Modern medical problems of microcirculation and hypoxic syndrome

Abstract

In this paper long known problems of microcirculation are shown, which were solved only during the last 40 years. They are concerned with the velocity and character of the capillary blood flow, the regulation of the capillary blood flow, the role of various vessels in the oxygen transport, the role of leukocytes in physiology and pathology of the capillary blood flow, with the special features of the function of lungs in supplying the whole organism with oxygen and with bioenergetic laws in the development of an organism adaptation to hypoxia. Here we considered a number of the most important medical problems of microcirculation and hypoxic syndrome. A relatively new factor in the capillary circulation is the fact that in the brain and heart capillaries there are sites with pO2 close to zero. They show that the capillary circulation has no central nervous regulation of the blood flow. The blood flow in these organs obeys only occasional oscillations. The new fact is that Krogh's rule about metabolism and oxygen exchange occurring only in the capillaries is abandoned. It is shown that almost 30% of consumed oxygen is delivered to the brain via arterioles, which changes our relation to the capillary circulation as a unique mechanism of the tissue supply with oxygen. The new fact is also the mass adhesion of leukocytes to the walls of microvessels, which results in the occlusion of the vessels followed by the development of the heart and brain ischemia. It was shown for the first time that contrary to previous ideas the alveoli in the lungs are supplied with blood from a powerful network of large microvessels from 20 to 50 microm in diameter rather than from thin arterioles. They make possible the passage of 6-121 of the blood in the norm and during stressed muscle activity--up to 18-231 of blood per minute. The principle is substantiated that during hypoxia only normal supply of an organism with oxygen may result in a complete adaptation of an organism to the deficit of oxygen.