Cigarette smoking is associated with worse symptoms in asthma and abnormal segmental airways in healthy subjects. We tested the hypothesis that current symptom control in smokers with asthma is associated with altered segmental airway dimensions measured by computed tomography (CT).
In 93 asthmatics with mild, moderate and severe disease (smokers and never-smokers) we recorded the asthma control questionnaire (ACQ6) score, spirometry [FEV1, FEF25-75], residual volume (RV), total lung capacity (TLC), and CT measures of right bronchial (RB) and left bronchial (LB) segmental airway dimensions, [wall thickness, mm; lumen area, mm2] in RB3/LB3, RB6/LB6 and RB10/LB10 (smaller) airways.
CT segmental airway (RB10 and LB10) lumen area was reduced in smokers with asthma compared to never smokers with asthma; RB10 16.6 mm2 (interquartile range (IQR), 12.4, 19.2) versus 19.6 mm2 (IQR 14.7, 24.2, p=0.01); LB10 14.8 mm2 (12.1, 19.0) versus 19.9 mm2 (14.5, 25.0), p=0.003, particularly in severe disease, with no differences in wall thickness or in larger airway (RB3 and LB3) dimensions. In smokers with asthma, a reduced lumen area in 5th generation airways (RB10 or LB10) was associated with poor symptom control (higher ACQ6 score) [-0.463 (-0.666, -0.196), p=0.001 and -0.401 (-0.619, -0.126), p=0.007 respectively] and reduced FEF25-75 post-bronchodilator [0.521 (0.292, 0.694), p<0.001 and [0.471 (0.236, 0.654), p=0.001] respectively] and higher RV/TLC %.
CT segmental airway lumen area is reduced in smokers with asthma compared to never smokers with asthma, particularly in severe disease and is associated with worse current symptom control and small airway dysfunction.