Fig. 1: From the EIT measurements to the MOR parameter.

a1 EIT impedance sum signal of an LRM. a2 The episode of CDP 19 mbar with the manually selected 30-s interval shaded in gray. b1 Median of the selected 30-s interval at the initial CDP (11 mbar). b2 Median of the selected 30-s interval at CDP open (21 mbar). b3 difference image of (b2, b1) with the black contours surrounding the pixels that exceed the 25% of the maximal value of the difference image. C1 Median of the local minima within a 30-s interval of (a2), filtered using a narrow band-pass filter centered at the HFOV frequency. c2 Median of local minima of the 30-s interval of (a2), filtered using a narrow band-pass filter centered at the HFOV frequency. c3 Difference image between (c1) and (c2), illustrating the regional distribution of EIT-based oscillating tidal volume. Contours mark air-containing regions from (b3), extended by areas where pixel values exceed 50% of the maximum in (c3). d MOR for all CDP levels of the lung recruitment maneuver (inflation blue, deflation black). The gray diamonds at CDP levels lower than the initial CDP are shown to illustrate the MOR change used to define recruitability with respect to MOR. The MOR value corresponding to (c3) is highlighted with a bright blue circle and amounts to 47.1, calculated as 396 multiplied by 0.119. In this example, the MOR gain between inflation and deflation at the initial CDP is 15.4%, meeting the recruitability criterion for MOR. a.u. arbitrary units, CDP continuous distending pressure, EIT electrical impedance tomography, HFOV high-frequency oscillatory ventilation, LRM lung recruitment maneuver, MOR median of oscillatory impedance amplitudes within the aerated region.