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Shallow-Water Blackout Is No Joke

It's a beautiful, bright, sunny, summer day--the temperature is 85 degrees, and there is a light breeze. You're at a pool party with your family and friends. The kids are splashing and having fun swimming, diving and playing games. A group of teenage boys are in the deep end of the pool, seeing who can stay underwater the longest while swimming down to the drain 12 feet below.

You see these boys taking multiple deep breaths and hyperventilating to increase their air-storage capacity, but you think nothing about it and continue enjoying the beautiful day. A few minutes later, you realize that one young boy has been underwater for a long time. The kids think he is joking by lying still deep below. Although the boy appears to be moving, something doesn't look right. An adult dives into the pool and finds the boy isn't joking. He requires CPR, which paramedics administer as they take him to a hospital.

The victim ends up with a sore chest but resumes a normal life after a few days of hospitalization and intensive care.

What happened? This boy suffered from shallow-water blackout (SWB1), an all-too-common occurrence that is caused by oxygen starvation. He had manipulated the brain's automatic breathing-control device through hyperventilation. The effect of hyperventilation is to wash carbon dioxide out of the lungs, resulting in an extremely low CO2 level.

While underwater swimmers burn up oxygen through exertion. They never get a signal from the brain to breathe because of the low level of CO2 in the lungs and blood. Without the CO2 stimulus, the brain doesn't recognize the need to breathe, and the swimmer blacks out from hypoxia (a lack of oxygen to the brain).

Swimmers in this unconscious state often will fool observers because they don't appear to be in danger. Rather, they appear to make coordinated movements. At this point, physiological brain damage from a lack of oxygen is only minutes away. Even if they are saved from death, the brain damage often is irreversible.

Here's how you can avoid shallow-water blackout:

  • Don't hyperventilate.
  • Recognize that any strenuous exercise you do while underwater will drastically limit the time you can stay underwater. Head for the surface much sooner.
  • Include shallow-water blackout as a topic prior to all training for water activities.
  • Explain (in simple terms) to children at a young age what SWB is and why they never should practice breath-hold diving.

The intent of this introduction to shallow-water blackout is to raise awareness, particularly in the off-duty and non-dive communities. That's why I didn't get too involved in the technical or medical nature of SWB during this discussion. Think about this topic, and include it in all briefs where some element of water submersion is required for mission accomplishment. Assess the risk involved by applying the principles of ORM. Include an explanation of SWB as one of the water-safety topics in your next command safety stand-down before the kickoff of the summer swimming season. Remember, we lose most of our Sailors and Marines in off-duty mishaps.

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