Performed as a prospective case-control crossover trial of NAVA and SIMV (PC) PS, differences of impedances were assessed by segmentography using the Angelie→ device. Ventilatory monitoring has been mainly limited to overall information and radiation-associated imaging methods without real-time information of regional dynamic lung mechanism. Therefore, as a bedside tool, the AngelieⓇ segmentography device is simple to implement in children; causing no distress during electrode placement or skin irritation. As a case-control trial, each child served as its own control to reduce interpersonal differences. By further performing a crossover of NAVA and SIMV (PC) PS, potential influences of each initial ventilation mode were presumably diminished. Recruitment of dependent lung areas during spontaneous ventilation has been documented by various authors (18, 19). Our study design allowed for conclusions to be drawn from the reduction and vertical shift of impedance from transthoracic to lower lung segments during NAVA in comparison to SIMV (PC) PS. This effect has shown to be particularly pronounced in NAVA ventilation, by improved patient-ventilator synchronization, which can be attributed to a neurally-driven trigger mechanism.(4, 8–10, 20) However, it could also be assumed that this shift of impedance was exaggerated due to the lack of segmental data in some children. When excluding data measured by single electrodes, the aforementioned vertical shift was shown to be less pronounced. In our analysis, neither VT, PEEP or minute volume differed between NAVA and SIMV (PC) PS. Documented ventilatory settings of this present study, therefore, were comparable to a recent study by Baez Hernandez et al that reported no change of VT during NAVA ventilation(4). However, other interventions comparing NAVA and conventional ventilation in pediatric patients have reported decreased PIP levels on NAVA.(17, 20, 21) Some authors have described reduced VT in NAVA-ventilated children (17) and increased respiratory rates when compared to pressure-supported ventilation.(21) Ventilation mode did not seem to impact total electrical impedance in our study. Furthermore, no differences in total, vertical or horizontal impedance were detected irrespective of whether NAVA or SIMV (PC) PS was the first ventilation mode. Throughout all crossover sequences, no differences in total impedance concerning ventilation modes were observed. However, there was a difference in vertical impedance after the first and second changes between NAVA and SIMV (PC) PS. Summarizing these results, measured by a case-control trial with a crossover of two ventilation modes, electrical impedance segmentography did not appear to reliably measure changes of impedance between NAVA and SIMV (PC) PS, as various studies have also shown performing different methods.(17, 22, 23) A recent study utilizing the same EIS monitoring system on healthy, non-sedated and spontaneously-breathing infants reported technical and clinical difficulties in obtaining reliable impedance measurements and described a high patient dropout of 33%.(14) Children of our current study, however, were all intubated and sedated; hence, individual measurement biases, such as movement, could be ruled out. Nevertheless, impedance segmentography has shown to be a useful tool in spontaneously-breathing four year-olds with bronchopulmonary dysplasia for segmental evaluation after inhalation of salbutamol.(24) Nevertheless, singular segmental impedance data was not consistently measurable in our cohort. Data was particularly lacking when measuring the apical sections. In upper right segments, electrical impedance could only be measured in half of our children. By its crossover design, initial data from three children with few or no segmental measurements in the calculation of relative differences were included. When excluding these children from the analysis, in whom at least two segments accounted for less than four percent of total impedance, a segmental shift of distribution in impedance was found, similar to the results of Reiterer et al.(14) Optimal placement of the electrodes, therefore, should be highlighted since the lack of a segmental impedance measurement was potentially caused by the use of single electrodes. The butterfly electrode ensures equal distance between each of the incorporated electrodes. Since half of our study population previously underwent extensive heart surgeries, only single electrodes could be used. In these patients, the central electrode was placed on one side (on the left side) of the scar. Therefore, interference with correct and comparable measurements cannot be ruled out completely as the measuring area appears to be displaced (Fig. 5). On the other hand, it should be mentioned that only one size of butterfly electrodes are available. Size-adjusted electrodes for different patients would be preferable to increase accuracy of segmental data. By not excluding patients with measurements performed by single electrodes, it could be shown that the application of butterfly electrodes is limited in indication and children’s size. Furthermore, this also underlines the limitation of the use of single electrodes due to a potentially altered measuring area. Further, segmentography data performed by AngelieⓇ could mainly be measured in children weighing more than 3500 grams. One reason for this could be the amount of lung tissue between segmental electrodes, allowing a more distinctive differentiation between each sector and minimizing interference. Increased VT might be the leading cause of these lack of measurements. In contrast to EIS, EIT provides impedance changes of the cross-section of the thorax. Studies of EIT have provided highly-reliable impedance data; also in smaller infants.(13, 25) Although our study population in relation to age and weight, as well as the median days of PICU stay were inhomogeneous, it should be pointed out that all children underwent the same length of intervention. On the basis of a sensitive study population, the time period of intervention for each child was kept to a minimum. Applied and investigated ventilation techniques, however, are known to be clinically beneficial when patients are ventilated for longer periods.(2, 8, 10) For patients requiring long-term ventilation, EIS may therefore be a useful device for dynamic continuous monitoring. Immediate benefits of personalized ventilatory strategies can result when using this simple-to-apply bedside tool measuring lung impedance.