Dying for air: prolonged underwater breath holding is a silent, often overlooked, killer. Here's why the practice should be banned.(Perspectives)

More than a decade ago, Stephen Praisner, a collegiate triathlete and experienced SCUBA diver, swimmer and lifeguard, died at the University of North Carolina at the young age of 19 during a public swim in his university swimming pool. He was found in a lap lane in just 4 feet of water with his swimming goggles in place, the next day. His logbook indicated that he would be pushing his limits doing hypoxic training (competitive and repetitive breath-hold swimming) that evening.

His killer? A condition known as "shallow-water blackout," which causes swimmers to lose consciousness underwater during competitive and repetitive breath holding. Although Praisner's death happened more than 10 years ago, the industry still seems to be in the dark about the dangers that killed him.

Statistics about shallow-water blackout deaths are difficult to come by, but anecdotally, we have seen a significant increase in these types of deaths in recent years.

Unfortunately, many aquatics professionals don't seem to understand the risks. When we encourage them to ban the activity, the most common response is "why?" Indeed, many professionals and coaches believe that this extremely dangerous activity is actually good for swimmers, that it is a shortcut to endurance. Some Web sites even encourage breath-holding competitions and advocate the therapeutic effects of holding your breath underwater for more than five minutes!

Part of the problem is the typical profile for repetitive breath holders. Competitive swimmers, Navy Seal divers, free divers and just well-rounded, high-achieving student athletes are typical hypoxic trainers. Not only are they good athletes but they are usually good students as well. In short, they do not fit the profile of an at-risk swimmer, and lifeguards are more likely to ignore these individuals and rarely appreciate how dangerous the underwater swimming activity is.

That danger happens when lower levels of carbon dioxide combine with diminished levels of oxygen in the bloodstream. Basically, the C[O.sub.2] levels in the bloodstream are what tell humans when to breathe. When exercising strenuously we exhale forcefully, lowering C[O.sub.2] levels.

Athletes, coaches and military personnel have also learned that if they hyperventilate voluntarily for an extended period, they can virtually eliminate the urge to breathe underwater. Whether performed voluntarily by sustained forceful expiration or involuntarily by lengthy, strenuous exercise, hyperventilation can greatly enhance breath-holding ability.