Regional Ventilation by Electrical Impedance Tomography* A Comparison With Ventilation Scintigraphy in Pigs Jose ´ Hinz, MD; Peter Neumann, MD, PhD; Taras Dudykevych, DIng; Lars Goran Andersson, MD; Hermann Wrigge, MD; Hilmar Burchardi, MD, PhD; and Goran Hedenstierna, MD, PhD, FCCP Study objective: The validation of electrical impedance tomography (EIT) for measuring regional ventilation distribution by comparing it with single photon emission CT (SPECT) scanning. Design: Randomized, prospective animal study. Settings: Animal laboratories and nuclear medicine laboratories at a university hospital. Participants: Twelve anesthetized and mechanically ventilated pigs. Interventions: Lung injury was induced by central venous injection of oleic acid. Then pigs were randomized to pressure-controlled mechanical ventilation, airway pressure-release ventilation, or spontaneous breathing. Measurements and results: Ventilation distribution was assessed by EIT using cross-sectional electrotomographic measurements of the thorax, and simultaneously by single SPECT scanning with the inhalation of 99m Tc-labeled carbon particles. For both methods, the evaluation of ventilation distribution was performed in the same transverse slice that was approximately 4 cm in thickness. The transverse slice then was divided into 20 coronal segments (going from the sternum to the spine). We compared the percentage of ventilation in each segment, normalized to the entire ventilation in the observed slice. Our data showed an excellent linear correlation between the ventilation distribution measured by SPECT scanning and EIT according to the following equation: y  0.82x  0.7 (R 2  0.92; range, 0.86 to 0.97). Conclusion: Based on these data, EIT seems to allow, at least in comparable states of lung injury, real-time monitoring of regional ventilation distribution at the bedside. (CHEST 2003; 124:314 –322) Key words: regional ventilation; thoracic electrical impedance tomography Abbreviations: APRV = airway pressure release ventilation; CPAP = continuous positive airway pressure; EIT = electrical impedance tomography; f-EIT = functional electrical impedance tomography; EVLWI = extravascular lung water index; Fio 2 = fraction of inspired oxygen; PCV = pressure-controlled ventilation; SPECT = single photon emission CT; Vreg = registered volume; Vt = tidal volume E lectrical impedance tomography (EIT), which was developed in the early 1980s by Barber and Brown, 1 generates cross-sectional images of the im- pedance distribution within a measured object. The basic principle of EIT is based on an alternate- current injection and voltage measurement via sur- face electrodes. If surface electrodes are placed around the thorax, changes in the electrical imped- ance during ventilatory maneuvers parallel to changes of aeration within the lungs can be mea- sured. This enables the measurement of regional ventilation. EIT has been used increasingly as an experimental, noninvasive, lung-imaging tech- nique. 2–14 EIT has been shown to detect physiologic events related to anatomic settings. 2,5,8,15 Validation of the technique by an established clinical method, *From the Department of Anesthesiology, Emergency, and Intensive Care Medicine (Drs. Hinz, Neumann, Dudykevych, and Burchardi), University of Go ¨ ttingen, Go ¨ ttingen, Germany; the Department of Clinical Physiology (Drs. Andersson and Hedenstierna), University of Uppsala, Uppsala, Sweden; and the Department of Anesthesiology and Intensive Care Medicine (Dr. Wrigge), University of Bonn, Bonn, Germany. This study was supported by grants from the Swedish Medical and Technical Research Councils (5315 and 299-2000-688), the Swedish Heart and Lung Foundation, and departmental funds. Manuscript received July 11, 2002; revision accepted January 29, 2003. Reproduction of this article is prohibited without written permis- sion from the American College of Chest Physicians (e-mail: permissions@chestnet.org). Correspondence to: Jose ´ Hinz, MD, Department of Anesthesiol- ogy, Emergency, and Intensive Care Medicine, Georg-August- University, Robert-Koch-Str 40, D-37075 Go ¨ ttingen, Germany; e-mail: mail@josehinz.de 314 Laboratory and Animal Investigations Downloaded From: http://publications.chestnet.org/pdfaccess.ashx?url=/data/journals/chest/21996/ on 06/16/2017