Water sorption capacity of airway mucus in COPD patients vs. mucus of patients without lung pathology following mechanical ventilation

<bold>Background:</bold> One of the predominant symptoms in chronic obstructive pulmonary disease (COPD) patients is mucus hypersecretion. The study aims to compare the water sorption properties of mucus of COPD patients with those in subjects without lung diseases. <bold>Methods:</bold> Mucus from COPD patients (N17) was collected during routine bronchoscopy, and from patients without lungs pathology undergoing elective surgical procedures under mechanical ventilation (N14), serving as a control group. A microbalance instrument (DVS Intrinsic, SMS, London, UK) detected mass changes under isothermal condition (37°C) during a stepwise change of relative humidity (RH) in nitrogen from 0 to 95% and back to 0. <bold>Results:</bold> Both COPD and control mucus samples had similar initial mass and high solid content (8.9% (SD5.5) vs. 6.1% (SD2.0) (p=0.112)). However, COPD mucus took longer to reach equilibrium at RH5% and RH0 (p=0.0016). At RH95%, it re-absorbed significantly less water (147.3±63.2 %) than the control samples from subjects without lung diseases (184.4±35.6 %), p=0.035. During the desorption cycle from RH 95%, COPD mucus showed distinct hysteresis at RH85% and RH75%. <bold>Conclusion:</bold> Dynamic water sorption analyses revealed reduced water sorption capacity in COPD airway mucus. The high solids content in the control samples could be associated with insufficient humidification and hypersecretion of mucins during the elective surgery. The findings may contribute to understanding the compromised mucus clearance in COPD patients.