Numerical investigation of the impact of saber-sheath trachea severity on microparticle deposition in the lower respiratory airway

Understanding the complex mechanisms underpinning the transport and deposition of aerosols in the human airways is important for improving the effectiveness of oral inhaled drug delivery. This study investigates the impact of the saber-sheath trachea index on particle deposition in the lung using computational fluid dynamics (CFD). Magnetic resonance imaging (MRI) was performed on a healthy volunteer using a mock-up inhaler. Five three-dimensional models were reconstructed from MRI with different saber-sheath trachea indices, ranging from 0.4 to 0.6, representing different severity of the saber-sheath features. CFD simulations coupled with discrete phase modelling with monodisperse particles were performed using two different transient flow profiles with peak inspiratory flow rates of 60 L/min and 120 L/min using a zero-resistance inhaler. Model predictions were validated against measurement data obtained from Particle Image Velocimetry. The results demonstrated that increased saber-sheath trachea severity amplifies differences in particle distribution between the right and left lungs, with a saber-sheath index of 0.5 being the most restrictive in terms of particles reaching the subjectspecific lower airways.