Simplified Model of the Impedance of the Thorax

Медицинские приборы. Разработка и применение.Джон Г. Вебстер, Джон В. Кларк мл., Майкл Р. Ньюман, Валтер Х. Олсон и др. 652 стр., 2004 г.

In a very simple model, the impedance of the thorax can be considered to be divided into two parts: the impedance of both tissue and fluids, as illustrated in Figure 25.5. If the patient does not breathe, all components forming the impedance of the thorax are constant, except the amount and distribution of blood.
The amount of blood in the thorax changes as a function of the heart cycle. During systole, the right ventricle ejects an amount of blood into the lungs which equals the stroke volume. At the same time blood flows from the lungs to the left atrium. The effect of these changes in the distribution of blood in the thorax as a function of the heart cycle can be determined by measuring the impedance changes of the thorax. The problem is to determine cardiac stroke volume as a function of changes in thoracic impedance.

Fig. 25.5 Simplified cylindrical model of the average thorax containing a uniform blood and tissue compartment for determining the net torso impedance.

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