Physical and Transport Properties of Sputum From Children With Idiopathic Bronchiectasis

BackgroundChildhood idiopathic bronchiectasis (IB) unrelated to cystic fibrosis (CF) or known immunodeficiency remains a common problem among indigenous populations in developed and developing countries. The physical and transport properties of sputum among children with IB have not been described, and these properties may suggest therapies that would be particularly effective for this group of children.MethodsSputum from children in stable condition with IB and chronic daily productive cough was collected to measure viscosity, elasticity, cohesivity, adhesivity, and mucociliary and cough transportability in vitro. The results were compared to banked data from the sputa of children with CF and adults with chronic bronchitis (CB) measured by the same methods.ResultsSputa from children with CF and adults with CB had similar values for viscosity, elasticity, frictional adhesion, cough transportability, and mucociliary transportability. The elasticity of sputum from children with IB was 12 to 20%, respectively, of the value of CB and CF sputum (p < 0.01). The viscosity of sputum from children with IB was 23 to 32%, respectively, of the value of CB and CF sputum (p < 0.02). The surface frictional adhesion for sputum from children with IB was 55% of the values from both CF and CB sputa (p < 0.0001). Cough transportability for sputum from children with IB was 43 to 54% greater, respectively, than that for sputum from CB and CF patients (p < 0.0001). Mucociliary transportability was similar for all three groups (p > 0.05).ConclusionsThe physical and transport properties of sputum from children with IB who are stable in the outpatient setting are substantially different and lead to improved cough transportability compared to sputum from children with CF or adults with CB. Therapies that focus on cough may be sufficient to improve airway mucus clearance in children with IB. Sputum properties may explain in part the different clinical course of children with IB compared to children with CF.