[Changes in the blood vessels of the lungs under physical loads at high altitude].

Changes of the pulmonary artery branches in rats at the state of relative physiological rest undergo two stages during the process of individual adaptation for 60 days. The first is characterized with generalized decrease of the lumen and with thickening of the vascular wall as a result of reflectory spasm and edematous swelling of the arteries, the second--with a relative dilatation of the lumen and with decreasing thickness of the vascular wall, as a result of decreasing reflectory spasm and edematous phenomena. The physical load increases the organism's elevated oxygen consumption under conditions of high-altitude, which is increased by itself; this intensifies the function of the pulmonary blood bed. In combination with the edematous phenomena, the wall of the pulmonary artery becomes sharply thickened in the first stage. In the second stage the tissue mechanisms are switched on for satisfaction of oxygen consumption. Therefore, the load on the right part of the heart and on the pulmonary vessels decreases edematous phenomena, the thickness of the wall in the pulmonary artery branches decline, in comparison with the data of the first stage. The thickness of the wall in the first stage is combined with a manifested constriction of the lumen, and the relative thinning of the vascular wall--with dilatation.