Clinical Investigation
Pulmonary Function Parameters in High-resolution Computed Tomography Phenotypes of Chronic Obstructive Pulmonary Disease

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Abstract

Background

Heterogeneity of clinical presentation of chronic obstructive pulmonary disease (COPD) attributes to different pathological basis. High-resolution computed tomography (HRCT) phenotypes of COPD may reflex the pathological basis of COPD indirectly by evaluating the small airway inflammation and emphysema. How the pulmonary function related with different HRCT phenotypes has not been well known. The aim was to explore the features of pulmonary function parameters in the 3 phenotypes.

Methods

Sixty-three stable COPD patients were allocated in 3 groups based on HRCT findings: phenotype A (absence of emphysema, with minimal evidence of emphysema with or without bronchial wall thickening [BWT]), phenotype E (emphysema without BWT) and phenotype M (emphysema with BWT). The pulmonary function testing was also analyzed.

Results

The values of forced expiratory volume in 1 second (FEV1)/forced vital capacity (FVC%), FEV1% and maximum expiratory flows (MEF)50% were the highest in phenotype A (P < 0.05), so was residual volume (RV)/total lung capacity (TLC%) in phenotype E (P < 0.05). Those with MEF50/MEF25 ratio > 4.0 were more prevalence in phenotype A than in E and M (odds ratio = 2.214; P < 0.05). The occurrences of RV/TLC% > 40% were higher in phenotype E than in A and M (odds ratio = 3.906; P < 0.05). Receiver operating characteristic analysis showed that the cutoff value of MEF50/MEF25 ratio for identifying phenotype A was 2.5, with sensitivity 66.7% and specificity 92.9%. The cutoff value of RV/TLC% for identifying phenotype E was 57.4%, with sensitivity 75.0% and specificity 79.1%.

Conclusions

The different features of pulmonary function parameters were found in various HRCT phenotypes; MEF50/MEF25 ratio could imply phenotype A, whereas RV/TLC% may be the indicator of phenotype E.

Section snippets

Study Population

A total of 63 stable COPD patients presenting beyond 40 years old were recruited from the outpatient clinic of Ruijin Hospital, Shanghai Jiao Tong University School of Medicine, from October 2012 to September 2013. Diagnosis was made according to the Global Initiative for Chronic Obstructive Lung Disease Guidelines (GOLD).9 The study was approved by the Ethics Boards of Ruijin Hospital, and all subjects gave written informed consent before participating. Patients were excluded if they had a

Demographics and HRCT Phenotypes

A total of 63 patients with COPD (average age: 69 years; 43 male/20 female) were classified into 3 groups based on the HRCT findings, that is, phenotype A group (21 cases), phenotype E (20 cases) and phenotype M (22 cases) (Table 1).

Ages were not significantly different among the 3 phenotypes (P > 0.05). As for gender difference, there was a higher proportion of females (13/21) in phenotype A than phenotype E (3/20) and phenotype M (4/22) (P = 0.002). Higher BMI was found in patients in

DISCUSSION

Until now, FEV1 and its ratio to FVC have been the gold standard for assessment of COPD for it is the most reproducible standard and objective way of measuring airflow limitations.21 But pulmonary function is influenced by age, sex, height and ethnicity. Therefore, there are limitations in the classification of COPD severity according to FEVi only.22., 23., 24. Furthermore, our results also showed that it is impossible to clarify the pathologic basis at the same degree of FEV1 level.

Clinically,

CONCLUSIONS

In summary, the results of this study provided evidence that different features of pulmonary function parameters related with various HRCT phenotypes, which reflects the pathologic basis, MEF50/MEF25 ratio could imply phenotype A for chronic bronchitis, whereas RV/TLC% may be the indicator of phenotype E for emphysema.

ACKNOWLEDGMENTS

The authors acknowledge Wei Min Chai for HRCT analysis support.

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    Supported by “Clinical Medicine Research Fund” (07010210029) from the Chinese Medical Association.

    The authors have no conflicts of interest to disclose.

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