BIOMECHANICS AND REGULATION OF THE EXTERNAL RESPIRATION IN THE CONDITIONS OF 5-DAY DRY IMMERSION
The work was concerned with evaluation of the external respiration function and regulation in healthy human subjects participating in simulation of the microgravity effects by dry immersion (DI). In the baseline data collection period, in DI (days 2 and 4) and after DI completion pulmonary volumes were registered, the ratio of thoracic and abdominal components of quiet breathing and respiratory maneuvers calculated, and parameters of respiration regulation, i.e. length of breath-holding and ability to voluntary control breathing motions, were determined. It was shown that breathing pattern did not undergo gross changes in immersion as compared with pre-DI test data; however, inspiratory reserve volume grew ( р < 0.05) and expiratory RV reduced ( р < 0.01). DI did not alter the ventilation function of lungs; yet, most of the subjects trended to increase the abdominal component of quiet breathing and displayed a statistically significant increase of the parameter during the maneuver made to determine the vital capacity of lungs. Maximum breath-holding, equally in the course of inspiration and expiration in DI, did not differ from baseline values. Accuracy of voluntary breathing control was better in immersion. We believe that similar to microgravity, exposure in DI produces regular alterations of pulmonary RV (partly because of changed body position), thoracic-abdominal ratio in breathing motions, and shifts in voluntary respiration regulation.