Use of Rheology and portable Low-Field NMR for the monitoring of lung functions in cystic fibrosis patients

Use of Rheology and portable Low-Field NMR for the monitoring of lung functions in cystic fibrosis patients Gabriele Grassi5*, Michela Abrami1, Massimo Maschio2, Massimo Conese3, Marco Confalonieri4, Fabio Gerin1, Barbara Dapas5, Rossella Farra6, Alessandra Adrover7, Lucio Torelli6, Barbara Ruaro4, Mario Grassi1, 1 Department of Engineering and Architecture, University of Trieste, Via Valerio 6/A, I-34127 Trieste, Italy 2 Institute for Maternal and Child Health, IRCCS Burlo Garofolo, Via dell'Istria, 65, I-34137, Trieste, Italy 3 Department of Medical and Surgical Sciences, Foggia University, Ospedali Riuniti, Via L. Pinto, 1, I-71122 Foggia, Italy 4 Cattinara University Hospital, Pulmonology Department, Strada di Fiume 447, I-34149 Trieste, Italy 5 Department of Life Sciences, Cattinara University Hospital, Trieste University, Strada di Fiume 447, I-34149 Trieste, Italy 6 Clinical Department of Medical, Surgical and Health Sciences, Cattinara University Hospital, Trieste University, Strada di Fiume 447, I-34149 Trieste, Italy. 7 Department of Chemical Engineering, Materials and Environment, Sapienza University of Roma, Via Eudossiana 18, I-00184 Rome, Italy *Corresponding author: Gabriele Grassi Department of Life Sciences Cattinara University Hospital Trieste University Strada di Fiume 447, I-34149 Trieste, Italy e-mail: ggrassi@units.it “Declarations of interest: none”. Abstract Background. Cystic fibrosis (CF) is an autosomal recessive disease caused by mutations in the gene encoding of the cystic fibrosis transmembrane conductance regulator (CFTR) responsible for chloride and sodium ion exchange across epithelial membranes. Dysfunctional CFTR induces the production of thick/viscous mucoid secretions in multiple organs, in particular the airways, where an augmented mucus viscosity is determined by the pathological increase in proteins, mucin and biological polymers. This process impairs mucociliary clearance, promoting chronic inflammation and bacterial infection leading to airway remodeling, which, in turn, may progress to respiratory failure, the most common cause of death for CF patients. Therefore, as sputum is a rich and noninvasive source of biomarkers of inflammation/infection, the determination of mucus properties is a relevant parameter able to indirectly monitor lung disease. We previously (Abrami et al Magn Res Med, p.427, 2020; Abrami et al Magn Res Med, p. 2323, 2018;) employed Low Field Nuclear Magnetic Resonance (LF-NMR) to measure the spin-spin relaxation time (T2m) of the water hydrogens present in the CF sputum. These data showed that the T2m measured in CF sputum had an indirect correlation with circulating/local inflammation markers and a direct correlation with FEV1 (forced expiratory volume in the first second, i.e. the amount that is exhaled in the first second purposefully trying to breath out as much air as possible). Thus, the assessment of the physical properties of sputum by T2m, may well provide a useful tool for the indirect monitoring of lung disease in CF patients. Here the T2m significance in the monitoring of CF lung disease was further investigated by studying the correlation of T2m with: 1) sputum viscoelasticity, 2) mucociliary clearability index(MCI)/cough clearability index(CCI) and 3) sputum average mesh-size. Methods. Sputum samples from 25 consenting CF subjects were analyzed by rheology tests (elastic modulus G and zero shear viscosity 0) and Low Field Nuclear Magnetic resonance (T2m). MCI/CCI were calculated from the rheological parameters. The average mesh-size () of the sputum structure was then evaluated by rheology/LF-NMR, together with FEV1 for each patient. Results. There was an inverse correlation between G/ and T2m, indicating that a worsening of the lung condition (T2m-FEV1 drop) is paralleled by an increase in sputum viscoelasticity (G and 0) favoring mucus stasis/inflammation. A direct correlation was also observed between T2m and MCI/CCI, showing that T2m provides information as to airway mucus clearing. Moreover, there was a direct correlation between T2m and the average sputum mesh size ( Conclusions. We demonstrated a correlation between T2m and the sputum viscoelasticity/average mesh-size and with MCI/CCI, parameters related to airway mucus clearing. This correlation was assessed, for the first time, by a combined analysis based on rheology and LF-NMR. This novel approach provided information as to the macro- (viscosity, elasticity, average magnetic relaxation time) and micro-scale (mesh size distribution) characteristics of CF sputum. In conclusion, the present data strengthen the potential of our test to provide indirect monitoring of airway disease course in CF patients.