[The physiological analysis of the possible reasons of hypoxemia in weightlessness].

In spaceflight at cosmonauts decrease of oxygen partial pressure in capillary blood on 12-30% in comparison with preflight values is revealed. The analysis of the possible reasons and mechanisms of hypoxemia in weightlessness is carried out. On the basis of this analysis the conclusion becomes that the principal cause of oxygen partial pressure decrease in blood of cosmonauts at microgravity, with the big degree of probability, is venoarterial bypassing. It is connected with increasing of venous blood passage through lungs, without full gas exchange in capillaries of small circulation circle.