Combined use of rheology and portable low-field NMR in cystic fibrosis patients.

BACKGROUND

As most cystic fibrosis (CF) patients progress to respiratory failure, lung functionality assessment is pivotal. We previously developed a test that indirectly monitors airways (inflammation/functional test) by measuring the spin-spin relaxation time (T) of the water hydrogens present in CF sputum. Here the T significance in the monitoring of CF lung disease was further investigated by studying the correlation of T 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 η) and Low Field Nuclear Magnetic (LF-NMR) resonance (T). MCI/CCI were calculated from the rheological parameters. The average mesh-size (ξ) of the sputum structure was then evaluated by rheology/LF-NMR, together with FEV for each patient.

RESULTS

There was an inverse correlation between G and η versus T, indicating that a worsening of the lung condition (T-FEV drop) is paralleled by an increase in sputum viscoelasticity (G and η) favoring mucus stasis/inflammation. A direct correlation was also observed between T and MCI/CCI, showing that T provides information as to airway mucus clearing. Moreover, there was a direct correlation between T and the average sputum mesh size (ξ).

CONCLUSIONS

We demonstrated a correlation between T (measured in CF patient's sputum) and the sputum viscoelasticity/average mesh-size and with MCI/CCI, parameters related to airway mucus clearing. Thus, the present data strengthen the potential of our test to provide indirect monitoring of airway disease course in CF patients as T depends on mucus solid concentration and nanostructure.