Critical flicker fusion frequency testing shows similar changes at a measure of cognitive performance and may be a useful tool to warn of early nitrogen narcosis.

Clinical Bottom Line

1. Critical flicker fusion frequency could be a measure of cognitive decrement due to inert gas narcosis in divers.


Citation/s:1.Lafère P, Hemelryck W, Germonpré P, Matity L, Guerrero F, Balestra C. Early detection of diving-related cognitive impairment of different nitrogen-oxygen gas mixtures using critical flicker fusion frequency. Diving Hyperb. Med. 2019 Jun 1;49:119-26.
Lead author's name and fax: Pierre Lafere

Three-part Clinical Question:For adult divers, does cognitive performance vary under different conditions and can Critical Flicker Fusion Frequency (CFFF) serve as an indicator of threatened cognitive performance.
Search Terms: Critical Flicker Fusion Frequency; Inert Gas Narcosis; cognitive testing

The Study:Double-blinded crossover concealed randomised controlled trial with intention-to-treat.
The Study Patients: Fit volunteer divers.
Control group (N = 8; analysed): Dry chamber dive breathing compressed air to 30 msw for 22 minutes
Experimental group (N = 8; analysed): As above but breathing 40% oxygen (EAN).

The Evidence:

Multiple regression and ANOVA results given in paper.

1. Many outcomes subject to wide statistical analysis. No simple event or mean -based outcomes.
2. CFFF and a measure of cognitive performance broadly agree and suggest a decline in cognition at depth that may be assessable with CFFF.
3. Oxygen-dependent activation of the prefrontal cortex accompanies these changes.
Appraised by: Mike Bennett ; Sunday, 2 August 2020
Kill or Update By: August 2024