Volumetric dynamics of respiration as measured by electrical impedance plethysmography

Abstract

Electrical resistive impedance changes of the chest related to pulmonary air volumes were quantitatively evaluated in ten normal male adults. A four-electrode, 100-kc, electrical impedance plethysmograph was used for these determinations. A 13.5-liter Collins respirometer was used to measure changes in pulmonary gas volume. In all studies reported the electrodes were positioned on the posterior aspect of the thorax. The current was delivered to the outer pair with one attached to the neck and the other below the level of the diaphragm. The voltage drop related to variations in resistance was detected between the inner two electrodes at a constant length of 30 cm. Inspiration and expiration were associated with changes in electrical resistive impedance. Calculations of changes in pulmonary gas volumes were based on electrical variations associated with respiration. The calculated values closely approximated recorded volumes on the spirometer for values of 100–2,500 ml. This technique would eliminate carbon dioxide absorbents, nose clips, conventional airway hindrances and have adequate frequency response for a normal range of test conditions. Some of the limitations in the practical application of the system currently under study are discussed. pulmonary air volume determination; resistive impedance; measurements of the chest; pulmonary function; respiration Submitted on April 17, 1963