Systolic and minute volume of a blood-groove

The basic physiological function of heart is forcing blood in vascular system. The quantity of the blood which is thrown out by ventricle of heart in minute is one of the major parameters of a functional condition of heart and is called minute volume of a blood-groove, or minute volume of heart. It is identical for right and left ventricle.

When the person is in a condition of rest, the minute volume is equal to on the average 4,5-5,0 litres. Having divided minute volume on number of reductions of heart in a minute, it is possible to calculate systolic volume of a blood-groove. At a rhythm of cardiac reductions 70-75 in a minute systolic volume is equal 65-70 ml of blood. Definition of minute volume of a blood-groove of the person is applied in a clinical practice. The most exact way of definition of minute volume of a blood-groove at the person has been offered by Fick (1870). It consists in indirect calculation of minute volume of heart which makes, knowing: 1) a difference between the maintenance of oxygen in arterial and venous blood; 2) volume of the oxygen consumed by the person in minute. We shall admit, that in 1 mines through lungs in blood 400 ml of oxygen have acted, everyone 100 ml of blood absorb 8 ml of oxygen in lungs; hence, to acquire all quantity of oxygen, which has acted through lungs in blood for a minute (in ours example - 400 ml), it is necessary that through lungs has passed 100*400/8 = 5000 ml of blood. This quantity of blood makes minute volume of a blood-groove, which in this case is equal to 5000 ml.

For definition minute and consequently systolic volume other methods are developed. Now widely apply some paints and radioactive substances. The substance entered into a vein passes through the right heart, a small circle of blood circulation, the left heart and acts in an artery of the big circle where is defined its concentration. First it wavy accrues, and then falls. Through some time when the portion of blood contained its maximal quantity, again will pass through the left heart, its concentration in arterial blood again increase.

Time from the moment of introduction of substance prior to the beginning of circulation is measured also a curve of change of concentration (increase and a loss) investigated substance in blood can be received. Knowing quantity of the substance entered into blood and containing in arterial blood, and also time which has demanded on passage of all quantity of entered substance through system of blood circulation, it is possible to calculate minute volume (MV) a blood-groove under the formula: MV=60∙I/C∙T

Where I - quantity of the entered substance in milligrams; C - its average concentration in milligrams on 1 litre, calculated by a curve of cultivation; Т - duration of the first wave of circulation in seconds.

Now the method integrated rheography is offered. Rheography (impedancemetry) is a method of registration of electric resistance of tissues of a human body to an electric current passed through a body. Currents of ultrahigh frequency and very small force are used. Resistance of blood is much less, than resistance of tissues; therefore increase filling of the tissues by blood considerably reduces their electric resistance. If to register total electric resistance of a thorax in several directions, then it periodic sharp reduction arise during the moment of emission by heart in an aorta and a pulmonary artery of systolic volume of blood. Thus the size of reduction of resistance is proportional to size systolic volume.Remembering the formulas considering the sizes of a body, feature of the constitution it used, etc., it is possible to define size of systolic volume of blood by rheographic curves, and having multiplied it on number of cardiac reductions it is possible to receive value of minute volume of heart.

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