Correlation between different biophysical properties of sputum in bronchiectasis patients

<bold>Background:</bold> Previous research suggests that biophysical properties of sputum, especially the rheological ones could serve as emerging biomarkers in muco-obstructive lung diseases, but evidence in bronchiectasis (BE) is scarce. <bold>Aims:</bold> To analyze the main rheological characteristics of sputum in BE patients and study their correlation with solid content. <bold>Methods:</bold> A post-hoc analysis (Herrero-Cortina B, et al. J Aerosol Med Pulm Drug Deliv 2018) was conducted. Spontaneous sputum samples from 37 BE patients were collected during stable period. Their storage (Gʹ) and loss (Gʹʹ) modulus were measured with a rheometer with a 35mm diameter plate-plate spindle and 0.4mm gap, at 37°C when applying a shear stress of 1 Pa, complex viscosity (|η*|) and cohesive strength (τ) were calculated from the G’ and G’’ measurements. Additionally, the solids concentration (%) for each sample was determined through freeze-drying. <bold>Results:</bold> Significant positive correlations were found between sputum solids concentration and rheological properties: complex viscosity (|η*|;R=0.78,p<0.01) and cohesion strength (τ;r=0.37, p=0.02). Furthermore, moderate positive correlations were noted between cohesion strength and and|η*|(r=0.46,p<0.01). <bold>Conclusion:</bold> Solid concentrations are positively associated with complex viscosity and internal cohesive strength within the sputum of BE patients, which may be related to an increased difficulty for displacing secretions. <fig><object-id>erj;64/suppl_68/PA1428/F1</object-id><object-id>F1</object-id><object-id>F1</object-id><graphic></graphic></fig>