[Repeated action of hyperbaria on rat blood system].

There are considered reactions of male Wistar rat blood system to repeated action of nitrogen-oxygen hyperbaria (pressure 0.5 MPa, density of gas medium 6 g/l, pO2 = 0.02-0.03 MPa). Rats were placed into a barochamber for 5 h 24, 72, and 120 h after the first exposition (control in air without the increased pressure). Parameters of red blood were studied and the general state of the animals was estimated. It has been established that after the first hyperbaria séance the stress-reaction develops in rats with all objective stress parameters (level of corticosteroids and content of ascorbic acid in adrenals). At repeated exposure after 24 h the almost complete normalization of all stress parameters was observed, except for the increased hemoglobin content in plasma as a result of impair of permeability of erythrocytic membranes. After repeated actions 72 and 120 h later, the stress parameters manifested again. After exposure 120 h later, the general state of animals was sharply deteriorated they did not move in the "open" field, could not be hold on a horizontal bar, and mainly were lying. The performed control with the immobilization stress showed that after the initial stress-reaction the rats were recovered completely and at repeated exposures no changes were observed in the blood system and in the general state of the animals. We belive that the hyperbaria-produced stress is connected with difficult breathing under pressure. Thereby, the repeated action of hyperbaria is a harmful factor and habituation to it does not occur.

[Hyperbaria and stress].

Causes of the appearance of stress-reaction at action of hyperbaira on the organism were studied on rats. It has been established that at the 5-h action of gas mixtures (oxygen-nitrogen and oxygen-argon) under pressure 0.35 and 0.5 MPa and partial pressure of oxygen 0.02-0.03 MPa in the chamber of the volume of 300 1 there is obviously manifested stress confirmed by the corresponding markers. The appearance of stress was connected with the gas mixture density that amounts to 6 g/l, which interferes with respiration mechanically. Use of helium at the same pressure of the gas mixture did not cause stress, as its pressure did not exceed the normal air density. On the other hand, use for respiratory mixtures of elegas (SF6) with density of 6 g/l at the normal pressure produced obvious stress. No difference was revealed in action of nitrogen, argon or elegas at equal density. Thus, use of high pressures needs light gases (helium, hydrogen, neon) that have low density.