As we approach swim season, we want to remind everybody about the dangers associated with prolonged breath-holding, especially when preceded by hyperventilating or excessive physical activity before swimming.
How We Breathe
The buildup of carbon dioxide (CO2) in the bloodstream triggers the body’s urge to breathe. When the body exceeds its normal level of CO2, it sends a signal to the brain. The message: it’s time to refresh the oxygen supply. Once received, the body breathes automatically. When a swimmer attempts to override this urge so they can stay under water longer, they begin by hyperventilating.
Shallow Water Blackout: What it is
Hypoxic training is the practice of hyperventilating combined with prolonged breath-holding.
Individuals do it to stay underwater longer. This is how it works: The swimmer practices taking a series of deep breaths. Then, he rapidly expels the air taken in, and follows this with prolonged breath-holding before swimming underwater. This reduces the CO2 far below the threshold. This results in the swimmer’s brain not receiving the signal to breathe. Therefore, the swimmer does not come to the surface for air.
Because of the lack of fresh oxygen, the brain “faints” and the next automatic response by the body is to take a breath. When this occurs underwater, the swimmer usually drowns. A victim of shallow water blackout will do so in two minutes or less.
Regrettably, many children have died from shallow water blackout.
Many attribute these deaths to excessive physical exertion (which has the same effect as hyperventilating) in or out of the water, and then playing breath-holding games in the water.
These common but potentially deadly games include Marco Polo, challenging other children to see who can swim the most laps under water, or just playing to see who can stay under water the longest.
Unless we know the pre-swimming activities of a shallow water blackout victim, it is almost impossible to assign it as the cause. Therefore, related drowning victims are simply labeled as “accidental.”
Shallow water blackout can occur at any water depth.
The Live Like Benjo Foundation recognizes that holding one’s breath is required during swimming and, of course, we do not advocate for the prohibition of swimming! However, we do advocate for the prohibition of prolonged breath-holding, especially when preceded by hyperventilating. Additionally, we advocate for the prohibition of breath-holding games, the close monitoring of children’s activities and physical exertion before swimming, always swimming with a buddy and constant vigilance of everybody in the water.
Dean E. Haller is the president of the Live Like Benjo Foundation. He founded it shortly after his son drowned as a result of Shallow Water Blackout on August 1, 2014.