Emphysematous subjects whose airflow obstruction is due to loss of parenchymal tethering of the airways experience greater benefit from lung volume reduction surgery (LVRS) than individuals with fixed small airway obstruction. Inspiratory resistance is a useful measure of intrinsic airway disease and has been used in subject selection for LVRS. In-vivo radiologic assessment of airway remodeling in chronic obstructive pulmonary disease (COPD) is challenging because the size of the peripheral airways (<2mm) exceeds the capabilities of current CT techniques for accurate assessment. We hypothesized that cartilaginous airway wall thickening as assessed by CT scan correlates with inspiratory resistance.
Chest CT scans, pulmonary function tests, and inspiratory resistance measurements were examined in 152 subjects assessed at Brigham and Women’s Hospital between 1998 and 2005. Thirty two scans demonstrated the origin of the apical segment of the right upper lobe without wall interruption or motion artifact in one slice, conditions necessary for accurate measurement. Automated lung mask detection and manual wall delineation of 5, 8, or 10mm thickness images were performed using Slicer. (http://www.slicer.org). Airway wall area is expressed as the percentage wall area (WA%) where WA%=Wall area/Lumen area*100.
The Pearson Correlation coefficient for the linear regression of percentage wall area and inspiratory resistance is 0.51 (p = 0.0039).
The percentage airway wall area of cartilaginous airways correlates with a subject’s inspiratory resistance.
This relationship may assist in the determination of the degree of a subject’s airway disease and potential benefit from LVRS. Further investigation with high resolution CT scans is necessary to confirm these results.
George Washko, Product/procedure echnique that is considered research and is NOT yet approved for any purpose. Slicer is open source software which provides a visualization and processing environment allowing segmentation and quantification of medical data for research.