Abstract
The man has suffered high pressure accidents like oxygen toxicity and nitrogen narcosis under hyperbaric air breathing. Heliox mixture gas (He-o2) was employed in order to prevent a man from the impairment. The increase of the ambient pressure, however, had influence on various physiological functions. This manuscript reviewed chiefly the study of hyperbaric physiology for heliox gas, that is, (a) high pressure nervous syndrome (HPNS), (b) the effect on respiration, (c) the effect on cardiac function, and (d) the effect on comfortable ambient temperature. The physical feature of inert gas under high pressure was also investigated. As for the countermeasure for HPNS, the following procedures were known : That is, (i) temporary stop at a compression stage, (ii) excursion, (iii) the use of trimix gas (He-O2-N2), and (iv) the decrease of compression rate has been studied. The hyperbaric environment denoted the limit of intense physical labour. The cause of bradycardia under hyperbaric environment showed both the dependency of pressure and that of respiration gas (i, e., oxygen, nitrogen and helium). The environment of heliox gas needed high room temperature (32°C The present condition of the limit which mankind reached the deepest sea level was investigated.
