Relationships between diffusing capacity for carbon monoxide (DLCO), and quantitative computed tomography measurements and visual assessment for chronic obstructive pulmonary disease

Diffusing capacity as an independent predictor of acute exacerbations in chronic obstructive pulmonary disease

A weak correlation between diffusing capacity of the lung for carbon monoxide (DLCO) and emphysema has been reported. This study investigated whether impaired DLCO in chronic obstructive pulmonary disease (COPD) is associated with increased risk of acute exacerbation independent of the presence or extent of emphysema. This retrospective cohort study included patients with COPD between January 2004 and December 2019. The participants were divided into four groups based on visually detected emphysema and impaired DLCO. Among 597 patients with COPD, 8.5% had no emphysema and impaired DLCO whereas 36.3% had emphysema without impaired DLCO. Among the four groups, patients with impaired DLCO and emphysema showed a higher risk of moderate-to-severe or severe exacerbation than those with normal DLCO. Impaired DLCO was an independent risk factor for severe exacerbation (hazard ratio, 1.524 [95% confidence interval 1.121-2.072]), whereas the presence of emphysema was not. The risk of moderate-to-severe or severe exacerbation increases with the severity of impaired DLCO. After propensity-score matching for the extent of emphysema, impaired DLCO was significantly associated with a higher risk of moderate-to-severe (p = 0.041) or severe exacerbation (p = 0.020). In patients with COPD and heterogeneous parenchymal abnormalities, DLCO can be considered an independent biomarker of acute exacerbation.

Diffusing Capacity as a Predictor of Hospitalizations in a Clinical Cohort of Chronic Obstructive Pulmonary Disease

Rationale: Chronic obstructive pulmonary disease (COPD) hospitalizations are a major burden on patients. Diffusing capacity of the lung for carbon monoxide (DlCO) is a potential predictor that has not been studied in large cohorts. Objectives: This study used electronic health record data to evaluate whether clinically obtained DlCO predicts COPD hospitalizations. Methods: We performed time-to-event analyses of individuals with COPD and DlCO measurements from the Johns Hopkins COPD Precision Medicine Center of Excellence. Cox proportional hazard methods were used to model time from DlCO measurement to first COPD hospitalization and composite first hospitalization or death, adjusting for age, sex, race, body mass index, smoking status, forced expiratory volume in 1 second (FEV1), history of prior COPD hospitalization, and comorbidities. To identify the utility of including DlCO in risk models, area under the receiver operating curve (AUC) values were calculated for models with and without DlCO. Results were externally validated in a separate analogous cohort. Results: Of 2,793 participants, 368 (13%) had a COPD hospitalization within 3 years. In adjusted analyses, for every 10% decrease in DlCO% predicted, risk of COPD hospitalization increased by 10% (hazard ratio, 1.1; 95% confidence interval, 1.1-1.2; P < 0.001). Similar associations were observed for COPD hospitalizations or death. The model including demographics, comorbidities, FEV1, DlCO, and prior COPD hospitalizations performed well, with an AUC of 0.85 and an AUC of 0.84 in an external validation cohort. Conclusions: Diffusing capacity is a strong predictor of COPD hospitalizations in a clinical cohort of individuals with COPD, independent of airflow obstruction and prior hospitalizations. These findings support incorporation of DlCO in risk assessment of patients with COPD.

Reintubation After Lung Cancer Resection: Development and External Validation of a Predictive Score

BACKGROUND

Reintubation after lung cancer resection is an important quality metric because of increased disability, mortality and cost. However, no validated predictive instrument is in use to reduce reintubation after lung resection. This study aimed to create and validate the PRediction Of REintubation After Lung cancer resection (PROREAL) score.

METHODS

The study analyzed lung resection cases from 2 university hospitals. The primary end point was reintubation within 7 days after surgery. Predictors were selected through backward stepwise logistic regression and bootstrap resampling. The investigators used reclassification and receiver-operating characteristic (ROC) curve analyses to assess score performance and compare it with an established score for all surgical patients (Score for Prediction of Postoperative Respiratory Complications [SPORC]).

RESULTS

The study included 2672 patients who underwent resection for lung cancer (1754, development cohort; 918, validation cohort) between 2008 and 2020, of whom 71 (2.7%) were reintubated within 7 days after surgery. Identified score variables were surgical extent and approach, American Society of Anesthesiologists physical status, heart failure, renal disease, and diffusing capacity of the lung for carbon monoxide. The score achieved excellent discrimination in the development cohort (ROC AUC, 0.90; 95% CI, 0.87-0.94) and good discrimination in the validation cohort (ROC AUC, 0.74, 95% CI; 0.66-0.82), thus outperforming the SPORC in both cohorts (P < .001 and P = .018, respectively; validation cohort net reclassification improvement, 0.39; 95% CI, 0.18-0.60; P = .001). The score cutoff of ≥5 yielded a sensitivity of 88% (95% CI, 72-95) and a specificity of 81% (95% CI,79-83) in the development cohort.

CONCLUSIONS

A simple score (PROREAL) specific to lung cancer predicts postoperative reintubation more accurately than the nonspecific SPORC score. Operative candidates at risk may be identified for preventive intervention or alternative oncologic therapy.

Early Diagnosis of High-Risk Chronic Obstructive Pulmonary Disease Based on Quantitative High-Resolution Computed Tomography Measurements

Purpose

Quantitative computed tomography (QCT) techniques, focusing on airway anatomy and emphysema, may help to detect early structural changes of COPD disease. This retrospective study aims to identify high-risk COPD participants by using QCT measurements.

Patients and Methods

We enrolled 140 participants from the Second Affiliated Hospital of Shenyang Medical College who completed inspiratory high-resolution CT scans, pulmonary function tests (PFTs), and clinical characteristics recorded. They were diagnosed Non-COPD by PFT value of FEV1/FVC >70% and divided into two groups according percentage predicted FEV1 (FEV1%), low-risk COPD group: FEV1% ≥ 95%, high-risk group: 80% < FEV1% < 95%. The QCT measurements were analyzed by the Student's t-test (or Mann-Whitney U-test) method. Then, feature candidates were identified using the LASSO method. Meanwhile, the correlation between QCT measurements and PFTs was assessed by the Spearman rank correlation test. Furthermore, support vector machine (SVM) was performed to identify high-risk COPD participants. The performance of the models was evaluated in terms of accuracy (ACC), sensitivity (SEN), specificity (SPE), F1-score, and area under the ROC curve (AUC), with p <0.05 considered statistically significant.

Results

The SVM based on QCT measurements achieved good performance in identifying high-risk COPD patients with 85.71% of ACC, 88.34% of SEN, 84.00% of SPE, 83.33% of F1-score, and 0.93 of AUC. Further, QCT measurements integration of clinical data improved the performance with an ACC of 90.48%. The emphysema index (%LAA-950) of left lower lung was negatively correlated with PFTs (P < 0.001). The airway anatomy indexes of lumen diameter (LD) were correlated with PFTs.

Conclusion

QCT measurements combined with clinical information could provide an effective tool for an early diagnosis of high-risk COPD. The QCT indexes can be used to assess the pulmonary function status of high-risk COPD.

Quantitative emphysema on computed tomography imaging of chest is a risk factor for prognosis of esophagectomy: A retrospective cohort study

The low attenuation area percentage (LAA%) is gaining popularity. LAA% is an index of quantitative emphysema on computed tomography (CT) imaging of the chest. This study aims to retrospectively investigate whether preoperative LAA% is associated with postoperative prognosis in patients with esophageal cancer who were scheduled for esophagectomy. From January 2016 to March 2020, 105 patients with esophageal cancer underwent esophagectomy via right thoracotomy and neoadjuvant chemotherapy. A Synapse Vincent volume analyzer (Fujifilm Medical, Tokyo, Japan) was used for measurement. The software automatically quantified LAA% using a threshold of less than - 950 Hounsfield units on CT images of lung regions. Cox proportional hazard analyses were performed in univariable and multivariable forms. Estimates of the receiver operating curve are used to determine the cutoff value for death of LAA%, and the binary value is then inserted into Cox proportional hazard analyses. The preoperative LAA% cutoff value was ≥ 6.3%. Patients with a preoperative LAA% ≥6.3% had a significantly worse prognosis than those with a preoperative LAA% of < 6.3%. LAA% ≥6.3% (hazard ratio: 6.76; 95% confidence interval: 2.56-17.90, P < .001) was the most influential preoperative factor for overall survival after esophagectomy in multivariate Cox proportional hazard analyses. LAA% is one of the preoperative risk factors for survival after esophagectomy and an indicator of lung condition using routinely performed preoperative CT images. We quantified the extent of preoperative emphysema in patients with esophageal cancer, who were scheduled for surgery, and for the first time, reported LAA% as one of the preoperative risk factors for survival after esophagectomy.

Differential impacts between fat mass index and fat-free mass index on patients with COPD

BACKGROUND

Differences in the clinical impacts of fat mass index (FMI) and fat-free mass index (FFMI) remain unclear in patients with chronic obstructive pulmonary disease (COPD). We hypothesized that FMI and FFMI have different impacts on 1) emphysema and 2) pulmonary function and health-related quality of life of COPD patients.

METHODS

Patients with COPD (n = 228), enrolled in a multicenter prospective 3-year cohort were classified into four groups based on baseline median FMI and FFMI values. Emphysema assessed as the ratio of low attenuation area to total lung volume (LAA%) on computed tomography, pulmonary function, and health-related quality of life assessed using the St. George's Respiratory Questionnaire (SGRQ) were compared.

RESULTS

The four groups had statistically significant differences in LAA%, pulmonary function, and SGRQ scores. The Low FMI Low FFMI group exhibited the highest LAA%, lowest pulmonary function, and worst SGRQ scores among the four groups. In addition, these differences were consistent over 3 years. Multivariate analysis showed that low FMI was associated with high LAA%, low inspiratory capacity/total lung capacity (IC/TLC), and carbon monoxide transfer coefficient (KCO). In contrast, low FFMI was associated with these factors as well as worse SGRQ scores.

CONCLUSION

FMI and FFMI have different effects on the clinical manifestations of COPD. Both low fat and muscle mass contributed to severe emphysema, whereas only low muscle mass contributed to worse health-related quality of life in patients with COPD.

Alpha1-antitrypsin deficiency: An updated review

Alpha1-antitrypsin deficiency (AATD) is a rare autosomal recessive disease associated with the homozygous Z variant of the SERPINA1 gene. Clinical expression of AATD, reported 60 years ago associate a severe deficiency, pulmonary emphysema and/or liver fibrosis. Pulmonary emphysema is due to the severe alpha1-antitrypsin deficiency of the ZZ homozygous status and is favored by smoking. Liver fibrosis is due to the ZZ homozygous status and is favored by obesity and excessive chronic alcohol intake, with a risk of liver cancer. Diagnosis is based on serum level and either isoelectric focusing determination of the biochemical phenotype or PCR detection of some variants. SERPINA1 gene sequencing is necessary in case of discrepancies between the results of these tests. No treatment is available for the liver disease in AATD. Although no specific trial has been performed, COPD in AATD should be treated as per COPD recommendations. Based on a randomized clinical trial, augmentation therapy is indicated in non-smoking adults less than 70 years of age with emphysema at chest CT, confirmed homozygous AATD, and FEV1 between 35% and 70% of predicted. In contrast Z heterozygosis (MZ or SZ) brings a risk of lung or liver disease only in association with further risk factors. Early detection, in all patients with COPD and chronic liver disease, is critical for the correct information of Z variant carriers. News ways of correcting the liver production of alpha1-antitrypsin will modify the care of AATD patients.

Prevalence of reduced lung diffusing capacity and CT scan findings in smokers without airflow limitation: a population-based study

BACKGROUND

Population distribution of reduced diffusing capacity of the lungs for carbon monoxide (DLCO) in smokers and main consequences are not properly recognised. The objectives of this study were to describe the prevalence of reduced DLCO in a population-based sample of current and former smoker subjects without airflow limitation and to describe its morphological, functional and clinical implications.

METHODS

A sample of 405 subjects aged 40 years or older with postbronchodilator forced expiratory volume in 1 s/forced vital capacity (FVC) >0.70 was obtained from a random population-based sample of 9092 subjects evaluated in the EPISCAN II study. Baseline evaluation included clinical questionnaires, exhaled carbon monoxide (CO) measurement, spirometry, DLCO determination, 6 min walk test, routine blood analysis and low-dose CT scan with evaluation of lung density and airway wall thickness.

RESULTS

In never, former and current smokers, prevalence of reduced DLCO was 6.7%, 14.4% and 26.7%, respectively. Current and former smokers with reduced DLCO without airflow limitation were younger than the subjects with normal DLCO, and they had greater levels of dyspnoea and exhaled CO, greater pulmonary artery diameter and lower spirometric parameters, 6 min walk distance, daily physical activity and plasma albumin levels (all p<0.05), with no significant differences in other chronic respiratory symptoms or CT findings. FVC and exhaled CO were identified as independent risk factors for low DLCO.

CONCLUSION

Reduced DLCO is a frequent disorder among smokers without airflow limitation, associated with decreased exercise capacity and with CT findings suggesting that it may be a marker of smoking-induced early vascular damage.

TRIAL REGISTRATION NUMBER

NCT03028207.

Distinct COPD subtypes in former smokers revealed by gene network perturbation analysis

BACKGROUND

Chronic obstructive pulmonary disease (COPD) varies significantly in symptomatic and physiologic presentation. Identifying disease subtypes from molecular data, collected from easily accessible blood samples, can help stratify patients and guide disease management and treatment.

METHODS

Blood gene expression measured by RNA-sequencing in the COPDGene Study was analyzed using a network perturbation analysis method. Each COPD sample was compared against a learned reference gene network to determine the part that is deregulated. Gene deregulation values were used to cluster the disease samples.

RESULTS

The discovery set included 617 former smokers from COPDGene. Four distinct gene network subtypes are identified with significant differences in symptoms, exercise capacity and mortality. These clusters do not necessarily correspond with the levels of lung function impairment and are independently validated in two external cohorts: 769 former smokers from COPDGene and 431 former smokers in the Multi-Ethnic Study of Atherosclerosis (MESA). Additionally, we identify several genes that are significantly deregulated across these subtypes, including DSP and GSTM1, which have been previously associated with COPD through genome-wide association study (GWAS).

CONCLUSIONS

The identified subtypes differ in mortality and in their clinical and functional characteristics, underlining the need for multi-dimensional assessment potentially supplemented by selected markers of gene expression. The subtypes were consistent across cohorts and could be used for new patient stratification and disease prognosis.

Quantitative CT parameters correlate with lung function in chronic obstructive pulmonary disease: A systematic review and meta-analysis

Objective

This study aimed to analyze the correlation between quantitative computed tomography (CT) parameters and airflow obstruction in patients with COPD.

Methods

PubMed, Embase, Cochrane and Web of Knowledge were searched by two investigators from inception to July 2022, using a combination of pertinent items to discover articles that investigated the relationship between CT measurements and lung function parameters in patients with COPD. Five reviewers independently extracted data, and evaluated it for quality and bias. The correlation coefficient was calculated, and heterogeneity was explored. The following CT measurements were extracted: percentage of lung attenuation area <-950 Hounsfield Units (HU), mean lung density, percentage of airway wall area, air trapping index, and airway wall thickness. Two airflow obstruction parameters were extracted: forced expiratory volume in the first second as a percentage of prediction (FEV₁%pred) and FEV₁ divided by forced expiratory volume lung capacity.

Results

A total of 141 studies (25,214 participants) were identified, which 64 (6,341 participants) were suitable for our meta-analysis. Results from our analysis demonstrated that there was a significant correlation between quantitative CT parameters and lung function. The absolute pooled correlation coefficients ranged from 0.26 (95% CI, 0.18 to 0.33) to 0.70 (95% CI, 0.65 to 0.75) for inspiratory CT and 0.56 (95% CI, 0.51 to 0.60) to 0.74 (95% CI, 0.68 to 0.80) for expiratory CT.

Conclusions

Results from this analysis demonstrated that quantitative CT parameters are significantly correlated with lung function in patients with COPD. With recent advances in chest CT, we can evaluate morphological features in the lungs that cannot be obtained by other clinical indices, such as pulmonary function tests. Therefore, CT can provide a quantitative method to advance the development and testing of new interventions and therapies for patients with COPD.

Lung and physical function in post COVID-19 and clinical and functional associations: a cross-sectional study in Brazil

OBJECTIVE

The purpose of this study was to assess exercise capacity, lung and physical function in COVID-19 survivors, and the association of lesion-level characteristics assessed by chest computed tomography, probable sarcopenia, and percentage of diffusing capacity of the lung for carbon monoxide with clinical and functional variables.

METHODS

This study was conducted in Salvador, Bahia, Brazil. All patients had a laboratory-confirmed SARS-CoV-2 infection. The sociodemographic characteristics, COVID-19 exposure history, pulmonary function, computed tomography, and functionality of the participants between 1 and 3 months of diagnosis of the disease were collected.

RESULTS

A total of 135 patients after COVID-19 recovery were included in this study. Probable sarcopenia, reduction in percentage of diffusing capacity of the lung for carbon monoxide, and a lower 6-min walk distance were observed after COVID-19 infection. Computed tomography>50% was associated with a longer length of stay and a lower percentage of diffusing capacity of the lung for carbon monoxide. Probable sarcopenia diagnosis was associated with a worse percentage of the predicted 6-min walk distance in relation to the predicted, absolute 6-min walk distance (m), percentage of diffusing capacity of the lung for carbon monoxide, and percentage of total lung capacity.

CONCLUSION

Muscle disability and lung dysfunction are common in COVID-19 survivors. Hospitalization was associated with the worst muscle force and diffusing capacity of the lung for carbon monoxide. Computed tomography characteristics could be a marker of prolonged hospital stay after the acute phase of COVID-19. Additionally, the probable diagnosis of sarcopenia could be a marker of impact on walking distance. These results highlight the need for long-term follow-up of those patients and rehabilitation programs.

Prediction of exercise-induced desaturation in COPD patients without resting hypoxemia: a retrospective study

Background

There is no universally accepted criterion for assessing exercise-induced desaturation (EID). The purpose of this study is to compare the two methods regularly used for determining EID in COPD patients, as well as to explore the risk factors and predictors related to EID.

Methods

The 6MWT was performed with continuous SpO₂ monitoring on patients with stable COPD. Using two methods (method A: “SpO_2rest–SpO_2min ≥ 4% and/or SpO_2min < 90%”, method B: “SpO_2rest–SpO_2end ≥ 4% and/or SpO_2end < 90%”) as EID determination criteria to assess the incidence of EID. The differences and consistency of the two methods are compared. Moreover, we collected data through the pulmonary function test, mMRC dyspnea score, COPD assessment test, BODE index and CT-defined emphysema. Univariate and multivariate logistic regression analyses were used to identify factors affecting the EID. For the parameters that predict EID in 6MWT, a receiver operating characteristic (ROC) curve analysis was employed.

Results

The analysis included 124 patients. The overall incidence of EID was 62.1% by using method A as the criterion and 51.6% by method B. All of the EID patients found by method B were included in the EID patients identified by method A, as well as 13 new-EID patients. The difference in diagnostic outcomes between the two approaches was not statistically significant (P > 0.05), but they were in excellent agreement (Kappa = 0.807, P = 0.001). Logistic regression analyses found that D_LCO SB% pred, D_LCO/VA% pred, CAT score, mean density, PD15, emphysema volume and %LAA were significant determinants of the EID. For predicting EID, the ROC analysis produced AUC and cutoffs of 0.689 and 50.45% (D_LCO SB% pred), 0.707 and 75.0% (D_LCO/VA% pred), 0.727 and 15 points (CAT score), 0.691 and − 955.00HU (PD15), 0.671 and − 856.46HU (mean density), 0.668 and 338.14 ml (emphysema volume) and 0.656 and 7.63% (%LAA), respectively.

Conclusions

Two methods evaluating EID in this research are in a good agreement, method A can find more EID patients by focusing on SpO_2min. When conditions are constrained, it is also sufficient to assess EID in COPD patients by method B. In terms of the predictors of EID, D_LCO SB% pred, D_LCO/VA% pred, CAT score and CT-defined emphysema are all statistically significant test variables to determine EID.

Chest three-dimensional-computed tomography imaging data analysis for the variation of exercise capacity after lung lobectomy

BACKGROUND

Postoperative loss of exercise capacity and pulmonary function is a major concern among lung cancer patients. In this study, the time for a stair-climbing to 12-m height was used to investigate whether preoperative chest 3D-computed tomography (CT) could be a useful tool for predicting postoperative variations in exercise capacity and pulmonary function.

METHODS

Seventy-eight patients undergoing lobectomy for suspected stage I lung cancer were prospectively enrolled. Preoperatively, lobe volume and low attenuation volume (LAV) were evaluated using the SYNAPSE VINCENT system. Preoperative data on stair-climbing time, spirometry, and diffusing capacity of the lung for carbon monoxide (DL_CO ) at baseline and 6-month postoperative data were used to evaluate variations in exercise capacity and pulmonary function. Maximal oxygen uptake (VO₂ t) was evaluated based on the stair-climbing time.

RESULTS

Significant differences in the variation of exercise capacity at 6 months postoperatively were found between the groups categorized by target lobe volume and LAV status: The large volume/LAV (+) group had a greater decline in VO₂ t. Mean loss of VO₂ t was -6.2%, -1.4%, -1.6%, and -0.1% in the large volume/LAV (+), large volume/LAV (-), small volume/LAV (+), and small volume/LAV (-) groups, respectively. The large volume/LAV (-) group had a greater decline in forced expiratory volume in 1 s. The small volume/LAV (+) group showed a reduced decline in the DL_CO .

CONCLUSIONS

Analysis of chest 3D-CT scans is a potential tool for predicting the loss of exercise capacity and pulmonary function after lung lobectomy. This article is protected by copyright. All rights reserved.

[Alpha 1-antitrypsin deficiency]

INTRODUCTION

Pulmonary emphysema and liver disease are the clinical expressions of alpha 1-antitrypsin deficiency, an autosomal recessive genetic disease.

STATE OF THE ART

Alpha 1-antitrypsin deficiency is usually associated with the homozygous Z variant of the SERPINA1 gene. Its clinical expression always consists in a substantial reduction of alpha 1-antitrypsin serum concentration and its variants are analyzed by isoelectric focalization or molecular techniques. Assessed by CO transfer alteration and CT scan, risk of pulmonary emphysema is increased by tobacco consumption. Assessed by transient elastography and liver ultrasound, risk of liver disease is increased by alcohol consumption or obesity. Treatment of COPD-associated alpha 1-antitrypsin deficiency does not differ from that of other forms of COPD. In patients presenting with severe deficiency, augmentation therapy with plasma-derived alpha 1-antitrypsin reduces the progression of emphysema, as shown in terms of CT-based lung density metrics. Patients with alpha 1-antitrypsin deficiency with a ZZ genotype should refrain from alcohol or tobacco consumption, and watch their weight; so should their close relatives.

PERSPECTIVES

Modulation of alpha 1-antitrypsin liver production offers an interesting new therapeutic perspective.

CONCLUSION

Homozygous (Z) variants of the SERPINA1 gene confer an increased risk of pulmonary emphysema and liver disease, particularly among smokers, drinkers and obese persons.

Impaired Ventilatory Efficiency, Dyspnea and Exercise Intolerance in Chronic Obstructive Pulmonary Disease: Results from the CanCOLD Study

RATIONALE

Impaired exercise ventilatory efficiency (high ventilatory requirements for CO2 [V̇E/V̇CO2]) provides an indication of pulmonary gas exchange abnormalities in chronic obstructive pulmonary disease (COPD).

OBJECTIVES

To determine: 1) the association between high V̇E/V̇CO2 and clinical outcomes (dyspnea and exercise capacity) and its relationship to lung function and structural radiographic abnormalities; and 2) its prevalence in a large population-based cohort.

METHODS

Participants were recruited randomly from the population and underwent clinical evaluation, pulmonary function, cardiopulmonary exercise testing and chest computed tomography (CT). Impaired exercise ventilatory efficiency was defined by a nadir V̇E/V̇CO2 above the upper limit of normal (V̇E/V̇CO2>ULN), using population-based normative values.

MEASUREMENTS AND MAIN RESULTS

Participants included 445 never-smokers, 381 ever-smokers without airflow obstruction, 224 with GOLD 1 COPD, and 200 with GOLD 2-4 COPD. Participants with V̇E/V̇CO2>ULN were more likely to have activity-related dyspnea (Medical Research Council dyspnea scale≥2, odds ratio=1.77[1.31-2.39]) and abnormally low peak oxygen uptake (V̇O2peak<LLN, odds ratio=4.58[3.06-6.86]). The carbon monoxide transfer coefficient (KCO) had a stronger correlation with nadir V̇E/V̇CO2 (r=-0.38, p<0.001) than other relevant lung function and CT metrics. The prevalence of V̇E/V̇CO2>ULN was 24% in COPD (similar in GOLD 1 and 2-4), which was greater than in never-smokers (13%) and ever-smokers (12%).

CONCLUSIONS

V̇E/V̇CO2>ULN was associated with greater dyspnea and low VO2peak and was present in 24% of all participants with COPD, regardless of GOLD stage. The results show the importance of recognizing impaired exercise ventilatory efficiency as a potential contributor to dyspnea and exercise limitation, even in mild COPD.

Telomere Length but Not Mitochondrial DNA Copy Number Is Altered in Both Young and Old COPD

Accelerated ageing is implicated in the pathogenesis of respiratory diseases as chronic obstructive pulmonary disease (COPD), but recent evidence indicates that the COPD can have roots early in life. Here we hypothesise that the accelerated ageing markers might have a role in the pathobiology of young COPD. The objective of this study was to compare two hallmarks of ageing, telomere length (TL), and mitochondrial DNA copy number (mtDNA-CN, as a surrogate marker of mitochondrial dysfunction) in young (≤ 50 years) and old (>50 years) smokers, with and without COPD. Both, TL and mtDNA-CN were measured in whole blood DNA by quantitative PCR [qPCR] in: (1) young ever smokers with (n = 81) or without (n = 166) COPD; and (2) old ever smokers with (n = 159) or without (n = 29) COPD. A multivariable linear regression was used to assess the association of TL and mtDNA-CN with lung function. We observed that in the entire study population, TL and mtDNA-CN decreased with age, and the former but not the latter related to FEV₁/FVC (%), FEV₁ (% ref.), and DLCO (% ref.). The short telomeres were found both in the young and old patients with severe COPD (FEV₁ <50% ref.). In addition, we found that TL and mtDNA-CN were significantly correlated, but their relationship was positive in younger while negative in the older patients with COPD, suggesting a mitochondrial dysfunction. We conclude that TL, but not mtDNA-CN, is associated with the lung function impairment. Both young and old patients with severe COPD have evidence of accelerated ageing (shorter TL) but differ in the direction of the correlation between TL and mtDNA-CN in relation to age.

Adverse effects of short-term personal exposure to fine particulate matter on the lung function of patients with chronic obstructive pulmonary disease and asthma: a longitudinal panel study in Beijing, China

Fine particulate matter (PM_2.5) is an important environmental factor affecting human health. However, most studies on PM_2.5 and health have used data from fixed monitoring sites to assess PM_2.5 exposure, which may have introduced misleading information on the exposure-response relationship. We aimed to assess the effect of short-term personal PM_2.5 exposure on lung function in patients with chronic obstructive pulmonary disease (COPD) and asthma. To achieve this, we conducted a longitudinal panel study among 37 COPD patients and 45 asthma patients from Beijing, China. The COPD group and the asthma group completed 148 and 180 lung function tests, respectively. We found that in COPD patients, for every 10-μg/m³ increase in PM_2.5 exposure at lag2, the FEV₁, FVC and DLco decreased by -0.014 L (95% CI -0.025, -0.003), -0.025 L (95% CI -0.050, -0.003) and -0.089 mmol/min/kPa (95% CI -0.156, -0.023), respectively. There was also a decrease of -0.023 L/s (95% CI -0.042, -0.003) and -0.017 L/s (95% CI -0.032, -0.002) in MMEF at lag3 and lag03, respectively. In the asthma group, every 10-μg/m³ increase in PM_2.5 exposure led to a reduction of -0.012 L (95% CI -0.023, -0.001), -0.042 L (95% CI -0.081, -0.003) and -0.061 L/s (95% CI -0.116, -0.004) in the FEV₁, FVC and PEF at lag3, respectively. Our findings suggest that PM_2.5 exposure may primarily affect both airway function and lung diffusion function in COPD patients, and airway function in asthma patients.

Reduced exercise tolerance in mild chronic obstructive pulmonary disease: The contribution of combined abnormalities of diffusing capacity for carbon monoxide and ventilatory efficiency

BACKGROUND AND OBJECTIVE

The combination of both reduced resting diffusing capacity of the lung for carbon monoxide (DL_CO ) and ventilatory efficiency (increased ventilatory requirement for CO₂ clearance [V˙_E /V˙CO₂ ]) has been linked to exertional dyspnoea and exercise intolerance in chronic obstructive pulmonary disease (COPD) but the underlying mechanisms are poorly understood. The current study examined if low resting DL_CO and higher exercise ventilatory requirements were associated with earlier critical dynamic mechanical constraints, dyspnoea and exercise limitation in patients with mild COPD.

METHODS

In this retrospective analysis, we compared V˙_E /V˙CO₂ , dynamic inspiratory reserve volume (IRV), dyspnoea and exercise capacity in groups of patients with Global Initiative for Chronic Obstructive Lung Disease stage 1 COPD with (1) a resting DL_CO at or greater than the lower limit of normal (≥LLN; Global Lung Function Initiative reference equations [n = 44]) or (2) below the <LLN (n = 33), and age- and sex-matched healthy controls (n = 81).

RESULTS

Spirometry and resting lung volumes were similar in the two COPD groups. During exercise, V˙_E /V˙CO₂ (nadir and slope) was consistently higher in the DL_CO  < LLN compared with the other groups (all p < 0.05). The DL_CO  < LLN group had lower IRV and greater dyspnoea intensity at standardized submaximal work rates and lower peak work rate and oxygen uptake than the other two groups (all p < 0.05).

CONCLUSION

Reduced exercise capacity in patients with DL_CO  < LLN was related to higher ventilatory requirements, a faster rate of decline in dynamic IRV and greater dyspnoea during exercise. These simple measurements should be considered for the clinical evaluation of unexplained exercise intolerance in individuals with ostensibly mild COPD.

The effects of lung volume reduction treatment on diffusing capacity and gas exchange

Lung volume reduction (LVR) treatment in patients with severe emphysema has been shown to have a positive effect on hyperinflation, expiratory flow, exercise capacity and quality of life. However, the effects on diffusing capacity of the lungs and gas exchange are less clear. In this review, the possible mechanisms by which LVR treatment can affect diffusing capacity of the lung for carbon monoxide (D _LCO) and arterial gas parameters are discussed, the use of D _LCO in LVR treatment is evaluated and other diagnostic techniques reflecting diffusing capacity and regional ventilation (V')/perfusion (Q') mismatch are considered.A systematic review of the literature was performed for studies reporting on D _LCO and arterial blood gas parameters before and after LVR surgery or endoscopic LVR with endobronchial valves (EBV). D _LCO after these LVR treatments improved (40 studies, n=1855) and the mean absolute change from baseline in % predicted D _LCO was +5.7% (range -4.6% to +29%), with no real change in blood gas parameters. Improvement in V' inhomogeneity and V'/Q' mismatch are plausible explanations for the improvement in D _LCO after LVR treatment.

Decline in Carbon Monoxide Transfer Coefficient in Chronic Obstructive Pulmonary Disease

Background: Although a reduced carbon monoxide transfer coefficient (Kco) is an important feature in chronic obstructive pulmonary disease (COPD), how it changes over time and its relationship with other clinical outcomes remain unclear. This study evaluated longitudinal changes in Kco and their relationship with other clinical outcomes. Methods: We evaluated patients with COPD from the Korean Obstructive Lung Disease cohort, followed up for up to ten years. Random coefficient models were used to assess the annual change in Kco over time. Participants were categorized into tertiles according to Kco decline rate. Baseline characteristics and outcomes, including changes in FEV1 and emphysema index, incidence of exacerbations, and mortality, were compared between categories. Results: A decline in Kco was observed in 92.9% of the 211 enrolled participants with COPD. Those with the most rapid decline (tertile 1) had a lower FEV1/FVC% (tertile 1: 43.8% ± 9.7%, tertile 2: 46.4% ± 10.5%, tertile 3: 49.2% ± 10.4%, p = 0.008) and a higher emphysema index at baseline (27.7 ± 14.8, 22.4 ± 16.1, 18.1 ± 14.5, respectively, p = 0.001). Tertile 3 showed a lower decline rate in FEV1 (16.3 vs. 27.1 mL/yr, p = 0.017) and a lower incidence of exacerbations (incidence rate ratio = 0.66, 95% CI = 0.44–0.99) than tertile 1. There were no differences in the change in emphysema index and mortality between categories. Conclusion: Most patients with COPD experienced Kco decline over time, which was greater in patients with more severe airflow limitation and emphysema. Decline in Kco was associated with an accelerated decline in FEV1 and more frequent exacerbations; hence, this should be considered as an important outcome measure in further studies.

Diffusing Capacity Is an Independent Predictor of Outcomes in Pulmonary Hypertension Associated With COPD

BACKGROUND

Patients with COPD who experience pulmonary hypertension (PH) have worse mortality than those with COPD alone. Predictors of poor outcomes in COPD-PH are not well-described. Diffusing capacity of the lung (Dlco) assesses the integrity of the alveolar-capillary interface and thus may be a useful prognostic tool among those with COPD-PH.

RESEARCH QUESTION

Using a single center registry, we sought to evaluate Dlco as a predictor of mortality in a cohort of patients with COPD-PH.

STUDY DESIGN AND METHODS

This retrospective cohort study analyzed 71 COPD-PH patients from the Johns Hopkins Pulmonary Hypertension Registry with right-sided heart catheterization (RHC)-proven PH and pulmonary function testing data within one year of diagnostic RHC. Transplant-free survival was calculated from index RHC. Adjusted transplant-free survival was modelled using Cox proportional hazard methods; age, pulmonary vascular resistance, FEV₁, oxygen use, and N-terminal pro-brain natriuretic peptide were included as covariates.

RESULTS

Overall unadjusted transplant-free 1-, 3-, and 5-year survivals were 87%, 60%, and 51%, respectively. Survival was associated with reduced Dlco across the observed range of pulmonary artery pressures and pulmonary vascular resistance. Severe Dlco impairment was associated with poorer survival (log-rank χ² 13.07) (P < .001); adjusting for covariates, for every percent predicted decrease in Dlco, mortality rates increased by 4% (hazard ratio, 1.04; 95% CI, 1.01-1.07).

INTERPRETATION

Among patients with COPD-PH, severe gas transfer impairment is associated with higher mortality, even with adjustment for airflow obstruction and hemodynamics, which suggests that Dlco may be a useful prognostic marker in this population. Future studies are needed to further investigate the association between Dlco and morbidity and to determine the utility of Dlco as a biomarker for disease risk and severity in COPD-PH.

Endobronchial Valve Treatment in Emphysema Patients with a Very Low DLCO

BACKGROUND

For selected patients with severe emphysema, bronchoscopic lung volume reduction with endobronchial valves (EBV) is recognized as an additional treatment option. In most trials investigating EBV treatment, patients with a very low diffusing capacity (DLCO) were excluded from participation.

OBJECTIVES

Our goal was to investigate whether EBV treatment in patients with emphysema with a very low DLCO is safe and effective.

METHODS

This was a single-center retrospective analysis including patients with emphysema and a DLCO ≤20%pred who underwent EBV treatment. Follow-up was performed 6 months post-treatment. Outcome parameters were compared to a historical matched control group (DLCO >20%pred, matched for sex, age, forced expiratory volume in 1 s [FEV1], and residual volume [RV]).

RESULTS

Twenty patients (80% female, 64 ± 6 years, FEV1 26 ± 6%pred, RV 233 ± 45%pred, DLCO 18 ± 1.6%pred) underwent EBV treatment. At 6 months follow-up, we found a statistically significant improvement in FEV1 (0.08 ± 0.12 L), RV (-0.45 ± 0.95 L), 6-min walking distance (38 ± 65 m), and St. George's Respiratory Questionnaire (-12 ± 13 points). With the exception of FEV1, all exceeded the minimal clinically important difference. The most common serious adverse event was a pneumothorax requiring intervention (15%). There were no significant differences in outcome compared to the DLCO >20%pred control group.

CONCLUSIONS

In this single-center retrospective analysis, we showed statistically significant and clinically relevant improvements in lung function, exercise capacity, and quality of life up to 6 months after EBV treatment in emphysema patients with a DLCO ≤20% (14-20%) of predicted with no increased risk of serious adverse events.

Factors Contributing to CO Uptake and Elimination in the Body: A Critical Review

BACKGROUND

Carbon monoxide (CO) poisoning is an important public health issue around the world. Research indicates that many factors may be related to the rate of CO uptake and elimination in the human body. However, some factors related to CO uptake and elimination are considered controversial. Relatively little attention has been devoted to review and synthesis of factors affecting CO uptake and elimination.

PURPOSE

This paper provides a critical scoping review of the factors and divides them into four aspects, including environmental, demographic, physiological and treatment factors.

METHODS

We searched the scientific databases for research that has proposed a mathematical equation as a synthesis of quantities related to CO poisoning, CO elimination, CO uptake, CO half-life, CO uptake and elimination and their relationships. After excluding the studies that did not meet the study criteria, there were 39 studies included in the review and the search was completed before 16 December 2019.

RESULTS AND CONCLUSION

This review discusses most of the factors that impact the rate of CO uptake and elimination. Several factors may be related to CO uptake and elimination, such as CO concentration, the duration of exposure to CO, age, sex, exercise, minute ventilation, alveolar ventilation, total haemoglobin mass and different treatments for CO poisoning. Although some potential factors were not included in the review, the findings are useful by presenting an overview for discussing factors affecting CO uptake and elimination and provide a starting point for further study regarding strategies for CO poisoning and the environmental standard of CO.

Hypermethylation of Anti-oncogenic MicroRNA 7 is Increased in Emphysema Patients

INTRODUCTION

MicroRNA-7 (miR-7) has a suppressive role in lung cancer and alterations in its DNA methylation may contribute to tumorigenesis. As COPD patients with emphysema have a higher risk of lung cancer than other COPD phenotypes, we compared the miR-7 methylation status among smoker subjects and patients with various COPD phenotypes to identify its main determinants.

METHODS

30 smoker subjects without airflow limitation and 136 COPD patients without evidence of cancer were recruited in a prospective study. Clinical and functional characteristics were assessed and patients were classified into: frequent exacerbator, emphysema, chronic bronchitis and asthma COPD overlap (ACO). DNA collected from buccal epithelial samples was isolated and bisulfite modified. miR-7 methylation status was evaluated by quantitative methylation-specific polymerase chain reaction (qMSP).

RESULTS

miR-7 Methylated levels were higher in COPD patients than in smokers without airflow limitation (23.7±12.4 vs. 18.5±8.8%, p=0.018). Among COPD patients, those with emphysema had higher values of methylated miR-7 (27.1±10.2%) than those with exacerbator (19.4±9.9%, p=0.004), chronic bronchitis (17.3±9.0%, p=0.002) or ACO phenotypes (16.0±7.2%, p=0.010). After adjusting for clinical parameters, differences between emphysematous patients and those with other phenotypes were retained. In COPD patients, advanced age, mild-moderate airflow limitation, reduced diffusing capacity and increased functional residual capacity were identified as independent predictors of methylated miR-7 levels.

CONCLUSION

The increase of miR-7 methylation levels experienced by COPD patients occurs mainly at the expense of the emphysema phenotype, which might contribute to explain the higher incidence of lung cancer in these patients.

Imaging Advances in Chronic Obstructive Pulmonary Disease. Insights from the Genetic Epidemiology of Chronic Obstructive Pulmonary Disease (COPDGene) Study

The Genetic Epidemiology of Chronic Obstructive Pulmonary Disease (COPDGene) study, which began in 2007, is an ongoing multicenter observational cohort study of more than 10,000 current and former smokers. The study is aimed at understanding the etiology, progression, and heterogeneity of chronic obstructive pulmonary disease (COPD). In addition to genetic analysis, the participants have been extensively characterized by clinical questionnaires, spirometry, volumetric inspiratory and expiratory computed tomography, and longitudinal follow-up, including follow-up computed tomography at 5 years after enrollment. The purpose of this state-of-the-art review is to summarize the major advances in our understanding of COPD resulting from the imaging findings in the COPDGene study. Imaging features that are associated with adverse clinical outcomes include early interstitial lung abnormalities, visual presence and pattern of emphysema, the ratio of pulmonary artery to ascending aortic diameter, quantitative evaluation of emphysema, airway wall thickness, and expiratory gas trapping. COPD is characterized by the early involvement of the small conducting airways, and the addition of expiratory scans has enabled measurement of small airway disease. Computational advances have enabled indirect measurement of nonemphysematous gas trapping. These metrics have provided insights into the pathogenesis and prognosis of COPD and have aided early identification of disease. Important quantifiable extrapulmonary findings include coronary artery calcification, cardiac morphology, intrathoracic and extrathoracic fat, and osteoporosis. Current active research includes identification of novel quantitative measures for emphysema and airway disease, evaluation of dose reduction techniques, and use of deep learning for phenotyping COPD.

Low resting diffusion capacity, dyspnea, and exercise intolerance in chronic obstructive pulmonary disease

The mechanisms linking reduced diffusing capacity of the lung for carbon monoxide (DlCO) to dyspnea and exercise intolerance across the chronic obstructive pulmonary disease (COPD) continuum are poorly understood. COPD progression generally involves both DlCO decline and worsening respiratory mechanics, and their relative contribution to dyspnea has not been determined. In a retrospective analysis of 300 COPD patients who completed symptom-limited incremental cardiopulmonary exercise tests, we tested the association between peak oxygen-uptake (V̇o2), DlCO, and other resting physiological measures. Then, we stratified the sample into tertiles of forced expiratory volume in 1 s (FEV1) and inspiratory capacity (IC) and compared dyspnea ratings, pulmonary gas exchange, and respiratory mechanics during exercise in groups with normal and low DlCO [i.e., <lower limit of normal (LLN)] using Global Lung Function Initiative reference values. DlCO was associated with peak V̇o2 ( P = 0.006), peak work-rate ( P = 0.005), and dyspnea/V̇o2 slope ( P < 0.001) after adjustment for other independent variables (airway obstruction and hyperinflation). Within FEV1 and IC tertiles, peak V̇o2 and work rate were lower ( P < 0.05) in low versus normal DlCO groups. Across all tertiles, low DlCO groups had higher dyspnea ratings, greater ventilatory inefficiency and arterial oxygen desaturation, and showed greater mechanical volume constraints at a lower ventilation during exercise than the normal DlCO group (all P < 0.05). After accounting for baseline resting respiratory mechanical abnormalities, DlCO<LLN was consistently associated with greater dyspnea and poorer exercise performance compared with preserved DlCO. The higher dyspnea ratings and earlier exercise termination in low DlCO groups were linked to significantly greater pulmonary gas exchange abnormalities, higher ventilatory demand, and associated accelerated dynamic mechanical constraints.

NEW & NOTEWORTHY Our study demonstrated that chronic obstructive pulmonary disease patients with diffusing capacity of the lung for carbon monoxide (DlCO) less than the lower limit of normal had greater pulmonary gas exchange abnormalities, which resulted in higher ventilatory demand and greater dynamic mechanical constraints at lower ventilation during exercise. This, in turn, led to greater exertional dyspnea and exercise intolerance compared with patients with normal DlCO.

Diffusing Capacity of Carbon Monoxide in Assessment of COPD

BACKGROUND

Diffusing capacity of the lung for carbon monoxide (Dlco) is inconsistently obtained in patients with COPD, and the added benefit of Dlco testing beyond that of more common tools is unknown.

OBJECTIVE

The goal of this study was to determine whether lower Dlco is associated with increased COPD morbidity independent of emphysema assessed via spirometry and CT imaging.

METHODS

Data for 1,806 participants with COPD from the Genetic Epidemiology of COPD (COPDGene) study 5-year visit were analyzed, including pulmonary function testing, quality of life, symptoms, exercise performance, and exacerbation rates. Dlco percent predicted was primarily analyzed as a continuous variable and additionally categorized into four groups: (1) Dlco and FEV₁ > 50% (reference); (2) only Dlco ≤ 50%; (3) only FEV₁ ≤ 50%; and (4) both ≤ 50% predicted. Outcomes were modeled by using multivariable linear and negative binomial regression, including emphysema and FEV₁ percent predicted among other confounders.

RESULTS

In multivariable analyses, every 10% predicted decrease in Dlco was associated with symptoms and quality of life (COPD Assessment Test, 0.53 [P < .001]; St. George's Respiratory Questionnaire, 1.67 [P < .001]; Medical Outcomes Study Short Form 36 Physical Function, -0.89 [P < .001]), exercise performance (6-min walk distance, -45.35 feet; P < .001), and severe exacerbation rate (rate ratio, 1.14; P < .001). When categorized, severe impairment in Dlco alone, FEV₁ alone, or both Dlco and FEV₁ were associated with significantly worse morbidity compared with the reference group (P < .05 for all outcomes).

CONCLUSIONS

Impairment in Dlco was associated with increased COPD symptoms, reduced exercise performance, and severe exacerbation risk even after accounting for spirometry and CT evidence of emphysema. These findings suggest that Dlco should be considered for inclusion in future multidimensional tools assessing COPD.

The relationship between steps of 6MWT and COPD severity: a cross-sectional study

Background and objective

The distance of 6-minute walk test (D6MWT) has been widely used in the assessment of functional status in patients with COPD, while very little attention has been paid to the role of steps of 6-minute walk test (S6MWT). The purpose of this study was to investigate the relationship between S6MWT and other physiologic parameters of COPD.

Patients and methods

Seventy patients with stable COPD were enrolled consecutively in this cross-sectional study. Pulmonary function tests, including spirometry, impulse oscillometry (IOS) and the single-breath diffusing capacity of the lungs for carbon monoxide (DL_CO), were carried out at rest. Quality of life was assessed by health-related quality of life (HRQoL) questionnaires, including modified Medical Research Council dyspnea scale (mMRC), St George’s Respiratory Questionnaire, Chronic Obstructive Pulmonary Disease Assessment Test (CAT) and Clinical Chronic Obstructive Pulmonary Questionnaire. Both steps and distance were measured in the following 6-minute walk test (6MWT).

Results

Both S6MWT and D6MWT showed significant correlation with spirometry, IOS, DL_CO parameters and HRQoL questionnaires score. Both pre- and post-6MWT inspiratory capacity showed significant correlation with S6MWT (ρ=0.338, P=0.004; ρ=0.359, P=0.002, respectively), whereas did not correlate with D6MWT (ρ=0.145, P=0.230; ρ=0.160, P=0.189, respectively). In stepwise multiple regression analysis, mMRC grade, age and CAT score remained as significant predictors in the final model for D6MWT (adjusted R²=0.445, P<0.01). DL_CO and CAT score remained as significant predictors in the final model for S6MWT (adjusted R²=0.417, P<0.01).

Conclusion

S6MWT is efficient in the evaluation of functional status and quality of life in COPD and has significant correlation with various parameters indicating disease severity. Additionally, S6MWT might be better in predicting lung hyperinflation in COPD compared with D6MWT.

Interstitial Features at Chest CT Enhance the Deleterious Effects of Emphysema in the COPDGene Cohort

Purpose To determine if interstitial features at chest CT enhance the effect of emphysema on clinical disease severity in smokers without clinical pulmonary fibrosis. Materials and Methods In this retrospective cohort study, an objective CT analysis tool was used to measure interstitial features (reticular changes, honeycombing, centrilobular nodules, linear scar, nodular changes, subpleural lines, and ground-glass opacities) and emphysema in 8266 participants in a study of chronic obstructive pulmonary disease (COPD) called COPDGene (recruited between October 2006 and January 2011). Additive differences in patients with emphysema with interstitial features and in those without interstitial features were analyzed by using t tests, multivariable linear regression, and Kaplan-Meier analysis. Multivariable linear and Cox regression were used to determine if interstitial features modified the effect of continuously measured emphysema on clinical measures of disease severity and mortality. Results Compared with individuals with emphysema alone, those with emphysema and interstitial features had a higher percentage predicted forced expiratory volume in 1 second (absolute difference, 6.4%; P < .001), a lower percentage predicted diffusing capacity of lung for carbon monoxide (DLCO) (absolute difference, 7.4%; P = .034), a 0.019 higher right ventricular-to-left ventricular (RVLV) volume ratio (P = .029), a 43.2-m shorter 6-minute walk distance (6MWD) (P < .001), a 5.9-point higher St George's Respiratory Questionnaire (SGRQ) score (P < .001), and 82% higher mortality (P < .001). In addition, interstitial features modified the effect of emphysema on percentage predicted DLCO, RVLV volume ratio, 6WMD, SGRQ score, and mortality (P for interaction < .05 for all). Conclusion In smokers, the combined presence of interstitial features and emphysema was associated with worse clinical disease severity and higher mortality than was emphysema alone. In addition, interstitial features enhanced the deleterious effects of emphysema on clinical disease severity and mortality.

Clinical and quantitative computed tomography predictors of response to endobronchial lung volume reduction therapy using coils

Objectives

Bronchoscopic lung volume reduction using coils (LVRC) is a well-known treatment option for severe emphysema. The purpose of this study was to identify quantitative computed tomography (QCT) and clinical parameters associated with positive treatment outcome.

Patients and methods

The CT scans, pulmonary function tests (PFT), and 6-minute walk test (6-MWT) data were collected from 72 patients with advanced emphysema prior to and at 3 months after LVRC treatment. The procedure involved placing 10 coils unilaterally. Various QCT parameters were derived using Apollo imaging software (VIDA). Independent predictors of clinically relevant outcome (Δ6-MWT ≥ 26 m, ΔFEV₁ ≥ 12%, ΔRV ≥ 10%) were identified through stepwise linear regression analysis.

Results

The response outcome for Δ6-MWT, for ΔFEV₁ and for ΔRV was met by 55%, 32% and 42%, respectively. For Δ6-MWT ≥ 26 m a lower baseline 6-MWT (p = 0.0003) and a larger standard deviation (SD) of low attenuation cluster (LAC) sizes in peripheral regions of treated lung (p = 0.0037) were significantly associated with positive outcome. For ΔFEV₁ ≥ 12%, lower baseline FEV₁ (p = 0.02) and larger median LAC sizes in the central regions of treated lobe (p = 0.0018) were significant predictors of good response. For ΔRV ≥ 10% a greater baseline TLC (p = 0.0014) and a larger SD of LAC sizes in peripheral regions of treated lung (p = 0.007) tended to respond better.

Conclusion

Patients with lower FEV₁ and 6-MWT, with higher TLC and specific QCT characteristics responded more positively to LVRC treatment, suggesting a more targeted CT-based approach to patient selection could lead to greater efficacy in treatment response.

Impact of advanced detector technology and iterative reconstruction on low-dose quantitative assessment of lung computed tomography density in a biological lung model

PURPOSE

Quantitative computed tomography (QCT)-derived measures of lung density are valued methods for objectively characterizing lung parenchymal and peripheral airways disease and are being used in a growing number of lung disease focused trials. Detector and reconstruction improvements in CT technology have allowed for significant radiation dose reduction in image acquisition with comparable qualitative image quality. We report the impact of detector type and reconstruction type on QCT lung density measures in relation to decreasing dose indices.

METHODS

Two sets of studies were completed in an in vivo pig model with a SOMATOM Definition Flash CT system: (a) prior to system upgrade with conventional detectors (UFC) and filtered back projection (FBP), and (b) post system upgrade with integrated electronic detectors (STELLAR) and iterative reconstruction (SAFIRE). CT data were acquired across estimated CT volume dose indices (CTDIvol ) ranging from 0.75 to 15 mGy at both inspiratory and expiratory breath holds. Semiautomated lung segmentations allowed calculation of histogram median, kurtosis, and 15th percentile. Percentage of voxels below -910 HU and -950 HU (inspiratory), and -856 HU (expiratory) were also examined. The changes in these QCT metrics from dose reduction (15 mGy down to 0.75 mGy) were calculated relative to paired reference values (15 mGy). Results were compared based on detector and reconstruction type.

RESULTS

In this study, STELLAR detectors improved concordance with 15 mGy values down to 3 mGy for inspiratory scans and 6 mGy for expiratory scans. The addition of SAFIRE reconstruction in all acquired measurements resulted in minimal deviation from reference values at 0.75 mGy.

CONCLUSION

The use of STELLAR integrated electronic detectors and SAFIRE iterative reconstruction may allow for comparable lung density measures with CT dose indices down to 0.75 mGy.

CT densitometry in emphysema: a systematic review of its clinical utility

BACKGROUND

The aim of the study was to assess the relationship between computed tomography (CT) densitometry and routine clinical markers in patients with chronic obstructive pulmonary disease (COPD) and alpha-1 anti-trypsin deficiency (AATD).

METHODS

Multiple databases were searched using a combination of pertinent terms and those articles relating quantitatively measured CT densitometry to clinical outcomes. Studies that used visual scoring only were excluded, as were those measured in expiration only. A thorough review of abstracts and full manuscripts was conducted by 2 reviewers; data extraction and assessment of bias was conducted by 1 reviewer and the 4 reviewers independently assessed for quality. Pooled correlation coefficients were calculated, and heterogeneity was explored.

RESULTS

A total of 112 studies were identified, 82 being suitable for meta-analysis. The most commonly used density threshold was -950 HU, and a significant association between CT density and all included clinical parameters was demonstrated. There was marked heterogeneity between studies secondary to large variety of disease severity within commonly included cohorts and differences in CT acquisition parameters.

CONCLUSION

CT density shows a good relationship to clinically relevant parameters; however, study heterogeneity and lack of longitudinal data mean that it is difficult to compare studies or derive a minimal clinically important difference. We recommend that international consensus is reached to standardize CT conduct and analysis in future COPD and AATD studies.

Quantitative evaluation of interstitial pneumonia using 3D-curved high-resolution CT imaging parallel to the chest wall: A pilot study

Objectives

To quantify the imaging findings of patients with interstitial pneumonia (IP) and emphysema using three-dimensional curved high-resolution computed tomography (3D-cHRCT) at a constant depth from the chest wall, and compare the results to visual assessment of IP and each patient’s diffusing capacity of the lungs for carbon monoxide (DLco).

Methods

We retrospectively reviewed the axial CT findings and pulmonary function test results of 95 patients with lung cancer (72 men and 23 women, aged 45–84 years) with or without IP, as follows: non-IP (n = 47), mild IP (n = 31), and moderate IP (n = 17). The 3D-cHRCT images of the lung at a 1-cm depth from the chest wall were reconstructed automatically using original software; total area (TA), high-attenuation area (HAA) >-500 HU, and low-attenuation area (LAA) <-950 HU were calculated on a workstation. The %HAA and %LAA were calculated as follows: %HAA=HAATA×100, and %LAA=LAATA×100.

Results

The %HAA and %LAA respective values were 3.2±0.9 and 27.7±8.2, 3.9±1.2 and 27.6±5.9, and 6.9±2.2 and 25.4±8.7 in non-IP, mild IP, and moderate IP patients, respectively. There were significant differences in %HAA between the 3 groups of patients (P<0.001), but no differences in %LAA (P = 0.558). Multiple linear regression analysis revealed that %HAA and %LAA were negatively correlated with predicted DLco (standard partial regression coefficient [b*] = -0.453, P<0.001; b* = -0.447, P<0.001, respectively).

Conclusions

The %HAA and %LAA values computed using 3D-cHRCT were significantly correlated with DLco and may be important quantitative parameters for both IP and emphysema.

Computed tomography quantification of pulmonary vessels in chronic obstructive pulmonary disease as identified by 3D automated approach

The aim of this study was to investigate the vascular alteration of the whole lung and individual lobes in patients with COPD, and assess the association between pulmonary vessels and the extent and distribution of emphysema as well as pulmonary function by a 3-dimensional automated approach.A total of 83 computed tomography images from COPD patients were analyzed. Automated computerized approach was used to measure the total number of vessels at the fifth generation. The extent of emphysema (%LAA-950) in the whole lung and individual lobes were also calculated automatically. The association between the vascular number and the extent and distribution of emphysema, as well as the pulmonary function were assessed.Both the vascular number of fifth generation in the upper lobe and in the lower lobe were significantly negatively correlated with %LAA-950 (P < 0.05). Furthermore, there were significant, yet weak correlations between the vascular number and FEV1% predicted (R = 0.556, P = 0.039) and FEV1/FVC (R = 0.538, P = 0.047). In contrast, the vascular numbers were strongly correlated with DLco (R = 0.770, P = 0.003). Finally, the vascular number correlated closer with %LAA-950 of upper lobes than with %LAA-950 of lower lobes.Pulmonary vessel alteration can be measured; it is related to the extent of emphysema rather than the distribution of emphysema.