Diffusing Capacity of Carbon Monoxide in Assessment of COPD

Advances in COPD imaging using CT and MRI: linkage with lung physiology and clinical outcomes

Recent years have witnessed major advances in lung imaging in patients with COPD. These include significant refinements in images obtained by computed tomography (CT) scans together with the introduction of new techniques and software that aim for obtaining the best image whilst using the lowest possible radiation dose. Magnetic resonance imaging (MRI) has also emerged as a useful radiation-free tool in assessing structural and more importantly functional derangements in patients with well-established COPD and smokers without COPD, even before the existence of overt changes in resting physiological lung function tests. Together, CT and MRI now allow objective quantification and assessment of structural changes within the airways, lung parenchyma and pulmonary vessels. Furthermore, CT and MRI can now provide objective assessments of regional lung ventilation and perfusion, and multinuclear MRI provides further insight into gas exchange; this can help in structured decisions regarding treatment plans. These advances in chest imaging techniques have brought new insights into our understanding of disease pathophysiology and characterising different disease phenotypes. The present review discusses, in detail, the advances in lung imaging in patients with COPD and how structural and functional imaging are linked with common resting physiological tests and important clinical outcomes.

Dynamic hyperinflation is a risk factor for mortality and severe exacerbations in COPD patients

OBJECTIVE

To assess if dynamic hyperinflation is an independent risk factor for mortality and severe exacerbations in COPD patients.

METHODS

A cohort of 141 patients with stable COPD and moderate to very severe airflow limitation, treated according to conventional guidelines, was followed for a median of 9 years. Clinical characteristics were recorded and arterial blood gases, pulmonary function tests, 6-min walk and incremental exercise test with measurement of respiratory pattern and operative lung volumes were performed. Endpoints were all-cause mortality and hospitalization for COPD exacerbation.

RESULTS

58 patients died during the follow-up period (1228 patients x year). The mortality rate was higher in patients with dynamic hyperinflation (n = 106) than in those without it (n = 35) (14.6; 95% CI, 14.5-14.8 vs. 7.2; 95% CI, 7.1-7.4 per 1000 patients-year). After adjusting for sex, age, body mass index, pack-years and treatment with inhaled corticosteroids, dynamic hyperinflation was associated with a higher mortality risk (adjusted hazard ratio [aHR], 2.725; 95% CI, 1.010-8.161), and in a multivariate model, comorbidity, peak oxygen uptake and dynamic hyperinflation were retained as independent predictors of mortality. The time until first severe exacerbation was shorter for patients with dynamic hyperinflation (aHR, 3.961; 95% CI, 1.385-11.328), and dynamic hyperinflation, FEV1 and diffusing capacity were retained as independent risk factors for severe exacerbation. Moreover, patients with dynamic hyperinflation had a higher hospitalization risk than those without it (adjusted incidence rate ratio, 1.574; 95% CI, 1.087-2.581).

CONCLUSION

In stable COPD patients, dynamic hyperinflation is an independent prognostic factor for mortality and severe exacerbations.

Predicting Exacerbations in Alpha-1 Antitrypsin Deficiency Using Clinical and Pulmonary Function Tests: Portuguese EARCO Registry

INTRODUCTION

Exacerbations are common in individuals with alpha-1 antitrypsin deficiency (AATD)-related lung disease. This study intended to identify independent predictive factors for exacerbations in AATD using the Portuguese European Alpha-1 Research Collaboration (EARCO) registry.

METHODS

This study includes patients from the Portuguese EARCO registry, a prospective multicenter cohort (NCT04180319). From October 2020 to April 2023, this registry enrolled 137 patients, 14 of whom were excluded for analysis for either missing 12 months of follow-up or baseline pulmonary function.

RESULTS

Among the 123 AATD patients, 27 (22.0%) had at least one exacerbation in the last 12 months of follow-up. Patients with Pi*ZZ phenotype were three times more likely than the rest of the population to experience any exacerbation (32.7 vs. 14.1%, p = 0.014; OR 3.0). BODE index was significantly higher in exacerbators than in non-exacerbators (3.9 ± 2.4 vs. 1.3 ± 1.2; p < 0.001), including on multivariate analysis (p = 0.002). Similar results were found for BODEx (multivariate p < 0.001). DLCO was the only functional parameter independently associated with exacerbations (p = 0.024).

CONCLUSIONS

DLCO, BODE, and BODEx were independent predictors of exacerbations at 12 months in AATD patients. Understanding these risk factors can aid decision-making on AATD-related lung disease management and improve patient outcomes.

The total-breath method yields higher values of DLCO and TLC than the conventional method

BACKGROUND

The 2017 ATS/ERS technical standard for measuring the single-breath diffusing capacity (DLCO) proposed the "rapid-gas-analyzer" (RGA) or, equivalently, "total-breath" (TB) method for the determination of total lung capacity (TLC). In this study, we compared DLCO and TLC values estimated using the TB and conventional method, and how estimated TLC using these two methods compared to that determined by body plethysmography.

METHOD

A total of 95 people with COPD (GOLD grades 1-4) and 23 healthy subjects were studied using the EasyOne Pro (ndd Medical Technologies, Switzerland) and Master Screen Body (Vyaire Medical, Höchberg, Germany).

RESULTS

On average the TB method resulted in higher values of DLCO (mean ± SD Δ = 0.469 ± 0.267; 95%CI: 0.420; 0.517 mmol*min-1*kPa-1) and TLC (Δ = 0.495 ± 0.371; 95%CI: 0.427; 0.562 L) compared with the conventional method. In healthy subjects the ratio between TB and conventional DLCO was close to one. TLC estimated using both methods was lower than that determined by plethysmography. The difference was smaller for the TB method (Δ = 1.064 ± 0.740; 95%CI: 0.929; 1.199 L) compared with the conventional method (Δ = 1.558 ± 0.940; 95%CI: 1.387; 1.739 L). TLC from body plethysmography could be estimated as a function of TB TLC and FEV1 Z-Score with an accuracy (normalized root mean square difference) of 9.1%.

CONCLUSION

The total-breath method yielded higher values of DLCO and TLC than the conventional analysis, especially in subjects with COPD. TLC from the total-breath method can also be used to estimate plethysmographic TLC with better accuracy than the conventional method. The study is registered under clinicaltrial.gov NCT04531293.

Respiratory function after 30+ years following sulfur mustard exposure in survivors in Sweden

Background

Sulfur mustard (SM) exposure causes acute and chronic respiratory diseases. The extent of small airway dysfunction (SAD) in individuals exposed to SM is unclear. This study evaluated and compared SAD in SM-exposed and SM-unexposed participants using noninvasive lung function tests assessing small airway function.

Methods

This retrospective cohort study involved SM-exposed (n = 15, mean age: 53 ± 8 years) and SM-unexposed (n = 15, mean age: 53 ± 7 years) Kurdish-Swedish individuals in Sweden. Small airway resistance and reactance were assessed using impulse oscillometry (IOS). Nitrogen (N2) multiple breath washout (MBW) was employed to assess lung ventilation heterogeneity. The gas-exchanging capacity of the lungs was assessed using the diffusing capacity of the lungs for the carbon monoxide (DLCO) test. Lung function outcomes were reported as absolute values and z-scores. Group comparisons were performed using the Mann-Whitney U test.

Results

No statistically significant differences in age, height, or body mass index were observed between the two groups. IOS showed significantly increased small airway resistance, while N2MBW exhibited significantly increased global and acinar ventilation heterogeneity in SM-exposed individuals compared to that in unexposed individuals. SAD was identified in 14 of 15 SM-exposed individuals, defined as at least one abnormal IOS difference between resistance at 5 and 20 Hz (R5-R20) and/or area of reactance (AX) or N2MBW lung's acinar zone (Sacin), and DLCO adjusted to the alveolar volume (DLCO/VA) outcome. Of these 14 individuals, only 5 demonstrated concordant findings across the IOS and N2MBW tests.

Conclusion

Exposure to SM was positively associated with long-term impairment of respiratory tract function in the small airways in the majority of the previously SM-exposed individuals in the present study. Furthermore, both IOS and N2MBW should be employed to detect SAD in SM-exposed survivors as they provide complementary information. Identifying and characterizing the remaining pathology of the small airways in survivors of SM exposure is a first step toward improved treatment and follow-up.

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.

Resolving the Complexity: A Comprehensive Review on Carbon Monoxide Diffusion Capacity in Chronic Obstructive Pulmonary Disease Patients

This review comprehensively examines the intricate relationship between carbon monoxide (CO) diffusion capacity and chronic obstructive pulmonary disease (COPD). COPD, comprising chronic bronchitis and emphysema, presents a substantial global health burden, necessitating a nuanced understanding of pulmonary function parameters for effective diagnosis and management. The review delves into the physiological underpinnings, measurement techniques, and factors influencing CO diffusion capacity, emphasizing its pivotal role in assessing alveolar gas exchange efficiency. Key findings elucidate correlations between altered diffusion capacity and the severity of COPD, providing clinicians with valuable insights into disease progression. Considerations of age, gender, and ethnic disparities in normal CO diffusion capacity values highlight the importance of personalized interpretations. The clinical implications extend beyond diagnosis, influencing COPD management and prognostication, with potential applications in predicting treatment response. The review outlines avenues for future research, including advancements in measurement technologies and the exploration of novel imaging modalities and biomarkers. Ultimately, this review serves as a foundation for refining diagnostic approaches and treatment strategies and enhancing patient care in the dynamic landscape of COPD.

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.

Low diffusion capacity predicts poor prognosis in extensive stage small cell lung cancer: a single-center analysis of 10 years

BACKGROUND

Poor pulmonary function and chronic obstructive pulmonary disease (COPD) are associated with poorer overall survival (OS) in non-small-cell lung cancer (NSCLC) patients. Few studies have investigated the association between pulmonary function and OS in small-cell lung cancer (SCLC) patients. We compared the clinical characteristics of extensive disease SCLC (ED-SCLC) with or without moderately impaired diffusion capacity for carbon monoxide (DLco) and investigated the factors associated with survival in ED-SCLC patients.

METHODS

This retrospective single-center study was performed between January 2011 and December 2020. Of the 307 SCLC patients who received cancer therapy during the study, 142 with ED-SCLC were analyzed. The patients were divided into DLco < 60% group and DLco ≥ 60% groups. OS and predictors of poor OS were analyzed.

RESULTS

The median OS of the 142 ED-SCLC patients was 9.3 months and the median age was 68 years. In total, 129 (90.8%) patients had a history of smoking, and 60 (42.3%) had COPD. Thirty-five (24.6%) patients were assigned to the DLco < 60% group. Multivariate analysis revealed that DLco < 60% (odds ratio [OR], 1.609; 95% confidence interval [CI], 1.062-2.437; P = 0.025), number of metastases (OR, 1.488; 95% CI, 1.262-1.756; P < 0.001), and < 4 cycles of first-line chemotherapy (OR, 3.793; 95% CI, 2.530-5.686; P < 0.001) were associated with poor OS. Forty (28.2%) patients received < 4 cycles of first-line chemotherapy; the most common reason for this was death (n = 22, 55%) from grade 4 febrile neutropenia (n = 15), infection (n = 5), or massive hemoptysis (n = 2). The DLco < 60% group had a shorter median OS than the DLco ≥ 60% group (10.6 ± 0.8 vs. 4.9 ± 0.9 months, P = 0.003).

CONCLUSIONS

In this study, approximately one quarter of the ED-SCLC patients had DLco < 60%. Low DLco (but not forced expiratory volume in 1 s or forced vital capacity), a large number of metastases, and < 4 cycles of first-line chemotherapy were independent risk factors for poor survival outcomes in patients with ED-SCLC.

Isolated abnormal diffusing capacity for carbon monoxide (iso↓DLco) is associated with increased respiratory symptom burden in people with HIV infection

OBJECTIVES

An isolated reduction in the diffusing capacity for carbon monoxide (DLco; iso↓DLco) is one of the most common pulmonary function test (PFT) abnormalities in people living with HIV (PWH), but its clinical implications are incompletely understood. In this study, we explored whether iso↓DLco in PWH is associated with a greater respiratory symptom burden.

STUDY DESIGN

Cross-sectional analysis.

METHODS

We used ATS/ERS compliant PFTs from PWH with normal spirometry (post-bronchodilator FEV1/FVC ≥0.7; FEV1, FVC ≥80% predicted) from the I AM OLD cohort in San Francisco, CA and Seattle, WA, grouped by DLco categorized as normal (DLco ≥lower limit of normal, LLN), mild iso↓DLco (LLN >DLco >60% predicted), and moderate-severe iso↓DLco (DLco ≤60% predicted). We performed multivariable analyses to test for associations between DLco and validated symptom-severity and quality of life questionnaires, including the modified Medical Research Council dyspnea scale (mMRC), the COPD Assessment Test (CAT), and St. George's Respiratory Questionnaire (SGRQ), as well as between DLco and individual CAT symptoms.

RESULTS

Mild iso↓DLco was associated only with a significantly higher SGRQ score. Moderate-severe iso↓DLco was associated with significantly higher odds of mMRC ≥2 and significantly higher CAT and SGRQ scores. PWH with moderate-severe iso↓DLco had increased odds of breathlessness, decreased activity, lower confidence leaving home, and less energy.

CONCLUSIONS

Iso↓DLco is associated with worse respiratory symptom scores, and this association becomes stronger with worsening DLco, suggesting that impaired gas exchange alone has a significant negative impact on the quality of life in PWH. Additional studies are ongoing to understand the etiology of this finding and design appropriate interventions.

The Role of Pulmonary Function Testing in the Diagnosis and Management of COPD

Pulmonary function testing (PFT) has a long and rich history in the definition, diagnosis, and management of COPD. For decades, spirometry has been regarded as the standard for diagnosing COPD; however, numerous studies have shown that COPD symptoms, pathology, and associated poor outcomes can occur, despite normal spirometry. Diffusing capacity and imaging studies have called into question the need for spirometry to put the "O" (obstruction) in COPD. The role of exercise testing and the ability of PFTs to phenotype COPD are reviewed. Although PFTs play an important role in diagnosis, treatment decisions are primarily determined by symptom intensity and exacerbation history. Although a seminal study positioned FEV1 as the primary predictor of survival, numerous studies have shown that tests other than spirometry are superior predictors of mortality. In years past, using spirometry to screen for COPD was promulgated; however, this only seems appropriate for individuals who are symptomatic and at risk for developing COPD.

Prognostic Biomarkers Based on Proteomic Technology in COPD: A Recent Review

Chronic obstructive pulmonary disease (COPD) is a common heterogeneous respiratory disease which is characterized by persistent and incompletely reversible airflow limitation. Due to the heterogeneity and phenotypic complexity of COPD, traditional diagnostic methods provide limited information and pose a great challenge to clinical management. In recent years, with the development of omics technologies, proteomics, metabolomics, transcriptomics, etc., have been widely used in the study of COPD, providing great help to discover new biomarkers and elucidate the complex mechanisms of COPD. In this review, we summarize the prognostic biomarkers of COPD based on proteomic studies in recent years and evaluate their association with COPD prognosis. Finally, we present the prospects and challenges of COPD prognostic-related studies. This review is expected to provide cutting-edge evidence in prognostic evaluation of clinical patients with COPD and to inform future proteomic studies on prognostic biomarkers of COPD.

Prevalence of and Factors Associated with Respiratory Symptoms Among Patients with Inflammatory Bowel Disease: A Prospective Study

BACKGROUND

No large, prospective study has investigated respiratory symptoms in patients with inflammatory bowel diseases. We aimed to describe the prevalence of and factors associated with respiratory symptoms in patients with inflammatory bowel disease.

METHODS

In an observational, prospective, cross-sectional study, we evaluated the frequency of respiratory symptoms using a validated self-reporting questionnaire from February 2019 to February 2021 during routine follow-up outpatient visits of patients with inflammatory bowel disease followed in the Gastroenterology Department of the Nancy University Hospital. In case of a positive questionnaire, patients were systematically offered a consultation with a pulmonologist in order to investigate a potential underlying respiratory disease.

RESULTS

There were 325 patients included, and 180 patients had a positive questionnaire (144 with Crohn's disease). Of the included patients, 165 (50.8%) presented with respiratory symptoms, with dyspnea being the most frequent symptom (102 patients). There were 102 patients (56.7%) who benefited from a consultation in the pulmonology department: 43 (42.2%) were diagnosed with a respiratory disease, mainly asthma (n = 13) or chronic obstructive pulmonary disease (n = 10). Fourteen patients (13.7%) had obstructive sleep apnea. A body mass index increase, being a smoker or ex-smoker, and having articular extra-intestinal manifestations were independently associated with a higher prevalence of respiratory symptoms.

CONCLUSIONS

Half of patients with inflammatory bowel disease reported respiratory symptoms in our study. Patients with inflammatory bowel disease should be systematically screened, as pulmonary disease is frequently present in this population, with specific attention being given to smokers or ex-smokers and patients with extra-articular intestinal manifestations.

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.

Key Factors Associated With Pulmonary Sequelae in the Follow-Up of Critically Ill COVID-19 Patients

INTRODUCTION

Critical COVID-19 survivors have a high risk of respiratory sequelae. Therefore, we aimed to identify key factors associated with altered lung function and CT scan abnormalities at a follow-up visit in a cohort of critical COVID-19 survivors.

METHODS

Multicenter ambispective observational study in 52 Spanish intensive care units. Up to 1327 PCR-confirmed critical COVID-19 patients had sociodemographic, anthropometric, comorbidity and lifestyle characteristics collected at hospital admission; clinical and biological parameters throughout hospital stay; and, lung function and CT scan at a follow-up visit.

RESULTS

The median [p₂₅-p₇₅] time from discharge to follow-up was 3.57 [2.77-4.92] months. Median age was 60 [53-67] years, 27.8% women. The mean (SD) percentage of predicted diffusing lung capacity for carbon monoxide (D_LCO) at follow-up was 72.02 (18.33)% predicted, with 66% of patients having D_LCO<80% and 24% having D_LCO<60%. CT scan showed persistent pulmonary infiltrates, fibrotic lesions, and emphysema in 33%, 25% and 6% of patients, respectively. Key variables associated with D_LCO<60% were chronic lung disease (CLD) (OR: 1.86 (1.18-2.92)), duration of invasive mechanical ventilation (IMV) (OR: 1.56 (1.37-1.77)), age (OR [per-1-SD] (95%CI): 1.39 (1.18-1.63)), urea (OR: 1.16 (0.97-1.39)) and estimated glomerular filtration rate at ICU admission (OR: 0.88 (0.73-1.06)). Bacterial pneumonia (1.62 (1.11-2.35)) and duration of ventilation (NIMV (1.23 (1.06-1.42), IMV (1.21 (1.01-1.45)) and prone positioning (1.17 (0.98-1.39)) were associated with fibrotic lesions.

CONCLUSION

Age and CLD, reflecting patients' baseline vulnerability, and markers of COVID-19 severity, such as duration of IMV and renal failure, were key factors associated with impaired D_LCO and CT abnormalities.

Diffusing Capacity and Mortality in Chronic Obstructive Pulmonary Disease

Rationale: Chronic obstructive pulmonary disease (COPD) mortality risk is often estimated using the BODE (body mass index, obstruction, dyspnea, exercise capacity) index, including body mass index, forced expiratory volume in 1 second, dyspnea score, and 6-minute walk distance. Diffusing capacity of the lung for carbon monoxide (DlCO) is a potential predictor of mortality that reflects physiology distinct from that in the BODE index. Objectives: This study evaluated DlCO as a predictor of mortality using participants from the COPDGene study. Methods: We performed time-to-event analyses of individuals with COPD (former or current smokers with forced expiratory volume in 1 second/forced vital capacity < 0.7) and DlCO measurements from the COPDGene phase 2 visit. Cox proportional hazard methods were used to model survival, adjusting for age, sex, pack-years, smoking status, BODE index, computed tomography (CT) percent emphysema (low attenuation areas below -950 Hounsfield units), CT airway wall thickness, and history of cardiovascular or kidney diseases. C statistics for models with DlCO and BODE scores were used to compare discriminative accuracy. Results: Of 2,329 participants, 393 (16.8%) died during the follow-up period (median = 4.9 yr). In adjusted analyses, for every 10% decrease in DlCO percent predicted, mortality increased by 28% (hazard ratio = 1.28; 95% confidence interval, 1.17-1.41, P < 0.001). When compared with other clinical predictors, DlCO percent predicted performed similarly to BODE (C statistic DlCO = 0.68; BODE = 0.70), and the addition of DlCO to BODE improved its discriminative accuracy (C statistic = 0.71). Conclusions: Diffusing capacity, a measure of gas transfer, strongly predicted all-cause mortality in individuals with COPD, independent of BODE index and CT evidence of emphysema and airway wall thickness. These findings support inclusion of DlCO in prognostic models for COPD.

Comparison of health-related quality of life measures in asthma-COPD overlap

OBJECTIVE

The Asthma Quality of Life Questionnaire (AQLQ) and COPD assessment test (CAT) are used to assess the health status of asthma and chronic obstructive pulmonary disease (COPD), respectively. However, whether these questionnaires are appropriate in patients with asthma-COPD overlap (ACO) has not been reported. This study aimed to evaluate the performance of the AQLQ and CAT in subjects with ACO.

METHODS

Subjects were enrolled from two previously described observational studies in Beijing, China. ACO was defined by a consensus definition from a roundtable discussion. All subjects completed the AQLQ, CAT, St George's Respiratory Questionnaire (SGRQ), pulmonary function tests, and the Asthma Control Questionnaire (ACQ)-5. Cross-sectional construct validity was evaluated by correlating the AQLQ and CAT with SGRQ score and other measures of asthma and COPD severity.

RESULTS

147 subjects with ACO were recruited. There were floor effects on non-respiratory components of the CAT, and ceiling effects on emotion domains of the AQLQ. Both questionnaires were significantly correlated with ACQ-5 score but were not correlated with FEV1% predicted or FVC% predicted. The AQLQ and CAT were strongly correlated with SGRQ score (r = -0.657 and r = 0.623, respectively). Multivariable linear regression analysis showed that the AQLQ (standardized β-coefficient = -0.449, p < .001) had a stronger association with SGRQ score compared with CAT (standardized β-coefficient = 0.211, p = .023).

DISCUSSION

The AQLQ and CAT were both valid for assessing the health-related quality of life in subjects with ACO, but the AQLQ performed better than CAT.

Lipidomic Profile Analysis of Lung Tissues Revealed Lipointoxication in Pulmonary Veno-Occlusive Disease

Pulmonary veno-occlusive disease (PVOD) is a rare form of pulmonary arterial hypertension (PAH) occurring in a heritable form (hPVOD) due to biallelic inactivating mutations of EIF2AK4 (encoding GCN2, general control nonderepressible 2) or in a sporadic form in older age (sPVOD), following exposure to chemotherapy or organic solvents. In contrast to PAH, PVOD is characterized by a particular remodeling of the pulmonary venous system and the obliteration of small pulmonary veins by fibrous intimal thickening and patchy capillary proliferation. The pathobiological knowledge of PVOD is poor, explaining the absence of medical therapy for PVOD. Lung transplantation remains the only therapy for eligible PVOD patients. As we recently demonstrated, respiratory diseases, chronic obstructive pulmonary disease, or cystic fibrosis exhibit lipointoxication signatures characterized by excessive levels of saturated phospholipids contributing to the pathological features of these diseases, including endoplasmic reticulum stress, pro-inflammatory cytokines production, and bronchoconstriction. In this study, we investigated and compared the clinical data and lung lipid signature of control (10 patients), idiopathic PAH (7 patients), heritable PAH (9 BMPR2 mutations carriers), hPVOD (10 EIF2AK4 mutation carriers), and sPVOD (6 non-carriers) subjects. Mass spectrometry analyses demonstrated lung lipointoxication only in hPVOD patients, characterized by an increased abundance of saturated phosphatidylcholine (PC) at the expense of the polyunsaturated species in the lungs of hPVOD patients. The present data suggest that lipointoxication could be a potential player in the etiology of PVOD.

Clinical, imaging, and blood biomarkers to assess 1-year progression risk in fibrotic interstitial lung diseases-Development and validation of the honeycombing, traction bronchiectasis, and monocyte (HTM)-score

INTRODUCTION

Progression of fibrotic interstitial lung disease (ILD) leads to irreversible loss of lung function and increased mortality. Based on an institutional ILD registry, we aimed to evaluate biomarkers derived from baseline patient characteristics, computed tomography (CT), and peripheral blood for prognosis of disease progression in fibrotic ILD patients.

METHODS

Of 209 subsequent ILD-board patients enregistered, 142 had complete follow-up information and were classified fibrotic ILD as defined by presence of reticulation or honeycombing using a standardized semi-quantitative CT evaluation, adding up typical ILD findings in 0-6 defined lung fields. Progression at 1 year was defined as relative loss of ≥10% in forced vital capacity, of ≥15% in diffusion capacity for carbon monoxide, death, or lung transplant. Two-thirds of the patients were randomly assigned to a derivation cohort evaluated for the impact of age, sex, baseline lung function, CT finding scores, and blood biomarkers on disease progression. Significant variables were included into a regression model, its results were used to derive a progression-risk score which was then applied to the validation cohort.

RESULTS

In the derivation cohort, age, monocyte count ≥0.65 G/L, honeycombing and traction bronchiectasis extent had significant impact. Multivariate analyses revealed the variables monocyte count ≥0.65 G/L (1 point) and combined honeycombing or traction bronchiectasis score [0 vs. 1-4 (1 point) vs. 5-6 lung fields (2 points)] as significant, so these were used for score development. In the derivation cohort, resulting scores of 0, 1, 2, and 3 accounted for 1-year progression rates of 20, 25, 46.9, and 88.9%, respectively. Similarly, in the validation cohort, progression at 1 year occurred in 0, 23.8, 53.9, and 62.5%, respectively. A score ≥2 showed 70.6% sensitivity and 67.9% specificity, receiver operating characteristic analysis for the scoring model had an area under the curve of 71.7%.

CONCLUSION

The extent of honeycombing and traction bronchiectasis, as well as elevated blood monocyte count predicted progression within 1 year in fibrotic ILD patients.

The Prognostic Performance of Lung Diffusing Capacity in Preserved Ratio Impaired Spirometry: An Observational Cohort Study

Purpose

Similar to chronic obstructive pulmonary disease (COPD), the diffusing capacity of the lung (D_LCO) might be decreased and associated with poor prognosis in preserved ratio impaired spirometry (PRISm), a clinical entity as a prodromal phase of COPD. The aims of the present study were to evaluate the distributions of D_LCO and to assess the association between D_LCO and mortality among subjects with PRISm.

Patients and Methods

We conducted an observational cohort study at the National Hospital Organization Fukuoka National Hospital. We classified the 899 patients ≥ 40 years of age with an assessment of D_LCO into five groups based on spirometry: preserved spirometry, PRISm, mild COPD, moderate COPD, and severe/very severe COPD. The prevalence of low D_LCO (< 80% per predicted) was compared among the five groups. Using PRISm patients with follow-up data, we further investigated the association of low D_LCO with all-cause mortality.

Results

The prevalence of low D_LCO in the PRISm group (58.8%) was significantly higher than that in the preserved-spirometry group (21.8%), the mild-COPD group (23.5%), and the moderate-COPD group (36.0%) (all P < 0.01), and it was comparable to that in the severe/very severe-COPD group (63.2%). The results remained unchanged after adjusting for potential confounders. Among the PRISm subjects, the overall survival rate was significantly lower in the low-D_LCO group than in the preserved-D_LCO group (P < 0.01). The multivariable-adjusted hazard ratio (HR) for all-cause mortality was significantly higher in the low-D_LCO group than in the preserved-D_LCO group (HR = 10.10 (95% confidence interval 2.33–43.89)).

Conclusion

Diffusing capacity was more impaired in PRISm subjects than in those with preserved spirometry or mild to moderate COPD. Regarding PRISm, low D_LCO was a significant risk factor for all-cause mortality. Clinicians should assess D_LCO in the management of PRISm to predict the future risk of overall death.

Assessment of Long-Term Effects on Pulmonary Functions Between Severe and Non-Severe Convalescent COVID-19 Patients: A Single-Center Study in China

Objective

To explore the long-term effects of SARS-Cov-2 infection on the pulmonary function in the severe convalescent COVID-19 patients for 6 to 9 months follow-up in Beijing, China.

Methods

A total of 64 cases of COVID-19 patients were recruited for the study and discharged from the Beijing Ditan Hospital, Capital Medical University, for 6 to 9 months. COVID-19 patients were divided into non-severe (mild and moderate) and severe groups. The follow-up investigated the lung function tests, the novel coronavirus antibody (IgM and IgG), chest CT and blood tests.

Results

About 25.00% (16/64) patients had pulmonary ventilation dysfunction and 35.9% (23/64) had diffusion dysfunction. In the severe group, 56.50% (13/23) individuals showed decreased diffusion function. The diffusion dysfunction of the severe group was significantly decreased than the non-severe group (P = 0.01). Among 56 cases, the positive rate of IgG titers was 73.2% (41/56). The result of chest CT showed 55.36% (31/56) cases in nodules, 44.64% (25/56) in strip-like changes, 37.5% (21/56) in-ground glass shadow, and 5.36% (3/56) in grid shadow, which was significantly different between the severe group and the non-severe group. Patients tended to have ground glass changes in the severe group while nodules in the non-severe group.

Conclusion

For the 6 to 9 months in convalescent COVID-19 patients, 56.50% (13/23) of severe patients had pulmonary diffusion dysfunction. Convalescent COVID-19 patients should have their pulmonary function regularly tested, especially those with severe illness.

Indications for Lung Transplantation and Patient Selection

Globally, thousands of patients undergo lung transplantation owing to end-stage lung disease each year. As lung transplantation evolves, recommendations and indications are constantly being updated. In 2021, the International Society for Heart and Lung Transplantation published a new consensus document for selecting candidates for lung transplantation. However, it is still difficult to determine appropriate candidates for lung transplantation among patients with complex medical conditions and various diseases. Therefore, it is necessary to analyze each patient’s overall situation and medical condition from various perspectives, and ongoing efforts to optimize the analysis will be necessary. The purpose of this study is to review the extant literature and discuss recent updates.

Respiratory Impedance is Associated with Ventilation and Diffusing Capacity in Patients with Idiopathic Pulmonary Fibrosis Combined with Emphysema

Purpose

Pulmonary fibrosis and emphysema result in relatively maintained ventilation and reduced diffusing capacity. This pulmonary functional impairment complicates the evaluation of pulmonary function in patients with combined pulmonary fibrosis and emphysema (CPFE). Therefore, a single and easy-to-use pulmonary function index to evaluate patients with CPFE warrants further studies. Respiratory impedance can easily be provided by oscillometry and might be a candidate index to evaluate pulmonary function in patients with CPFE. As a preliminary study to assess the utility of respiratory impedance, we investigated the associations of physiological indices, including respiratory impedance, in patients with idiopathic pulmonary fibrosis (IPF) with and without emphysema.

Patients and Methods

This retrospective study evaluated patients with IPF who did and did not satisfy the diagnostic criteria of CPFE. All patients underwent oscillometry, spirometry, and diffusing capacity for carbon monoxide (D_LCO). Correlations of the obtained physiological indices were analyzed.

Results

In total, 47 patients were included (18 and 29 patients with CPFE and IPF, respectively). Respiratory reactance (Xrs) at 5 Hz (X5) in the inspiratory phase was associated with forced vital capacity (FVC) % predicted in patients with CPFE (r_S=0.576, P=0.012) and IPF (r_S=0.539, P=0.003). Inspiratory X5 positively correlated with D_LCO % predicted only in patients CPFE (r_S=0.637, P=0.004).

Conclusion

Emphysema might associate Xrs with ventilation and diffusing capacity in patients with IPF and emphysema. Given the multiple correlations of Xrs with FVC and D_LCO, this study warrants further studies to verify the utility of oscillometry in a large-scale study for patients with CPFE.

CD19 and POU2AF1 are Potential Immune-Related Biomarkers Involved in the Emphysema of COPD: On Multiple Microarray Analysis

Purpose

Emphysema is the main cause of the progression of chronic obstructive pulmonary disease (COPD). This study aimed to identify the key genes involved in COPD-related emphysema.

Patients and Methods

GSE76925 was downloaded from Gene Expression Omnibus database. Protein–protein interaction networks of differentially expressed genes (DEGs) between control and COPD groups were constructed to identify hub genes using Cytoscape. Diagnostic performance of hub genes was evaluated using receiver operating characteristic analysis. Correlation analysis was performed to identify the key genes by analyzing the relationship between the hub genes and lung function and computed tomography (CT) indexes of emphysema. COPD patients were then divided into two groups based on the median expression of key genes and DEGs between these two groups were identified. Enrichment analysis of DEGs and correlation analysis between key genes and the infiltration of the immune cells were also analyzed. Finally, the role of key genes was evaluated in a lung tissues dataset (GSE47460) and a blood dataset (GSE76705). Additionally, the expression of key genes was validated by quantitative real-time polymerase chain reaction and immunohistochemistry.

Results

CD19 and POU2AF1 had diagnostic efficacy for COPD and were significantly correlated with lung function and CT indexes of emphysema. Enrichment and immune analyses revealed that CD19 and POU2AF1 were correlated with the B cells in COPD. These results were consistent in GSE47460. The expression of CD19 and POU2AF1 in blood was the opposite of that in lung tissues, and CD19 and POU2AF1 were both significantly upregulated in COPD lung tissues at both the mRNA and protein levels.

Conclusion

CD19 and POU2AF1 may serve as key regulators of emphysema and contribute to the progression of COPD by regulating the B-cell immunology. Targeting B cells may be a promising strategy for treating COPD.

Reduced decline of lung diffusing capacity in COPD patients with diabetes and metformin treatment

We studied whether in patients with COPD the use of metformin for diabetes treatment was linked to a pattern of lung function decline consistent with the hypothesis of anti-aging effects of metformin. Patients of GOLD grades 1–4 of the COSYCONET cohort with follow-up data of up to 4.5 y were included. The annual decline in lung function (FEV₁, FVC) and CO diffusing capacity (KCO, TLCO) in %predicted at baseline was evaluated for associations with age, sex, BMI, pack-years, smoking status, baseline lung function, exacerbation risk, respiratory symptoms, cardiac disease, as well as metformin-containing therapy compared to patients without diabetes and metformin. Among 2741 patients, 1541 (mean age 64.4 y, 601 female) fulfilled the inclusion criteria. In the group with metformin treatment vs. non-diabetes the mean annual decline in KCO and TLCO was significantly lower (0.2 vs 2.3, 0.8 vs. 2.8%predicted, respectively; p < 0.05 each), but not the decline of FEV₁ and FVC. These results were confirmed using multiple regression and propensity score analyses. Our findings demonstrate an association between the annual decline of lung diffusing capacity and the intake of metformin in patients with COPD consistent with the hypothesis of anti-aging effects of metformin as reflected in a surrogate marker of emphysema.

The association between transfer coefficient of the lung and the risk of exacerbation in asthma-COPD overlap: an observational cohort study

BACKGROUND

Asthma-chronic obstructive pulmonary disease (COPD) overlap (ACO) patients experience exacerbations more frequently than those with asthma or COPD alone. Since low diffusing capacity of the lung for carbon monoxide (DLCO) is known as a strong risk factor for severe exacerbation in COPD, DLCO or a transfer coefficient of the lung for carbon monoxide (KCO) is speculated to also be associated with the risk of exacerbations in ACO.

METHODS

This study was conducted as an observational cohort survey at the National Hospital Organization Fukuoka National Hospital. DLCO and KCO were measured in 94 patients aged ≥ 40 years with a confirmed diagnosis of ACO. Multivariable-adjusted hazard ratios (HRs) for the exacerbation-free rate over one year were estimated and compared across the levels of DLCO and KCO.

RESULTS

Within one year, 33.3% of the cohort experienced exacerbations. After adjustment for potential confounders, low KCO (< 80% per predicted) was positively associated with the incidence of exacerbation (multivariable-adjusted HR = 3.71 (95% confidence interval 1.32-10.4)). The association between low DLCO (< 80% per predicted) and exacerbations showed similar trends, although it failed to reach statistical significance (multivariable-adjusted HR = 1.31 (95% confidence interval 0.55-3.11)).

CONCLUSIONS

Low KCO was a significant risk factor for exacerbations among patients with ACO. Clinicians should be aware that ACO patients with impaired KCO are at increased risk of exacerbations and that careful management in such a population is mandatory.

Brief Report: HIV Is Associated With Impaired Pulmonary Diffusing Capacity Independent of Emphysema

BACKGROUND

HIV is associated with accelerated decline in lung function and increased risk for chronic obstructive pulmonary disease (COPD). Recently, there has been growing attention toward the impairment in the diffusing capacity of the lungs for carbon monoxide (DLCO), a marker of pulmonary gas exchange, observed among persons living with HIV. Although increased emphysema can contribute to the DLCO impairment observed, other factors may drive this association.

METHODS

Using cross-sectional data from the Study of HIV in the Etiology of Lung Disease, we studied the association between HIV and DLCO independent of emphysema. We also analyzed the joint influence of HIV and COPD on DLCO impairment. An analysis was conducted among 339 participants (229 with HIV) with lung function and chest CT imaging data. Multivariable regression models were generated with percent predicted DLCO and odds of DLCO impairment as outcomes.

RESULTS

After adjusting for confounders, including emphysema severity, HIV was associated with lower DLCO (β -4.02%; P = 0.020) and higher odds of DLCO impairment (odds ratio 1.93; P = 0.017). Even among those without COPD, HIV was independently associated with lower DLCO (β -3.89%; P = 0.049). Compared with HIV-uninfected participants without COPD, those with both HIV and COPD experienced the greatest impairment in DLCO (β -14.81; P < 0.001).

CONCLUSIONS

HIV is associated with impaired pulmonary gas exchange independent of emphysema severity. Our data also suggest a potentially additive influence between HIV and COPD on DLCO impairment. Further studies should investigate the other factors, including pulmonary vascular disease, which may contribute to DLCO impairment among persons living with HIV.

Early Diagnosis and Real-Time Monitoring of Regional Lung Function Changes to Prevent Chronic Obstructive Pulmonary Disease Progression to Severe Emphysema

First- and second-hand exposure to smoke or air pollutants is the primary cause of chronic obstructive pulmonary disease (COPD) pathogenesis, where genetic and age-related factors predispose the subject to the initiation and progression of obstructive lung disease. Briefly, airway inflammation, specifically bronchitis, initiates the lung disease, leading to difficulty in breathing (dyspnea) and coughing as initial symptoms, followed by air trapping and inhibition of the flow of air into the lungs due to damage to the alveoli (emphysema). In addition, mucus obstruction and impaired lung clearance mechanisms lead to recurring acute exacerbations causing progressive decline in lung function, eventually requiring lung transplant and other lifesaving interventions to prevent mortality. It is noteworthy that COPD is much more common in the population than currently diagnosed, as only 16 million adult Americans were reported to be diagnosed with COPD as of 2018, although an additional 14 million American adults were estimated to be suffering from COPD but undiagnosed by the current standard of care (SOC) diagnostic, namely the spirometry-based pulmonary function test (PFT). Thus, the main issue driving the adverse disease outcome and significant mortality for COPD is lack of timely diagnosis in the early stages of the disease. The current treatment regime for COPD emphysema is most effective when implemented early, on COPD onset, where alleviating symptoms and exacerbations with timely intervention(s) can prevent steep lung function decline(s) and disease progression to severe emphysema. Therefore, the key to efficiently combatting COPD relies on early detection. Thus, it is important to detect early regional pulmonary function and structural changes to monitor modest disease progression for implementing timely interventions and effectively eliminating emphysema progression. Currently, COPD diagnosis involves using techniques such as COPD screening questionnaires, PFT, arterial blood gas analysis, and/or lung imaging, but these modalities are limited in their capability for early diagnosis and real-time disease monitoring of regional lung function changes. Hence, promising emerging techniques, such as X-ray phase contrast, photoacoustic tomography, ultrasound computed tomography, electrical impedance tomography, the forced oscillation technique, and the impulse oscillometry system powered by robust artificial intelligence and machine learning analysis capability are emerging as novel solutions for early detection and real time monitoring of COPD progression for timely intervention. We discuss here the scope, risks, and limitations of current SOC and emerging COPD diagnostics, with perspective on novel diagnostics providing real time regional lung function monitoring, and predicting exacerbation and/or disease onset for prognosis-based timely intervention(s) to limit COPD–emphysema progression.

Instructional Training Compared with Self-Study for Pulmonary Function Test Interpretation

Background

Pulmonary diseases have considerable prognostic relevance for all-cause mortality. Most patients with lung diseases such as chronic obstructive pulmonary disease are treated by general practitioners. Understanding the clinical consequences such as pulmonary hyperinflation or reduced diffusion capacity is important for the management and prognosis of patients with chronic respiratory disorders. Therefore, the interpretation of pulmonary function testing (PFT) results needs to see more emphasis in the medical education curriculum.

Objective

To develop PFT training for final-year medical students and to compare the efficacy of instructional training to self-reliant textbook study.

Methods

A two-armed randomized control trial compares learning outcomes in PFT interpretation. A total of 25 final-year medical students were selected at random into the 1) instructional training group or 2) self-reliant textbook study group on PFT interpretation. The learning time for both groups was 2 hours. The duration of the written pre- and post-training examinations was 60 minutes each. Both exams had a knowledge section (30 questions, maximum 120 points) and a skills section (11 case studies, maximum 75 points).

Results

The instructional training group acquired significantly more knowledge and, in particular, higher skill levels when compared with the self-reliant reading group. In the reading group, knowledge scores increased from 48 to 60% (12%) and skills scores increased from 14 to 22% (8%), whereas in the instructional group, knowledge increased from 47 to 71% (24%) and skills from 18 to 58% (40%). A multivariate analysis (Pillai’s Trace: 0.633; P < 0.001) as well as follow-up univariate analyses reveal that these differences are statistically significant (knowledge: F = 8.811, df = 1, P = 0.007; skills F = 33.965, df = 1, P < 0.001). Interestingly, there was no significant group effect in the pure knowledge gain about respiratory disorders per se.

Conclusion

The self-reliant study group was less able to translate their newly acquired knowledge into interpretation of comprehensive PFT reports. A mandatory 2-hour instructional training greatly enhances the students’ knowledge and skills about PFT interpretation. Obligatory PFT instructional training should therefore be included in the students’ curriculum.

Development of lung diffusion to adulthood following extremely preterm birth

Background

Gas exchange in extremely preterm (EP) infants must take place in fetal lungs. Childhood lung diffusing capacity of the lung for carbon monoxide (D_LCO) is reduced; however, longitudinal development has not been investigated. We describe the growth of D_LCO and its subcomponents to adulthood in EP compared with term-born subjects.

Methods

Two area-based cohorts born at gestational age ≤28 weeks or birthweight ≤1000 g in 1982–1985 (n=48) and 1991–1992 (n=35) were examined twice, at ages 18 and 25 years and 10 and 18 years, respectively, and compared with matched term-born controls. Single-breath D_LCO was measured at two oxygen pressures, with subcomponents (membrane diffusion (D_M) and pulmonary capillary blood volume (V_C)) calculated using the Roughton–Forster equation.

Results

Age-, sex- and height-standardised transfer coefficients for carbon monoxide (K_CO) and D_LCO were reduced in EP compared with term-born subjects, and remained so during puberty and early adulthood (p-values for all time-points and both cohorts ≤0.04), whereas alveolar volume (V_A) was similar. Development occurred in parallel to term-born controls, with no signs of pubertal catch-up growth nor decline at age 25 years (p-values for lack of parallelism within cohorts 0.99, 0.65, 0.71, 0.94 and 0.44 for z-D_LCO, z-V_A, z-K_CO, D_M and V_C, respectively). Split by membrane and blood volume components, findings were less clear; however, membrane diffusion seemed most affected.

Conclusions

Pulmonary diffusing capacity was reduced in EP compared with term-born subjects, and development from childhood to adulthood tracked in parallel to term-born subjects, with no signs of catch-up growth nor decline at age 25 years.

Pulmonary diffusing capacity following extremely preterm (EP) birth was reduced compared with term-born subjects. From mid-childhood to adulthood, development tracked in parallel in the EP and term-born groups, with preterms following lower trajectories.https://bit.ly/3ARPD7D

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.

Consensus document for the selection of lung transplant candidates: An update from the International Society for Heart and Lung Transplantation

Tens of thousands of patients with advanced lung diseases may be eligible to be considered as potential candidates for lung transplant around the world each year. The timing of referral, evaluation, determination of candidacy, and listing of candidates continues to pose challenges and even ethical dilemmas. To address these challenges, the International Society for Heart and Lung Transplantation appointed an international group of members to review the literature, to consider recent advances in the management of advanced lung diseases, and to update prior consensus documents on the selection of lung transplant candidates. The purpose of this updated consensus document is to assist providers throughout the world who are caring for patients with pulmonary disease to identify potential candidates for lung transplant, to optimize the timing of the referral of these patients to lung transplant centers, and to provide transplant centers with a framework for evaluating and selecting candidates. In addition to addressing general considerations and providing disease specific recommendations for referral and listing, this updated consensus document includes an ethical framework, a recognition of the variability in acceptance of risk between transplant centers, and establishes a system to account for how a combination of risk factors may be taken into consideration in candidate selection for lung transplantation.

The correlation between quadriceps muscle strength and endurance and exercise performance in patients with COPD

To determine the association between quadriceps muscle strength (QMS) and endurance (QME) and exercise capacity in patients with COPD after stratification for sex and resting lung function (LF). Data were collected from 3,246 patients with COPD (60% men, 64 ± 9 yr), including measures of exercise capacity [peak aerobic capacity (peakV̇o₂), 6-min walk distance (6MWD)] and isokinetic QMS and QME. Patients were stratified for sex, forced expiratory volume in 1 s (>50/≤50% predicted), single breath carbon monoxide diffusing capacity (>50/≤50% predicted), and residual volume (>140/≤140% predicted). After stratification for resting LF, QMS and QME were significantly associated with peakV̇o₂ (r range: 0.47-0.61 and 0.49-0.65 for men and 0.53-0.66 and 0.48-0.67 for women, respectively) and 6MWD (r range: 0.29-0.42 and 0.44-0.55 for men and 0.25-0.54 and 0.34-0.55 for women, respectively) (P < 0.001). Regression models demonstrated that QMS and QME were significant determinants of peakV̇o₂ (explained variance R² range: 35.6%-48.8% for men and 36.8%-49.0% for women) and 6MWD (R² range: 24.3%-43.3% for men and 28.4%-40.3% for women), independent of age and fat-free mass. Quadriceps muscle function was significantly associated with peakV̇o₂ and 6MWD in male and female patients with COPD after stratification for resting LF, in which QME appear to be a more important determinant than QMS. This underlines the importance of systematically evaluating both quadriceps muscle strength and endurance in in all patients with COPD.NEW & NOTEWORTHY Our findings identified quadriceps muscle function as an important determinant of exercise capacity across a wide spectrum of lung function. Quadriceps muscle endurance appears to be a more important determinant than quadriceps muscle strength, underlining the importance of including both the measurement of quadriceps muscle strength and endurance in routine assessment for all patient with COPD.

Markers of inflammation and immune activation are associated with lung function in a multi-center cohort of persons with HIV

OBJECTIVES

Studies have shown that people with HIV (PWH) may be at increased risk for chronic lung diseases and lung function abnormalities, which may be associated with immune activation. We tested the association of a panel of 12 immune activation and inflammation biomarkers with spirometry and single-breath diffusing capacity for carbon monoxide (DLco).

DESIGN

Cross-sectional, observational study.

METHODS

Participants were enrolled from the Inflammation, Aging, Microbes and Obstructive Lung Disease cohort of PWH at two US sites. Biomarkers were examined and standardized spirometry and DLco testing were performed. We tested associations between each biomarker and lung function, examined individually and in combination, using multi-variable linear and logistic regression.

RESULTS

Among 199 participants, median forced expiratory volume in 1 s (FEV1) was normal (90% predicted) and median DLco was abnormal (69% predicted). The most common lung function abnormality (57%) was a normal FEV1 to forced vital capacity ratio with an abnormal DLco of 80% or less predicted (iso↓DLco). Two markers (IL-6, high-sensitivity C-reactive protein) were associated with FEV1% predicted, whereas eight markers (soluble CD14, soluble CD163, inducible protein-10, soluble CD27, IL-6, soluble tumor necrosis factor receptors 1 and 2, D-dimer) were associated with DLco% predicted. Compared with those participants with normal spirometry and DLco, five markers (soluble CD14, soluble CD163, interferon gamma inducible protein-10, soluble tumor necrosis factor receptors 1 and 2) were associated with iso↓DLco.

CONCLUSION

Among PWH, different markers of immune activation and inflammation are associated with FEV1% predicted than with DLco% predicted and with an iso↓DLco, representing possible unique pathways of chronic lung disease. Identifying plausible drivers of these inflammatory pathways may clarify mechanisms underlying impaired lung function in HIV infection and may identify therapeutic avenues.

Risk of Acute Lung Injury after Esophagectomy

To develop a new approach for identifying acute lung injury (ALI) in surgical ward setting and to assess incidence rate, clinical outcomes, and risk factors for ALI cases after esophagectomy. We also compare the degree of lung injury between operative and non-operative sides. Consecutive esophageal cancer patients (n=1022) who underwent esophagectomy from Dec 2012 to Nov 2018 in our hospital were studied. An approach for identifying ALI was proposed that integrated radiographic assessment of lung edema (RALE) score to quantify degree of lung edema. Stepwise logistic regression identified risk factors for postoperative ALI incidence. The degree of bilateral lung injury was compared using the RALE score. The approach for identifying ALI in surgical ward setting was defined as acute onset, PaO₂/FiO₂≤300 mmHg, bilateral opacities on bedside chest radiograph with a RALE score≥16, and exclusion of cardiogenic pulmonary edema. Incidence rate of ALI was estimated to be 9.7%. ALI diagnosis was associated with multiple clinical complications, prolonged hospital stay, higher medical bills, and higher perioperative mortality. Nine risk factors including BMI, ASA class, DLCO%, duration of surgery, neutrophil percentage, high-density lipoprotein, and electrolyte disorders were identified. The RALE score of the lung lobes of the operative side was higher than the non-operative side. A new approach for identifying ALI in esophageal cancer patients receiving esophagectomy was proposed and several risk factors were identified. ALI is common and has severe outcomes. The lung lobes on the operative side are more likely to be affected than the non-operative side.

Prognostic marker for severe acute exacerbation of chronic obstructive pulmonary disease: analysis of diffusing capacity of the lung for carbon monoxide (DLCO) and forced expiratory volume in one second (FEV1)

Background

It is important to assess the prognosis of patients with chronic obstructive pulmonary disease (COPD) and acute exacerbation of COPD (AECOPD). Recently, it was suggested that diffusing capacity of the lung for carbon monoxide (D_LCO) should be added to multidimensional tools for assessing COPD. This study aimed to compare the D_LCO and forced expiratory volume in one second (FEV₁) to identify better prognostic factors for admitted patients with AECOPD.

Methods

We retrospectively analyzed 342 patients with AECOPD receiving inpatient treatment. We classified 342 severe AECOPD patients by severity of D_LCO and FEV₁ (≤ vs. > 50% predicted). We tested the association of FEV₁ and D_LCO with the following outcomes: in-hospital mortality, need for mechanical ventilation, need for intensive care unit (ICU) care. We analyzed the prognostic factors by multivariate analysis using logistic regression. In addition, we conducted a correlation analysis and receiver operating characteristic (ROC) curve analysis.

Results

In multivariate analyses, D_LCO was associated with mortality (odds ratio = 4.408; 95% CI 1.070–18.167; P = 0.040) and need for mechanical ventilation (odds ratio = 2.855; 95% CI 1.216–6.704; P = 0.016) and ICU care (odds ratios = 2.685; 95% CI 1.290–5.590; P = 0.008). However, there was no statistically significant difference in mortality rate when using FEV₁ classification (P = 0.075). In multivariate linear regression analyses, D_LCO (B = − 0.542 ± 0.121, P < 0.001) and FEV₁ (B = − 0.106 ± 0.106, P = 0.006) were negatively associated with length of hospital stay. In addition, D_LCO showed better predictive ability than FEV₁ in ROC curve analysis. The area under the curve (AUC) of D_LCO was greater than 0.68 for all prognostic factors, and in contrast, the AUC of FEV₁ was less than 0.68.

Conclusion

D_LCO was likely to be as good as or better prognostic marker than FEV₁ in severe AECOPD.

Clinical and Prognostic Impact of Low Diffusing Capacity for Carbon Monoxide Values in Patients With Global Initiative for Obstructive Lung Disease I COPD

BACKGROUND

The Global Initiative for Obstructive Lung Disease (GOLD) does not promote diffusing capacity for carbon monoxide (Dlco) values in the evaluation of COPD. In GOLD spirometric stage I COPD patients, the clinical and prognostic impact of a low Dlco has not been explored.

RESEARCH QUESTION

Could a Dlco threshold help define an increased risk of death and a different clinical presentation in these patients?

STUDY DESIGN AND METHODS

GOLD stage I COPD patients (n = 360) were enrolled and followed over 109 ± 50 months. Age, sex, pack-years' history, BMI, dyspnea, lung function measurements, exercise capacity, BODE index, and history of exacerbations were recorded. A cutoff value for Dlco was identified for all-cause mortality and the clinical and physiological characteristics of patients above and below the threshold compared. Cox regression analysis explored the predictive power of that cutoff value for all-cause mortality.

RESULTS

A Dlco cutoff value of <60% predicted was associated with all-cause mortality (Dlco ≥ 60%: 9% vs Dlco < 60%: 23%, P = .01). At a same FEV₁% predicted and Charlson score, patients with Dlco < 60% had lower BMI, more dyspnea, lower inspiratory capacity (IC)/total lung capacity (TLC) ratio, lower 6-min walk distance (6MWD), and higher BODE. Cox multiple regression analysis confirmed that after adjusting for age, sex, pack-years history, smoking status, and BMI, a Dlco < 60% is associated with all-cause mortality (hazard ratio [HR], 95% CI = 3.37, 1.35-8.39; P = .009) INTERPRETATION: In GOLD I COPD patients, a Dlco < 60% predicted is associated with increased risk of death and worse clinical presentation. What the cause(s) of this association are and whether they can be treated need to be determined.

Natural Course of the Diffusing Capacity of the Lungs for Carbon Monoxide in COPD: Importance of Sex

BACKGROUND

The value of the single-breath diffusing capacity of the lungs for carbon monoxide (Dlco) relates to outcomes for patients with COPD. However, little is known about the natural course of Dlco over time, intersubject variability, and factors that may influence Dlco progression.

RESEARCH QUESTION

What is the natural course of Dlco in patients with COPD over time, and which other factors, including sex differences, could influence this progression?

STUDY DESIGN AND METHODS

We phenotyped 602 smokers (women, 33%), of whom 506 (84%) had COPD and 96 (16%) had no airflow limitation. Lung function, including Dlco, was monitored annually over 5 years. A random coefficients model was used to evaluate Dlco changes over time.

RESULTS

The mean (± SE) yearly decline in Dlco % in patients with COPD was 1.34% ± 0.015%/y. This was steeper compared with non-COPD control subjects (0.04% ± 0.032%/y; P = .004). Sixteen percent of the patients with COPD, vs 4.3% of the control subjects, had a statistically significant Dlco % slope annual decline (4.14%/y). At baseline, women with COPD had lower Dlco values (11.37% ± 2.27%; P < .001) in spite of a higher FEV₁ % than men. Compared with men, women with COPD had a steeper Dlco annual decline of 0.89% ± 0.42%/y (P = .039).

INTERPRETATION

Patients with COPD have an accelerated decline in Dlco compared with smokers without the disease. However, the decline is slow, and a testing interval of 3 to 4 years may be clinically informative. The lower and more rapid decline in Dlco values in women, compared with men, suggests a differential impact of sex in gas exchange function.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT01122758; URL: www.clinicaltrials.gov.

Near-normal aerobic capacity in long-term survivors after lung transplantation

The clinical course of lung transplantation (LT) is diverse: some patients present chronic lung allograft dysfunction (CLAD) and progressive decline in pulmonary function, but others maintain normal spirometric values and active lives.

This is a multicentre study reporting, for the first time, near-normal peak V′_O2 values during cardiopulmonary exercise testing and normal exercise capacity in long-term lung transplant recipients without CLADhttps://bit.ly/35ftce3

Ultra-Small Lung Cysts Impair Diffusion Without Obstructing Air Flow in Lymphangioleiomyomatosis

Background

Lymphangioleiomyomatosis (LAM) is a rare lung disease found primarily in women of childbearing age, characterized by the formation of air-filled cysts, which may be associated with reductions in lung function. An experimental, regional ultra-high resolution CT scan identified an additional volume of cysts relative to standard chest CT imaging, which consisted primarily of ultra-small cysts.

Research Question

What is the impact of these ultra-small cysts on the pulmonary function of patients with LAM?

Study Design and Methods

A group of 103 patients with LAM received pulmonary function tests and a CT examination in the same visit. Cyst score, the percentage lung volume occupied by cysts, was measured by using commercial software approved by the US Food and Drug Administration. The association between cyst scores and pulmonary function tests of diffusing capacity of the lungs for carbon monoxide (Dlco) (% predicted), FEV₁ (% predicted), and FEV₁/FVC (% predicted) was assessed with statistical analysis adjusted for demographic variables. The distributions of average cyst size and ultra-small cyst fraction among the patients were evaluated.

Results

The additional cyst volume identified by the experimental, higher resolution scan consisted of cysts of 2.2 ± 0.8 mm diameter on average and are thus labeled the “ultra-small cyst fraction.” It accounted for 27.9 ± 19.0% of the total cyst volume among the patients. The resulting adjusted, whole-lung cyst scores better explained the variance of Dlco (P < .001 adjusted for multiple comparisons) but not FEV₁ and FEV₁/FVC (P = 1.00). The ultra-small cyst fraction contributed to the reduction in Dlco (P < .001) but not to FEV₁ and FEV₁/FVC (P = .760 and .575, respectively). The ultra-small cyst fraction and average cyst size were correlated with cyst burden, FEV₁, and FEV₁/FVC but less with Dlco.

Interpretation

The ultra-small cysts primarily contributed to the reduction in Dlco, with minimal effects on FEV₁ and FEV₁/FVC. Patients with lower cyst burden and better FEV₁ and FEV₁/FVC tended to have smaller average cyst size and higher ultra-small cyst fraction.

Clinical Trial Registration

ClinicalTrials.gov; No.: NCT00001465; URL: www.clinicaltrials.gov

The Impact of Tobacco Smoking on Adult Asthma Outcomes

Background: Tobacco smoking is associated with more severe asthma symptoms, an accelerated decline in lung function, and reduced responses to corticosteroids. Our objective was to compare asthma outcomes in terms of disease control, exacerbation rates, and lung function in a population of asthmatic patients according to their smoking status. Methods: We compared patients’ demographics, disease characteristics, and lung-function parameters in current-smokers (CS, n = 48), former-smokers (FS, n = 38), and never-smokers (NS, n = 90), and identified predictive factors for asthma control. Results: CS had a higher prevalence of family asthma/atopy, a lower rate of controlled asthma, impaired perception of dyspnea, an increased number of exacerbations, and poorer lung function compared to NS. The mean asthma control questionnaire’s (ACQ) score was higher in CS vs. NS and FS (1.9 vs. 1.2, p = 0.02). Compared to CS, FS had a lower rate of exacerbations, a better ACQ score (similar to NS), a higher prevalence of dyspnea, and greater lung-diffusion capacity. Non-smoking status, the absence of dyspnea and exacerbations, and a forced expiratory volume in one second ≥80% of predicted were associated with controlled asthma. Conclusions: CS with asthma exhibit worse clinical and functional respiratory outcomes compared to NS and FS, supporting the importance of smoking cessation in this population.

Diffusing capacity in chronic obstructive pulmonary disease assessment: A meta-analysis

To achieve a multidimensional evaluation of chronic obstructive pulmonary disease (COPD) patients, the spirometry measures are supplemented by assessment of symptoms, risk of exacerbations, and CT imaging. However, the measurement of diffusing capacity of the lung for carbon monoxide (DLCO) is not included in most common used models of COPD assessment. Here, we conducted a meta-analysis to evaluate the role of DLCO in COPD assessment.The studies were identified by searching the terms "diffusing capacity" OR "diffusing capacity for carbon monoxide" or "DLCO" AND "COPD" AND "assessment" in Pubmed, Cochrane Central Register of Controlled Trials (CENTRAL), MEDLINE, Embase, Scopus, and Web of Science databases. The mean difference of DLCO % predict was assessed in COPD patient with different severity (according to GOLD stage and GOLD group), between COPD patients with or without with frequent exacerbation, between survivors and non-survivors, between emphysema dominant and non-emphysema dominant COPD patients, and between COPD patients with or without pulmonary hypertension.43 studies were included in the meta-analysis. DLCO % predicted was significantly lower in COPD patients with more severe airflow limitation (stage II/IV), more symptoms (group B/D), and high exacerbation risk (group C/D). Lower DLCO % predicted was also found in exacerbation patients and non-survivors. Low DLCO % predicted was related to emphysema dominant phenotype, and COPD patients with PH.The current meta-analysis suggested that DLCO % predicted might be an important measurement for COPD patients in terms of severity, exacerbation risk, mortality, emphysema domination, and presence of pulmonary hypertension. As diffusion capacity reflects pulmonary ventilation and perfusion at the same time, the predictive value of DLCO or DLCO combined with other criteria worth further exploration.

Disproportionally Impaired Diffusion Capacity Relative to Airflow Limitation in COPD

Forced expiratory volume in 1 s (FEV₁) is a standard physiological index of chronic obstructive pulmonary disease (COPD), but reflects emphysema and vascular abnormalities less sensitively than diffusion capacity for carbon monoxide (D_LCO). This study tested whether a disproportionally impaired D_LCO relative to FEV₁ (FEV₁ z-score>-3 and D_LCO z-score≤-3) is a common functional COPD phenotype associated with distinct clinical and structural features and the prognosis of two cohorts. The cross-sectional analyses of the Korea COPD Subgroup Study (KOCOSS) cohort (multicenter study in Korea) included 743 males with COPD whose D_LCO was available. The cross-sectional and longitudinal analyses of the Kyoto University Cohort (single-center study in Japan) included 195 males with COPD who were prospectively followed for 10 years. A disproportionally impaired D_LCO relative to FEV₁ was observed in 29% and 31% of patients in the KOCOSS and Kyoto University cohorts, respectively. In the multivariable analysis, the disproportionally impaired D_LCO was associated with worse symptoms, shorter 6-minute walking distance, paraseptal and centrilobular emphysema on computed tomography, and reduced arterial oxygen and carbon dioxide pressures compared to the reference (FEV₁ z-score>-3 and D_LCO z-score>-3). In the multivariable Cox proportional hazard model, a higher long-term mortality was observed in the disproportionally impaired D_LCO group than in the reference group (hazard ratio [95% confidence interval] = 3.09 [1.52-6.29]) and similar to the D_LCO z-score≤-3 and FEV₁ z-score≤-3 group. The disproportionally impaired D_LCO relative to FEV₁ is common and associated with increased symptoms, emphysema, arterial blood gas abnormalities, and increased long-term mortality in patients with COPD.

Assessment of Global Lung Function Initiative (GLI) reference equations for diffusing capacity in relation to respiratory burden in the Swedish CArdioPulmonary bioImage Study (SCAPIS)

The Global Lung Function Initiative (GLI) has recently published international reference values for diffusing capacity of the lung for carbon monoxide (D _LCO). Lower limit of normal (LLN), i.e. the 5th percentile, usually defines impaired D _LCO We examined if the GLI LLN for D _LCO differs from the LLN in a Swedish population of healthy, never-smoking individuals and how any such differences affect identification of subjects with respiratory burden.Spirometry, D _LCO, chest high-resolution computed tomography (HRCT) and questionnaires were obtained from the first 15 040 participants, aged 50-64 years, of the Swedish CArdioPulmonary bioImage Study (SCAPIS). Both GLI reference values and the lambda-mu-sigma (LMS) method were used to define the LLN in asymptomatic never-smokers without respiratory disease (n=4903, of which 2329 were women).Both the median and LLN for D _LCO from SCAPIS were above the median and LLN from the GLI (p<0.05). The prevalence of D _LCO <GLI LLN (and also <SCAPIS LLN) was 3.9%, while the prevalence of D _LCO >GLI LLN but <SCAPIS LLN was 5.7%. Subjects with D _LCO >GLI LLN but <SCAPIS LLN (n=860) had more emphysema (14.3% versus 4.5%, p<0.001), chronic airflow limitation (8.5% versus 3.9%, p<0.001) and chronic bronchitis (8.3% versus 4.4%, p<0.01) than subjects (n=13 600) with normal D _LCO (>GLI LLN and >SCAPIS LLN). No differences were found with regard to physician-diagnosed asthma.The GLI LLN for D _LCO is lower than the estimated LLN in healthy, never-smoking, middle-aged Swedish adults. Individuals with D _LCO above the GLI LLN but below the SCAPIS LLN had, to a larger extent, an increased respiratory burden. This suggests clinical implications for choosing an adequate LLN for studied populations.