Critical flicker frequency (CFF) and subjective fatigue during an oxyhelium saturation dive at 62 ATA.

Two divers spent over 50 hours at 610 msw in a helium-oxygen mixture (PO2:0.38-0.52 ATA). The dive duration was 27 days, including predive stages of confinement, compression, time at maximum pressure, and decompression. The divers were asked to answer 30 questions on their feelings of mental and physical fatigue and to indicate on a nine-point scale their estimation of a general feeling of fatigue. Subjective feelings of fatigue reported in this dive suggested that the divers were in good condition. Hyperbaric arthralgia and physical complaints were reported, especially during decompression, with some postdive persistence, but they should be considered as distinct signs of feelings of fatigue. The critical flicker frequency (CFF), measured throughout the dive for the two divers, showed systematic variations and a relationship between compression and pressure. These variations were grossly parallel to EEG modifications reported in other studies and probably reveal neurophysiological troubles that were not apparent from subjective reports.