Inhaled hyperosmolar agents for bronchiectasis

Mucus retention in the lungs is a prominent feature of bronchiectasis. The stagnant mucus becomes chronically colonised with bacteria, which elicit a host neutrophilic response. This fails to eliminate the bacteria, and the large concentration of host-derived protease may contribute to the airway damage. The sensation of retained mucus is itself a cause of suffering, and the failure to maintain airway sterility probably contributes to the frequent respiratory infections experienced by many patients. Hypertonic saline inhalation is known to accelerate tracheobronchial clearance in many conditions, probably by inducing a liquid flux into the airway surface, which alters mucus rheology in a way favourable to mucociliary clearance. Inhaled dry powder mannitol has a similar effect. Such agents are an attractive approach to the problem of mucostasis, and deserve further clinical evaluation.

To determine whether inhaled hyperosmolar substances are efficacious in the treatment of bronchiectasis

The Cochrane Airways Group Specialised Register was searched, and leaders in the field were contacted. Searches were current as of October 2005. Search updates will be run annually.

Any trial using hyperosmolar inhalation in patients with bronchiectasis not caused by cystic fibrosis.

Two reviewers assessed studies for suitability.

Two small studies met the inclusion criteria of the review (28 participants). One study reported tracheobronchial clearance of a particulate radio aerosol after inhalation of dry mannitol on a single occasion, with appropriate control. Airway clearance doubled in the central and intermediate regions of the lung, but not in the peripheral region, after mannitol administration. No side effects were observed, but two patients were premedicated with nedocromil to prevent bronchospasm. Findings from one further trial indicated that one domain of a sensitive health status instrument showed a favourable response to mannitol.

Dry powder mannitol has been shown to improve tracheobronchial clearance in bronchiectasis, as well as cystic fibrosis, asthmatics, and normal subjects. Hypertonic saline has not been specifically tested in bronchiectasis, but improves clearance in these other conditions and in chronic bronchitis. The measurement of health status in one of the studies should be repeated in future longer term randomised controlled studies of mannitol and hypertonic saline. Consideration should also be given to exacerbations and symptom scores, as well as drug-related adverse events.