Lower and upper inflection point distribution. Lower and upper inflection points distribution moving from nondependent (region of interest 1, black continuous line) to dependent lung (region of interest 4, black dotted line) at electrical impedance tomography examination. At pressure-impedance/volume curve, the lower inflection point of dependent lung (black hollow circle) is higher compared to the lower inflection points of the remaining regions of interest, while the upper inflection point of nondependent lung (black solid circle) is lower compared to the upper inflection points of the other regions of interest. The opening and closing pressure are lower in nondependent lung compared to the opening and closing pressure in dependent lung. Black line, Pressure-impedance/volume curve of region of interest 1; gray line, pressure-impedance/volume curve of region of interest 2; gray dotted line, pressure-impedance/volume curve of region of interest 3; black dotted line, pressure-impedance/volume curve of region of interest 4.