• Yasuhiro Shibuya, Peter J Wills, and Peter J Cole.
• Host Defence Unit, Royal Brompton National Heart and Lung Institute, Imperial College, London, UK. shibuyay@hiroo-hospital.metro.tokyo.jp
• Respirology. 2003 Jun 1;8(2):181-5.

ObjectiveWater is the main constituent of mucus, and its concentration is likely to be important in all aspects of mucus function, including ciliary clearance. The objective of this study was to investigate the effect of water content and osmolality of the mucus on mucociliary transportability.MethodologyRheology and ciliary transportability of 10 sputum samples that had been subjected to various manipulations were measured using a mucus-depleted bovine trachea model.ResultsIt was shown that addition of sodium chloride 0.2 Osmoles/kg (0.585% weight for weight) increased the transportability by 41% (P < 0.01). Evaporation of the sputum to 50% of its original weight caused a 118% increase in transportability (P < 0.0006), but iso-osmolal removal of 50% of the liquid with filter cards led to a non-significant, 25% increase in transportability. Parallel plate viscoelasticity was approximately doubled in both the evaporated and liquid-depleted samples, but was not changed by the addition of 0.2 Osmoles/kg of sodium chloride. The correlation between the osmolality of sputum and ciliary transportability (r = 0.54, P= 0.005) was better than the correlations between the viscosity (r = 0.21, P= 0.27) or elasticity (r = 0.23, P= 0.23) and ciliary transportability.ConclusionsThese results suggest that the osmolality of sputum exerts a greater influence on mucociliary clearance than its viscoelastic properties.

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