Competitive swimmers sometimes hyperventilate prior to a race as do some participants in other water sports, such as underwater hockey, spear fishing and free diving, believing wrongly that it increases the amount of oxygen saturation in the blood. Many swimming coaches teach their swimmers to hold their breath for extended periods, known as hypoxic breathing, mistakenly believing that it improves their lung capacity. Many such swimmers experience convulsions on surfacing which, if not noticed immediately, can result in loss of consciousness and drowning. Others simply drown quietly, unnoticed and without the victim having any particular bodily sensation.
Holding the breath is also a common play activity among children and teenagers, especially boys (‘I can hold my breath longer than you’, they say as they dive down). Every year, many of these young people are found on the bottom of a pool after they have lost consciousness, water has entered their lungs and they drown. Alcohol is often a contributing factor in such drownings.
All these dangerous aquatic activities can result in a shutdown of the body’s natural breathing mechanism. Carbon dioxide build up in the blood and lungs normally triggers the impulse to breathe. But hyperventilation results in below normal levels of CO2 in the blood, thereby reducing the impulse to breathe. In addition, the lack of oxygen to the brain caused by not inhaling can result in a detached mental state leading the swimmer to feel euphoric and empowered to continue breath-holding. A loss of consciousness results. And, of course, loss of consciousness in water can result in drowning.
Unlike regular drowning where there can be between six and eight minutes before brain damage and death after loss of oxygen to the brain, in this type of drowning, in which the brain has already been oxygen deprived, there are only about two and a half minutes before brain damage then death.
So, what are the lessons?
· Don’t hold your breath in the water – not ever
· Don’t do hypoxic breathing (which is just holding your breath)
· Don’t hyperventilate
· Don’t hold your breath when you do the breathing ladder (progressively increasing the number of strokes before you inhale). If you can’t continue to exhale with an increasing number of strokes, you have reached your limit
· Always remember the maxim: ‘Every time your face is in the water, and for the whole time your face is in the water, exhale – no exceptions’
· If you are doing an activity which requires you to be submerged, exhale slowly for the entire time you are under the water.
· For a deeper medical analysis, see https://www.mja.com.au/journal/2010/192/11/don-t-hold-your-breath-anoxic-convulsions-coupled-hyperventilation-underwater