Changes in systemic and regional hemodynamics during intensive muscular activity (experimental study)

Aim. The article deals with evaluating the changes in minute volume of blood circulation and the features of regional hemodynamics in somatic and visceral organs during intensive muscular activity. Materials and methods. Studies were conducted on outbred laboratory dogs (n = 16). At rest and at maximum physical exertion (running on a treadmill to failure), oxygen consumption (VO2), blood gas composition, the minute volume of respiration (VE) and blood circulation (Q) (according to Fick) were determined. The volumetric blood flow velocity in skeletal muscles and visceral organs (qt) was determined by introducing iodine-131-labeled microspheres into the heart cavity. Results. At maximum physical exertion, VO2 significantly increases by 11.7 times, Q - by 5.3 times. The volumetric blood flow velocity significantly (P ≤ 0.001) increases in locomotor (6.2-7.5 times) and respiratory (6.5-8.0 times) muscles. In postural muscles, blood flow does not change. In the myocardium, blood flow increases by 4.5 times and corresponds to changes in cardiac performance. In the adrenal gland, blood flow increases by 1.6 times (p ≤ 0.001), in the thyroid gland, it remains unchanged. In the kidney, blood flow decreases by 21.5%, in the liver by 23.0%, with an increase in the arterial fraction by 56.3% of organs. In organs of the splanchnic region (spleen, organs of the gastrointestinal tract), the volumetric blood flow velocity decreases by 44.9% (P ≤ 0.001). Conclusion. During extreme physical exertion, most of the cardiac output is distributed into the locomotor, respiratory muscles and organs involved in muscle activity, while reducing the volumetric blood flow in the visceral organs. It is postulated that against the background of high oxygen demand and arterial hypoxemia in the somatic and visceral organs, there are competitive relationships for blood flow and the prerequisites for the development of total tissue hypoxia.