Chronic Obstructive Pulmonary Disease: CT Quantification of Airway Dimensions, Numbers of Airways to Measure, and Effect of Bronchodilation.

Wall thickness in third-generation airways and square root of wall area at an internal perimeter of 10 mm (√WAPi10) are not significantly different before and after bronchodilation and are different in patients with chronic obstructive pulmonary disease and control subjects; twelve is the minimum number of third- or fourth-generation airways required to ensure a maximal 10% error of √WAPi10.