Above Cuff Vocalisation in Tracheostomised Patients: Defining Optimal Airflow Thresholds Using Computational Fluid Dynamics
Tracheostomised patients with inflated cuffs experience impaired verbal communication due to blocked airflow through the vocal cords. Above-cuff vocalisation (ACV) enables speech by directing airflow via the subglottic suction port, yet current practice relies on trial-and-error methods due to limited quantitative understanding of airflow dynamics. This study employs computational fluid dynamics (CFD) to quantitatively characterise subglottic airflow during ACV, aiming to establish optimal, evidence-based guidelines for clinical practice.
A validated two-dimensional CFD model was developed from computed tomography scans of a healthy male airway, simulating airflow through a tracheostomy tube at clinically relevant ACV flow rates (2, 5, and 10 L/min). Airflow velocities, pressures, and turbulence were analysed to determine safe and physiologically optimal conditions for effective vocalisation.
CFD simulations demonstrated that ACV flow rates around 2.17 L/min closely matched natural exhalation velocities and pressures, providing physiologically appropriate conditions for vocalisation. Conversely, higher flow rates (≥5 L/min) generated significant turbulence and elevated pressures, increasing the risk of mucosal trauma without proportional improvement in vocal outcomes.
This pioneering study provides critical mechanistic insights into ACV airflow dynamics, shifting clinical practice from empirical methods toward precise, quantitative protocols. By defining safe operational thresholds, this research significantly influences clinical practice, airway management guidelines, and medical device design, marking a substantial advancement in respiratory care for tracheostomised patients.