Measurement of Thoracic Impedance and Approximations: A Diagnosis Technique for Clinical Utilization

The purpose of this paper is to facilitate readers and researchers about the implementations and applications of thoracic impedance measurements and approximations for diagnosis of several related disease. In this study two entirely non-invasive approaches and simple assumptions are taken into consideration to measure Transthoracic Electrical Impedance (TEI) and lung volume. In the first method the fluid volume is calculated by considering a predefined curve and anthropometric dimensions of the human thorax, whereas in the second method the thorax is considered a cylinder and cylindrical mathematical standard formulae are being utilized for approximation of lung volume. The thoracic impedance is measured directly by placing the tetra polar electrodes on the right side of human thorax. Right side of the thorax is considered to avoid incorporation of the geometrical aspects and behaviour of heart. Anthropometric dimensions are taken for 6 normal male subjects of sound health. With the help of these parameters the thoracic fluid volume is predicted with two methods. In the first method the thoracic volume has been predicted by considering the thorax as cylinder and by using basic relations of the periphery and volume of the cylinder. Human thorax dimensions are approximated as height and breadth of the cylinder and certain approximations have been adopted. Anthropometric dimensions are being made for the chest at normal resting condition and at breathe hold positions. In both the approaches the difference of measured and predicted impedances and volumes are clearly observable.