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Diving Hyperb Med. 2019 Jun 30;49(2):119-126. doi: 10.28920/dhm49.2.119-126.

Early detection of diving-related cognitive impairment of different nitrogen-oxygen gas mixtures using critical flicker fusion frequency.

Author information

1
DAN Europe Research Division, Roseto, Italy.
2
Laboratoire ORPHY, EA 4324, UFR sciences et techniques, Université de Bretagne Occidentale, Brest, France.
3
Environmental, Occupational, Ageing (Integrative) Physiology Laboratory, Haute Ecole Bruxelles-Brabant (HE2B), Brussels, Belgium.
4
Corresponding author: Pierre Lafère, Laboratoire ORPHY, EA 4324, UFR sciences et techniques, Université de Bretagne Occidentale, 6 Avenue Le Gorgeu - CS 93837, 29238 Brest Cedex 3, France, doc.lafere@sfr.fr.
5
Centre for Hyperbaric Oxygen Therapy, Military Hospital 'Queen Astrid', Brussels.
6
Hyperbaric Unit, Mater Dei Hospital, Msida, Malta.
7
Anatomical Research and Clinical Studies (ARCS), Vrije Universiteit Brussel (V.U.B.), Brussels.
8
Anatomical Research Training and Education (ARTE), Vrije Universiteit Brussel (V.U.B.).
9
Motor Sciences, Université Libre De Bruxelles (U.L.B.), Brussels.

Abstract

INTRODUCTION:

Cognitive impairment related to inert gas narcosis (IGN) is a threat to diving safety and operations at depth that might be reduced by using enriched air nitrox (EANx) mixtures. Using critical flicker fusion frequency (CFFF), a possible early detection of cognitive abilities/cerebral arousal impairment when breathing different oxygen (O2) fractions was investigated.

METHODS:

Eight male volunteers performed, in random order, two dry chamber dives breathing either air or EANx40 (40% O₂-60% nitrogen) for 20 minutes (min) at 0.4 MPa. Cognition and arousal were assessed before the dive; upon arrival at 0.4 MPa; after 15 min exposure at 0.4 MPa; on surfacing and 30 min post-dive using behavioural computer-based testing psychology experiment building language (PEBL) and by CFFF while continuously recording brain oxygenation with near-infrared spectroscopy.

RESULTS:

In both breathing conditions, CFFF and PEBL demonstrated a significant inverse correlation (Pearson r of -0.90, P < 0.0001), improved cognitive abilities/cerebral arousal occurred upon arrival at 0.4 MPa followed by a progressive deterioration. Initial brain activation was associated with a significant increase in oxyhaemoglobin (HbO2) and a simultaneous decrease of deoxyhaemoglobin (HHb). The magnitude of the changes was significantly greater under EANx (P = 0.038).

CONCLUSIONS:

Since changes were not related to haemodynamic variables, HbO₂ and HHb values indicate a significant, O₂-dependent activation in the prefrontal cortex. Owing to the correlation with some tests from the PEBL, CFFF could be a convenient measure of cognitive performance/ability in extreme environments, likely under the direct influence of oxygen partial pressure, a potent modulator of IGN symptoms.

KEYWORDS:

Enriched air – nitrox; Narcosis; Near-infrared spectroscopy; Oxygen; Risk management

PMID:
31177518
DOI:
10.28920/dhm49.2.119-126
[Indexed for MEDLINE]

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