Effects of Voluntary Neck Extension on Cerebral Blood Flow, in Breath-hold Divers Ending an Apnoea of Two Minutes or More.

Not Applicable

Completed

Brief Summary: 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.

Detailed Description: 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.

Recruitment & Eligibility

Inclusion Criteria

Major (≥18 years), under the age of 51
Male
Can hold an apnea of 2 minutes or more
Practicing for less than 2 years the apnea at the rate of at least 10 sessions of apnea in the year
Not having a known cardiovascular history : any form of heart rhythm disorder, Ischemic heart disease, angina, arteriopathy, any valvular pathology, high blood pressure ...
No known respiratory history (asthma, Chronic Obstructive Pulmonary Disease, bronchiectasis, pulmonary emphysema, pneumothorax, pleurisy, pulmonary infection, lobectomy ...)
No neurological history of type: epilepsy, deficit syndrome, iterative loss of knowledge, recent head trauma with loss of consciousness

Arm && Interventions

Group	Intervention	Description
apnea performing	apnea performing	The included subjects will make an apnea of two minutes or more, sitting on a chair with cold strips on the face, initially with the head in neutral position. Then, when they feel the end of their apnea, they will have to raise their left hand to signal it to the Doppler manipulator, who will then realize the apnea reference measurement. As soon as this is done, the subjects will be asked to perform an extension of the neck, so as to look at the ceiling. A final measurement will then be made in apnea, the head always in extension. Subjects then resume their breathing in this same position. A final measurement will then be made.

Primary Outcome Measures

Name	Time	Method
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	2 minutes or more: at the breaking point of apnea.	To demonstrate the potential implication of cervical extension in the decrease of cerebral blood flow in amateur diver apnea by measuring the variation in the pulsatility index of the right internal carotid artery (RICAPI), by the intra-individual comparison of the RICAPI in amateur diver in rupture of apnea with neck extension (NE) versus the RICAPI of amateur diver in rupture of apnea without NE.

Secondary Outcome Measures

Name	Time	Method