The complexities of nasal airflow: theory and practice

Area of Science:

• Fluid dynamics
• Respiratory physiology
• Biomedical engineering

Background:

• Nasal airflow is complex, influenced by anatomical structures like the nasal valve and turbinates.
• Previous models simplified nasal airflow mechanics, potentially leading to inaccuracies.
• Understanding these dynamics is crucial for diagnosing and treating nasal obstruction.

Purpose of the Study:

• To investigate the impact of nasal valve area, stiffness, and turbinate cross-sectional area on nasal airflow parameters.
• To refine a mathematical model of nasal airflow by incorporating unsteady flow and Reynolds number dependence.
• To explain discrepancies between nasal resistance measurements and acoustic rhinometry findings.

Main Methods:

• An improved mathematical model of nasal airflow was developed, building upon O'Neill and Tolley's work.
• The model incorporated airflow through the turbinate region, flow coefficients dependent on Reynolds number, and unsteady flow effects.
• Simulations included normal, congested, and decongested states, as well as nasal flaring.

Main Results:

• The enhanced model accurately predicted normal nasal resistance and pressure-flow curves for various states.
• It elucidated the relative contributions of the nasal valve and turbinate region to overall nasal resistance.
• The model generated inspiratory hysteresis loops consistent with experimental data and showed realistic responses to nasal flaring.

Conclusions:

• The refined model offers significant insights into clinical and technical aspects of nasal airflow.
• It highlights fundamental errors in the long-standing description of nasal airflow mechanics based on Hagen-Poiseuille and laminar-turbulent transition.
• This work provides a more accurate framework for understanding nasal airflow dynamics and its clinical implications.