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.
Chemical Spray Pyrolysis (CSP) of ZnO and SnO2 is of interest for gas sensor applications. The structural properties of the deposited film can be strongly influenced by deposition conditions. In this work, two solutions consisting of Tin Chloride and Zinc Chloride was sprayed on a heated substrate, where temperature was varied from 400° C to 450° C for ZnO, and from 350° C to 500° C for SnO2. X-ray diffraction and scanning electron microscopy, indicating a non-homogenous-structured film formed at low temperature for both oxides. At 450° C, a porous structure is observed for SnO2. This structure becomes homogenous at higher temperature. It was also found that at temperatures lower than 450° C, substrate temperature has significant impact on the composition of the synthesized films.
Computational Fluid Dynamics is used to model airflow and penetrant behaviour under cough reflex in human airway. The airway geometry segment from the oral cavity to the primary bronchi is reconstructed from CT scan images of a human subject in the standing posture. The inlet flow condition is derived from dynamic cough profiles obtained from two subjects. The mathematical model allows the laryngopharyngeal wall of the airway to remodel. A k-ω turbulence model is used to represent the transitional flow. A Lagrangian approach is used to track solid penetrants in the flow field as a function of penetrant size and density. High velocities are predicted at peak expiratory cough phase. The penetrant size significantly influences the particle residence time and drag force is largely responsible for changes in the penetrant momentum. The smaller penetrants act like tracers in the flow and can escape the airway faster than larger penetrants.
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