Assessment of Effects of Selective Airway Luminal Expansion on Inhaled Particle Deposition in Severe Asthmatic Human Lungs - A Numerical Study

The aim of the study is to assess the effects of luminal expansion of constricted proximal airways on inhaled particle deposition in severe asthmatic lungs. A recent imaging-based cluster analysis found that one of the two severe asthma clusters was characterized by proximal airway constriction. We performed computational fluid and particle simulations on computed tomography (CT)-based airway models before and after numerically enlarging luminal areas of constricted airways in representative cluster subjects. After constriction reduction, a high-speed air stream, which impinged on the bifurcating wall in the original constricted geometry, disappeared. Consequently, particle deposition density in the region decreased and downstream particle delivery increased. Specifically, after expanding the constricted left lower bronchus of a subject, particle deposition fraction in the left lower lobe decreased by 22-35% for 1-8 µm particles, and hence distal particle advection increased up to 23% for 8 µm. The results imply that the use of imaging-based clustering and enlargement of constricted proximal airway may help improve delivery of orally inhaled drug aerosols to small airways in severe asthmatic lungs.