Fluid mechanics approach to assess airflow dynamics during the respiratory cycle in a child nasal airway with adenoid hypertrophy

The airflow mechanics in adult nasal airways, whether healthy or abnormal, are extensively studied and investigated, but the flow mechanics in child nasal airways remain underexplored. This study investigates the airflow mechanics in the child’s nasal upper airway with adenoid hypertrophy, with an adenoid nasopharyngeal ratio (AN of 0.9), under cyclic inhalation and exhalation. An inlet respiratory cycle with three different flow rates (3.2 L/min calm breathing, 8.6 L/min normal breathing, and 19.3 L/min intensive breathing) was simulated by using the computational fluid dynamics approach. To better capture the interaction between airflow and the flexible airway tissue, fluid-structure interaction analysis was performed at the normal breathing rate. Comparing the airflow dynamics during inhalation and exhalation, the pressure drops, nasal resistance, and wall shear stress show significant differences in the nasopharyngeal region for all different flow rates. This observation suggests that the inertial effect associated with the transient flow is important during exhalation and inhalation. Furthermore, the considerable temporal variation in flow rate distribution across a specific cross-section of the nasal airway highlights the critical role of transient data in virtual surgery planning and data for clinical decisions.