Rheological and Low Field NMR Characterisation of Cystic Fibrosis Patient’s Sputum

The shear modulus G of the sputum obtained by expectoration from cystic fibrosis patients is fundamental to determine the mesh size of the polymeric network pervading the sputum, a parameter related to lung functionality.The Akaike criterion revealed that in 55.2 % of the examined samples, the best approach (among those considered) to determine G relied on the mechanical spectrum fitting by the generalised Maxwell model with relaxation times scaled by a factor 10. Thus, this approach was adopted to evaluate the mesh size distribution combining G knowledge with the determination of the average magnetic relaxation time (T 2m ) of sputum.As G and T 2m determination can be negatively affected by sputum contamination by saliva, whose presence increases T 2m and depresses G, we developed a proper "decontamination" procedure to obtain more reliable T 2m and G estimations (necessary in 21 % of the samples).This procedure allowed to strengthen the T 2m correlation with lung functionality evaluated by FEV 1 (normalised air volume emitted in the first second during a spirometry test).