Fluid flow and particle transport in mechanically ventilated airways. Part II: particle transport

The flow mechanisms that play a role on aerosol deposition were identified and presented in a companion paper (Timothy et al. in Med Biol Eng Comput. doi:10.1007/s11517-015-1407-3, 2015). In the current paper, the effects of invasive conventional mechanical ventilation waveforms and endotracheal tube (ETT) on the aerosol transport were investigated. In addition to the enhanced deposition seen at the carinas of the airway bifurcations, enhanced deposition was also seen in the right main bronchus due to impaction and turbulent dispersion resulting from the fluid structures created by jet caused by the ETT. The orientation of the ETT toward right bronchus resulted in a substantial deposition inside right lung compared to left lung. The deposition inside right lung was similar to 12-fold higher than left lung for all considered cases, except for the case of using pressure-controlled sinusoidal waveform where a reduction of this ratio by similar to 50 % was found. The total deposition during pressure constant, volume ramp, and ascending ramp waveforms was similar and similar to 1.44 times higher than deposition fraction when using pressure sinusoidal waveform. Varying respiratory waveform demonstrated a significant role on the deposition enhancement factors and give evidence of drug aerosol concentrations in key deposition sites, which may be significant for drugs with negative side effects in high concentrations. These observations are thought to be important for ventilation treatment strategy.