Asthma: imaging of the smaller airways.

Small airways are not easily visualized with current technology, but some successes have been achieved with improved methods. High-resolution computed tomography can reveal small airway anatomy, but may be more valuable for detecting functional changes such as regional air trapping in the distal airways. This technique may be especially valuable for patients who have mild asthma with subtle changes not discernable with conventional measures. Assessment of air trapping in small airways may have diagnostic value, distinguishing those patients who are likely to experience frequent asthmatic exacerbations.