Estimation of pressure drop in pediatric endotracheal tubes during HFPV

High-frequency percussive ventilation (HFPV) is a ventilation modality which has been proved useful as an alternative to conventional mechanical ventilation. In clinical practice the ventilator measures the pressure that represents the sum of the pressure drop due to the endotracheal tube (ΔPEET) and the pressure dissipated to inflate lung. From the clinical point of view, it is of paramount importance to estimate the real amount of ΔPEET. This study aimed at identifying in vitro the most adequate model and parameters for estimating ΔPEET of pediatric endotracheal tube during HFPV, under different working pressures, percussive frequencies and resistive and elastic lung loads. The results show that it is possible to estimate ΔPEET in pediatric endotracheal tubes by using a simple Blasius’ model, considering the presence of inertance. The Blasius’ model presents the same estimation error as Rohrer’s model and its coefficients result largely independent from ventilator settings and lung loads.