Upper Airway Structural Abnormality and the Impact on Air Flow in Chronic Obstructive Pulmonary Disease Patients*

While chronic obstructive pulmonary disease (COPD) is a lung disease with lower airway obstruction with declined lung function, there is growing interest in upper airway abnormality in COPD regarding its importance in drug inhalation. We used quantitative computed tomography (QCT) analysis and computational fluid dynamics (CFD) simulations to investigate upper airway structural abnormality in COPD and the associated impact on air flow. From 40 COPD patients and 24 healthy subjects, mouth-throat CT images were acquired during at deep inspiration, with an empty dry power inhaler. From volumetric and length measurements, we found enlarged pharyngeal length and luminal narrowing at the 6th cervical vertebrae (C6). Three representative subjects were selected in each group, and large eddy simulations equipped with passive scale transport were conducted for tidal breathing and deep inhalation cases. We compare regional distributions of velocity, pressure, wall shear stress, temperature, and relative humidity from the mouth entrance to the tracheal entrance. Vortical structures are also compared.