The Science Journal of the American Association for Respiratory Care

2010 OPEN FORUM Abstracts

EVALUATION OF ELECTRICAL IMPEDANCE TOMOGRAPHY TO IDENTIFY REGIONAL CHANGES IN VENTILATION ASSOCIATED WITH CHANGE IN SUBJECT POSITION.

Mark Stronati1, Roger Reichenbach1, Rena Laliberte1, Shirley Smith1, Nikolai Pamukov1, Nancy Patel2, Alan Betensley2; 1Respiratory Therapy, Henry Ford Hospital, Detroit, MI; 2Pulmonary and Critical Care Medicine, Henry Ford Hospital, Detroit, MI

BACKGROUND: Electrical Impedance Tomography (EIT) is a non-invasive radiation-free monitoring tool that is capable of monitoring imbalances in regional lung ventilation. Realization of a medical application was detailed in 1984 by Barber and Brown. Using a system of 16 electrodes, plus a reference, low alternating current is injected resulting voltages are measured in a rotating sequence and tomography images are reconstructed. We hypothesized that EIT would be able to demonstrate an increase in the Impedance Ratio (IR) with the change from supine to upright position. METHOD: For data analysis we used ANOVA for repeated measures which assessed differences across breaths and between positions using the IR between anterior and posterior.10 “healthy” subjects were instructed to tidal breathe. We recorded one minute of data for each subject and position, then averaged the means of 5 tidal breaths and calculated a ratio of anterior and posterior ventilation in both supine and standing positions. Table1 illustrates the mean IR for standing and supine positions. RESULTS: We anticipated a regional shift in ventilation from supine to standing position with a corresponding increase in the IR closer to1. Statistically this appeared not to be the case. For our calculations we utilized the tidal variation arbitrary units from the EIT device. Raw data analysis demonstrated the anticipated result for 7 of 10 subjects. We were unable to determine why 3 did not have the same result. Some of the possibilities for not obtaining predicted results could be related to defining, healthy volunteers, anthropometric measures, or other pathological conditions. CONCLUSION: Use of EIT bedside for images of increased ventilation is fairly well documented. In this case EIT was not able to reliably demonstrate the relative decrease in posterior ventilation with position change from supine to standing, using the tidal variation number. Sponsored Research - None