Small airway dysfunction in asthma: diagnostic, pathogenetic and therapeutic aspects

In recent years, increasing attention has been paid to the role of the small airways (SA) in the pathophysiological and clinical aspects of asthma. The article summarizes the main methods for assessing impaired SA function—spirometry, body plethysmography, impulse oscillometry, fractional exhaled-nitric-oxide analysis, inert-gas washout tests and computed tomography—and notes the absence of a single standard technique for identifying SA dysfunction. The pathogenetic mechanisms underlying SA dysfunction in asthma are discussed, with an emphasis on the key roles of cytokines, eicosanoids (polyunsaturated-fatty-acid metabolites) and plasmalogens in the complex network of mediators that regulate chronic airway inflammation. The potential for correcting SA dysfunction with modern pharmacological agents aimed at restoring lung function is considered. The studies analyzed highlight the importance of early evaluation of SA status and identification of triggers that drive SA dysfunction in asthma.