Healthy Amateur Divers Clinical Trial
Official title:
Effect of Voluntary Neck Extension in the Occurrence of an Increase in the Pulsatility Index of Right Internal Carotid Artery in the Amateur Diver, Performing an Apnoea of Two Minutes or More: a Prospective, Monocentric, Open Interventional Study
The aim of this study is to demonstrate the effect of the voluntary neck extension in the occurrence of an increase in the pulsatility index of the right internal carotid artery in the amateur diver, realizing an apnea of two minutes or more.
In literature concerning apnoea, accidents have been described during neck extension.
Accidental drowning are frequent on the French coast every year and many of them concern
apneists victims of apnoeic blackout.
Neck extension is thus suspected to possibly produce an apnoeic blackout at the end of the
dive since 1965, when Sir Sciarli (diving medicine pioneer) suspected this hypothesis.
Physiologically, during a dive in apnea, the human cardiovascular system is subjected to a
parasympathetic dominance, via the apnea reflex and the diving reflex. This parasympathetic
dominant could be reinforced during a neck extension at the end of snorkeling during the
ascent.
Hypothesis: the neck extension at the end of apnea contributes to increase the pulsatility
index of the right internal carotid artery by vagal component and thus causes a decrease in
cerebral blood flow and may lead to the initiation of syncope in the healthy amateur free
diver or underwater fisherman.
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