Shallow Breathing One mistake that divers make is to breathe too shallowly. If you breathe too shallowly, you do not exchange enough air with each breath. Only a small amount of carbon dioxide is eliminated when you breathe out. If you have too much carbon dioxide in your lungs, your body will not allow much carbon dioxide to pass out of your bloodstream and into your lungs. The increased level of carbon dioxide in your blood will stimulate your desire to breathe. This need to breathe will get worse if you continue breathing shallowly. You will feel as if you cannot get enough air. The simple solution to this problem is stop your activity and concentrate on breathing slowly and deeply. Be especially sure to exhale fully with each breathing cycle. Hyperventilation You can also get into trouble if you deliberately breathe deeply and rapidly. This type of breathing is called hyperventilation and has the effect of lowering your body’s carbon dioxide level. Deliberate hyperventilation can be hazardous when you follow it with a breath-hold skin dive. If you hold your breath after excessive hyperventilation, your body will continue using oxygen, but your carbon dioxide level will not reach the point where your brain senses it is time to breathe. Therefore, you can Chapter 4- Diving Science pass out from a lack of oxygen before you ever feel the need to breathe. This is called shallow water blackout. Moderate hyperventilation can extend your breath-holding time without a high level of risk, but only if you take a few breaths. You should only take a maximum of three or four deep breaths before any breath-hold dive. Skip Breathing Skip breathing is a dangerous technique some divers use because, incorrectly, they think it will extend the amount of time their cylinder of air will last under water. When a diver skip breathes, they hold each breath for an extended period of time rather than breathing normally. Underwater photographers will skip breathe to minimize the interference of bubbles. You have already read about the extreme danger of lung overexpansion injuries if you hold your breath (Lung Overexpansion Injuries, page 112). The additional danger in skip breathing is the buildup of carbon dioxide in the body. If the carbon dioxide builds up, the diver is unable to breathe enough air for comfort in any situation that calls for them to exert themselves under water. They feel as if they are suffocating. Divers who skip breathe can also develop painful headaches. Air Starvation You should also avoid overexertion under water. Regulators have a limit as to how much air they can give you. Basically, you are breathing through a restriction like a straw. Should you try to work hard under water, the carbon dioxide level will build up in your body, even if you are breathing deeply because of the added effort of breathing through a restriction. When this happens, you feel starved for air, and you feel that your regulator is not supplying you with the amount of air you need. If you do not take prompt action to resolve the situation, you will begin to have feelings of anxiety and possibly panic. The action to take is to stop what you are doing, rest, and breathe slowly and deeply until you recover, being sure to exhale fully with each breath. By taking it easy under water and learning your limits of exertion at various depths, you can avoid over- Diving Science 115 FIGURE 4-30. YOUR BREATHING SHOULD BE SLOWER THAN NORMAL AND DEEPER THAN YOU USUALLY BREATHE.
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