Electrical Impedance Tomography for Identification of Optimal Positive End-expiratory Pressure in Newborn Infants

EIT is the measurement of impedance changes of the lung against the flow of alternating electrical currents applied to the thorax. The signal of the electrodes is transmitted to a monitor, which enables real-time assessment of lung aeration and changes in lung volume. EIT is able to reconstruct impedance changes with a high temporal resolution and allows calculation of tidal volumes, relative stretch of lung tissue and areas of poor ventilation. Areas with impedance changes of \< 10 % of the maximum impedance changes are called 'Silent Spaces'.

FOT enables non-invasive assessment of lung mechanics using sound waves to inform about the respiratory impedance of the respiratory system (Zrs). Reactance of the respiratory system (Xrs) as part of Zrs is a surrogate measure of compliance of the respiratory system. Xrs was previously used to identify optimal PEEP level, i.e., the PEEP at highest compliance equivalent, in newborn infants using a setup requiring research-specific hardware and software. The FOT module integrated in the commercially available neonatal ventilator is routinely used. FOT measurements are performed twice at each PEEP level to assess the reproducibility of the measurements.

SOPI is assessed non-invasively and calculated from standard monitoring parameters such as PEEP, fraction of inspired oxygen pressure (FiO2) and peripheral oxyhaemoglobin saturation (SpO2) (PEEP x FiO2 x 100) / SpO2). SOPI is used to provide information on ventilation to perfusion ratio dependent on PEEP level.