Computational Modelling of Cough Function and Airway Penetrant Behavior in Patients with Disorders of Laryngeal Function

Abstract

Objective/HypothesisPatients with laryngeal disorders often exhibit changes to cough function contributing to aspiration episodes. Two primary cough variables (peak cough flow: PCF and compression phase duration: CPD) were examined within a biomechanical model to determine their impact on characteristics that impact airway compromise.Study DesignComputational studyMethodsA Computational Fluid Dynamics (CFD) technique was used to simulate fluid flow within an upper airway model reconstructed from patient CT images. The model utilized a finite‐volume numerical scheme to simulate cough‐induced airflow, allowing for turbulent particle interaction, collision, and break‐up. Liquid penetrants at 8 anatomical release locations were tracked during the simulated cough. Cough flow velocity was computed for a base case and four simulated cases. Airway clearance was evaluated through assessment of the fate of particles in the airway following simulated cough.ResultsPeak‐expiratory phase resulted in very high airway velocities for all simulated cases modelled. The highest velocity predicted was 49.96 m/s, 88 m/s, and 117 m/s for Cases 1 and 3, Base case, and Cases 2 and 4 respectively. In the base case, 25% of the penetrants cleared the laryngeal airway. The highest percentage (50%) of penetrants clearing the laryngeal airway are observed in Case 2 (with −40% CPD, +40% PCF), while only 12.5% cleared in Case 3 (with +40% CPD, −40% PCF). The proportion that cleared in Cases 1 and 4 was 37.5%.ConclusionAirway modelling may be beneficial to the study of aspiration in patients with impaired cough function including those with upper airway and neurological diseases. It can be used to enhance understanding of cough flow dynamics within the airway and to inform strategies for treatment with “cough‐assist devices” or devices to improve cough strength.Level of EvidenceN/A.

Verification of Turbulence Models for Flow in a Constricted Pipe at Low Reynolds Number

“…One of the most important and least understood aspects of turbulence is when the local Reynolds number of the turbulence is relatively low [1]. Effects of turbulence is of interest in various industrial [2][3][4][5][6] and biomedical [7][8][9][10][11] applications. Most fluid flows are characterized by irregularly fluctuating flow quantities that often occur at small scales and high frequencies.…”

CFD Simulation of Airflow Dynamics During Cough Based on CT-Scanned Respiratory Airway Geometries

“…Coughing is an important human defense reflex that protects the respiratory system from infections and improves the clearance of secretions [1][2][3][4]. It is usually caused by inflammation and respiratory infections of the respiratory airways or larynx.…”

Upper Airway Assessment and Responses During Mechanically Assisted Cough

“…50,51 Duration of the cough compression phase has been suggested to primarily manipulate the pace of cough (fast/slow), whereas CPF affects the power of cough (strong/weak). 52 The threshold for clinically effective secretion removal has been proposed at CPF of 160-180 l/min. 6,[53][54][55][56] CPF constitutes the most commonly used measure to determine the effect of spontaneous or assisted cough in persons with NMDs.…”

“…86 Lachal et al 87 enhance our understanding of airflow dynamics, and a wide range of MI-E settings may be systematically applied to suggest possible combinations to be applied subsequently in patients. 52,88 The dogma that upper airway collapse during exsufflation causes MI-E treatment failure, highly influenced former evaluation methods, assessing the exsufflation phase alone. Sancho et al's CT-scannings 25 and Lacombe's flow-curve shapes 84 confirmed Bach's postulate that exsufflation caused upper airway collapse in subjects with bulbar dysfunction.…”