Small airway inflammation and asthma

Evidence derived from large airways has shown that asthma involves mucosal inflammation and structural airway changes including fibroblast proliferation and collagen deposition. Techniques, such as transbronchial biopsy and bronchoalveolar lavage as well as analysis of resected or post-mortem tissue, indicate that similar inflammatory and structural airway changes exist in the small airways in asthma. This paper reviews the evidence that inflammatory and structural changes occur throughout the airways in asthma and discusses the relevance of these considerations. In addition, analysis of resected lung tissue from asthmatic subjects has revealed increased numbers of activated eosinophils within the small airways, when compared with the large airways. Transbronchial biopsy studies in patients with nocturnal asthma have now also identified eosinophilic inflammation within the alveolar walls which correlates with the nocturnal physiological changes. The implications of these findings is that anti-inflammatory treatment needs to be directed to both the large and small airways to achieve the maximal suppression of inflammation throughout the airways.