It is possible to record changes of volume caused by variations of the blood supply to each lung by measuring the transthoracic electrical impedance. A theoretical study was performed beforehand to define the variations of the impedance of the deep-lying structures. The form, number and distribution of the electrodes were determined by experiments on a model so that only variations of the impedance of the pulmonary parenchyma, and not of the mediastinum, were recorded. In this way the origins of the signals recorded were known. The validity of the method was tested on patients having undergone pneumonectomy and on patients with defects of pulmonary perfusion. Using the data obtained during the preceding experimental studies it was possible to defect perfusion defects caused by pulmonary embolism. Five cases of pulmonary embolism, confirmed by angiography and lung scan, of varying severity and chronicity, are reported. The amplitude of the impedance curve was reduced on the affected side, the difference of amplitude between the two being related to the degree of vascular amputation.
Adult Aged