Biomechanical analysis of upper airway airflow characteristics in children

Upper airway airflow biomechanics in children are inextricably linked to regional anatomy and physiological function. This study integrates advanced medical imaging with computational fluid dynamics (CFD) to characterize the aerodynamic properties of the pediatric upper airway via three-dimensional (3D) reconstruction. These biomechanical insights aim to clarify the pathogenesis of airway disorders and inform diagnostic and therapeutic strategies.

We enrolled four healthy pediatric subjects (aged 6.8-11.9 years; two males, two females) with no history of upper respiratory pathology. DICOM datasets were imported into Mimics 21.0 to segment the air-fluid volumes (nasal cavity, nasopharynx, and pharynx) via Hounsfield unit thresholding. Subsequent 3D surface models were smoothed in Geomagic Studio 17.0 and volumetrically meshed using Ansys ICEM 21.0. Steady-state aerodynamic simulations were executed in Ansys Fluent 21.0 at a physiological flow rate of 500 mL/s.

Under quiet breathing conditions, inlet flow velocities ranged from 2.122 to 9.8 m/s (specifically 3.959, 2.122, 3.070, and 9.8 m/s for Subjects A-D, respectively). The distances from the nasal vestibule to the choanae ranged from 5.37 to 6.38 cm. Nasal resistance was measured at 0.1148, 0.1002, 0.109, and 0.42 Pa/(cm³/s), respectively. Aerodynamic analyses revealed localized turbulence and pronounced pressure gradients primarily at the nasal valve, Little's area, bilateral choanae, and the epiglottis. While wall shear stress (WSS) was largely uniform throughout the airway, distinct peaks were identified at the nasal valve and Little's area. The elevated nasal resistance in Subject D correlated with localized anatomical narrowing and high inlet velocity, reflecting normal pediatric physiological variance.

Pediatric upper airway aerodynamics exhibit substantial intra-regional and inter-individual heterogeneity, characterized by elevated turbulence and shear stress concentrated at the nasal valve and nasopharynx. The synergy of 3D anatomical modeling and CFD simulation establishes a robust paradigm for evaluating airway biomechanics. Clinically, these CFD-derived metrics hold significant promise for localizing functional stenoses, enhancing diagnostic precision, and facilitating personalized surgical interventions for pediatric upper airway obstruction.