Understanding Shallow-Water Blackout

Shallow-water blackout is a condition that renders a victim unconscious in the first couple of feet of water while using a closed-circuit oxygen breathing apparatus. It usually results when an inexperienced swimmer or snorkeler takes multiple deep breaths to increase the time that he/she can spend underwater, and hyperventilates.

The medical explanation for shallow-water blackout is highly technical. In simple terms, this condition is the result of purging the body of carbon dioxide--the stimulus that causes the brain to recognize the need to take a breath. In absence of this breathing stimulus, a swimmer may be rendered unconscious from hypoxia, or a shortage of oxygen. Looking For Signs

Shallow-water blackout is exceptionally dangerous because there are seldom any of the recognizable signs associated with an active drowning as taught in textbooks. This makes the condition extremely difficult to identify, even by experienced lifeguards. An autopsy report seldom, if ever, lists shallow-water blackout as a cause of death because any physical indicators of the condition are not revealed. Instead, drowning is listed as the cause.

Case Studies

My analysis suggests that this condition predominately occurs among teenage and young adult males. This makes sense because these individuals are usually considered to be “risk takers.”

I recently assisted in two shallow-water blackout cases involving young adult males engaged in breath-holding contests. In a similar exercise, I myself experienced no pain or any signs that I was about to lose consciousness. My only memory of the incident was a burning sensation as my knees scraped against the pool wall as I was being extricated by two observant lifeguards.

Considering that snorkeling is a common activity on many beaches, this potentially life-threatening condition deserves more attention. I’m especially concerned about beaches where snorkeling is actively encouraged in marketing literature, but there are no lifeguards.

Education For Safety

Should snorkeling be banned? Recently I conducted a survey of a number of Florida Beach Patrol Chiefs and senior lifeguards, who said it should not be banned. I also posed the question to Randy Shaw, education director for the National Association of Underwater Instructors. He felt that education was a better response to this problem than banning snorkeling.

There are several recommendations on how to make people aware of the risks associated with shallow-water blackout:

· Provide better in-service training to lifeguards working on beaches where snorkeling commonly occurs.

· Have lifeguards provide information handouts and/or verbal instruction to snorkelers.

· Include information about shallow-water blackout in learn-to-swim programs.

· Ban breath-holding games and competitions.

· Eliminate training that requires prolonged breath-holding.

· Consider posting warning signs about the danger of hyperventilating and breath-holding.

Another recommendation encourages the manufacturers of skin-diving equipment (masks, fins and snorkels) to publish warnings about shallow-water blackout. In the course of researching this article, I visited more than ten stores selling youth diving equipment. There wasn’t a single case where the manufacturer included information or warnings about shallow-water blackout. This needs to change. Education is the key to preventing further fatalities.

Dr. John R. Fletemeyer is a professor in Laboratory for Coastal Research at Florida International University. He can be reached via e-mail at jfletemeyer@aol.com