title: A comparison of simple reaction time, visual discrimination and critical flicker fusion frequency in professional divers at elevated pressure.
abstract: BACKGROUND
  Inert gas narcosis (IGN) impairs cognitive performance and some divers are more susceptible to IGN than others. We compared the sensitivity of two reaction time tests to detect changes in performance at pressure and compared these results with critical flicker fusion frequency (CFF) changes at the same ambient pressures.
  
  
  METHODS
  The study assessed simple reaction time (RT), mean time correct of the discrimination reaction time (MTC) and CFF in 30 professional divers breathing air at 101 kPa and 608 kPa in a hyperbaric chamber.
  
  
  RESULTS
  RT and MTC increased at 608 kPa by 5.1 ± 9.4% (P = 0.04) and 7.3 ± 12.3% (P = 0.01) respectively. RT decreased to pre-compression level after decompression and MTC decreased to a level lower than pre-compression (P < 0.001) values. CFF increased by 2.5 ± 2.8% (P < 0.001) at 608 kPa. CFF decreased to pre-compression level after decompression. An increase in CFF was inversely correlated with a decrease in RT (r = 0.38, P = 0.04) and in MTC (r = 0.43, P = 0.02) at 608 kPa.
  
  
  CONCLUSIONS
  Response speeds of the same subjects were impaired in both reaction time tasks at 608 kPa, whereas CFF increased at depth. An association between changes in response times and changes in CFF suggests that divers susceptible to IGN may also be susceptible to the effects of elevated oxygen partial pressure. If this holds true, the future selection of professional divers could be improved by the use of simple cognitive tests.
authors.affiliation: Diving Medical Centre, Centre for Military Medicine, SLK, PL 5, FIN-02471, Upinniemi, Finland, janne.tikkinen@mil.fi.|Diagnostic-Therapeutic Department, University of Helsinki, Finland.
authors.forename: Janne
authors.initials: J
authors.lastname: Tikkinen
authors.affiliation: Diving Medical Centre, Centre for Military Medicine, Finland.
authors.forename: Tomi
authors.initials: T
authors.lastname: Wuorimaa
authors.affiliation: Diving Medical Centre, Centre for Military Medicine, Finland.
authors.forename: Martti A
authors.initials: MA
authors.lastname: Siimes
mesh_terms: D000328:Adult; D001274:Atmospheric Pressure; D004198:Disease Susceptibility / Q000175:diagnosis; D004242:Diving / Q000502:physiology*; D005425:Flicker Fusion / Q000502:physiology*; D006801:Humans; D007222:Inert Gas Narcosis / Q000209:etiology; D008297:Male; D008875:Middle Aged; D011312:Pressure; D011597:Psychomotor Performance / Q000502:physiology; D011930:Reaction Time / Q000502:physiology*; D012623:Seawater; D055815:Young Adult
keywords: Narcosis; nitrogen; performance; psychology