Shallow-water blackout

Shallow-water blackout refers to a loss of consciousness caused by hypoxia (insufficient oxygen) in the brain, occurring in shallow water typically during breath-hold diving or free-diving. Unlike deep-water blackouts, which can occur due to changes in pressure affecting the body's ability to absorb oxygen, shallow-water blackouts happen at or near the surface where these pressure changes are minimal. The condition is particularly insidious because it can strike without warning, even in experienced swimmers or divers.

Causes

Shallow-water blackout is primarily caused by hyperventilation before submersion. Hyperventilation lowers the level of carbon dioxide (CO2) in the blood, which can delay the body's natural urge to breathe and increase the risk of the diver losing consciousness underwater due to a lack of oxygen. The body's oxygen demand increases with physical exertion, and during breath-hold diving, the oxygen levels can drop to a point where the brain can no longer function properly, leading to unconsciousness.

Symptoms and Signs

The onset of shallow-water blackout is usually sudden and without warning signs. However, some divers may experience symptoms such as light-headedness, tingling in the fingers and toes, or visual disturbances before losing consciousness. Because the blackout occurs quickly and silently, it is often unnoticed by others until it is too late.

Prevention

Prevention of shallow-water blackout involves education and awareness of the risks associated with breath-hold diving. Divers are advised to avoid hyperventilation before diving, dive with a buddy, and limit the depth and duration of their dives. Training in breath-hold diving under the guidance of a certified instructor can also help divers recognize their limits and understand the importance of safety measures.

Treatment

Immediate response to a shallow-water blackout involves bringing the affected individual to the surface and administering rescue breaths or CPR if necessary. Quick and effective response is crucial for the recovery of the individual, as prolonged oxygen deprivation can lead to brain damage or death. After initial treatment, medical evaluation is necessary to assess any potential long-term effects of the incident.

See Also

• Freediving
• Hypoxia (medical)
• Diving medicine

External Links

• Divers Alert Network
• Freediving Instructors International