Computed tomographic emphysema distribution: relationship to clinical features in a cohort of smokers

Basilar Predominant Emphysema: Thinking beyond Alpha-1-Antitrypsin Deficiency

Basilar predominant emphysema, or disproportionate emphysematous involvement of the lung bases compared to the apices, is an uncommon radiographic pattern of emphysema traditionally associated with alpha-1-antitrypsin deficiency (AATD). We present a case of a 59-year-old female with 41 pack-year tobacco use, Stage IV COPD with supplemental oxygen, and bibasilar predominant emphysema who successfully underwent bronchoscopic lung volume reduction. She presented with recurrent hospitalizations for frequent exacerbations. After lung reduction, the patient displayed improvement in functional status without hospitalizations at the 15-month follow-up. Careful history taking is essential for any patients diagnosed with lower lobe emphysema to elucidate the underlying etiology. This case challenges the notion that basilar emphysema is sensitive or specific for AATD and emphasizes that this pattern of emphysema has a broad differential diagnosis and alternative etiologies should be considered. Our patient was ultimately diagnosed with smoking-related emphysema, with atypical bibasilar involvement. Furthermore, basilar predominant emphysema should be considered a separate entity from its apical predominant counterpart.

Diagnostic Performance of Dual-Energy Subtraction Radiography for the Detection of Pulmonary Emphysema: An Intra-Individual Comparison

PURPOSE/OBJECTIVES

To compare the diagnostic performance of dual-energy subtraction (DE) and conventional radiography (CR) for detecting pulmonary emphysema using computed tomography (CT) as a reference standard.

METHODS AND MATERIALS

Sixty-six patients (24 female, median age 73) were retrospectively included after obtaining lateral and posteroanterior chest X-rays with a dual-shot DE technique and chest CT within ±3 months. Two experienced radiologists first evaluated the standard CR images and, second, the bone-/soft tissue weighted DE images for the presence (yes/no), degree (1-4), and quadrant-based distribution of emphysema. CT was used as a reference standard. Inter-reader agreement was calculated. Sensitivity and specificity for the correct detection and localization of emphysema was calculated. Further degree of emphysema on CR and DE was correlated with results from CT. A p-value < 0.05 was considered as statistically significant.

RESULTS

The mean interreader agreement was substantial for CR and moderate for DE (kCR = 0.611 vs. kDE = 0.433; respectively). Sensitivity, as well as specificity for the detection of emphysema, was comparable between CR and DE (sensitivityCR 96% and specificityCR 75% vs. sensitivityDE 91% and specificityDE 83%; p = 0.157). Similarly, there was no significant difference in the sensitivity or specificity for emphysema localization between CR and DE (sensitivityCR 50% and specificityCR 100% vs. sensitivityDE 57% and specificityDE 100%; p = 0.157). There was a slightly better correlation with CT of emphysema grading in DE compared to CR (rDE = 0.75 vs. rCR = 0.68; p = 0.108); these differences were not statistically significant, however.

CONCLUSION

Diagnostic accuracy for the detection, quantification, and localization of emphysema between CR and DE is comparable. Interreader agreement, however, is better with CR compared to DE.

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

Purpose

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.

Emphysema quantification on computed tomography and its value in predicting radiation pneumonitis in lung cancer treated by stereotactic body radiotherapy

A large portion of patients with early-stage non-small-cell lung cancer (NSCLC) who are receiving stereotactic body radiation therapy (SBRT) are medically inoperable due to compromised pulmonary function, and among these patients pulmonary emphysema (PE) is common. However, the relationship between PE and radiation-induced lung injuries remains unclear. In this study, we aimed to describe the full spectrum of computed tomography (CT) features after SBRT for NSCLC, and to explore their relationship with variables, including PE and dosimetric factors. In all, 71 patients were enrolled. PE was quantified as the percentage of low attenuation area [attenuation values of <-860 Hounsfield units (HU)] within the radiation field (%LAA-860). Spearman's correlation and logistic regression were used to explore factors related to radiological features and radiation pneumonitis (RP). At the 1-year follow-up, acute radiological changes included: (i) diffuse consolidation, 11.3%; (ii) patchy consolidation and ground-glass opacities, 42.3%; and (iii) patchy ground-glass opacity, 14.1%. Late morphological changes occurred in 61.9% of patients (50.7% with a modified conventional pattern, 5.6% with a mass-like pattern and 5.6% with a scar-like pattern). Lower %LAA-860 was the only factor that was significantly associated with consolidation changes at 6 months after SBRT [odds ratio (OR), 0.008; P = 0.009], and it was also a significant predictor for Grade ≥ 2 RP (OR, 0.003; P = 0.04). Our study showed that patients with PE can benefit from SBRT on the condition that good control of dose-volume constraints is achieved.

Relationship of CT-quantified emphysema, small airways disease and bronchial wall dimensions with physiological, inflammatory and infective measures in COPD

BACKGROUND

COPD is a complex, heterogeneous disease characterised by progressive development of airflow limitation. Spirometry provides little information about key aspects of pathology and is poorly related to clinical outcome, so other tools are required to investigate the disease. We sought to explore the relationships between quantitative CT analysis with functional, inflammatory and infective assessments of disease to identify the utility of imaging to stratify disease to better predict outcomes and disease response.

METHODS

Patients from the AERIS study with moderate-very severe COPD underwent HRCT, with image analysis determining the quantity of emphysema (%LAA_<- 950), small airways disease (E/I MLD) and bronchial wall thickening (Pi10). At enrolment subjects underwent lung function testing, six-minute walk testing (6MWT), blood sampling for inflammatory markers and sputum sampling for white cell differential and microbiological culture and PCR.

RESULTS

122 subjects were included in this analysis. Emphysema and small airways disease had independent associations with airflow obstruction (β = - 0.34, p < 0.001 and β = - 0.56, p < 0.001). %LAA_<- 950 had independent associations with gas transfer (β = - 0.37, p < 0.001) and E/I MLD with RV/TLC (β = 0.30, p =0.003). The distance walked during the 6MWT was not associated with CT parameters, but exertional desaturation was independently associated with emphysema (β = 0.73, p < 0.001). Pi10 did not show any independent associations with lung function or functional parameters. No CT parameters had any associations with sputum inflammatory cells. Greater emphysema was associated with lower levels of systemic inflammation (CRP β = - 0.34, p < 0.001 and fibrinogen β = - 0.28, p =0.003). There was no significant difference in any of the CT parameters between subjects where potentially pathogenic bacteria were detected in sputum and those where it was not.

CONCLUSIONS

This study provides further validation for the use of quantitative CT measures of emphysema and small airways disease in COPD as they showed strong associations with pulmonary physiology and functional status. In contrast to this quantitative CT measures showed few convincing associations with biological measures of disease, suggesting it is not an effective tool at measuring disease activity.

Performance of quantitative CT parameters in assessment of disease severity in COPD: A prospective study

BACKGROUND

Both emphysematous destruction of lung parenchyma and airway remodeling is thought to contribute to airflow limitation in cases of chronic obstructive pulmonary disease (COPD).

OBJECTIVE

To evaluate the value of quantitative computed tomography (QCT) parameters of emphysema and airway disease with disease severity in patients with COPD.

MATERIALS AND METHODS

We prospectively studied 50 patients with COPD, which included nonsmokers and patients with different degrees of cumulative smoking exposure. Three QCT parameters namely LAA% (low attenuation area percentage), WA% (Wall area percentage), and pi10 were calculated as per the standard technique. Forced expiratory volume in 1 s (FEV1), BODE score, and MMRC dyspnea scale were used as measures of disease severity.

RESULTS

FEV1 was inversely and significantly associated with all three QCT parameters. Receiver operated characteristic curves in prediction of GOLD class 3 COPD yielded cut-off values of 12.2, 61.45, and 3.5 for LAA%, WA%, and pi10, respectively, with high sensitivities and specificities. In multiple linear regression model, however, only LAA% proved to be significantly associated with FEV1, BODE, and dyspnea.

CONCLUSION

QCT indices of both emphysema and airway disease influence FEV1, dyspnea, and BODE score in patients with COPD. Emphysema, however, appears to be more closely related to disease severity.

ADRB2 gene polymorphism and emphysema heterogeneity can modulate bronchodilator response in patients with emphysema

BACKGROUND

Genetic variation in the β₂-adrenergic receptor (ADRB2) gene has been thought to have an important role in the differential response to β₂-agonist therapy for asthma. However, previous studies have shown little evidence for an association between these ADRB2 variants and the bronchial dilator response (BDR) in chronic obstructive pulmonary disease (COPD) patients. This discrepancy could be explained by differences in the distribution and heterogeneity of pulmonary emphysema in COPD patients, since emphysema distribution and heterogeneity are thought to have a role in pulmonary function in COPD patients. We hypothesized that differences in emphysema distribution and heterogeneity may have masked significant alterations of the bronchodilator response among ADRB2 genotypes in COPD patients in previous studies.

METHODS

The BDR (induced by 20 μg of procaterol) was measured in 211 patients who had a smoking history of more than 10 pack/years and had undergone chest high resolution computed tomography examination. A low attenuations area (<960 Hounsfield Units) was identified and the emphysema heterogeneity index (EHI%) was calculated with a range in value from -100% to 100%. ADRB2 Arg16Gly genotyping was performed using polymerase chain reaction-restriction fragment length polymorphism analysis.

RESULTS

The BDR was augmented in patients with homogenous emphysema compared with those with upper-dominant emphysema. In patients carrying the AA genotype of ADRB2, the BDR was significantly increased in patients with upper-dominant emphysema, but not in patients with lower-dominant emphysema.

CONCLUSION

Combination analysis of ADRB2 Arg16Gly polymorphism and EHI% may predict the effectiveness of β₂-adrenergic receptor agonist treatment in patients with COPD and emphysema.

Lobar Emphysema Distribution Is Associated With 5-Year Radiological Disease Progression

BACKGROUND

Emphysema has considerable variability in its regional distribution. Craniocaudal emphysema distribution is an important predictor of the response to lung volume reduction. However, there is little consensus regarding how to define upper lobe-predominant and lower lobe-predominant emphysema subtypes. Consequently, the clinical and genetic associations with these subtypes are poorly characterized.

METHODS

We sought to identify subgroups characterized by upper-lobe or lower-lobe emphysema predominance and comparable amounts of total emphysema by analyzing data from 9,210 smokers without alpha-1-antitrypsin deficiency in the Genetic Epidemiology of COPD (COPDGene) cohort. CT densitometric emphysema was measured in each lung lobe. Random forest clustering was applied to lobar emphysema variables after regressing out the effects of total emphysema. Clusters were tested for association with clinical and imaging outcomes at baseline and at 5-year follow-up. Their associations with genetic variants were also compared.

RESULTS

Three clusters were identified: minimal emphysema (n = 1,312), upper lobe-predominant emphysema (n = 905), and lower lobe-predominant emphysema (n = 796). Despite a similar amount of total emphysema, the lower-lobe group had more severe airflow obstruction at baseline and higher rates of metabolic syndrome compared with subjects with upper-lobe predominance. The group with upper-lobe predominance had greater 5-year progression of emphysema, gas trapping, and dyspnea. Differential associations with known COPD genetic risk variants were noted.

CONCLUSIONS

Subgroups of smokers defined by upper-lobe or lower-lobe emphysema predominance exhibit different functional and radiological disease progression rates, and the upper-lobe predominant subtype shows evidence of association with known COPD genetic risk variants. These subgroups may be useful in the development of personalized treatments for COPD.

Genome-Wide Association Study of the Genetic Determinants of Emphysema Distribution

RATIONALE

Emphysema has considerable variability in the severity and distribution of parenchymal destruction throughout the lungs. Upper lobe-predominant emphysema has emerged as an important predictor of response to lung volume reduction surgery. Yet, aside from alpha-1 antitrypsin deficiency, the genetic determinants of emphysema distribution remain largely unknown.

OBJECTIVES

To identify the genetic influences of emphysema distribution in non-alpha-1 antitrypsin-deficient smokers.

METHODS

A total of 11,532 subjects with complete genotype and computed tomography densitometry data in the COPDGene (Genetic Epidemiology of Chronic Obstructive Pulmonary Disease [COPD]; non-Hispanic white and African American), ECLIPSE (Evaluation of COPD Longitudinally to Identify Predictive Surrogate Endpoints), and GenKOLS (Genetics of Chronic Obstructive Lung Disease) studies were analyzed. Two computed tomography scan emphysema distribution measures (difference between upper-third and lower-third emphysema; ratio of upper-third to lower-third emphysema) were tested for genetic associations in all study subjects. Separate analyses in each study population were followed by a fixed effect metaanalysis. Single-nucleotide polymorphism-, gene-, and pathway-based approaches were used. In silico functional evaluation was also performed.

MEASUREMENTS AND MAIN RESULTS

We identified five loci associated with emphysema distribution at genome-wide significance. These loci included two previously reported associations with COPD susceptibility (4q31 near HHIP and 15q25 near CHRNA5) and three new associations near SOWAHB, TRAPPC9, and KIAA1462. Gene set analysis and in silico functional evaluation revealed pathways and cell types that may potentially contribute to the pathogenesis of emphysema distribution.

CONCLUSIONS

This multicohort genome-wide association study identified new genomic loci associated with differential emphysematous destruction throughout the lungs. These findings may point to new biologic pathways on which to expand diagnostic and therapeutic approaches in chronic obstructive pulmonary disease. Clinical trial registered with www.clinicaltrials.gov (NCT 00608764).

Bronchoscopic lung volume reduction procedures for chronic obstructive pulmonary disease

BACKGROUND

In the recent years, a variety of bronchoscopic lung volume reduction (BLVR) procedures have emerged that may provide a treatment option to participants suffering from moderate to severe chronic obstructive pulmonary disease (COPD).

OBJECTIVES

To assess the effects of BLVR on the short- and long-term health outcomes in participants with moderate to severe COPD and determine the effectiveness and cost-effectiveness of each individual technique.

SEARCH METHODS

Studies were identified from the Cochrane Airways Group Specialised Register (CAGR) and by handsearching of respiratory journals and meeting abstracts. All searches are current until 07 December 2016.

SELECTION CRITERIA

We included randomized controlled trials (RCTs). We included studies reported as full text, those published as abstract only and unpublished data, if available.

DATA COLLECTION AND ANALYSIS

Two independent review authors assessed studies for inclusion and extracted data. Where possible, data from more than one study were combined in a meta-analysis using RevMan 5 software.

MAIN RESULTS

AeriSealOne RCT of 95 participants found that AeriSeal compared to control led to a significant median improvement in forced expiratory volume in one second (FEV₁) (18.9%, interquartile range (IQR) -0.7% to 41.9% versus 1.3%, IQR -8.2% to 12.9%), and higher quality of life, as measured by the St Georges Respiratory Questionnaire (SGRQ) (-12 units, IQR -22 units to -5 units, versus -3 units, IQR -5 units to 1 units), P = 0.043 and P = 0.0072 respectively. Although there was no significant difference in mortality (Odds Ratio (OR) 2.90, 95% CI 0.14 to 62.15), adverse events were more common for participants treated with AeriSeal (OR 3.71, 95% CI 1.34 to 10.24). The quality of evidence found in this prematurely terminated study was rated low to moderate. Airway bypass stentsTreatment with airway bypass stents compared to control did not lead to significant between-group changes in FEV₁ (0.95%, 95% CI -0.16% to 2.06%) or SGRQ scores (-2.00 units, 95% CI -5.58 units to 1.58 units), as found by one study comprising 315 participants. There was no significant difference in mortality (OR 0.76, 95% CI 0.21 to 2.77), nor were there significant differences in adverse events (OR 1.33, 95% CI 0.65 to 2.73) between the two groups. The quality of evidence was rated moderate to high. Endobronchial coilsThree studies comprising 461 participants showed that treatment with endobronchial coils compared to control led to a significant between-group mean difference in FEV₁ (10.88%, 95% CI 5.20% to 16.55%) and SGRQ (-9.14 units, 95% CI -11.59 units to -6.70 units). There were no significant differences in mortality (OR 1.49, 95% CI 0.67 to 3.29), but adverse events were significantly more common for participants treated with coils (OR 2.14, 95% CI 1.41 to 3.23). The quality of evidence ranged from low to high. Endobronchial valvesFive studies comprising 703 participants found that endobronchial valves versus control led to significant improvements in FEV₁ (standardized mean difference (SMD) 0.48, 95% CI 0.32 to 0.64) and scores on the SGRQ (-7.29 units, 95% CI -11.12 units to -3.45 units). There were no significant differences in mortality between the two groups (OR 1.07, 95% CI 0.47 to 2.43) but adverse events were more common in the endobronchial valve group (OR 5.85, 95% CI 2.16 to 15.84). Participant selection plays an important role as absence of collateral ventilation was associated with superior clinically significant improvements in health outcomes. The quality of evidence ranged from low to high. Intrabronchial valvesIn the comparison of partial bilateral placement of intrabronchial valves to control, one trial favoured control in FEV₁ (-2.11% versus 0.04%, P = 0.001) and one trial found no difference between the groups (0.9 L versus 0.87 L, P = 0.065). There were no significant differences in SGRQ scores (MD 2.64 units, 95% CI -0.28 units to 5.56 units) or mortality rates (OR 4.95, 95% CI 0.85 to 28.94), but adverse events were more frequent (OR 3.41, 95% CI 1.48 to 7.84) in participants treated with intrabronchial valves. The lack of functional benefits may be explained by the procedural strategy used, as another study (22 participants) compared unilateral versus partial bilateral placement, finding significant improvements in FEV₁ and SGRQ when using the unilateral approach. The quality of evidence ranged between moderate to high. Vapour ablationOne study of 69 participants found significant mean between-group differences in FEV₁ (14.70%, 95% CI 7.98% to 21.42%) and SGRQ (-9.70 units, 95% CI -15.62 units to -3.78 units), favouring vapour ablation over control. There was no significant between-group difference in mortality (OR 2.82, 95% CI 0.13 to 61.06), but vapour ablation led to significantly more adverse events (OR 3.86, 95% CI 1.00 to 14.97). The quality of evidence ranged from low to moderate.

AUTHORS' CONCLUSIONS

Results for selected BLVR procedures indicate they can provide significant and clinically meaningful short-term (up to one year) improvements in health outcomes, but this was at the expense of increased adverse events. The currently available evidence is not sufficient to assess the effect of BLVR procedures on mortality. These findings are limited by the lack of long-term follow-up data, limited availability of cost-effectiveness data, significant heterogeneity in results, presence of skew and high CIs, and the open-label character of a number of the studies.

Percent Emphysema and Daily Motor Activity Levels in the General Population: Multi-Ethnic Study of Atherosclerosis

BACKGROUND

COPD is associated with reduced physical capacity. However, it is unclear whether pulmonary emphysema, which can occur without COPD, is associated with reduced physical activity in daily life, particularly among people without COPD and never smokers. We hypothesized that greater percentage of emphysema-like lung on CT scan is associated with reduced physical activity assessed by actigraphy and self-report.

METHODS

The Multi-Ethnic Study of Atherosclerosis (MESA) enrolled participants free of clinical cardiovascular disease from the general population. Percent emphysema was defined as percentage of voxels < -950 Hounsfield units on full-lung CT scans. Physical activity was measured by wrist actigraphy over 7 days and a questionnaire. Multivariable linear regression was used to adjust for age, sex, race/ethnicity, height, weight, education, smoking, pack-years, and lung function.

RESULTS

Among 1,435 participants with actigraphy and lung measures, 47% had never smoked, and 8% had COPD. Percent emphysema was associated with lower activity levels on actigraphy (P = .001), corresponding to 1.5 hour less per week of moderately paced walking for the average participant in quintile 2 vs 4 of percent emphysema. This association was significant among participants without COPD (P = .004) and among ever (P = .01) and never smokers (P = .03). It was also independent of coronary artery calcium and left ventricular ejection fraction. There was no evidence that percent emphysema was associated with self-reported activity levels.

CONCLUSIONS

Percent emphysema was associated with decreased physical activity in daily life objectively assessed by actigraphy in the general population, among participants without COPD, and nonsmokers.

Lung volume reduction surgery for diffuse emphysema

BACKGROUND

Lung volume reduction surgery (LVRS) performed to treat patients with severe diffuse emphysema was reintroduced in the nineties. Lung volume reduction surgery aims to resect damaged emphysematous lung tissue, thereby increasing elastic properties of the lung. This treatment is hypothesised to improve long-term daily functioning and quality of life, although it may be costly and may be associated with risks of morbidity and mortality. Ten years have passed since the last version of this review was prepared, prompting us to perform an update.

OBJECTIVES

The objective of this review was to gather all available evidence from randomised controlled trials comparing the effectiveness of lung volume reduction surgery (LVRS) versus non-surgical standard therapy in improving health outcomes for patients with severe diffuse emphysema. Secondary objectives included determining which subgroup of patients benefit from LVRS and for which patients LVRS is contraindicated, to establish the postoperative complications of LVRS and its morbidity and mortality, to determine which surgical approaches for LVRS are most effective and to calculate the cost-effectiveness of LVRS.

SEARCH METHODS

We identified RCTs by using the Cochrane Airways Group Chronic Obstructive Pulmonary Disease (COPD) register, in addition to the online clinical trials registers. Searches are current to April 2016.

SELECTION CRITERIA

We included RCTs that studied the safety and efficacy of LVRS in participants with diffuse emphysema. We excluded studies that investigated giant or bullous emphysema.

DATA COLLECTION AND ANALYSIS

Two independent review authors assessed trials for inclusion and extracted data. When possible, we combined data from more than one study in a meta-analysis using RevMan 5 software.

MAIN RESULTS

We identified two new studies (89 participants) in this updated review. A total of 11 studies (1760 participants) met the entry criteria of the review, one of which accounted for 68% of recruited participants. The quality of evidence ranged from low to moderate owing to an unclear risk of bias across many studies, lack of blinding and low participant numbers for some outcomes. Eight of the studies compared LVRS versus standard medical care, one compared two closure techniques (stapling vs laser ablation), one looked at the effect of buttressing the staple line on the effectiveness of LVRS and one compared traditional 'resectional' LVRS with a non-resectional surgical approach. Participants completed a mandatory course of pulmonary rehabilitation/physical training before the procedure commenced. Short-term mortality was higher for LVRS (odds ratio (OR) 6.16, 95% confidence interval (CI) 3.22 to 11.79; 1489 participants; five studies; moderate-quality evidence) than for control, but long-term mortality favoured LVRS (OR 0.76, 95% CI 0.61 to 0.95; 1280 participants; two studies; moderate-quality evidence). Participants identified post hoc as being at high risk of death from surgery were those with particularly impaired lung function, poor diffusing capacity and/or homogenous emphysema. Participants with upper lobe-predominant emphysema and low baseline exercise capacity showed the most favourable outcomes related to mortality, as investigators reported no significant differences in early mortality between participants treated with LVRS and those in the control group (OR 0.87, 95% CI 0.23 to 3.29; 290 participants; one study), as well as significantly lower mortality at the end of follow-up for LVRS compared with control (OR 0.45, 95% CI 0.26 to 0.78; 290 participants; one study). Trials in this review furthermore provided evidence of low to moderate quality showing that improvements in lung function parameters other than forced expiratory volume in one second (FEV1), quality of life and exercise capacity were more likely with LVRS than with usual follow-up. Adverse events were more common with LVRS than with control, specifically the occurrence of (persistent) air leaks, pulmonary morbidity (e.g. pneumonia) and cardiovascular morbidity. Although LVRS leads to an increase in quality-adjusted life-years (QALYs), the procedure is relatively costly overall.

AUTHORS' CONCLUSIONS

Lung volume reduction surgery, an effective treatment for selected patients with severe emphysema, may lead to better health status and lung function outcomes, specifically for patients who have upper lobe-predominant emphysema with low exercise capacity, but the procedure is associated with risks of early mortality and adverse events.

Influence of emphysema distribution on pulmonary function parameters in COPD patients

OBJECTIVE:

To evaluate the impact that the distribution of emphysema has on clinical and functional severity in patients with COPD.

METHODS:

The distribution of the emphysema was analyzed in COPD patients, who were classified according to a 5-point visual classification system of lung CT findings. We assessed the influence of emphysema distribution type on the clinical and functional presentation of COPD. We also evaluated hypoxemia after the six-minute walk test (6MWT) and determined the six-minute walk distance (6MWD).

RESULTS:

Eighty-six patients were included. The mean age was 65.2 ± 12.2 years, 91.9% were male, and all but one were smokers (mean smoking history, 62.7 ± 38.4 pack-years). The emphysema distribution was categorized as obviously upper lung-predominant (type 1), in 36.0% of the patients; slightly upper lung-predominant (type 2), in 25.6%; homogeneous between the upper and lower lung (type 3), in 16.3%; and slightly lower lung-predominant (type 4), in 22.1%. Type 2 emphysema distribution was associated with lower FEV1, FVC, FEV1/FVC ratio, and DLCO. In comparison with the type 1 patients, the type 4 patients were more likely to have an FEV1 < 65% of the predicted value (OR = 6.91, 95% CI: 1.43-33.45; p = 0.016), a 6MWD < 350 m (OR = 6.36, 95% CI: 1.26-32.18; p = 0.025), and post-6MWT hypoxemia (OR = 32.66, 95% CI: 3.26-326.84; p = 0.003). The type 3 patients had a higher RV/TLC ratio, although the difference was not significant.

CONCLUSIONS:

The severity of COPD appears to be greater in type 4 patients, and type 3 patients tend to have greater hyperinflation. The distribution of emphysema could have a major impact on functional parameters and should be considered in the evaluation of COPD patients.

Diagnosis, assessment, and phenotyping of COPD: beyond FEV₁

COPD is now widely recognized as a complex heterogeneous syndrome, having both pulmonary and extrapulmonary features. In clinical practice, the diagnosis of COPD is based on the presence of chronic airflow limitation, as assessed by post-bronchodilator spirometry. The severity of the airflow limitation, as measured by percent predicted FEV1, provides important information to the physician to enable optimization of management. However, in order to accurately assess the complexity of COPD, there need to be other measures made beyond FEV1. At present, there is a lack of reliable and simple blood biomarkers to confirm and further assess the diagnosis of COPD. However, it is possible to identify patients who display different phenotypic characteristics of COPD that relate to clinically relevant outcomes. Currently, validated phenotypes of COPD include alpha-1 antitrypsin deficiency, and "frequent exacerbators". Recently, a definition and assessment of a new phenotype comprising patients with overlapping features of asthma and COPD has been suggested and is known as "asthma COPD overlap syndrome". Several other phenotypes have been proposed, but require validation against clinical outcomes. Defining phenotypes requires the assessment of multiple factors indicating disease severity, its impact, and its activity. Recognition and validation of COPD phenotypes has an important role to play in the selection of evidence-based targeted therapy in the future management of COPD, but regardless of the diagnostic terms, patients with COPD should be assessed and treated according to their individual treatable characteristics.

Regional Heterogeneity of Chronic Obstructive Pulmonary Disease Phenotypes: Pulmonary (3)He Magnetic Resonance Imaging and Computed Tomography

Pulmonary ventilation may be visualized and measured using hyperpolarized (3)He magnetic resonance imaging (MRI) while emphysema and its distribution can be quantified using thoracic computed tomography (CT). Our objective was to phenotype ex-smokers with COPD based on the apical-to-basal distribution of ventilation abnormalities and emphysema to better understand how these phenotypes change regionally as COPD progresses. We evaluated 100 COPD ex-smokers who provided written informed consent and underwent spirometry, CT and (3)He MRI. (3)He MRI ventilation imaging was used to quantify the ventilation defect percent (VDP) for whole-lung and individual lung lobes. Regional VDP was used to generate the apical-lung (AL)-to-basal-lung (BL) difference (ΔVDP); a positive ΔVDP indicated AL-predominant and negative ΔVDP indicated BL-predominant ventilation defects. Emphysema was quantified using the relative-area-of-the-lung ≤-950HU (RA950) of the CT density histogram for whole-lung and individual lung lobes. The AL-to-BL RA950 difference (ΔRA950) was generated with a positive ΔRA950 indicating AL-predominant emphysema and a negative ΔRA950 indicating BL-predominant emphysema. Seventy-two ex-smokers reported BL-predominant MRI ventilation defects and 71 reported AL-predominant CT emphysema. BL-predominant ventilation defects (AL/BL: GOLD I = 18%/82%, GOLD II = 24%/76%) and AL-predominant emphysema (AL/BL: GOLD I = 84%/16%, GOLD II = 72%/28%) were the major phenotypes in mild-moderate COPD. In severe COPD there was a more uniform distribution for ventilation defects (AL/BL: GOLD III = 40%/60%, GOLD IV = 43%/57%) and emphysema (AL/BL: GOLD III = 64%/36%, GOLD IV = 43%/57%). Basal-lung ventilation defects predominated in mild-moderate GOLD grades, and a more homogeneous distribution of ventilation defects was observed in more advanced grade COPD; these differences suggest that over time, regional ventilation abnormalities become more homogenously distributed during disease progression.

The Impact of Homogeneous Versus Heterogeneous Emphysema on Dynamic Hyperinflation in Patients With Severe COPD Assessed for Lung Volume Reduction

Dynamic hyperinflation (DH) is a pathophysiologic hallmark of Chronic Obstructive Pulmonary Disease (COPD). The aim of this study was to investigate the impact of emphysema distribution on DH during a maximal cardiopulmonary exercise test (CPET) in patients with severe COPD.

This was a retrospective analysis of prospectively collected data among severe COPD patients who underwent thoracic high-resolution computed tomography, full lung function measurements and maximal CPET with inspiratory manouvers as assessment for a lung volume reduction procedure. ΔIC was calculated by subtracting the end-exercise inspiratory capacity (eIC) from resting IC (rIC) and expressed as a percentage of rIC (ΔIC %). Emphysema quantification was conducted at 3 predefined levels using the syngo PULMO-CT (Siemens AG); a difference >25% between best and worse slice was defined as heterogeneous emphysema.

Fifty patients with heterogeneous (62.7% male; 60.9 ± 7.5 years old; FEV₁% = 32.4 ± 11.4) and 14 with homogeneous emphysema (61.5% male; 62.5 ± 5.9 years old; FEV₁% = 28.1 ± 10.3) fulfilled the enrolment criteria. The groups were matched for all baseline variables. ΔIC% was significantly higher in homogeneous emphysema (39.8% ± 9.8% vs.31.2% ± 13%, p = 0.031), while no other CPET parameter differed between the groups. Upper lobe predominance of emphysema correlated positively with peak oxygen pulse, peak oxygen uptake and peak respiratory rate, and negatively with ΔIC%. Homogeneous emphysema is associated with more DH during maximum exercise in COPD patients.

How Common Is Airflow Limitation in Patients With Emphysema on CT Scan of the Chest?

BACKGROUND

COPD has traditionally been defined by the presence of irreversible airflow limitation on spirometry using either the GOLD (Global Initiative for Chronic Obstructive Lung Disease) or American Thoracic Society/European Respiratory Society criteria (lower limit of normal [LLN]). We have observed that some patients with clinical COPD and emphysema on chest CT scan have no obstruction on spirometry. The purpose of this study was to assess the prevalence of obstruction by GOLD and LLN criteria in patients with emphysema on CT scan and determine which radiographic criteria were associated with a clinical diagnosis of COPD.

METHODS

We retrospectively analyzed the clinical records and spirometry of all patients who had radiographically defined emphysema on chest CT scans completed at the University of Vermont in 2011. We compared spirometric criteria and CT scan factors with the presence of clinical COPD based on chart review.

RESULTS

We identified 274 patients with CT scan-defined emphysema. GOLD criteria detected obstruction in 228 patients (83%), and LLN detected obstruction in 206 patients (75%). However, GOLD failed to correctly identify 19 patients (6.9%) and LLN failed to identify 38 patients (13.9%) (average 10.4%) who had radiographic emphysema and a clinical diagnosis of COPD. Obese patients had a lower prevalence of obstruction whether classified by LLN or GOLD. Among patients with spirometric obstruction, there were greater degrees of emphysema and more severely increased airway wall thickness. Factors that were independently associated with clinical COPD were lower FVC % predicted, lower FEV1/FVC ratio, and increasing airway wall thickness.

CONCLUSIONS

Spirometry missed 10.4% of patients with clinical COPD who have significant emphysema on chest CT scan.

Gender differences of chronic obstructive pulmonary disease associated with manifestations on HRCT

BACKGROUND AND AIMS

Patients with chronic obstructive pulmonary disease (COPD) have been shown to have significant gender differences in terms of susceptibility, severity and response to therapy. We hypothesized that this was due to differences in functional and pathologic changes in the airway, which can be revealed by high-resolution computed tomography (HRCT) in addition to pulmonary function test (PFT).

METHODS

A total of 84 patients with COPD were enrolled in the study. Within 1 week of enrollment, a history of each patient's current illness was obtained. PFT and chest HRCT scan were performed.

RESULTS

The patients were classified as phenotype A, E and M based on the chest HRCT presentations. No significant gender differences were found in COPD severity (χ²  = 4.993, P = 0.172). Male patients have more smoking history and smaller average age compared with female patients. Female patients showed a significantly higher FEV₁ /FVC, lower inspiratory capacity and milder residual volume/total lung capacity than that of male patients. Based on the HRCT results, more males were classified as phenotype M, whereas females tended to be phenotype A. Males had a greater grade of low attenuation areas and were more likely to show evidence of emphysema on a HRCT scan than females (χ²  = 15.373, P = 0.001), whereas females had less airway wall thickening than males, although this change had no statistical significance. (χ²  = 0.163, P = 0.922).

CONCLUSION

Gender differences of COPD patients were seen in ages of onset, smoking history, and PFT and HRCT presentations. The use of HRCT imaging indicates that there are significant gender differences in the clinical manifestations of COPD.

Correlation of a decline in aerobic capacity with development of emphysema in patients with chronic obstructive pulmonary disease: a prospective observational study

In patients with COPD, CT assessment of emphysema and airway disease is known to be associated with lung function and 6-minute walk distance. However, it remains to be determined whether low attenuation area (LAA) on CT is associated with aerobic capacity assessed using cardiopulmonary exercise testing (CPET). In this prospective observational study, we repeatedly conducted high-resolution CT and CPET using a treadmill in 81 COPD patients over a median interval of 3.5 years. Two investigators independently scored LAA on images obtained at the aortic arch level, tracheal bifurcation level, and supradiaphragmatic level. Grades for the images of each lung were added to yield the total LAA score. Total LAA score was negatively correlated with peak aerobic capacity ([Formula: see text]) (p<0.001, r = -0.485). LAA scores of the upper (aortic arch level) and the lower (supradiaphragmatic level) lungs were both significantly associated with peak [Formula: see text]. There was a significant correlation between total LAA score and peak CO2 output ([Formula: see text]) (p<0.001, r = -0.433). Total LAA score was correlated with oxygen saturation at peak exercise (p<0.001, r = -0.634) and the estimated dead space fraction (p<0.001, r = 0.416). The mean annual change in total LAA score was significantly correlated with those in peak [Formula: see text] (p<0.001, r = -0.546) and peak [Formula: see text] (p<0.001, r = -0.488). The extent of emphysema measured by CT was associated with the results of CPET. The time-dependent changes in CPET data were also correlated with that in total LAA score. CT assessment could be a non-invasive tool to predict aerobic capacity in patients with COPD.

Quantitative Emphysema Distribution in Anatomic and Non-anatomic Lung Regions

PURPOSE

The change of emphysema distribution with increasing COPD severity is not yet assessed. Especially, involvement of the upper aspect of the lower lobe is unknown. The primary aim was to quantitatively determine regional distribution of emphysema in anatomically (lung lobes) and non-anatomically defined lung regions (upper/lower lung halves as well as core and rind regions) in a cohort covering equally all COPD severity stages using CT.

MATERIAL AND METHODS

Basically 100 CT data sets were quantitatively evaluated for regional distribution of emphysema. Emphysema characteristics (emphysema index, mean lung density and 15th percentile of the attenuation values of lung voxels) were compared (t-test) in: upper lobes vs. upper halves, lower lobes vs. lower halves, core vs. rind region.

RESULTS

In patients with ≤ GOLD II, a significantly higher emphysema burden was found in the upper lobes as compared to upper halves. In subjects with GOLD III/IV the differences were not significant for all emphysema characteristics. A high difference between lobes and halves in subjects with ≤ GOLD II was found, in contrast to low difference in higher GOLD stages.

CONCLUSIONS

Lobar segmentation provides improved characterization of cranio-caudal emphysema distribution compared to a non-anatomic approach in subjects up to GOLD stage II.

Sputum matrix metalloproteinase-9 is associated with the degree of emphysema on computed tomography in COPD

BACKGROUND

Matrix-metalloproteinase (MMP)-9 has been implicated in the pathogenesis of COPD, although its link to disease severity is unclear. The purpose of the study was to examine the relationship between disease severity assessed by lung function and computed tomography (CT) and sputum MMP-9 expression, concentration and activity in patients with COPD.

FINDINGS

In 53 COPD subjects, smokers and ex-smokers; 46 healthy controls, smokers and never smokers, we measured sputum MMP-9 concentrations (ELISA) and enzyme activity (FRET), sputum MMP-9 mRNA expression, spirometry, diffusing capacity for carbon monoxide (DLco) and CT assessment of emphysema (% low attenuation areas below-950 Hounsfield units). Sputum MMP-9 concentrations and mRNA expression in COPD subjects were significantly greater than in healthy never-smokers (p = 0.007 and p = 0.001 respectively) and similar to those in healthy smokers. Disease severity when assessed by the extent of emphysema measured by CT, but not by spirometry or DLco values, was directly associated with sputum MMP-9 concentrations [r = 0.442 (0.171, 0.634), p = 0.020], and MMP-9 activity [r = 0.447 (0.219, 0.643), p = 0.010]. In moderate to severe COPD, increased MMP-9 mRNA expression levels were associated with reduced post-bronchodilator FEV1 [r = -0.530 (-0.686, -0.327), p < 0.001], FEV1/FVC ratio [r = -0.551 (-0.701, -0.354), p < 0.001] and reduced DLco [r = -0.399 (-539, -0.102), p = 0.048].

CONCLUSIONS

Sputum MMP-9 concentrations in COPD are directly associated with the extent of emphysema measured by CT and MMP-9 expression levels are inversely associated with DLco. These findings support a role for MMP-9 in the pathogenesis of COPD.

Impact of emphysema and airway wall thickness on quality of life in smoking-related COPD

BACKGROUND

Limited data are available as to the relationship between computed tomography (CT) derived data on emphysema and airway wall thickness, and quality of life in subjects with chronic obstructive pulmonary disease (COPD). Such data may work to clarify the clinical correlate of the CT findings.

METHODS

We included 1778 COPD subjects aged 40-75 years with a smoking history of at least 10 pack-years. They were examined with St George's Respiratory Questionnaire (SGRQ-C) and high-resolution chest CT. Level of emphysema was assessed as percent low-attenuation areas less than -950 Hounsfield units (%LAA). Airway wall thickness was estimated by calculating the square root of wall area of an imaginary airway with an internal perimeter of 10 mm (Pi10).

RESULTS

In both men and women, the mean total score and most of the subscores of SGRQ-C increased with increasing level of emphysema and increasing level of airway wall thickness, after adjusting for age, smoking status, pack years, body mass index and FEV1. The highest gradient was seen in the relationship between the activity score and the emphysema level. The activity score increased by 35% from the lowest to the highest emphysema tertile. The relationship between level of emphysema and the total SGRQ-C score became weaker with increasing GOLD (Global initiative for Chronic Obstructive Lung Disease) stages (p < 0.001), while the impact of gender was limited.

CONCLUSION

In subjects with COPD, increasing levels of emphysema and airway wall thickness are independently related to impaired quality of life.

Assessment of lung volume collapsibility in chronic obstructive lung disease patients using CT

OBJECTIVE

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.

METHODS

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.

RESULTS

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).

CONCLUSION

Severity of COPD appears associated with increased collapsibility in the upper lobes, but change (decline) in collapsibility is faster in the lower lobes.

KEY POINTS

• 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.

Sputum matrix metalloproteinase-12 in patients with chronic obstructive pulmonary disease and asthma: relationship to disease severity

BACKGROUND

Matrix metalloproteinase (MMP)-12 has been implicated in the pathogenesis of both chronic obstructive pulmonary disease (COPD) and asthma. The influence of disease severity on sputum MMP-12 concentrations and activity is not known.

OBJECTIVES

We sought to examine the relationship between disease severity assessed by means of lung function and computed tomography (CT) and induced sputum MMP-12 concentrations and activity in patients with asthma and COPD.

METHODS

In 208 subjects (109 asthmatic patients, smokers and never smokers, mild, moderate, and severe; 53 patients with COPD, smokers and exsmokers, mild, moderate, and severe; and 46 healthy control subjects, smokers and never smokers), we measured induced sputum MMP-12 concentrations (ELISA) and enzyme activity (fluorescence resonance energy transfer), sputum cell MMP12 mRNA expression (quantitative PCR [qPCR]), diffusing capacity for carbon monoxide (Dlco), and CT assessment of emphysema (percentage of low-attenuation areas at less -950 Hounsfield units).

RESULTS

Sputum MMP-12 concentrations are greater in patients with COPD and smokers with asthma than in healthy nonsmokers (P = .003 and P = .035, respectively) but similar to those seen in healthy smokers. In patients with COPD, disease severity, when measured by means of CT-assessed emphysema, but not by means of spirometry or Dlco values, is directly associated with sputum MMP-12 concentrations and activity. In the asthma groups there is no significant association between disease severity and sputum MMP-12 concentrations or activity.

CONCLUSIONS

Sputum MMP-12 concentrations and activity in patients with COPD are directly associated with the extent of emphysema measured by means of CT. This finding supports a role for MMP-12 in the pathogenesis of COPD and might suggest that blocking MMP-12 activity in patients with COPD could prevent the further development of emphysema.

In Vivo Computed Tomography as a Research Tool to Investigate Asthma and COPD: Where Do We Stand?

Computed tomography (CT) is a clinical tool widely used to assess and followup asthma and chonic obstructive pulmonary disease (COPD) in humans. Strong efforts have been made the last decade to improve this technique as a quantitative research tool. Using semiautomatic softwares, quantification of airway wall thickness, lumen area, and bronchial wall density are available from large to intermediate conductive airways. Skeletonization of the bronchial tree can be built to assess its three-dimensional geometry. Lung parenchyma density can be analysed as a surrogate of small airway disease and emphysema. Since resident cells involve airway wall and lung parenchyma abnormalities, CT provides an accurate and reliable research tool to assess their role in vivo. This litterature review highlights the most recent advances made to assess asthma and COPD with CT, and also their drawbacks and the place of CT in clarifying the complex physiopathology of both diseases.

Genome-wide association analysis of body mass in chronic obstructive pulmonary disease

Cachexia, whether assessed by body mass index (BMI) or fat-free mass index (FFMI), affects a significant proportion of patients with chronic obstructive pulmonary disease (COPD), and is an independent risk factor for increased mortality, increased emphysema, and more severe airflow obstruction. The variable development of cachexia among patients with COPD suggests a role for genetic susceptibility. The objective of the present study was to determine genetic susceptibility loci involved in the development of low BMI and FFMI in subjects with COPD. A genome-wide association study (GWAS) of BMI was conducted in three independent cohorts of European descent with Global Initiative for Chronic Obstructive Lung Disease stage II or higher COPD: Evaluation of COPD Longitudinally to Identify Predictive Surrogate End-Points (ECLIPSE; n = 1,734); Norway-Bergen cohort (n = 851); and a subset of subjects from the National Emphysema Treatment Trial (NETT; n = 365). A genome-wide association of FFMI was conducted in two of the cohorts (ECLIPSE and Norway). In the combined analyses, a significant association was found between rs8050136, located in the first intron of the fat mass and obesity-associated (FTO) gene, and BMI (P = 4.97 × 10(-7)) and FFMI (P = 1.19 × 10(-7)). We replicated the association in a fourth, independent cohort consisting of 502 subjects with COPD from COPDGene (P = 6 × 10(-3)). Within the largest contributing cohort of our analysis, lung function, as assessed by forced expiratory volume at 1 second, varied significantly by FTO genotype. Our analysis suggests a potential role for the FTO locus in the determination of anthropomorphic measures associated with COPD.

Emphysema presence, severity, and distribution has little impact on the clinical presentation of a cohort of patients with mild to moderate COPD

BACKGROUND

Phenotypic characterization of patients with COPD may have potential prognostic and therapeutic implications. Available information on the relationship between emphysema and the clinical presentation in patients with COPD is limited to advanced stages of the disease. The objective of this study was to describe emphysema presence, severity, and distribution and its impact on clinical presentation of patients with mild to moderate COPD.

METHODS

One hundred fifteen patients with COPD underwent clinical and chest CT scan evaluation for the presence, severity, and distribution of emphysema. Patients with and without emphysema and with different forms of emphysema distribution (upper/lower/core/peel) were compared. The impact of emphysema severity and distribution on clinical presentation was determined.

RESULTS

Fifty percent of the patients had mild homogeneously distributed emphysema (1.84; 0.76%-4.77%). Upper and core zones had the more severe degree of emphysema. Patients with emphysema were older, more frequently men, and had lower FEV(1)%, higher total lung capacity percentage, and lower diffusing capacity of the lung for carbon monoxide. No differences were found between the clinical or physiologic parameters of the different emphysema distributions.

CONCLUSIONS

In patients with mild to moderate COPD, although the presence of emphysema has an impact on physiologic presentation, its severity and distribution seem to have little impact on clinical presentation.

Relationship of emphysema and airway disease assessed by CT to exercise capacity in COPD

OBJECTIVE

To assess the association of emphysema and airway disease assessed by volumetric computed tomography (CT) with exercise capacity in subjects with chronic obstructive pulmonary disease (COPD).

METHODS

We studied 93 subjects with COPD (Forced Expiratory Volume in 1 s [FEV(1)] %predicted mean +/- SD 57.1 +/- 24.3%, female gender = 40) enrolled in the Lung Tissue Research Consortium. Emphysema was defined as percentage of low attenuation areas less than a threshold of -950 Hounsfield units (%LAA-950) on CT scan. The wall area percentage (WA%) of the 3rd to 6th generations of the apical bronchus of right upper lobe (RB1) were analyzed. The 6-min walk distance (6MWD) test was used as a measure of exercise capacity.

RESULTS

The 6MWD was inversely associated with %LAA-950 (r = -0.53, p < 0.0001) and with the WA% of 6th generation of RB1 only (r = -0.28, p = 0.009). In a multivariate regression model including CT indices of emphysema and airway disease that were adjusted for demographic and physiologic variables as well as brand of CT scanner, only the %LAA-950 remained significantly associated with exercise performance. Holding other covariates fixed, this model showed that a 10% increase of CT emphysema reduced the distance walked in 6 min 28.6 m (95% Confidence Interval = -51.2, -6.0, p = 0.01).

CONCLUSION

These results suggest that the extent of emphysema but not airway disease measured by volumetric CT contributes independently to exercise limitation in subjects with COPD.

Sex differences in emphysema and airway disease in smokers

BACKGROUND

The authors of previous reports have suggested that women are more susceptible to cigarette smoke and to an airway-predominant COPD phenotype rather than an emphysema-predominant COPD phenotype. The purpose of this study was to test for sex differences in COPD phenotypes by using high-resolution CT (HRCT) scanning in male and female smokers with and without COPD.

METHODS

All subjects completed spirometry and answered an epidemiologic respiratory questionnaire. Inspiratory HRCT scans were obtained on 688 smokers enrolled in a family-based study of COPD. Emphysema was assessed by using a density mask with a cutoff of -950 Hounsfield units to calculate the low-attenuation area percentage (LAA%) and by the fractal value D, which is the slope of a power law analysis defining the relationship between the number and size of the emphysematous lesions. Airway wall thickness was assessed by calculating the square root of the airway wall area (SQRTWA) and the percentage of the total airway area taken by the airway wall (WA%) relative to the internal perimeter.

RESULTS

Women had a similar FEV(1) (women, 65.5% +/- 31.9% predicted; men, 62.1% +/- 30.4% predicted; p = 0.16) but fewer pack-years of cigarette smoking (women, 37.8 +/- 19.7 pack-years; men, 47.8 +/- 27.4 pack-years; p < 0.0001). Men had a greater LAA% (24% +/- 12% vs 20% +/- 11%, respectively; p < 0.0001) and larger emphysematous spaces than women, and these differences persisted after adjusting for covariates (weight, pack-years of smoking, current smoking status, center of enrollment, and FEV(1) percent predicted; p = 0.0006). Women had a smaller SQRTWA and WA% after adjusting for covariates (p < 0.0001).

CONCLUSION

Male smokers have more emphysema than female smokers, but female smokers do not show increased wall thickness compared with men.