By lowering the amount of CO2 in the blood, the body is fooled into believing it doesn't need to breathe even though the oxygen level is going down. As a result swimmers can go longer periods of time before having to surface for air. The danger is the level of CO2 may fall so low that it is insufficient to signal the person to breathe before losing consciousness from lack of oxygen. If an unconscious swimmer is not immediately pulled from the water he will drown. The likelihood of such a tragedy is compounded by exercising strenuously, hyperventilating and breath-holding under water.
Exercise increases oxygen consumption and causes oxygen stores to be depleted faster than usual.
This can speed up the onset of hypoxia and loss of consciousness. Common sense and the application of basic risk management principles can prevent shallow water blackouts. There are no new accidents, only new victims who haven't been told of the dangers. The Naval Sea Systems Command, Arlington, Va., is the contracting activity. The Naval Air systems Command, Arlington, Va., is the contracting activity.