The effects of hyperbaric conditions on vibrotactile thresholds

Abstract

The effects of low-frequency, water-borne vibration upon swimmers and divers are virtually unknown. It has been reported that divers can ‘‘feel’’ underwater sounds on various parts of their bodies. The current experiments were conducted as an initial investigation of these reports to determine if barometric pressure and breathing mixture has an effect on vibrotactile thresholds measured in air. Vibrotactile thresholds at the thenar eminence were determined on four divers during a ‘‘saturation dive’’ (8 days) in a dry hyperbaric chamber. Measurements were made prior to the dive (pre-test) in a normobaric environment (sea level) at 132 ft of seawater (fsw), at 198 fsw, at 300 fsw, and following the dive at sea level (post-test). The gas mixture in which the divers lived was varied according to standard procedures to prevent adverse body reactions during compression and decompression. Vibrotactile thresholds were measured by standard procedures at 1, 10, 100, and 250 Hz. Results indicate that neither air pressure nor breathing mixture had any effect on vibrotactile thresholds within any of the four mechanoreceptor channels that innervate normal skin. The results are internally consistent within this experiment and also when compared to threshold standards accumulated over thirty years. [Work supported by Geo-Centers, Inc. under Navy Contract.]