Summary

Asthma is an airway disease, yet that airway extends all the way to the alveolar tissue area. Pathohistiological as well as physiological and clinical studies have recently documented this aspect of asthma. The implications of this are important for all asthmatic patients, but particularly for those whose asthma is more difficult to control. Many of the inhaled preparations used as therapy for asthma are of relatively large particle size. 
Thus, the deposition of these medications is mainly in the central and medium sized airways and very little of a given actuation gets to the distal airways. Ultrafine inhaled steroid particles have been shown to reach the more peripheral portions of the airway, and improvement in outcome variables such as air trapping as well as symptomatic outcomes have been demonstrated. This review focuses on anatomic airway changes, physiological changes of the distal airways, clinical outcome data, and particle size of inhaled preparations.