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Rôle de l'oxygène dans les phénomènes de narcose à l'azote

Abstract : During a dive subjects undergo many environmental stressors. Nitrogen narcosis through its effects on cognitive performance is one of them. Narcosis is indeed involved in many scuba diving accidents. It is therefore mandatory to develop a quantitative, reliable, reproducible tool to evaluate underwater diver’s cognitive performance. This tool should not be dependent on diver’s subjectivity. Once this tool (critical flicker fusion frequency - CFFF) is validated, we could then clarify the role of narcosis modulating factors in particular that of oxygen.Our investigations were performed in healthy volunteers specifically selected in a large group of recreational diver to obtain a standard population (gender, age, BMI, fitness and experience in diving). Cerebral performance analysis is carried out using psychometric tests, visual analogic scale and CFFF in different conditions (normobaria, simulated and open-water dives to a depth of 30 meters of fresh or salt water for 20 minutes) and with different gases (air and EANx 40%). The specific effect of oxygen is apprehended by use of near infrared spectroscopy (NIRS).On one hand, our measurements confirm the gradual deterioration of cognitive performance by both psychometric tests and CFFF, which share a good degree of correlation (Pearson from 0.86 to 0.93) and on the other hand diver’s inability to assess themselves.The evolution of cognitive performance is characterized by an improvement when arriving at depth followed by a progressive impairment that persists for at least 30 minutes after surfacing.The more oxygen in the breathing mixture, the better improvement in the early part of the dive and the less impairment in the following measurements are observed. Brain functional imaging (NIRS) allows us to pair the observed cognitive performance improvement with oxygen-dependent brain activation.It seems that Oxygen is an important modulator of the symptoms of nitrogen narcosis. In accordance with the neurochemical theory of narcosis we suggest that the net effect on cerebral performance depends on a balance between the activating effects of oxygen and the inhibitory effects of nitrogen.
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Submitted on : Wednesday, November 7, 2018 - 11:53:10 AM
Last modification on : Friday, October 23, 2020 - 4:58:31 PM
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  • HAL Id : tel-01915003, version 1



Pierre Lafère. Rôle de l'oxygène dans les phénomènes de narcose à l'azote. Physiologie [q-bio.TO]. Université de Bretagne occidentale - Brest, 2014. Français. ⟨NNT : 2014BRES0042⟩. ⟨tel-01915003⟩



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