Experimental investigation of airway pressures in human airway models with compliant components

A new manufacturing process to construct a human airway model with key complaint components was developed. Experimental analysis was then performed with the results compared to that of a rigid model to investigate the influence that soft tissues had on airway pressures during natural and nasal high flow therapy (NHFT) assisted breathing and investigate the validity of previous rigid wall assumptions in experimental investigation. The airway geometry was obtained from CT scan data and 3D printing technology was used to fabricate the anatomically correct polymer model. A soft silicone was used to simulate the compliance of the tongue, soft palate and vocal fold regions. Breathing was simulated in both the rigid and compliant model using a computer controlled pulsatile pump. The results revealed that the compliant airway model experienced different static pressures during both natural and NHFT assisted breathing. Natural breathing results showed similar oscillatory pressure profiles between compliant and rigid airways, however the compliant airway had larger pressures on peak expiration and lower pressures on peak inspiration at the velopharynx and oropharynx regions. With the application of NHFT at 30 L/min, the compliant airway had greater pressures than the rigid airway for both breathing phases, upstream of the site of compliance. Below the soft palate, only peak expiratory pressures were affected. At NHFT at 60 L/min, the compliant airway pressures were greater than their corresponding rigid pressures for both breathing phases, at all regions.