A comparison of ventilatory and cardiac related changes in EIT images of normal human lungs and of lungs with pulmonary emboli.

EIT images have been recorded from the upper thorax of 10 normal subjects and from two patients with pulmonary emboli. The Sheffield Mk2 system was used to obtain the EIT images during quiet tidal breathing and the images were then analysed to extract the cardiac and respiratory related components. In the 10 normal subjects the mean measured change in resistivity during tidal breathing was 9% (SD 3%) with no significant difference in four lung regions. The mean changes during the cardiac cycle were different in the four regions, ranging from -0.9% to -2.6%. The two patients showed very different cardiac related changes from those found in the normals in the posterior lung regions. The sign of the changes was positive, whereas it was negative in the normals. The changes in the anterior lung regions were within the range found in our normal group.