Low-dose CT measurements of airway dimensions and emphysema associated with airflow limitation in heavy smokers: a cross sectional study

Abstract

BackgroundIncreased airway wall thickness (AWT) and parenchymal lung destruction both contribute to airflow limitation. Advances in computed tomography (CT) post-processing imaging allow to quantify these features. The aim of this Dutch population study is to assess the relationships between AWT, lung function, emphysema and respiratory symptoms.MethodsAWT and emphysema were assessed by low-dose CT in 500 male heavy smokers, randomly selected from a lung cancer screening population. AWT was measured in each lung lobe in cross-sectionally reformatted images with an automated imaging program at locations with an internal diameter of 3.5 mm, and validated in smaller cohorts of patients. The 15th percentile method (Perc15) was used to assess the severity of emphysema. Information about respiratory symptoms and smoking behavior was collected by questionnaires and lung function by spirometry.ResultsMedian AWT in airways with an internal diameter of 3.5 mm (AWT3.5) was 0.57 (0.44 - 0.74) mm. Median AWT in subjects without symptoms was 0.52 (0.41-0.66) and in those with dyspnea and/or wheezing 0.65 (0.52-0.81) mm (p<0.001). In the multivariate analysis only AWT3.5 and emphysema independently explained 31.1%and 9.5%of the variance in FEV1%predicted, respectively, after adjustment for smoking behavior.ConclusionsPost processing standardization of airway wall measurements provides a reliable and useful method to assess airway wall thickness. Increased airway wall thickness contributes more to airflow limitation than emphysema in a smoking male population even after adjustment for smoking behavior.

Airway wall thickness associated with forced expiratory volume in 1 second decline and development of airflow limitation

“…The finding that CT-quantified emphysema is associated with accelerated lung function decline seems robust given the fact that several other groups have reported similar findings [5][6][7][8][9]. YUAN et al [7] showed that there was a trend between automatically quantified low-attenuation areas on CT and follow-up lung function in smokers without COPD.…”

“…However, they only reported results from univariate analyses and did not provide effect sizes. Other cross-sectional studies have shown that a higher airway wall thickness is associated with lower pulmonary function and the presence of COPD [5,[23][24][25][26].…”

“…Several studies found associations of emphysema and airway wall thickness with lung function, the presence of COPD and clinical symptoms. Previous studies showed an association between CT quantified emphysema and a more rapid lung function decline in smokers and subjects with COPD [5][6][7][8][9].…”

Novel Genes for Airway Wall Thickness Identified with Combined Genome-Wide Association and Expression Analyses

“…Nowadays, computed tomography (CT) can be used to more accurately measure the dimensions of the airway wall. Previous studies using low-dose CT have assessed airway dimensions, such as lumen area or diameter, or Pi10 with different airway sampling methods, particularly in relation to airflow limitation, respiratory symptoms, emphysema, and smoking habits (4). Research by Nakano and colleagues (1) revealed that CT measurements of larger airways could be used to estimate the dimensions of the small conducting airways.…”

“…AWT in COPD depends on the patient population and methods used to measure AWT (5-7). We used the actually measured AWT at a fixed lumen diameter in all lobes (4).…”