Influence of tidal-volume setting, emphysema and ARDS on human alveolar sacs mechanics

Mechanical ventilation (MV) devices help patients with lung disorders to breathe.Improper setting for MV devices lead to further lung injuries.Therefore,investigating influence of ventilator device settings on healthy and diseased alveolar sacs mechanics could prevent injuries while in use.To this aim,three-dimensional (3D) models for healthy and emphysematous alveolar sacs with and without acute respiratory distress syndrome (ARDS) were developed,and computational fluid dynamics (CFD) analysis and fluid-solid interaction (FSI) approach were employed to study the influence of alveolar sacs wall motion,tidal volume (TV) setting and disease on alveolar sac mechanics.The recirculation region was only monitored in alveolar sacs with rigid wall.Observations demonstrated an increase in compliance during air inhalation into the emphysematous alveolar sacs.Induced air penetrated deeper into healthy alveolar sacs compared to the emphysematous model and recommended TV for chronic obstructive pulmonary disease (COPD) increased applied strain,stress and wall shear stress (WSS) on emphysematous alveolar sacs.In addition,recommended TVs for patients with ARDS decreased strain and stress,but did not influence applied WSS significantly.In general,increasing TV raised stress and strain level and led to deeper air penetration into the alveolar sacs.Afterwards,lower TV decreased strain,stress and WSS for patients who had both ARDS and emphysema.This study can provide invaluable insights about diseased alveolar sacs mechanics and evaluate importance of ventilator devices setting in different disease conditions.