Numerical modeling of the effects of nasal mucosal thickness and dehydration on air conditioning for a 5-year-old with cystic fibrosis

Background The nasal cavity warms and humidifies inspired air to protect the lower respiratory tract. In cystic fibrosis (CF), thickened and dehydrated mucus alters airway surface liquid and may impair these conditioning functions, but the magnitude of these effects remains unknown.Objectives To quantify how mucosal layer thickness and surface dehydration influence intranasal temperature and humidity distributions in a 5-year-old child with CF.Methods A subject-specific nose-to-oropharynx model was generated from MRI data and simulated using large-eddy simulation with coupled heat and water-vapor transport including latent heat exchange on the mucus surface. Four wall-condition scenarios were evaluated by varying mucosal layer thickness (1 mm or 5 mm) and surface water mass fraction (100%, 75%, or 50% saturation). The predicted nasopharyngeal temperature (36 ± 1 °C) and relative humidity (95 ± 7%) are well compared with published in vivo measurements, supporting the validity of the coupled heat and moisture transfer model. Temperature, humidity, and plane-averaged profiles were compared across conditions.Results Mucus-layer thickening and reduced hydration both altered nasal air-conditioning. Thick, fully hydrated mucus increased evaporative cooling and slightly lowered posterior air temperature, whereas dehydrated surfaces reduced evaporation and significantly decreased intranasal humidity. Hydration-limited cases weakened anterior conditioning and reduced vapor mass fraction by up to ~50%.Conclusion These findings indicate that CF-related mucus abnormalities degrade nasal warming and humidification, potentially exposing the airways and lungs to drier air. The results also highlight the importance of realistic thermodynamic boundary conditions in nasal computational modeling.