[High density respiratory syndrome: III. The functional role of oscillation of respiratory flow during respiration in dense gas media].

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.