Assessment of lung volume collapsibility in chronic obstructive lung disease patients using CT
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To investigate the collapsibility of the lung and individual lobes in patients with COPD during inspiration/expiration and assess the association of whole lung and lobar volume changes with pulmonary function tests (PFTs) and disease severity.
PFT measures used were RV/TLC%, FEV1% predicted, FVC, FEV1/FVC%, DLco% predicted and GOLD category. A total of 360 paired inspiratory and expiratory CT examinations acquired in 180 subjects were analysed. Automated computerised algorithms were used to compute individual lobe and total lung volumes. Lung volume collapsibility was assessed quantitatively using the simple difference between CT computed inspiration (I) and expiration (E) volumes (I-E), and a relative measure of volume changes, (I-E)/I.
Mean absolute collapsibility (I-E) decreased in all lung lobes with increasing disease severity defined by GOLD classification. Relative collapsibility (I-E)/I showed a similar trend. Upper lobes had lower volume collapsibility across all GOLD categories and lower lobes collectively had the largest volume collapsibility. Whole lung and left lower lobe collapsibility measures tended to have the highest correlations with PFT measures. Collapsibility of lung lobes and whole lung was also negatively correlated with the degree of air trapping between expiration and inspiration, as measured by mean lung density. All measured associations were statistically significant (P < 0.01).
Severity of COPD appears associated with increased collapsibility in the upper lobes, but change (decline) in collapsibility is faster in the lower lobes.
• Inspiratory and expiratory computed tomography allows assessment of lung collapsibility
• Lobe volume collapsibility is significantly correlated with measures of lung function.
• As COPD severity increases, collapsibility of individual lung lobes decreases.
• Upper lobes exhibit more severe disease, while lower lobes decline faster.
KeywordsLung volume Collapsibility COPD Computed tomography Disease severity
Global initiative for chronic obstructive lung disease
Chronic obstructive pulmonary disease
Total lung capacity
Forced expiratory volume
Lung Tissue Research Consortium
Lung volume reduction surgery
Mean lung density
Forced vital capacity
Diffusion capacity for carbon monoxide
Pulmonary function tests
- LUL, RUL, LLL, RLL, RML
Right or left, upper or lower lobes
This work was supported in part by grants RO1 HL096613, P50 CA090440, P50 HL084948, R01 HL095397, U01 HL108642, RC2 HL101715, and 2013KTCL03-07 from the National Institute of Health, the Bonnie J. Addario Lung Cancer Foundation, and the SPORE in Lung Cancer Career development program.
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