Computed Tomography Severity Grading of Chronic Obstructive Pulmonary Disease based on Volumetric Assessment of Inspiratory and Expiratory Scans

Abstract

Background & Aims: To determine attenuation threshold for detection and quantification of air trapping in obstructive airway disease. Quantify airway dysfunction in patients of obstructive airway disease & its correlation with pulmonary function tests. Materials & Methods: Paired HRCT scans of 48 patients were done and correlated with Pulmonary Function Tests taken within 2 weeks of the study. Threshold attenuation value on expiratory scan that signifies air trapping was obtained by correlating relative volumes with PFT parameters (PEF 25-75% & RV/TLC). The lung volumes at this threshold were then correlated with PFT values signifying airway dysfunction (FEV1, FEV1/FVC and PEF 25-75%) and airway dysfunction was then quantified based on these volumes. Results: Maximum correlation of PFT parameters signifying air trapping is with relative volume of limited lung at -850HU (l850) (p -10%). Conclusion: l850 can be used as a CT parameter to quantify airway dysfunction irrespective of presence or absence of emphysema. Severity classification of obstructive airway disease was formulated based on l850.

Keywords

• fev1 forced expiratory volume in 1 sec
• fvc forced vital capacity
• hrct high-resolution computed tomography
• pef25-75% peak expiratory flow (25 – 75 %)
• pft pulmonary function test
• rv residual volume