Influence of hyperbaric environment on physiological tremor.

The effect of pressured environment from 1 to 24 ATA (Atmosphere Absolute) on total power spectrum (TP) of physiological tremor, whose value was the sum of power spectra for frequency range in 0.5-50 Hz, was investigated. The main effects obtained were as follows. (1) In the case of 3 ATA, TP during the pressure holding period denoted a similar value as the value in 1 ATA. In the latter half of the period, the TP increased. When the pressured environment is 4 ATA, in which the partial pressure of the nitrogen gas was 3.6 ATA, the TP decreased during the pressure holding period compared with the value in 1 ATA. Nitrogen narcosis was recognized at the partial pressure of 3.6 ATA, thus the effect denoted a decrease of TP. (2) In the cases of 16 and 19 ATA using heliox gas, during the pressure holding period, TP decreased compared with the value in 1 ATA, but in the case of 24 ATA the value increased. The partial pressure of helium gas of 23.6 ATA indicated a high pressure nervous syndrome, therefore, the influence of high pressure on TP was recognized as one of the causes of the increase of TP. (3) The influence of inhibitors of the autonomic nervous system on TP during the pressure holding period of 3 ATA was recognized. After intake of the inhibitor for the parasympathetic nerve (atropine) during the pressure period, TP increased, while for the intake of the inhibitor for the sympathetic nerve (propanol), TP decreased.