[Physical features of high-frequency artificial ventilation of lungs]

The authors analyze main features of high-frequency forced ventilation of the lungs (HF FVL). Estimations indicate that the end-respiration pulmonary positive pressure inevitably develops during HF FVL; its value is 30 cm H2O and it starts no later than 10 sec after the beginning of HF FVL. Experiments showed that the maximal and minimal pressure of the respiratory cycle measured at the site accessible for measurements outside the device (at the exit) differ appreciably from pulmonary pressure which is clinically impossible to measure but is much more valuable. For assessing this value the mean respiratory cycle pressure is to be measured whose values outside the device and inside the lungs are similar and virtually do not change if the frequency of HF FVL changes. The volume of dead space and internal elasticity of common FVL devices influence appreciably the created minute ventilation, particularly its alveolar component, and the probability of using such devices for HF FVL is doubtful. Requirements to the injector design for the most frequently used injection HF FVL are contradictory. A reasonable compromise on providing the needed consumption of inhaled gas and oxygen concentration in it within a sufficiently wide range of pressure may be attained by supplementing the device with a kit of special injectors. Estimations of gas movement in the airways do not validate the hypothesis on the turbulence in the transitory and respiratory zones of the tracheobronchial tree as a factor explaining the efficacy of HF FVL with low respiratory volumes.