THE REPEATABILITY AND VARIABILITY OF ELECTRICAL-IMPEDANCE TOMOGRAPHY INDEXES OF PHARYNGEAL TRANSIT-TIME IN NORMAL ADULTS

Two electrical impedance tomography (Err) indices of pharyngeal transi t time have been repeatedly measured in 20 normal adults. The time cou rse of change in pharyngeal conductivity whilst swallowing 5, 10 and 2 0 mi boluses was expressed either as a full width at 20% maximum (FW20 ) or as a full width at 50% maximum (FW50): the latter could be satisf actorily measured more frequently. Mean coefficients of variation for FW20 and FW50 tended to decrease with increasing bolus volume but this was statistically significant only for FW50 in men. FW20 and FW50 wer e significantly shorter in men than women and increased with increasin g age. FW50 was significantly smaller when larger bolus volumes were s wallowed. FW50 was significantly shorter when low-conductivity fluid w as used and there was an insignificant trend for it to be longer with electrodes in the highest position. The amplitude of the conductivity change recorded was significantly affected by all factors studied apar t from age. If EIT is to be used as a technique for monitoring changes in pharyngeal transit time in patients with neurogenic dysphagia, rep eat examinations should be performed under the same conditions and, if possible, large bolus volumes should be used.