Evolution of Views on Physiology of Breathing in Microgravity

The author summarizes the results of own long-term investigations of the human respiratory system onboard space objects. These results were analyzed and compared to the data of other authors who also had studied the breathing system in microgravity. The paper describes the logic of space experiments arrangement, sequence, progressive accumulation of the knowledge about breathing physiology and microgravity. Microgravity alters the structure of pulmonary volumes and respiratory rate and volume; it disturbs biomechanics of the respiratory muscles contraction that may expedite muscular fatigue and weaken the proprioceptive inputs to the respiratory center. The thoracic-abdominal breathing ratio changes for abdominal. Microgravity affects the cosmonaut’s ability to control respiratory movements intentionally and reduces sensitivity of the central respiratory mechanism to endogenous hypoxia and hypercapnia. The magnitude of these deviations as compared to the ground measurements is not critical for cosmonaut’s health and performance. However, in complex they may aggravate the effect of hypoxemia in microgravity, as has been noted by several authors, and be the reason for degradation of physical performance in space mission and, particularly, after landing.