Comparing square root method of measuring the cardiac output by means of aortic impedance change component to Kubicek's method.

Purpose: The aim of this study is to explore a calculated method used to measure the cardiac output using the aortic impedance change component of reconstructed impedance cardiography.

Methods: Routine impedance cardiography was measured using Kubicek's method with four ring electrodes. The thoracic mixed impedance changes were measured by six leads, which consisted of 15 electrodes.

Analyzing the formation of normal and abnormal O waves in thoracic impedance graph using the impedance change components for aorta, blood vessels in lung and ventricles.

Background: Many measurements of thoracic impedance graph show that the small C wave and big O wave appear often for patients with cardiac insufficiency, and the O/C ratio is bigger. And for the normal body, especially a younger one, the bigger O wave may also appear. But since the amplitude of the C wave of a normal body is bigger, the O/C ratio is smaller.

Studies on separating the impedance change components of blood vessels and ventricles in thorax from mixed impedance signals on chest surface.

Purpose: The aim of the present study is to separate the impedance change components of the blood vessels and ventricles in thorax from the mixed impedance signals detected on the chest surface.

Methods: The mixed impedance signals on the chest surface are measured with a 15 electrode lead system. The thoracic impedance equations are established and solved iteratively with the algebraic reconstructed technique.

Mechanism of the formation for thoracic impedance change.

The purpose of this study is to investigate the mechanism of the formation for thoracic impedance change. On the basis of Ohm's law and the electrical field distribution in the cylindrical volume conductor, the formula about the thoracic impedance change are deduced, and they are demonstrated with the model experiment. The results indicate that the thoracic impedance change caused by single blood vessel is directly proportional to the ratio of the impedance change to the basal impedance of the blood vessel itself, to the length of the blood vessel appearing between the current electrodes, and to the basal impedance between two detective electrodes on the chest surface, while it is inversely proportional to the distance between the blood vessel and the line joining two detective electrodes.