Airflow behavior changes in upper airway caused by different head and neck positions: Comparison by computational...

Area of Science:

• Medical Imaging
• Computational Fluid Dynamics
• Respiratory Mechanics

Background:

• The impact of head-neck positioning on upper airway airflow during mechanical ventilation is not well-established.
• Understanding these changes is crucial for optimizing ventilation strategies and patient outcomes.

Purpose of the Study:

• To evaluate the feasibility of computational fluid dynamics (CFD) in assessing upper airway airflow dynamics across different head-neck positions.
• To predict how anatomical and physiological airway changes in various positions influence mechanical ventilation.

Main Methods:

• Three-dimensional upper airway models were reconstructed from CT scans of a volunteer in neutral, extension, and sniffing positions.
• Computational fluid dynamics (CFD) simulations using the Spalart-Allmaras model analyzed airflow behavior.
• Key parameters measured included total airway volume (V) and the narrowest area (A_min).

Main Results:

• Airway volume (V) showed neutral < extension ≈ sniffing.
• The narrowest airway area (A_min) increased significantly in the sniffing position (3.0x neutral, 1.7x extension).
• Sniffing position demonstrated reduced pressure drop and stable velocity, unlike the neutral position.

Conclusions:

• The sniffing position enhances upper airway patency by increasing volume and decreasing resistance.
• CFD is a feasible tool for evaluating airflow characteristics in different head-neck positions.
• The sniffing position is suggested as optimal for mask ventilation due to improved airway dynamics.