The Electrical Resistivity of Lung Tissue Filled Either with Air or with Fluid
The cardiac electrical field at the body surface, produced by the heart generator, is decisively influenced among others by the electrical resistivities of the thoracic tissues. Probably, the lungs play a special role by surrounding and shielding the heart, their resistivity being 4 times that of the myocardium (Rush and Nelson, 1976). Measurements of the resistivity of lung tissue in adult dogs resulted in different values depending on the degree of aeration of the lungs (maximal inspiration versus maximal expiration (Rush et al., 1963)). This result could be seen in conformance with certain changes in the cardiac electrical field of human adults, which appear as a function of different respiratory phases. Concerning the lungs, the underlying mechanism is presumed mainly to be found in hemodynamic effects, resulting in an increase of electrical conductivity by an increase of pulmonary blood flow during deep inspiration, the amount of air within the lung tissue supposed to be of less importance (Ruttkay-Nedeck£, 1976). The prenatal development of mammals seems to provide a natural model for the study of the mechanisms underlying the physiological respiratory variability of the cardiac electrical field.
KeywordsElectrical Resistivity Lung Tissue Foetal Lung Pulmonary Blood Flow Electrode Spacing
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