Diuretic induced change in lung water assessed by electrical impedance tomography

Monitoring patients with left ventricular failure can be difficult. Electri cal impedance tomography (EIT) produces cross-sectional images of changes i n the impedance of the thorax. We measured changes in the electrical impeda nce of the lung in nine volunteers following a diuretic challenge. The hypo thesis was that lung impedance would increase with diuretic induced fluid l oss. Heart rate, blood pressure and urine output were also recorded. After diuretic the mean urine output was 1220 mi compared with 187 mi after place bo. Following diuretic administration, mean thoracic impedance increased by 13.6% (p < 0.01) and lung impedance increased by 7.8% (p < 0.05). Taken as a group there was a correlation between overall impedance change and total urine output. However, for each individual, the time course of change in i mpedance and urine output did not correlate significantly. Our findings sho w that EIT may offer a better guide to the response of the lung to diuretic treatment than simply measuring urine output. The urine output is neither specific nor sensitive in the assessment of lung water. Mean lung impedance , however, is largely determined by lung water The study showed that lung i mpedance can be recorded at supra-normal values. EIT may help in the manage ment of patients with excess lung water.