Name: Henk Smit


CompanyName: VU Acad. Medical Center

Country: The Netherlands

H.J. Smit, L.H. Handoko , A. Vonk Noordegraaf, Th.J.C. Faes*, P.E. Postmus, P.M.J.M. de Vries, A. Boonstra. Departments of Pulmonology and Clinical Physics*, Vrije Universiteit Medical Center, Amsterdam, The Netherlands.
Electrical Impedance Tomography (EIT) has proven to be a non-invasive
imaging technique using impedance to visualise and measure blood volume changes
in the lung. As an example for clinical applications, EIT has been proposed as
a method to monitor dynamic changes in the pulmonary vascular bed. Condition
for repeated measurements, under equal circumstances, is that variation in
results is limited.
In this study we examined the reproducibility of EIT (Mark I, Sheffield, England)
in the measurement of pulmonary circulation. Reproducibility between two
different researchers and within the same researcher was investigated. Twenty-four
healthy volunteers and six patients participated in this study. The 16 electrodes
were equidistantly positioned in the third intercostal space by the first
investigator. Subjects lay in supine position, with their arms above their head.
Two hundred heart cycles were averaged to obtain one data set. EIT measurements
were performed four times; for reproducibility purposes, only the first two
measurements were used. Then, the electrodes were removed. After 30 minutes,
new electrodes were applied and EIT measurements were repeated in duplicate by
a second investigator. Next, the protocol was repeated once more by the first
Analysis was performed with three different Regions Of Interest (ROI). Results
were expressed as reproducibility coefficient (r). Furthermore, correlation
between age, respectively body mass index (BMI) and impedance change was
investigated. Finally we investigated whether there is a significant difference
in pulmonary perfusion related impedance changes ( Zsys) between groups
concerning pulmonary disease and gender.
ROI Whole circle Inner half circle Contour
Same investigator r = 0.96 r = 0.89 r = 0.97
2 Different investigators r = 0.95 r = 0.89 r = 0.96

ROI Whole circle Inner half circle Contour
Age r = -0.65 r = -0.76 r = -0.70
Body Mass Index r = -0.62 r = -0.57 r = -0.63

ROI Whole circle Inner half circle Contour
 Zsys Healthy versus Pulmonary disease P = 0.0002 P = 0.0004 P = 0.0002
 Zsys Male versus Female P = 0.024 P = 0.15 P = 0.05

We conclude that the inter and intra investigator reproducibility for pulmonary
perfusion measured by means of EIT is quite high. These results also indicate
that many factors influence the EIT signal such as age, BMI, gender and
pulmonary pathology. This encourages further research for (clinical)
implications of EIT.

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