Frequently during its lifetime a human organism is subjected to the acoustical and similar to them vibrating impacts. Under the certain conditions such influence may cause physiological changes in the organs functioning. Thus the study of the oscillatory mechanical impacts to the organism is very important task of the numerical physiology. It allows to investigate the endurance limits of the organism and to develop protective measures in order to extend them. The noise nuisances affects to the most parts of the organism disrupting their functions. The vibrating disturbances caused to the lung function as one of the most sensitive to the acoustical impacts is considered in this work. The model proposed to describe the air motion in trachea-bronchial tree is based on the one dimensional no-linear theory including mass and momentum conservation for the air flow in flexible tubes.
Environmental vibrating impacts to the organism of a human play important role for his vital activity. For the most cases such impacts has anthropogenic origin. They affect as in some specific cases (industrial noises generated by different industrial machines and mechanisms) and in everyday life, in particular intensive road traffic in megapolis.
The kind and damage level of the disturbances caused by intensive vibrating impacts result in functioning changes of vestibular analyzer, cardiovascular system, liver and lungs functioning, neurohumoral system and others. Typical symptoms are the headache, coordination of movements disorder, dizziness, symptoms of neurosis-like syndrome and vegetative dysfunction, pain in back muscles and lumbar part of backbone etc. Vibrations may decrease visual acuity, impairment of chromatic sensitivity, loss of functional activity and others. Longduration acoustical impacts may result in essential changes of blood flow in small vessels of pulmonary circulation thereby reducing oxygen concentration in oxygenated blood. As is well known anoxia give rise to nonreversible processes in vitally important organs. For example risk of pulmonary edema in the presence of anoxia is much higher. Under the intensity of noise impacts exceeding threshold of 100 dB general disorder of organism functioning is observed. In the whole the progress of physiological and pathological changes in organism functioning depends on the nature of the impacts and peculiarities of particular organism.
Thus investigation of vibrating impacts to the human organism is very important task. In particular analysis of the processes causing different physiological and pathological phenomena, forecasting the behavior and looking for the endurance limits of the organism in order to develop protective measures are of great interest. The range of the frequencies up to 20 kHz (acoustical range) is considered in this work as it seems to cause the most crucial effect as it includes eigenfrequencies of most parts of the organism.
One of the parts of the organism most subjected to the acoustical impacts are the lungs. Therefore analysis of the processes excited by the acoustical impacts inside the tracheabronchial tree and alveolar volume is the final purpose of this work. At the beginning of the paper physiological basis will be discussed that determines mathematical approach to the lungs function modeling. After that the model describing trachea-bronchial tree functioning will be discussed. It will be extended by the model of alveolar volume and the model of aspiration and convective-diffusive substance transfer. Analysis of the acoustical impacts to the nasopharynx and thorax carried out. The results presented in the end of the paper reveal two eigenfrequencies when the thorax is affected and no resonance states for the actions to nasopharynx. Influence of the acoustical impacts to the processes of blood oxygenating will also be discussed. Decrease of oxygen concentration in pulmonary circulation depending on the frequency and amplitude of the disturbances will be evaluated.
Respiratory tract similar to the blood vessels constitutes branching structure that maximizes contact area for gas exchange. In accordance with symmetric morphometric model of the lungs inspirited air propagates through the branching tree of bronchial tubes that form dichotomic structure. Trachea-bronchial tree amounts up to 23 generations. Air cells, alveolar ducts and respiratory bronchioles form respiratory and transitional zone amounting 95% of the whole lungs. Conductive zone includes first 16 generations of bronchial tubes where convective component dominates. In other zones diffusion intermixing prevails over the convective transfer [1,2].
Air motion in the most parts of the air tract produce streamline flow. But in some areas in particular near bronchus forks and their pathological narrowing the flow turbulence may oc-cur. Gas composition in alveolar volume supposed to be uniform and gas itself supposed to be incompressible.
The most modern works dealing with lungs mechanics exploit the one-component lung model known from the beginning of XX century. According to this model the lungs are considered as elastic volume having gas-permeable surface. The volume of pleural cavity and air tract is supposed to be negligible with respect to the alveolar volume. Thus thorax volume is supposed to be equal to alveolar one. The air flows into this volume through the system of rigid gas-proof tract usually presented in such models as single channel having some hydraulic resistance. Breathing apparatus in the whole is placed into the elastic cover that is driven by externally defined muscle force. It is supposed that pressure between alveolar volume and thorax depends on time only and is defined by dynamic of respiratory cycle. Such models may explain a lot of experimental data obtained from healthy men. They still used for many problems including comp
