[Effect of short-term antiorthostatic hypokinesia on the pressure in various parts of the healthy human cardiovascular system].

Before and after 5-day head-down tilting (-4.5 degrees) blood pressure was measured in different cardiovascular compartments by the technique of selective catheterization: the upper bulb of the internal jugular vein, superior and inferior venae cavae, hepatic, renal and iliac veins, right atrium and right ventricle, coronary sinus, pulmonary and radial arteries. After exposure the pressure in extrathoracic vessels increased by 1.4 mm Hg on the average: in the internal jugular vein it rose by 1.7 mm Hg whereas in the iliac vein by 1.0 mm Hg. The blood pressure in the intrathoracic vessels of the systemic circulation increased, as a rule, by no more than 0.5--0.8 mm Hg. This elevation was characteristic of diastolic regions of the pressure curve (x- and y-collapse). The pressure in pulmonary vessels--pulmonary artery and left atrium--showed a trend for a decrease of 1.3 mm Hg. The factors that may be responsible for the dissimilar changes of pressure in different cardiovascular compartments under the influence of short-term simulated weightlessness are discussed.