Understanding the effects of respiratory flow profile on upper airway flow dynamics

The flow dynamics present in the human upper airway remain largely uninvestigated. With Asthma and Chronic Obstructive Pulmonary Disease (COPD) affecting an estimated 339 and 252 million people, and with inhaled therapy being the primary medical delivery system for these diseases, this is an important field to investigate. Before training, patients using inhalers typically exhibit a velocimetric inhalatory breathing profile like a developed parabolic curve. The author investigated the effect of this sinusoidal flow pattern, contrasted with the desired flow pattern for inhaler usage. This was achieved through the development of a deformable, low patency, and geometrically realistic airway replica. The region of focus was situated in the oropharynx, on a mouth breathing replicated model. All experiments were performed using Particle Imaging Velocimetry (PIV). The peak flow rates of 10, 15, 20L/min were tested. Realistic deformation of the upper airway, which includes both the passive deformation (collapse of the airway due to negative pressure acting on the lumen) and active deformation (airway dilator muscle activity) during breathing, was simulated which helps fill a void in the literature and allows for comparison to the industry standards. The results show that flow profile and active airway deformation can significantly affect flow stability and airway patency suggesting the importance of training for new inhaler users, also having implications in Obstructive Sleep Apnoea (OSA) research.