Abstract

The hypothesis that mist tent therapy decreases the viscosity of sputum by direct liquefaction of the sputum in the lower respiratory tract was tested in 6 patients with cystic fibrosis (CF). The first night all patients slept without the mist tent and the first morning sputum was collected for analysis. The following 2 nights patients were randomly allocated to a tent supplied by either a jet or ultrasonic nebulizer. The early morning sputum was analysed for volume, viscosity, water content, and DNA content, an index of purulence. There was no relation between sputum viscosity and DNA content, water content, or volume. Furthermore, there was no consistent relation between sputum viscosity or volume expectorated and the presence or absence of an 8-hour stay in the tent with either method of water nebulization. These results therefore suggest that mist therapy does not consistently influence sputum viscosity or volume in patients with CF. Above a sputum water content of 90%, further increases in water content do not influence viscosity.