Influence of Emphysema and Air Trapping Heterogeneity on Pulmonary Function in Patients with COPD

Abstract

Kun Li,1,* Yanli Gao,1,* Zhenyu Pan,1 Xiuqin Jia,1 Yuchang Yan,1 Xiaohong Min,1 Kewu Huang,2 Tao Jiang1 1Department of Radiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, Republic of China; 2Department of Pulmonary and Critical Care Medicine, Beijing Chao-Yang Hospital, Capital Medical University, Beijing Institute of Respiratory Medicine, Beijing, People’s Republic of China*These authors contributed equally to this workCorrespondence: Tao JiangDepartment of Radiology, Beijing Chao-Yang Hospital, Capital Medical University, Beijing, People’s Republic of ChinaTel [phone]Fax [phone]Email [email protected]: To explore the influence of emphysema and air trapping heterogeneity on pulmonary function changes in patients with stable chronic obstructive pulmonary disease (COPD).Patients and methods: One hundred and seventy-nine patients with stable COPD were enrolled in this prospective study. All patients underwent low-dose inspiratory and expiratory CT scanning and pulmonary-function tests. CT quantitative data for the emphysema index (EI) on full-inspiration and air trapping (AT) on full-expiration were measured for the whole lung, the right and left lungs, and the cranial-caudal lung zones. The heterogeneity index (HI) values for emphysema and air trapping were determined as the ratio of the difference to the sum of the respective indexes. The cranial-caudal HI and left–right lung HI were compared between mild-to-moderate (GOLD stage I and II) and severe (GOLD stage III and IV) disease groups. The associations between HI and pulmonary-function measurements adjusted for age, sex, height, smoking history, EI and AT of the total lung were assessed using multiple linear regression analysis.Results: The absolute values for cranial-caudal HI (AT_CC_HI) and left–right lung HI (AT_LR_HI) on full-expiration were significantly larger in the mild-to-moderate group, while no significant intergroup differences were observed on full-inspiration. COPD patients with lower-zone and/or left-lung predominance showed significantly lower pulmonary function than those with upper-zone and/or right-lung predominance on full-expiration, whereas no significant differences were observed on full-inspiration. The absolute values of AT_CC_HI and AT_LR_HI significantly correlated with pulmonary-function measurements. Higher AT_CC_HI and lower AT_LR_HI absolute values indicated better pulmonary function, after adjusting for age, sex, height, smoking history, EI and AT of the total lung.Conclusion: Subjects with more heterogeneous distribution and/or upper-zone predominant and/or right-lung predominant patterns on full-expiration tend to have better pulmonary function. Thus, in comparison with emphysema heterogeneity, AT heterogeneity better reflects the pulmonary function changes in COPD patients.Keywords: pulmonary disease, chronic obstructive, small airway disease, heterogeneous distribution, tomography, X-Ray computed

Keywords

• pulmonary disease
• chronic obstructive
• small airway disease
• heterogeneous distribution
• tomography
• x-ray computed.