1. Perioperative assessment of regional ventilation during changing body positions and ventilation conditions by electrical impedance tomography 
A. Ukere, A. März, K.H. Wodack, C.J. Trepte, A. Haese, A.D. Waldmann, S.H. Böhm, D.A. Reuter 
British Journal of Anaesthesia 
Volume 117, Issue 2, Pages (August 2016)
DOI: /bja/aew188
Copyright © 2016 The Author(s) Terms and Conditions

2. Fig 1
Schematic illustration of electrical impedance tomography-derived lung function parameters. (a) Relative stretch within the regions of interest (ROIs). Impedance changes during tidal breathing within the ROIs were measured as the difference between the end of inspiration and the end of the preceding expiration. For these impedance changes to be displayed as tidal images, their pixel values needed to be categorized and colour coded. (b) The amplitude of the pixel within the image showing the maximal impedance change or stretch during breathing served as a 100% reference (Ztotal). This amplitude was then divided by 10, which resulted in 10 different amplitude categories (c1 – c10). Depending on its amplitude, each pixel within the lung ROIs was then assigned to one of these categories. To determine the relative contribution (as a percentage) of each one of the 10 stretch categories to the overall tidal volume (Vttotal), the amplitude of each pixel within a given category was multiplied by its relative tidal stretch. From these values, a 10-bar histogram was created, whereby the sum of all 10 categories equalled the total impedance change of the tidal breath. (c) The silent spaces are visualized as grey areas within the ROIs. The blue dotted line marks the ventilation horizon. Silent spaces above the ventilation horizon are called ventral (non-dependent) silent spaces, whereas the areas below are called dorsal (dependent) silent spaces. The blue dot represents the centre of ventilation. (d) Dorsal (dependent) silent spaces and ventral (non-dependent) silent spaces expressed in a bar graph showing the percentage of the categories with the lowest impedance change in relation to the pixel with the highest change in impedance.
British Journal of Anaesthesia  , DOI: ( /bja/aew188)
Copyright © 2016 The Author(s) Terms and Conditions

3. Fig 2
Representative electrical impedance tomography images and electrical impedance tomography-derived parameters of one patient at time points from M1 to M5. Pictograms at the top of the figure symbolize the patient's position. (a) Picture of tidal ventilation within the region of interest. (b) Relative stretch within the region of interest. (c) Ten-bar histogram representing the distribution of stretch within these respective categories. (d) Silent spaces visualized as grey areas within the region of interest. The blue dotted line shows the ventilation horizon. The blue dot represents the centre of ventilation.
British Journal of Anaesthesia  , DOI: ( /bja/aew188)
Copyright © 2016 The Author(s) Terms and Conditions

4. Fig 3
Box plot of perioperative centre of ventilation (CoV) for all time points and for all patients. Boxes indicate 25th–75th percentile, the median is depicted by the line within the box, and the means by the cross. The whiskers mark the 5th and 95th confidence interval. Statistically significant differences (P <0.05) between time points are indicated as follows: *between time points M1 and M2;† between time points M2 and M3;‡ between time points M3 and M4;¶ between time points M4 and M5.
British Journal of Anaesthesia  , DOI: ( /bja/aew188)
Copyright © 2016 The Author(s) Terms and Conditions

5. Fig 4
Perioperative silent spaces with sd for all time points. Statistically significant differences (P <0.05) between time points are indicated as follows: *between time points M1 and M2;† between time points M2 and M3;‡ between time points M3 and M4;¶ between time points M4 and M5.
British Journal of Anaesthesia  , DOI: ( /bja/aew188)
Copyright © 2016 The Author(s) Terms and Conditions