Hypoxic Blackout

In the News: An experienced YMCA lifeguard preparing to enlist in the Navy SEAL program blacked out during a breath holding exercise. An on-duty lifeguard at the facility noticed him at the bottom of the pool and was forced to perform CPR. Sadly, the guard died at the hospital less than a week later. The YMCA had prohibited underwater breath holding, but did not actively enforce the rule. The lifeguard’s family brought suit against the YMCA and is seeking $10 million in damages.

What is a Hypoxic Blackout?

Hypoxic blackout is a loss of consciousness caused by a reduced supply of oxygen to the brain. It is often related to hyperventilation, which is a series of long deep breaths designed to decrease the amount of carbon dioxide in the blood.

Hyperventilation is a dangerous technique often used by competitive swimmers and divers in order to hold their breath longer. Without the appropriate levels of carbon dioxide, the body fails to recognize the need for oxygen as it traditionally does. This condition is called hypocapnia. The table below illustrates how individuals who hyperventilate develop hypocapnia and reach the blackout zone before experiencing the normal urge to breathe.

Hypoxic blackouts are especially dangerous because an individual simply loses consciousness and can drown without any sign of a struggle.  In some cases, an individual experiencing a hypoxic blackout will appear to be making coordinated movements because their body may continue to function temporarily.  This phenomenon is particularly dangerous because a lifeguard may assume the individual is conscious.

Who is Affected by Hypoxic Blackout?

Hypoxic blackouts can affect anyone at anytime. Victims typically have no prior medical problems, are physically fit, and give no warning. It is usually associated with individuals who are either participating in breath holding contests or are performing underwater distance swimming. Recently a series of deaths of young, healthy, athletic males aged 15 to 26 demonstrated the dangers of hypoxic blackouts. They were all engaging in underwater breath-holding contests for time and distance and were all found dead at the bottom of the shallow end of the pool.

For these reasons, lifeguards should be trained to stop ALL breath holding activities, regardless of the swimmers physical fitness or expertise.

Hypoxic Blackout Prevention Strategies

1. Institute and enforce a ban on any prolonged, repeated, and competitive breath holding activities.
2. Train lifeguards on the dangers of hyperventilation and hypoxic blackout.
3. Inform parents and swimmers why breath holding activities are not allowed.
4. Understand that any strenuous exercise performed underwater drastically decreases the amount of time a swimmer can stay submerged.
5. Never hesitate; if a swimmer is sitting motionless on the bottom of the pool pull them out immediately.