A new FOT set-up for the assessment of respiratory system mechanics in mechanically ventilated infants

The assessment of respiratory system mechanics in mechanically ventilated newborns would help in tailoring the ventilatory settings. The Forced Oscillations Technique (FOT) is a non-invasive method for the measurement of the mechanical properties of the respiratory system. The aim of the present work was to develop a measurement set-up suitable to apply FOT in mechanically ventilated newborns. Forced oscillations were generated by a servo-controlled linear motor connected to the inspiratory line of the ventilator. Pressure and flow were measured at the inlet of the tracheal tube and used to compute impedance. The set-up was tested on a mechanical analog of the infant´s respiratory system showing good agreement with a traditional FOT set-up. The performance of the system was not influenced by the positive pressures generated by the ventilator. Finally, the system was well tolerated by 5 preterm babies and the measurements allowed to track changes in respiratory mechanics associated to changes in the pressure delivered by the ventilator.