Fainting common during breath-hold diving

By Amy Norton

NEW YORK (Reuters Health) - People who compete in the extreme sport of breath-hold diving commonly faint or show other signs of poor oxygen circulation -- though no permanent harm seems to come of it, according to a new study.

Breath-hold diving is a competitive sport that includes various disciplines. One is called static apnea, in which competitors float motionless in a shallow pool, holding their breath for as long as possible.

A more adventurous, deep-water form of breath-hold competition is constant-weight diving, where competitors dive down as far as they can, guided by a rope, and then ascend -- all without any breathing apparatus.

To discourage athletes from staying underwater to the point of drowning, breath-hold competitions have certain rules. Competitors are disqualified if, after surfacing, they show signs of hypoxia -- inadequate oxygen supply to the body's tissues. Signs of hypoxia include fainting, confusion, spasms and difficulty standing.

In the new study, Dr. Peter Lindholm of the Karolinska Institute in Stockholm found that episodes of hypoxia are fairly common in breath-hold competitions.

In major events held between 1998 and 2004, about 10 percent of competitors were disqualified due to severe signs of brain hypoxia, Lindholm reports in the International Journal of Sports Medicine. On the other hand, there were no deaths or reports of permanent injuries among competitors who suffered hypoxia symptoms.

On balance, Lindholm told Reuters Health, breath-hold diving seems a "reasonably safe sport." It may be risky compared with tennis or chess, he noted, but within the realm of extreme sports, it's not especially dangerous.

Formal competitions involve well-trained divers and many safety precautions, Lindholm explained; constant-weight divers, for example, are monitored by cameras and scuba divers.

Breath-hold diving most certainly counts as a "don't-do-this-at-home" activity. Unfortunately, Lindholm pointed out, it's not hard for amateurs to attempt. "The inherent problem of the sport," he said, "is that you can buy a mask and fins and then go diving without any education."

SOURCE: International Journal of Sports Medicine, April 2007.