Regional ventilation and perfusion assessed by electrical impedance imaging

Electrical impedance images of the chest of a dog were made while ventilating the lung unilaterally using a tracheal divider. Admittivity of the lungs decreased with inspiration only on the ventilated side, to an extent proportional to tidal volume. During breath-holding, a Swan-Ganz catheter balloon was inflated in a major branch of the pulmonary artery, diverting flow from a substantial pulmonary segment. The phasic admittivity signal in one region of interest in the chest image increased abruptly when the occlusion was released. In a second region in the same images, a simultaneous decrease in admittivity was seen. We conclude that regional ventilation and perfusion can be assessed in impedance images.