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This paper presents a new hardware and software system that allows to not only record the EMG of different groups of the respiratory muscles, but also hold its amplitude-frequency analysis, which allows to determine the change in the contribution to the work of breathing of a respiratory muscles and detect early signs of fatigue of the respiratory muscles. Presented complex can be used for functional diagnostics of breath in patients and healthy people and sportsmen.

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We evaluated the maximal mouth inspiratory pressure and the EMG patterns of major respiratory and accessory muscles used in the generation of voluntary inspiratory maneuvers during different body positions. Ten healthy subjects (F/M-4/6), the mean age 22.000B10.6 years, participated in the study. The maximal inspiratory mouth pressure (MIP) during Müller's maneuver was measured from residual volume in the standing, sitting, right-sided (RSL) and left-sided lying (LSL), supine, and head-down-tilt (HDT) (3000B0; relatively horizon) positions. EMG of the diaphragmatic (D), parasternal (PS), sternocleidomastoid (SM), and genioglossus (GG) muscles were assessed in each body position. The baseline MIP was 105.3 00B1; 12.0 in men and 59.9 00B110.1 cmH(2)O in women in the standing position and did not appreciable differ in the other positions, except the HDT where it was lower by 23 and 27% in men and women, respectively (P003C0.05). During Müllers maneuver, diaphragmatic EMG activity also was similar in all the body positions, but it was significantly enhanced in the HDT. In contrast, PS EMG showed the highest level of activation in the standing position, taken as the control, reference level, and was lower in the HDT. Activation of SM during the maneuver was near the control in the sitting position, lower in the supine (79%), RSL (85%), LSL (80%), and HDT (72%) positions (P 003C0.05). GG EMG was significantly greater during maximal inspiratory effort in the supine and HDT positions (125and 130%, respectively), while it was lower in the sitting, LRS, and LLS positions (76, 57, and 43%) compared with standing (P 003C; 0.05). We conclude that the inspiratory pressure generated during Muller maneuver is a reflection of complex interactions between several muscle groups during changes in body positions.

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The effect of head-down tilt on respiration and diaphragmal and parasternal muscles activity was investigated in 11 healthy subjects. The short-time (30 min) head-down tilt posture (-30 degrees relatively horizont) increased the inspiratory time (P < 0.05), decreased breathing frequency (P < 0.05), inspiratory and expiratory flow rate (P < 0.05) and increased the airway resistance (P < 0.05) compared with values in vertical posture. There were no significant changes in tidal volume and minute ventilation. Constant values of tidal volume and minute ventilation during head-down tilt were provided by increasing in EMG activity of parasternal muscles more then twice. It was established that the contribution of chest wall inspiratory muscles increased while the diaphragm's contribution decreased during head-down spontaneous breathing. Maximal inspiratory effort (Muller's maneuver) during head-down tilt evoked the opposite EMG-activity pattern: the contribution of inspiratory thoracic muscles was decreased and diaphragm's EMG-activity was increased compared with vertical posture. These results suggest that coordinate modulations in inspiratory muscles activity allows to preserve the functional possibility of human inspiratory muscles during short-time head-down tilt.

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We investigated the effect of three types of respiratory support on respiratory parameters in conscious healthy humans. For each type of respiratory support set specific changes in the pattern of volume and temporal parameters. One response to all types of respiratory support was hyperventilating, although varying degrees, and as a consequence, hypocapnia. These changes are not related to the metabolic needs and probably are the result of the interaction mechanisms of automatic and voluntary regulation of breathing movements.

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We did Read CO2 rebreathing tests in 8 adult males. Both at natural breathing, and at self-controlled mechanical ventilation, volunteers increased ventilation proportionally to growth end-tidal PCO2. Inside individual distinctions of responses to CO2 during controlled mechanical ventilation are result of the voluntary motor control.

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We compared respiratory parameters during natural and self-controlled mechanical breathing to investigate mechanisms of respiratory control in alert humans. The self-control of mechanical breathing is realised manually: duration and velocity of air flow are controlled by left and right hands, resp. In this case, the respiratory afferent information is used to control activity of hand muscles but not of breathing muscles. The findings show that lung ventilation during self-controlled mechanical breathing increases by 7.5 l/min. at resting, by 6.3 l/min. during an exercise, as compared with the natural breathing. The increase in the lung ventilation occurs on account of an increase in the tidal volume but the frequency of the self-controlled mechanical breathing tends to be lesser at resting and was statistically significantly lower in exercise that at natural breathing. The exercise increases the lung ventilation by 13.0 l/min. at natural breathing and by 11.8 l/min. during self-controlled mechanical breathing. The findings suggest that the increased lung ventilation during self-controlled mechanical breathing is connected with creation of a new movement skill, and the modified pattern of self-controlled mechanical breathing is caused by a process of cortical transformation of respiratory afferents signals to efferent signals towards the hand muscles.

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To improve methods of offsetting the hemodynamic shifts in microgravity, applicability of breathing at negative pressure (BNP, pressure relief by -5.0 cm of water column) during inspiration and expiration was assessed in acute experiments with unconscious cats tilted head-down (-30 degrees). Direct measurement of pressure in v. cava superior and v. jugularis externa using a catheter revealed a concurrent significant (p < 0.05) growth of the parameter which should be considered a sign of impeded venous outflow from the craniocervical vessels. BNP added to the sucking effect of the thoracic cavity (the siphoning effect) and led to more massive venous outflow from cephalic vessels as evidenced by pressure drop in the jugular vein and v. cava superior to the values determined in the basic horizontal position. However, BNP did not significantly alter arterial hemodynamics, respiration pattern or gas exchange. Data of the investigation attest effectiveness of this method of moderating blood flow to the cat's head during HDT and possibility to apply it in the zero-g environment.

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In anaesthetised cats, antiorthostatic posture of the body with an inclination angle of 30 degrees increased pressure in the vena cava superior and in jugular vein. The rest of the cardio-respiratory parameters were changed insignificantly. Physical and physiological mechanisms of the blood regional redistribution in alteration of the body gravitation orientation, are discussed.

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The subjects were given the possibility to control the capacity of the artificial ventilation apparatus (AVA) at resting and during physical work. The subjects were able to find such a level of the artificial ventilation when he or she could delay natural respiratory movements. The subjects seem to orient themselves to afferents from the chemoreceptors in this task. The subjects could not delay the respiration during physical work, obvious hypocapnia being preserved at that.

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In divers, breathing with artificial gas mixtures of 14.3 g/l density, the maximal lung ventilation and the maximal velocity of forced expiration decrease along with an increase in the mixture density. The decrease of these parameters is unrelated to nitrogen anesthesia or exhaustion of respiratory muscles. The findings suggest that the value of both these parameters is only limited by expiratory dynamic compression of respiratory pathways.

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In healthy subjects, patterns of inhalation and exhalation durations during growing hypercapnia were studied in free breathing and under the effect of resistive inspiratory resistance 20 and 35 cm H2O/1/sec. Pattern of the inhalation duration was divided into two ranges: the inhalation elongated in the first range and shortened in the second one. The border between these ranges corresponded in free breathing to CO2 tension of exhalation terminal portion (PETCO2)--47.2 +/- 1.0 mm Hg (M +/- m). The 1st range was found in 2/3 of cases in the exhalation duration pattern. Under the effect of additional inspiratory resistance, the border between the two ranges of inhalation pattern shifted towards greater PETCO2 values and was 51.0 +/- 1.0 mm Hg for the greater resistance. The 1st range was found in 1/3 of cases in the exhalation duration dynamics. The shift of the border between the ranges of the inhalation duration pattern occurring in breathing with a resistive load in the course of growing hypercapnia seems to result from an augmentation of cortical effects upon breathing and/or weakening of afferent influences from the lung stretch receptors under these conditions.

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