Diving Technical Papers

Breath-hold diver Junko Kitahama
Breath-hold diver Junko Kitahama

Toward a Predictive Algorithm for Untoward Events in Elite Breath-Hold Divers

Breath-hold divers (also known as freedivers) have only one diving outcome that they strive for: the successful completion of a breath-hold dive. That requires freedivers to push their bodies to their physical and physiological limits. Yet, in pursuit of the elite breath-hold divers’ depth goals, occasionally those limits are exceeded, resulting in a breath-hold diver’s “untoward event.”

Breath-Hold diver mishaps share a remarkable similarity with the type of incidents that mar the safety and performance of U.S. Navy divers. When diving using underwater breathing apparatus (UBA), mishaps or “untoward events” are influenced by environmental and physiological factors such as depth and exercise rate (Clarke, 1989a and b).

There are two rare but significant physiological events for Navy and commercial divers. One event is a feeling of extreme breathlessness, which leads to a diver suddenly stopping his underwater work. The other and potentially fatal event is a sudden and unexpected loss of consciousness.

Just as in the case of a working diver using UBA, the breath-hold diver’s “event” can lead to a cessation of swimming effort due to loss of muscular coordination (loss of motor control or LMC, Lindholm, 2007), or to an unexpected loss of consciousness (Lindholm and Lundgren, 2006). In breath-hold diving competitions, untoward events are relatively common, occurring in 6-10% of dives (Lindholm, 2007).

These freediving neurological events have also been called Negative Neurological Events, NNEs, (Ridgeway and McFarland, 2006). Thanks to safety procedures established for both forms of diving, with and without breathing apparatus, untoward events are not often fatal…but they can be.

Like decompression sickness, untoward events in both forms of diving are probabilistic. That means that given enough opportunity, even improbable events will occur. The next section reviews the probability of everyday events in military diving and breath-hold diving.

The entirety of this technical paper is found in the following PDF.