DETECTION OF CHANGES IN INTRATHORACIC FLUID IN MAN USING ELECTRICAL-IMPEDANCE TOMOGRAPHY

1. The Sheffield electrical impedance tomography system produces infor mation on changes in the distribution of resistivity within tissue. We report on the assessment of electrical impedance tomography in monito ring changes in lung resistivity during a fluid challenge in normal ma n. 2. Eight normal subjects were studied. Electrical impedance tomogra phy recordings were made at three different lung volumes before, durin g and after the intravenous infusion of 1 litre of 0.9% NaCl (saline). 3. The mean fall in lung resistivity during the infusion was -22% at total lung capacity (range -10% to -28%), -24% at tidal breathing (-15 % to -37%) and -11% at residual volume (-5% to -19%) (P<0.05 mean pre- infusion resistivity compared with the nadir value after infusion, Wil coxon). 4. These changes in lung resistivity were probably due to a co mbination of a fall in haematocrit and an expansion of pulmonary blood volume.