Analysis of impedance characteristics of the respiratory system of animals and humans

Abstract

The aim of the study was to modify the method of pulsed oscillometry of the respiratory system of biological objects in the interests of the possibility of its application to extrapolate the medical and biological effects of extreme physical factors of the conditions of professional activity from animals to humans. The method is based on a verified algorithm for determining the impedance characteristics of the human lungs (resonant frequency, active and reactive frequency–dependent components of the impedance) using a two-microphone technique. The impedance characteristics of the respiratory system of animals (30 rats, 15 rabbits, and 15 sheep) in the frequency range from 5 to 100 Hz were measured on decapitated animals when the trachea was connected to an experimental setup including a loudspeaker, waveguide, two measuring microphones, an impedance wall, and a connecting tube designed to connect the installation to the trachea. The impedance characteristics of the respiratory system in humans (40 athletes aged 20–30 years) in the same frequency range were measured during free breathing: a standard mouthpiece was installed as a perforated panel at the end of the waveguide. As a result of the experiment, the resonance frequency of the respiratory system, the absorption coefficient of acoustic vibrations and the resistance at the resonance frequency and the acoustic quality factor of the respiratory system were determined. The results of theoretical and experimental studies indicate that the resonant frequencies of the respiratory system in humans, rabbits and sheep are close to each other, and the resonant frequencies of the respiratory system of rats and humans are significantly different. This allows the use of rabbits and sheep as an adequate biological model for extrapolating the effects of extreme factors from animals on humans in terms of the state of the respiratory system. Extrapolation of similar results from rats to humans should be carried out taking into account the ratio of the impedance characteristics of the respiratory systems.