A survey of neurological decompression illness in commercial breath-hold divers (Ama) of Japan

Introduction
A survey was conducted in the northern district of Yamaguchi, Japan to determine the relationship between neurological diving accidents and risk factors among commercial breath-hold divers (Ama).

Methods
A questionnaire was distributed to 381 Ama divers who are members of the Ama diving union. We sought information on their dive practices (depth of single dive, single dive time, surface interval, length of dive shifts, lunch break) and the presence or absence of medical problems, such as hypertension, cardiac arrhythmia, diabetic mellitus and other issues.

Results
Of the 381 Ama divers, 173 responded (45%): 29 were Funado (assisted-descent using weights) and 144 Cachido (unassisted) divers. Twelve had experienced strokelike symptoms during or after repetitive breath-hold diving; 11 were assisted and one unassisted (Funado vs. Cachido). Only two of 12 divers with neurological diving accidents had musculoskeletal symptoms. Neurological events were significantly correlated with dive depth, dive time, and surface interval; however, they were not related to medical history. Neurological diving accidents are more likely to happen among assisted Ama divers than unassisted ones.

Discussion
Repetitive breath-hold diving with a deep dive depth, long dive time, and short surface interval predisposes divers to decompression illness, which characteristically manifests as cerebral stroke.