The Science Journal of the American Association for Respiratory Care

2004 OPEN FORUM Abstracts

ELECTRICAL IMPEDANCE TOMOGRAPHY COMPARED TO COMPUTERIZED TOMOGRAPHY IMAGING OF RADIOLOGIST-CONFIRMED PULMONARY PATHOLOGY.

Amir Ghiassi MD, Alexander Adams RRT, MPH, Ives De Chazal MD, Dana Simonson BS, John Marini MD. HealthPartners/Regions Hospital, St.Paul, MN.

Background: Computerized Tomography (CT) provides high-resolution images of static pulmonary pathoanatomy. Knowledge of dynamic respiratory activity such as regional ventilation can only be inferred by CT images. Electrical impedance tomography (EIT) is a portable (bedside) monitor that produces active, 2-dimensional video imaging of ventilation by displaying a color grid via impedance changes of aerated vs. non-aerated tissue. Our goal was to compare the impedance change measurements by EIT with pulmonary pathology confirmed from CT imaging.

Methods:
Fourteen (14) patients with radiologist-confirmed distinct regions of pulmonary pathology were identified for EIT interrogation.
EIT was recorded at the patients' bedsides by applying 16 electrodes affixed circumferentially at the axilla level and obtaining 5-10 minutes of video imaging.

Results:
The mean impedance
change for regions of interest were: normal: 0.45, effusion: 0.002, infiltrate: 0.05, fibrosis: 0.011, mass: 0.0001.
Differences in impedance changes between normal and CT-identified pathology were significant (p<0.01). Note the CT and EIT images (below) illustrating unilateral pathology with ventilation seen in the contralateral lung field.

Conclusions:
For regions of pulmonary pathology where ventilation should be diminished according to CT, EIT imaging verifies that impedance change (ventilation) is minimal. EIT is a bedside device that can monitor regional lung ventilation. Limitations included compromised image quality in patients with excessive adipose tissue and less resolution than CT imaging.









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