[Diving: barometric pressure and neurochemical mechanisms]. / La plongée: pression barométrique et mécanismes neurochimiques.

The studies of Paul Bert, presented in his book "La Pression Barométrique" in 1878, were at the origin of the modern hyperbaric physiology. Indeed his research demonstrated the effects of oxygen at high pressure, that compression effects must be dissociated from decompression effects, and that neurological troubles and death of divers during or after decompression were due to the fast rate of decompression. However, it is only in 1935 that the work of Behnke et al. attributed the complaints reported at 3 bars and above in compressed air or nitrogen-oxygen mixture to the increase in partial pressure of nitrogen which induces nitrogen narcosis. Little is known about the origins and mechanisms of this narcosis. The traditional view was that anaesthesia or narcosis occurred when the volume of a hydrophobic membrane site was caused to expand beyond a critical amount by the absorption of molecules of a narcotic gas. The observation of the pressure reversal effect during general anaesthesia has long supported this lipid theory. However, recently, protein theories have met with increasing recognition since results with gaseous anaesthetics have been interpreted as evidence for a direct gas-protein interaction. The question is to know whether inert gases, that disrupt dopamine and GABA neurotransmissions and probably glutamatergic neurotransmission, act by binding to neurotransmitter protein receptors.

[Functional state of various physiological systems of the human body during respiration of neon-oxygen mixture at depth up to 400 meters]. / Funktsional'noe sostaianie nekotorykh fiziologicheskikh sistem organizma cheloveka pri dykhanii neono-kislorodnoi smes'iu na glubinakh do 400 metrov.

Hyperbaric neon-oxygen mixture has been studied for the effect of its high density under pressure of 41 ata on basic physiological functions of human organism. Typical changes of the cardiorespiratory system and tissue respiration parameters are revealed. Changes in physical working capacity are shown. Exposure to gaseous medium of high pressure and density is accompanied by the development of some compensatory-adaptive reactions. The possibility to perform mid-hard physical work is attained with overstrain of respiration and circulation function.

[High density respiratory syndrome: III. The functional role of oscillation of respiratory flow during respiration in dense gas media]. / Dykhatel'nyi sindrom vysokoi plotnosti: III. Funktsional'noe znachenie ostsilliatsii respiratornykh potokov pri dykhanii v plotnykh gazovykh sredakh.

It is found out that when reaching critical density of gas medium (20.4-24.0 kg/m3), the relative power of oscillations on the "flow-volume" curves and pneumotachograms sharply increases. At the same time the maximal rate of exhale, rates of expiratory flows in large bronchi decrease significantly and the rates of expiratory flows in bronchi of middle and small calibers reduce to zero. Within the range of densities of different gas medium (from 1.3 to 32.7 kg/m3) the changes in the relative power of oscillations of respiratory flows correlate well with the changes in permeability of upper respiratory tracts (r = -0.932 +/- 0.054). A regression equation describing this dependence is obtained. A detailed description is given to symptoms of high-density breathing syndrome: a decrease in rates of gas flows in tracheobronchial tree, early development of dynamic compression of airway, tremor of breathing muscles and appearance of respiratory flow oscillations, pronounced dyspnea and hypoventilation of alveoli. A hypothetic scheme of its development is presented. The functional significance of respiratory flow oscillations as a mechanism improving gas exchange in gas media with extremely high density is under discussion.