Abstract
INTRODUCTION: Drowning is likely to result from impairment of consciousness when scuba diving. Causes include toxic effects of breathing gas, including nitrogen narcosis and oxygen toxicity, and arterial gas embolism. METHODS: Review of the medical records of scuba divers who had impaired consciousness underwater that could not be attributed to toxic effects of breathing gas or arterial gas embolism. RESULTS: Four scuba divers had episodes of impaired consciousness when at shallow depths (8-18 m) underwater. The descriptions of the episodes were very similar. Three had histories of recurrent episodes of vasovagal syncope on land. CONLCUSIONS: Absence of other causes for their impaired consciousness underwater leads to the conclusion that the probable cause was vasovagal syncope.