Scaled experiments for improving diagnosis of pathological lower airway obstruction

Many lung diseases are characterized by obstructed airflow, particularly, in the lower airway. To explore the detectability of wake structures in the trachea due to regionalized lower-airway obstructions, a transparent patient-specific lung model, resolved down to the 5th daughter branches and scaled up to 1.8 times the human size, was constructed. 5 independently controlled piston pumps are used to prescribe the flowrate to the different lung lobes, simulating constant exhalation processes with both healthy and diseased/obstructed lobar flow fractions. Quantification of the complex 3D flow in the lower trachea is achieved by conducting stereo PIV measurements in both the coronal and transverse planes at different elevations. The Reynolds number is maintained at the lowest end of the physiology range (around 584, based upon the bulk flowrate and the tracheal diameter). Notable differences in the tracheal velocity profiles among different flow conditions were discovered and quantified by utilizing the method of proper orthogonal decomposition. The wake structures due to deficit flow in each single lobe are presented and their formations are discussed. These results will be used to discuss a potential means to identify a pathological flow condition using non-intrusive diagnostics.