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Diaz AA, Han MK, Come CE, San José Estépar R, Ross JC, Kim V, Dransfield MT, Curran-Everett D, Schroeder JD, Lynch DA, Tschirren J, Silverman EK, Washko GR. Effect of emphysema on CT scan measures of airway dimensions in smokers. Chest 2013; 143:687-693. [PMID: 23460155 DOI: 10.1378/chest.12-0039] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
BACKGROUND In CT scans of smokers with COPD, the subsegmental airway wall area percent (WA%) is greater and more strongly correlated with FEV1 % predicted than WA% obtained in the segmental airways. Because emphysema is linked to loss of airway tethering and may limit airway expansion, increases in WA% may be related to emphysema and not solely to remodeling. We aimed to first determine whether the stronger association of subsegmental vs segmental WA% with FEV1 % predicted is mitigated by emphysema and, second, to assess the relationships among emphysema, WA%, and total bronchial area (TBA). METHODS We analyzed CT scan segmental and subsegmental WA% (WA% = 100 × wall area/TBA) of six bronchial paths and corresponding lobar emphysema, lung function, and clinical data in 983 smokers with COPD. RESULTS Compared with segmental WA%, the subsegmental WA% had a greater effect on FEV1% predicted (-0.8% to -1.7% vs -1.9% to -2.6% per 1-unit increase in WA%, respectively; P < .05 for most bronchial paths). After adjusting for emphysema, the association between subsegmental WA% and FEV1 % predicted was weakened in two bronchial paths. Increases in WA% between bronchial segments correlated directly with emphysema in all bronchial paths (P < .05). In multivariate regression models, emphysema was directly related to subsegmental WA% in most bronchial paths and inversely related to subsegmental TBA in all bronchial paths. CONCLUSION The greater effect of subsegmental WA% on airflow obstruction is mitigated by emphysema. Part of the emphysema effect might be due to loss of airway tethering, leading to a reduction in TBA and an increase in WA%.
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Affiliation(s)
- Alejandro A Diaz
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA; Department of Pulmonary Diseases, Pontificia Universidad Católica de Chile, Santiago, Chile.
| | - MeiLan K Han
- University of Michigan School of Medicine, Ann Arbor, MI
| | - Carolyn E Come
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
| | - Raúl San José Estépar
- Surgical Planning Laboratory, Laboratory of Mathematics in Imaging, Department of Radiology, Brigham and Women's Hospital, Boston, MA
| | - James C Ross
- Surgical Planning Laboratory, Laboratory of Mathematics in Imaging, Department of Radiology, Brigham and Women's Hospital, Boston, MA
| | - Victor Kim
- School of Medicine, Temple University, Philadelphia, PA
| | - Mark T Dransfield
- Division of Pulmonary, Allergy, and Critical Care Medicine, The University of Alabama at Birmingham, Birmingham, AL
| | - Douglas Curran-Everett
- Division of Biostatistics and Bioinformatics, National Jewish Health, Denver, CO; Department of Biostatistics and Informatics, Colorado School of Public Health, Denver, CO
| | - Joyce D Schroeder
- Division of Radiology, National Jewish Health, University of Colorado, School of Medicine, Denver, CO
| | - David A Lynch
- Division of Radiology, National Jewish Health, University of Colorado, School of Medicine, Denver, CO
| | | | - Edwin K Silverman
- Channing Laboratory (Dr Silverman), Brigham and Women's Hospital, Boston, MA
| | - George R Washko
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA
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Brown RH. Registration-based metrics of lung function to describe COPD: the ultimate question of life, the universe, and everything. Acad Radiol 2013; 20:525-6. [PMID: 23570933 DOI: 10.1016/j.acra.2013.02.003] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/08/2013] [Revised: 02/08/2013] [Accepted: 02/08/2013] [Indexed: 01/23/2023]
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Martin C, Frija J, Burgel PR. Dysfunctional lung anatomy and small airways degeneration in COPD. Int J Chron Obstruct Pulmon Dis 2013; 8:7-13. [PMID: 23319856 PMCID: PMC3540907 DOI: 10.2147/copd.s28290] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Chronic obstructive pulmonary disease (COPD) is characterized by incompletely reversible airflow obstruction. Direct measurement of airways resistance using invasive techniques has revealed that the site of obstruction is located in the small conducting airways, ie, bronchioles with a diameter < 2 mm. Anatomical changes in these airways include structural abnormalities of the conducting airways (eg, peribronchiolar fibrosis, mucus plugging) and loss of alveolar attachments due to emphysema, which result in destabilization of these airways related to reduced elastic recoil. The relative contribution of structural abnormalities in small conducting airways and emphysema has been a matter of much debate. The present article reviews anatomical changes and inflammatory mechanisms in small conducting airways and in the adjacent lung parenchyma, with a special focus on recent anatomical and imaging data suggesting that the initial event takes place in the small conducting airways and results in a dramatic reduction in the number of airways, together with a reduction in the cross-sectional area of remaining airways. Implications of these findings for the development of novel therapies are briefly discussed.
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Affiliation(s)
- Clémence Martin
- Department of Respiratory Medicine, Cochin Hospital, AP-HP and Université Paris Descartes, Sorbonne Paris Cité, Paris, France
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Pu J, Leader JK, Meng X, Whiting B, Wilson D, Sciurba FC, Reilly JJ, Bigbee WL, Siegfried J, Gur D. Three-dimensional airway tree architecture and pulmonary function. Acad Radiol 2012; 19:1395-401. [PMID: 22884402 DOI: 10.1016/j.acra.2012.06.007] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2012] [Revised: 06/22/2012] [Accepted: 06/23/2012] [Indexed: 11/18/2022]
Abstract
RATIONALE AND OBJECTIVES The airway tree is a primary conductive structure, and airways' morphologic characteristics, or variations thereof, may have an impact on airflow, thereby affecting pulmonary function. The objective of this study was to investigate the correlation between airway tree architecture, as depicted on computed tomography, and pulmonary function. MATERIALS AND METHODS A total of 548 chest computed tomographic examinations acquired on different patients at full inspiration were included in this study. The patients were enrolled in a study of chronic obstructive pulmonary disease (Specialized Center for Clinically Oriented Research) and underwent pulmonary function testing in addition to computed tomographic examinations. A fully automated airway tree segmentation algorithm was used to extract the three-dimensional airway tree from each examination. Using a skeletonization algorithm, airway tree volume-normalized architectural measures, including total airway length, branch count, and trachea length, were computed. Correlations between airway tree measurements with pulmonary function testing parameters and chronic obstructive pulmonary disease severity in terms of the Global Initiative for Obstructive Lung Disease classification were computed using Spearman's rank correlations. RESULTS Non-normalized total airway volume and trachea length were associated (P < .01) with lung capacity measures (ie, functional residual capacity, total lung capacity, inspiratory capacity, vital capacity, residual volume, and forced expiratory vital capacity). Spearman's correlation coefficients ranged from 0.27 to 0.55 (P < .01). With the exception of trachea length, all normalized architecture-based measures (ie, total airway volume, total airway length, and total branch count) had statistically significant associations with the lung function measures (forced expiratory volume in 1 second and the ratio of forced expiratory volume in 1 second to forced expiratory vital capacity), and adjusted volume was associated with all three respiratory impedance measures (lung reactance at 5 Hz, lung resistance at 5 Hz, and lung resistance at 20 Hz), and adjusted branch count was associated with all respiratory impedance measures but lung resistance at 20 Hz. When normalized for lung volume, all airway architectural measures were statistically significantly associated with chronic obstructive pulmonary disease severity, with Spearman's correlation coefficients ranging from -0.338 to -0.546 (P < .01). CONCLUSIONS Despite the large variability in anatomic characteristics of the airway tree across subjects, architecture-based measures demonstrated statistically significant associations (P < .01) with nearly all pulmonary function testing measures, as well as with disease severity.
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Affiliation(s)
- Jiantao Pu
- University of Pittsburgh, Department of Radiology, PA 15213, USA.
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Paré PD, Nagano T, Coxson HO. Airway imaging in disease: gimmick or useful tool? J Appl Physiol (1985) 2012; 113:636-46. [PMID: 22604891 PMCID: PMC3424064 DOI: 10.1152/japplphysiol.00372.2012] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2012] [Accepted: 05/15/2012] [Indexed: 01/06/2023] Open
Abstract
Airway remodeling is an important pathophysiological mechanism in a variety of chronic airway diseases. Historically investigators have had to use invasive techniques such as histological examination of excised tissue to study airway wall structure. The last several years has seen a proliferation of relatively noninvasive techniques to assess the airway branching pattern, wall thickness, and more recently, airway wall tissue components. These methods include computed tomography, magnetic resonance imaging, and optical coherence tomography. These new imaging technologies have become popular because to understand the physiology of lung disease it is important we understand the underlying anatomy. However, these new approaches are not standardized or available in all centers so a review of their validity and clinical utility is appropriate. This review documents how investigators are working hard to correct for inconsistencies between techniques so that they become more accepted and utilized in clinical settings. These new imaging techniques are very likely to play a frontline role in the study of lung disease and will, hopefully, allow clinicians and investigators to better understand disease pathogenesis and to design and assess new therapeutic interventions.
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Affiliation(s)
- Peter D Paré
- University of British Columbia James Hogg Research Centre and Institute for Heart + Lung Health, Vancouver, British Columbia, Canada
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Washko GR, Parraga G, Coxson HO. Quantitative pulmonary imaging using computed tomography and magnetic resonance imaging. Respirology 2012; 17:432-44. [PMID: 22142490 DOI: 10.1111/j.1440-1843.2011.02117.x] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Measurements of lung function, including spirometry and body plethesmography, are easy to perform and are the current clinical standard for assessing disease severity. However, these lung functional techniques do not adequately explain the observed variability in clinical manifestations of disease and offer little insight into the relationship of lung structure and function. Lung imaging and the image-based assessment of lung disease has matured to the extent that it is common for clinical, epidemiologic and genetic investigation to have a component dedicated to image analysis. There are several exciting imaging modalities currently being used for the non-invasive study of lung anatomy and function. In this review, we will focus on two of them; X-ray computed tomography and magnetic resonance imaging. Following a brief introduction of each method, we detail some of the most recent work being done to characterize smoking-related lung disease and the clinical applications of such knowledge.
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Affiliation(s)
- George R Washko
- Department of Medicine, Division of Pulmonary and Critical Care Medicine, Brigham and Women's Hospital, Boston, Massachusetts, USA
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Pu J, Gu S, Liu S, Zhu S, Wilson D, Siegfried JM, Gur D. CT based computerized identification and analysis of human airways: a review. Med Phys 2012; 39:2603-16. [PMID: 22559631 DOI: 10.1118/1.4703901] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
As one of the most prevalent chronic disorders, airway disease is a major cause of morbidity and mortality worldwide. In order to understand its underlying mechanisms and to enable assessment of therapeutic efficacy of a variety of possible interventions, noninvasive investigation of the airways in a large number of subjects is of great research interest. Due to its high resolution in temporal and spatial domains, computed tomography (CT) has been widely used in clinical practices for studying the normal and abnormal manifestations of lung diseases, albeit there is a need to clearly demonstrate the benefits in light of the cost and radiation dose associated with CT examinations performed for the purpose of airway analysis. Whereas a single CT examination consists of a large number of images, manually identifying airway morphological characteristics and computing features to enable thorough investigations of airway and other lung diseases is very time-consuming and susceptible to errors. Hence, automated and semiautomated computerized analysis of human airways is becoming an important research area in medical imaging. A number of computerized techniques have been developed to date for the analysis of lung airways. In this review, we present a summary of the primary methods developed for computerized analysis of human airways, including airway segmentation, airway labeling, and airway morphometry, as well as a number of computer-aided clinical applications, such as virtual bronchoscopy. Both successes and underlying limitations of these approaches are discussed, while highlighting areas that may require additional work.
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Affiliation(s)
- Jiantao Pu
- Department of Radiology, University of Pittsburgh, Pittsburgh, PA 15213, USA.
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Abstract
Chronic obstructive pulmonary disease is a heterogeneous condition of the lungs and body. Techniques in chest imaging and quantitative image analysis provide novel in vivo insight into the disease and potentially examine divergent responses to therapy. This article reviews the strengths and limitations of the leading imaging techniques: computed tomography, magnetic resonance imaging, positron emission tomography, and optical coherence tomography. Following an explanation of the technique, each section details some of the useful information obtained with these examinations. Future clinical care and investigation will likely include some combination of these imaging modalities and more standard assessments of disease severity.
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Affiliation(s)
- George R Washko
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Brigham and Women's Hospital, Boston, MA 02115, USA.
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Biomarkers in chronic obstructive pulmonary disease. Transl Res 2012; 159:228-37. [PMID: 22424427 DOI: 10.1016/j.trsl.2012.01.019] [Citation(s) in RCA: 51] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 11/14/2011] [Revised: 01/19/2012] [Accepted: 01/19/2012] [Indexed: 01/02/2023]
Abstract
Chronic obstructive pulmonary disease (COPD) is a complex disease with multiple phenotypes that cannot be identified through measurement of lung function alone. The importance of COPD risk assessment, phenotype identification, and diagnosis of exacerbation magnify the need for validated biomarkers in COPD. A large number of potential biomarkers have already been assessed and some appear promising, in particular fibrinogen, which is likely to be the first COPD biomarker presented to the Food and Drug Administration for qualification in the drug approval process. Blood fibrinogen and c-reactive protein (CRP) have been associated with the presence of COPD and, in some instances, future risk of developing COPD in targeted populations. Sputum neutrophil counts have been used preliminarily as biomarkers of favorable response to therapy in COPD, but use in clinical settings may be limited. Other potential blood biomarkers include pulmonary and activation-regulated chemokine (PARC/CCL-18) and the clara cell secretory protein 16 (CC-16). Integrative indices, such as the BODE index, provide a framework to determine prognosis, predict outcome, and may be responsive to therapeutic interventions. Computed tomography provides a means to assess phenotypes and identify the relative extents of small airways disease and emphysema, which themselves may inform prognosis and therapeutic decision making. Fibrinogen and other markers of systemic inflammation are elevated in the context of acute COPD exacerbations and may also identify those at risk of accelerated lung function decline and hospitalization. So far, no single biomarker in COPD warrants wide acceptance emphasizing the need for future investigation of biomarkers in large-scale longitudinal studies.
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Camiciottoli G, Bigazzi F, Bartolucci M, Cestelli L, Paoletti M, Diciotti S, Cavigli E, Magni C, Buonasera L, Mascalchi M, Pistolesi M. BODE-index, modified BODE-index and ADO-score in chronic obstructive pulmonary disease: relationship with COPD phenotypes and CT lung density changes. COPD 2012; 9:297-304. [PMID: 22432964 DOI: 10.3109/15412555.2012.661000] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023]
Abstract
COPD is a heterogeneous disorder whose assessment is going to be increasingly multidimensional. Grading systems such as BODE (Body-Mass Index, Obstruction, Dyspnea, Exercise), mBODE (BODE modified in grading of walked distance), ADO (Age, Dyspnea, Obstruction) are proposed to assess COPD severity and outcome. Computed tomography (CT) is deemed to reflect COPD lung pathologic changes. We studied the relationship of multidimensional grading systems (MGS) with clinically determined COPD phenotypes and CT lung density. Seventy-two patients underwent clinical and chest x-ray evaluation, pulmonary function tests (PFT), 6-minute walking test (6MWT) to derive: predominant COPD clinical phenotype, BODE, mBODE, ADO. Inspiratory and expiratory CT was performed to calculate mean lung attenuation (MLA), relative area with density below-950 HU at inspiration (RAI(-950)), and below -910 HU at expiration (RAE(-910)). MGS, PFT, and CT data were compared between bronchial versus emphysematous COPD phenotype. MGS were correlated with CT data. The prediction of CT density by means of MGS was investigated by direct and stepwise multivariate regression. MGS did not differ in clinically determined COPD phenotypes. BODE was more closely related and better predicted CT findings than mBODE and ADO; the better predictive model was obtained for CT expiratory data; stepwise regression models of CT data did not include 6MWT distance; the dyspnea score MRC was included only to predict RA-950 and RA-910 which quantify emphysema extent. BODE reflect COPD severity better than other MGS, but not its clinical heterogeneity. 6MWT does not significantly increase BODE predictivity of CT lung density changes.
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Affiliation(s)
- Gianna Camiciottoli
- University of Florence, Department of Internal Medicine, Section of Respiratory Medicine, Florence, Italy. gianna.camiciottoli@unifi .it
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McDonough JE, Yuan R, Suzuki M, Seyednejad N, Elliott WM, Sanchez PG, Wright AC, Gefter WB, Litzky L, Coxson HO, Paré PD, Sin DD, Pierce RA, Woods JC, McWilliams AM, Mayo JR, Lam SC, Cooper JD, Hogg JC. Small-airway obstruction and emphysema in chronic obstructive pulmonary disease. N Engl J Med 2011; 365:1567-75. [PMID: 22029978 PMCID: PMC3238466 DOI: 10.1056/nejmoa1106955] [Citation(s) in RCA: 803] [Impact Index Per Article: 61.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
BACKGROUND The major sites of obstruction in chronic obstructive pulmonary disease (COPD) are small airways (<2 mm in diameter). We wanted to determine whether there was a relationship between small-airway obstruction and emphysematous destruction in COPD. METHODS We used multidetector computed tomography (CT) to compare the number of airways measuring 2.0 to 2.5 mm in 78 patients who had various stages of COPD, as judged by scoring on the Global Initiative for Chronic Obstructive Lung Disease (GOLD) scale, in isolated lungs removed from patients with COPD who underwent lung transplantation, and in donor (control) lungs. MicroCT was used to measure the extent of emphysema (mean linear intercept), the number of terminal bronchioles per milliliter of lung volume, and the minimum diameters and cross-sectional areas of terminal bronchioles. RESULTS On multidetector CT, in samples from patients with COPD, as compared with control samples, the number of airways measuring 2.0 to 2.5 mm in diameter was reduced in patients with GOLD stage 1 disease (P=0.001), GOLD stage 2 disease (P=0.02), and GOLD stage 3 or 4 disease (P<0.001). MicroCT of isolated samples of lungs removed from patients with GOLD stage 4 disease showed a reduction of 81 to 99.7% in the total cross-sectional area of terminal bronchioles and a reduction of 72 to 89% in the number of terminal bronchioles (P<0.001). A comparison of the number of terminal bronchioles and dimensions at different levels of emphysematous destruction (i.e., an increasing value for the mean linear intercept) showed that the narrowing and loss of terminal bronchioles preceded emphysematous destruction in COPD (P<0.001). CONCLUSIONS These results show that narrowing and disappearance of small conducting airways before the onset of emphysematous destruction can explain the increased peripheral airway resistance reported in COPD. (Funded by the National Heart, Lung, and Blood Institute and others.).
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Affiliation(s)
- John E McDonough
- University of British Columbia James Hogg Research Centre, St. Paul's Hospital, Vancouver, BC, Canada
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Rambod M, Porszasz J, Make BJ, Crapo JD, Casaburi R. Six-minute walk distance predictors, including CT scan measures, in the COPDGene cohort. Chest 2011; 141:867-875. [PMID: 21960696 DOI: 10.1378/chest.11-0870] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022] Open
Abstract
BACKGROUND Exercise tolerance in COPD is only moderately well predicted by airflow obstruction assessed by FEV(1). We determined whether other phenotypic characteristics, including CT scan measures, are independent predictors of 6-min walk distance (6MWD) in the COPDGene cohort. METHODS COPDGene recruits non-Hispanic Caucasian and African American current and ex-smokers. Phenotyping measures include postbronchodilator FEV(1) % predicted and inspiratory and expiratory CT lung scans. We defined % emphysema as the percentage of lung voxels < -950 Hounsfield units on the inspiratory scan and % gas trapping as the percentage of lung voxels < -856 Hounsfield units on the expiratory scan. RESULTS Data of the first 2,500 participants of the COPDGene cohort were analyzed. Participant age was 61 ± 9 years; 51% were men; 76% were non-Hispanic Caucasians, and 24% were African Americans. Fifty-six percent had spirometrically defined COPD, with 9.3%, 23.4%, 15.0%, and 8.3% in GOLD (Global Initiative for Chronic Obstructive Lung Disease) stages I to IV, respectively. Higher % emphysema and % gas trapping predicted lower 6MWD (P < .001). However, in a given spirometric group, after adjustment for age, sex, race, and BMI, neither % emphysema nor % gas trapping, or their interactions with FEV(1) % predicted, remained a significant 6MWD predictor. In a given spirometric group, only 16% to 27% of the variance in 6MWD could be explained by age, male sex, Caucasian race, and lower BMI as significant predictors of higher 6MWD. CONCLUSIONS In this large cohort of smokers in a given spirometric stage, phenotypic characteristics were only modestly predictive of 6MWD. CT scan measures of emphysema and gas trapping were not predictive of 6MWD after adjustment for other phenotypic characteristics.
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Affiliation(s)
- Mehdi Rambod
- Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA
| | - Janos Porszasz
- Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA
| | | | | | - Richard Casaburi
- Rehabilitation Clinical Trials Center, Los Angeles Biomedical Research Institute at Harbor-UCLA Medical Center, Torrance, CA.
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