Measurement of pharyngeal transit time by electrical impedance tomography.

The feasibility of using electrical impedance tomography (EIT) for measuring pharyngeal transit time has been investigated. Imaging sequences were obtained on the neck in a group of eight healthy subjects when swallowing solutions of different electrical conductivities. The solutions used were aqueous Dioralyte (1.5 S m−1) and tap water (0.04 S m−1). The effects of movement upon the images were large compared with the changes due to the solutions, but these were cancelled by a subtraction technique. The mean value of the EIT pharyngeal transit time prameter was 370 ± 120 ms. EIT has the advantage that repeated measurements could be performed without fear of hazard in contrast to the established technique of video fluoroscopy which involves ionising radiation.