Mechanical loads modulate tidal volume and lung washout during high-frequency percussive ventilation

Gas distribution in a two-compartment model ventilated in high-frequency percussive and pressure-controlled modes

“…We based our study on the two-compartment parallel model introduced by Otis et al [21], extending our previous studies [19,20]. In such a model the distribution of the overall flow in the separate branches depends on the impedances of each independent compartment.…”

“…HFPV provides tidal volume as the difference between its pulsatile in-and out-volumes [20]. In all instances, some amount of gas is washed out of the lungs throughout inspiration.…”

“…In all instances, some amount of gas is washed out of the lungs throughout inspiration. Characteristically the performance of the HFPV device varies according to the physiological/ physical feedback of the lung/model, i.e., with its impedance (or its resistive and/or elastic components) [19,20]. So far, some modeling of the interaction between HFPV and lung mechanical characteristics has been reported [19,20], but to our knowledge no two-compartment model with unequal time constants has been tested.…”

“…Ventilation of the mechanical model was provided by two different equipments: (1) HFPV was generated by a volumetric diffusive respirator (VDR-4; Percussionaire Corporation, Sandpoint, ID, USA) that delivers minibursts of respiratory gas mixtures in the proximal airways throughout the breath [19,20]. For the present purposes they were restricted to inspiration, 300 cycles/ min, and pulse inspiratory/expiratory duration ratio of 1:1, whereas breathing frequency amounted to 12 breaths/min, and inspiratory and expiratory duration (T I and T E ) ratio was 1:1 [21], reaching a tele-inspiratory peak pressure of 24 cmH 2 O.…”

“…Recently a one-compartment linear model of the respiratory system has been successfully used to demonstrate the effects of mechanical resistive and elastic loading on flow, tidal volume, and pressure curves generated by HFPV as well as on the resulting washout of gas from the lungs [19,20]. However, the consequences of HFPV on a mechanically heterogeneous lung have yet to be explored.…”