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

Shah, O and Suhai, J and Jan, R and Shafi, F and Gojwari, T and Choh, N and Shera, F (2020) Computed Tomography Severity Grading of Chronic Obstructive Pulmonary Disease based on Volumetric Assessment of Inspiratory and Expiratory Scans. Journal of Research in Applied and Basic Medical Sciences, 6 (4). pp. 241-251.

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Abstract

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<0.005) which was taken as the threshold for air trapping. Using this threshold (-850HU), we calculated the relative volume change of limited and whole lung (l850 & t850) and expiratory relative volume of limited and whole lung (ERV l850 & ERV t850). Significant correlation was seen between l850 and PFT parameters signifying airway dysfunction (p<0.005). A severity classification of obstructive airway disease was formulated based on l850 and classified patients into mild (l850<-30%), moderate (l850= -20 - -30%), severe (l850 =-10 - -20%), and very severe (l850 > -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.

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