small puff. Hold the valve down as you continue blowing. Your exhaled breath will now go into the BC and the holes will be sealed so no water can re-enter. Dont release your tight hold or water will leak back in through the holes. With older models, bend the mouthpiece up, seal your mouth, look down, and, as before, blow air in as you push the valve. The water will flow from the mouthpiece and become trapped in the hose, but air will be able to get past it.
Take your first breath cautiously. Inhale slowly and carefully. If you do cough or strangle on a few droplets, dont remove the mouthpiece or youll just have to go through the clearing process again. If you must cough, cough into the BC.
Control your ascent. Exhale normally and watch your ascent rate, because whether breathing from your tank or BC, you still face the danger of an embolism if you retain air that youve breathed at ambient pressure.
Dont let go of the valve or remove the mouthpiece from your mouth as you ascend. Releasing your hold on the valve of a mouthpiece that has no holes will not allow water to enter, but it will cut off your air from the BC. Avoid overfilling your BC as you rise by exhaling through your nose. Flaring out horizontally will also help slow your ascent.
If youre sharing air with a buddy, be sure his BC doesnt overinflate either. Using air from your tank. As long as your power inflator is working, you can add more fresh air to your BC as you rise, and you can continue to breathe that air at ambient pressure. Keep the mouthpiece valve closed tightly while putting air into your BC so none escapes. Open the valve from your tank intermittently, take a breath, and exhale it through your nose to insure a continuous supply of fresh air. Practice till youre confident that in an emergency you can handle both valves simultaneously.
You can also breathe from your BC while a buddy is breathing from your tank. Since your power inflator bypasses your regulators first stage, you can inhale from the BC at any time without over-breathing. If your buddy is in danger of over-breathing the second stage youve shared with him, wait to feed air into the BC until you see his bubbles. Keep feeding air in intermittently between your buddys inhalations, and try to calm him down.
With no air available from your tank. As we stated earlier, air in your BC will expand as you rise just as air in your tank does, allowing additional breaths as ambient pressure decreases. Start up immediately, keep trying to inhale and exhale, and air will become available.
If you have a BC-mounted safe second such as the Air II, you can access the air in your BC by pressing the deflate button when inhaling. In one study, basic scuba students were able to rebreathe this way for a minute in a 10-foot-deep pool with no problems. Staying relaxed is a crucial part of this exercise, because rising CO 2 levels will cause you to breathe faster and faster, which could lead to a sudden blackout.
Sound complicated? The industry obviously thinks so. Still, although no ones going to force you to learn these new skills, one day you might be glad you or your buddy did.
Copyright 1999 DSDL, Inc, publishers of Undercurrent] (
www.undercurrent.org)"
Best regards,
DocVikingo
