LABORATORY OF PHYSIOLOGY OF RESPIRATION

(Head N. P. Aleksandrova)

The Laboratory was founded in 1960 by Prof. A. G. Zhironkin to solve mainly the applied problems, particularly the problem of selection of the optimal gas medium for manned cabins. At this period, the main achievements were discovery of phenomenon of gas preference in humans and animals, identification of early signs of oxygen toxic effects, evidence for the existence of reserve chemoreceptors, establishment of a thermoneutral zone in the helium-oxygen environment under pressure.

Dr. G.G.Isaev, Dr. N.P.Aleksandrova with co-workersIn 1973, the Laboratory was transformed into the Sector headed by Biological Sciences Doctor I. S. Breslav. The research interests of the Sector were focused on studying regularities and mechanisms of voluntary regulation of human respiration, role of afferent stimuli in the respiration response to different loads. Changes in the respiratory rhythmogenesis during muscular activity were shown to be due to interactions of the chemoreceptor and neurogenic stimuli modulated by biomechanical factors. This results in formation of a respiration pattern that is energetically optimal for the given exercise level and corresponding to individual features of the respiration biomechanics.

In 1986, the Laboratory of physiology of respiration was founded again, its head becoming Prof. G. G. Isaev. At present, the main direction of studies is analysis of mechanisms of compensation of exercise and formation of respiration sensations at a forced respiration.

The most important factor that limits tolerability of the muscular work at an additional resistance to respiration on the background of increased chemoreceptor stimulation has been established to be limitation of functional possibilities of respiratory muscles, up to their fatigue. It is suggested that an increased afferent impulsation from respiratory muscles serves as a source of perception of dyspnea and forces a man to stop working, thereby preventing an extra load of the respiratory apparatus activity. Mechanisms of the respiratory muscle fatigue and causes of the respiratory arrest were studied on experimental animals. A role of the central and peripheral components was established in development of the respiratory muscle fatigue at resistive loads. It was shown that, apart from the central mechanism, there was also a peripheral apnea mechanism due to functional insufficiency of respiratory muscles in association with disturbances of the neuromuscular transmission and the excitation-contraction process in muscle fibers. The central structures and their stereotaxic coordinates activated during a resistive load were established using positron-emission tomography. Reliable activation zones during inspiration load as compared with free respiration were revealed in the parietal and frontal cortices, the right insular area, basal ganglia, midbrain, and bilaterally in many cerebellar areas. It is suggested that cerebellum, on the base of comparison of signals from the higher motor centers to respiratory muscles (a copy of motor command from the motor cortex) and from receptors of these muscles that signal about the real performance of the inspiration act, introduced its correction in activity of respiratory centers, which is manifested as a change of the respiration pattern. Mechanisms of the respiratory muscle fatigue and causes of the respiratory arrest are studied on experimental animals. A role of the central and peripheral components was established in development of the respiratory muscle fatigue at resistive loads. It was shown that, apart from the central mechanism, there also existed a peripheral apnea mechanism due to functional insufficiency of respiratory muscles in association with disturbances of the neuromuscular transmission and the excitation-contraction process in muscle fibers.