The Science Journal of the American Association for Respiratory Care

2006 OPEN FORUM Abstracts

THE DEVELOPMENT OF LIPOPOLYSACCCHARIDE INDUCED LUNG INJURY IN SWINE CAN BE MONITORED BY ELECTRICAL IMPEDANCE TOMOGRAPHY

Marcia Volpe RPT, Alexander Adams FAARC, RRT, Joel Holger  MD, John Marini MD, Marcelo Amato MD. Healthpartners/Regions Hospital, St. Paul, MN and Sao Paulo, Brazil.



Background: Electrical impedance tomography (EIT) provides dynamic images of ventilation by comparing impedance differences between electrodes equi-positioned around the mid-chest. Determining the degree and localization of gas/tissue ratios by EIT allows active monitoring of the primary regions of pathophysiology and could directly assist in PEEP titration. In a model of progressive lung injury induced by lipopolysaccharide (LPS) infusion in swine, EIT was applied to assess regional ventilation as injury developed.

Methods: Six (6) juvenile swine were deeply anesthetized in the supine position for a LPS shock model study. A low-frequency electrical current was transmitted between leads (32) positioned around the mid-chest to create continuous impedance mapping of ventilation. An initial normal-ventilation image was obtained and, during LPS infusion at 20 mgm/kg/hr for 5 hours, EIT images were obtained at 30 min intervals. Subsequent analysis of the images compared identical regions.

Results: A significant decline in PaO2/FIO2 from 450 to 170 confirmed the developing lung injury. From an analysis of regional functional impedance differences, ventilation shifted from a relative balance between ventral and dorsal regions to predominantly ventral ventilation (figure). A decrease in relative impedance change during the study and an increase in WW/DW indicate that dorsal edema formation caused the shift.

Conclusions: Using continuous EIT imaging, a ventral/dorsal image comparison can monitor developing lung injury.

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