Classifying Future Healthcare Utilization in COPD Using Quantitative CT Lung Imaging and Two-Step Feature Selection via Sparse Subspace Learning with the CanCOLD Study.

RATIONALE: Although numerous candidate features exist for predicting risk of higher risk of healthcare utilization in patients with chronic obstructive pulmonary disease (COPD), the process for selecting the most discriminative features remains unclear. OBJECTIVE: The objective of this study was to develop a robust feature selection method to identify the most discriminative candidate features for predicting healthcare utilization in COPD, and compare the model performance with other common feature selection methods. MATERIALS AND METHODS: In this retrospective study, demographic, lung function measurements and CT images were collected from 454 COPD participants from the Canadian Cohort Obstructive Lung Disease study from 2010-2017. A follow-up visit was completed approximately 1.5 years later and participants reported healthcare utilization. CT analysis was performed for feature extraction. A two-step hybrid feature selection method was proposed that utilized: (1) sparse subspace learning with nonnegative matrix factorization, and, (2) genetic algorithm. Seven commonly used feature selection methods were also implemented that reported the top 10 or 20 features for comparison. Performance was evaluated using accuracy. RESULTS: Of the 454 COPD participants evaluated, 161 (35%) utilized healthcare services at follow-up. The accuracy for predicting subsequent healthcare utilization for the seven commonly used feature selection methods ranged from 72%-76% with the top 10 features, and 77%-80% with the top 20 features. Relative to these methods, hybrid feature selection obtained significantly higher accuracy for predicting subsequent healthcare utilization at 82% ± 3% (p < 0.05). Selected features with the proposed method included: DLCO, FEV1, RV, FVC, TAC, LAA950, Pi-10, LAA856, LAC total hole count, outer area RB1, wall area RB1, wall area and Jacobian. CONCLUSION: The hybrid feature selection method identified the most discriminative features for classifying individuals with and without future healthcare utilization, and increased the accuracy compared to other state-of-the-art approaches.

Haemodynamic compensations for exercise tissue oxygenation in early stages of COPD: an integrated cardiorespiratory assessment study.

BACKGROUND: Cardiovascular comorbidities are increasingly being recognised in early stages of chronic obstructive pulmonary disease (COPD) yet complete cardiorespiratory functional assessments of individuals with mild COPD or presenting with COPD risk factors are lacking. This paper reports on the effectiveness of the cardiocirculatory-limb muscles oxygen delivery and utilisation axis in smokers exhibiting no, or mild to moderate degrees of airflow obstruction using standardised cardiopulmonary exercise testing (CPET). METHODS: Post-bronchodilator spirometry was used to classify participants as 'ever smokers without' (n=88), with 'mild' (n=63) or 'mild-moderate' COPD (n=56). All underwent CPET with continuous concurrent monitoring of oxygen uptake (V'O2) and of bioimpedance cardiac output (Qc) enabling computation of arteriovenous differences (a-vO2). Mean values of Qc and a-vO2 were mapped across set ranges of V'O2 and Qc isolines to allow for meaningful group comparisons, at same metabolic and circulatory requirements. RESULTS: Peak exercise capacity was significantly reduced in the 'mild-moderate COPD' as compared with the two other groups who showed similar pulmonary function and exercise capacity. Self-reported cardiovascular and skeletal muscle comorbidities were not different between groups, yet disease impact and exercise intolerance scores were three times higher in the 'mild-moderate COPD' compared with the other groups. Mapping of exercise Qc and a-vO2 also showed a leftward shift of values in this group, indicative of a deficit in peripheral O2 extraction even for submaximal exercise demands. Concurrent with lung hyperinflation, a distinctive blunting of exercise stroke volume expansion was also observed in this group. CONCLUSION: Contrary to the traditional view that cardiovascular complications were the hallmark of advanced disease, this study of early COPD spectrum showed a reduced exercise O2 delivery and utilisation in individuals meeting spirometry criteria for stage II COPD. These findings reinforce the preventive clinical management approach to preserve peripheral muscle circulatory and oxidative capacities.

Abnormal Exertional Breathlessness on Cardiopulmonary Cycle Exercise Testing in Relation to Self-Reported and Physiological Responses in Chronic Airflow Limitation.

BACKGROUND: Exertional breathlessness is a cardinal symptom of cardiorespiratory disease. RESEARCH QUESTION: How does breathlessness abnormality, graded using normative reference equations during cardiopulmonary exercise testing (CPET), relate to self-reported and physiological responses in people with chronic airflow limitation (CAL)? STUDY DESIGN AND METHODS: An analysis was done of people aged ≥ 40 years with CAL undergoing CPET in the Canadian Cohort Obstructive Lung Disease study. Breathlessness intensity ratings (Borg CR10 scale [0-10 category-ratio scale for breathlessness intensity rating]) were evaluated in relation to power output (W), rate of oxygen uptake (V˙o2), and minute ventilation (V˙e) at peak exercise, using normative reference equations as follows: (1) probability of breathlessness normality (probability of having an equal or greater Borg CR10 rating among healthy; lower probability reflecting more severe breathlessness) and (2) presence of abnormal breathlessness (rating above the upper limit of normal). Associations with relevant participant-reported and physiologic outcomes were evaluated. RESULTS: We included 330 participants (44% women): mean ± SD age, 64 ± 10 years (range, 40-89 years); FEV1/FVC, 57.3% ± 8.2%; FEV1, 75.6% ± 17.9% predicted. Abnormally low exercise capacity (peak V˙o2 < lower limit of normal) was present in 26%. Relative to peak W, V˙o2, and V˙e, abnormally high breathlessness was present in 26%, 25%, and 18% of participants. For all equations, abnormally high exertional breathlessness was associated with worse lung function, exercise capacity, self-reported symptom burden, physical activity, and health-related quality of life; and greater physiological abnormalities during CPET. INTERPRETATION: Abnormal breathlessness graded using CPET normative reference equations was associated with worse clinical, physiological, and functional outcomes in people with CAL, supporting construct validity of abnormal exertional breathlessness.

Airway tree caliber heterogeneity and airflow obstruction among older adults.

INTRODUCTION: Smaller mean airway tree caliber is associated with airflow obstruction and chronic obstructive pulmonary disease (COPD). We investigated whether airway tree caliber heterogeneity was associated with airflow obstruction and COPD. METHODS: Two community-based cohorts (MESA Lung, CanCOLD) and a longitudinal case-control study of COPD (SPIROMICS) performed spirometry and computed tomography measurements of airway lumen diameters at standard anatomic locations and total lung volume. Percent-predicted airway lumen diameters were calculated using sex-specific reference equations accounting for age, height and lung volume. The association of airway tree caliber heterogeneity, quantified as the standard deviation (SD) of percent-predicted airway lumen diameters, with baseline forced expired volume in 1-second (FEV1), FEV1/forced vital capacity (FEV1/FVC) and COPD, as well as longitudinal spirometry, were assessed using regression models adjusted for age, sex, height, race-ethnicity, and mean airway tree caliber. RESULTS: Among 2,505 MESA Lung participants (mean±SD age: 69±9 years; 53% female, mean airway tree caliber: 99±10% predicted, airway tree caliber heterogeneity: 14±5%; median follow-up: 6.1 years), participants in the highest quartile of airway tree caliber heterogeneity exhibited lower FEV1 (adjusted mean difference: -125 ml, 95%CI:-171,-79), lower FEV1/FVC (adjusted mean difference: -0.01, 95%CI:-0.02,-0.01), and higher odds of COPD (adjusted OR 1.42, 95%CI:1.01-2.02) when compared with the lowest quartile, whereas longitudinal changes in FEV1 and FEV1/FVC did not differ significantly. Observations in CanCOLD and SPIROMICS were consistent. CONCLUSION: Among older adults, airway tree caliber heterogeneity was associated with airflow obstruction and COPD at baseline but was not associated with longitudinal changes in spirometry.

Physiological Characterization of Preserved Ratio Impaired Spirometry in the CanCOLD Study: Implications for Exertional Dyspnea and Exercise Intolerance.

RATIONALE: It is increasingly recognized that adults with preserved ratio impaired spirometry (PRISm) are prone to increased morbidity. However, the underlying pathophysiological mechanisms are unknown. OBJECTIVES: Evaluate the mechanisms of increased dyspnea and reduced exercise capacity in PRISm. METHODS: We completed a cross-sectional analysis of the CanCOLD population-based study. We compared physiological responses in 59 participants meeting PRISm spirometric criteria (post-bronchodilator FEV1<80% predicted and FEV1/FVC≥0.7), 264 controls, and 170 ever-smokers with chronic obstructive pulmonary disease (COPD), at rest and during cardiopulmonary exercise testing (CPET). MEASUREMENTS AND MAIN RESULTS: PRISm had lower total lung, vital and inspiratory capacities than controls (all p<0.05), and minimal small airway, pulmonary gas-exchange, and radiographic parenchymal lung abnormalities. Compared with control, PRISm had higher dyspnea/oxygen uptake [V̇O2] ratio at peak exercise (4.0±2.2vs2.9±1.9, Borg units/L/min, p<0.001) and lower V̇O2peak (74±22vs96±25% predicted, p<0.001). At standardized submaximal work rates, PRISm had greater tidal volume/inspiratory capacity (VT%IC, p<0.001), reflecting inspiratory mechanical constraint. In contrast to PRISm, COPD had characteristic small airways dysfunction, dynamic hyperinflation, and pulmonary gas-exchange abnormalities. Despite these physiological differences between the 3 groups, the relationship between increasing dyspnea and VT%IC during CPET was similar. Resting IC significantly correlated with V̇O2peak (r=0.65, p<0.001) in the entire sample, even after adjusting for airflow limitation, gas-trapping and diffusing capacity. CONCLUSION: In PRISm, lower exercise capacity and higher exertional dyspnea than healthy controls were mainly explained by lower resting lung volumes and earlier onset of dynamic inspiratory mechanical constraints at relatively low work rates.

A fully automated pipeline for the extraction of pectoralis muscle area from chest computed tomography scans.

Background: Computed tomography (CT)-derived pectoralis muscle area (PMA) measurements are prognostic in people with or at-risk of COPD, but fully automated PMA extraction has yet to be developed. Our objective was to develop and validate a PMA extraction pipeline that can automatically: 1) identify the aortic arch slice; and 2) perform pectoralis segmentation at that slice. Methods: CT images from the Canadian Cohort of Obstructive Lung Disease (CanCOLD) study were used for pipeline development. Aorta atlases were used to automatically identify the slice containing the aortic arch by group-based registration. A deep learning model was trained to segment the PMA. The pipeline was evaluated in comparison to manual segmentation. An external dataset was used to evaluate generalisability. Model performance was assessed using the Dice-Sorensen coefficient (DSC) and PMA error. Results: In total 90 participants were used for training (age 67.0±9.9 years; forced expiratory volume in 1 s (FEV1) 93±21% predicted; FEV1/forced vital capacity (FVC) 0.69±0.10; 47 men), and 32 for external testing (age 68.6±7.4 years; FEV1 65±17% predicted; FEV1/FVC 0.50±0.09; 16 men). Compared with manual segmentation, the deep learning model achieved a DSC of 0.94±0.02, 0.94±0.01 and 0.90±0.04 on the true aortic arch slice in the train, validation and external test sets, respectively. Automated aortic arch slice detection obtained distance errors of 1.2±1.3 mm and 1.6±1.5 mm on the train and test data, respectively. Fully automated PMA measurements were not different from manual segmentation (p>0.05). PMA measurements were different between people with and without COPD (p=0.01) and correlated with FEV1 % predicted (p<0.05). Conclusion: A fully automated CT PMA extraction pipeline was developed and validated for use in research and clinical practice.

Biological Anti-IL-5/IL-5R Therapeutics for Chronic Obstructive Pulmonary Disease (COPD) with Specific Treatable Traits: A Real-World Retrospective Analysis.

Introduction: We describe the use of anti-IL-5 monoclonal antibodies from a COPD clinic, a source other than traditional clinical trials. The objectives were to characterize the patient subgroup prescribed anti-IL-5 monoclonal antibodies and to report potential benefits. Methods: This is a retrospective case series study of 17 patients treated in a COPD subspecialty clinic. All patients had a diagnosis of COPD (post-bronchodilator FEV1/FVC <0.7) and had been prescribed an anti-IL-5 biologic for at least 8 months. Acute exacerbations of COPD (AECOPDs) were collected as reported in electronic medical records. Results: All patients (17) enrolled were treated with biologics for ≥8 months, and 13 (76%) for ≥1 year. Patients were characterized by severe disease traits, FEV1 <50% predicted, recurrent exacerbations (3.5 moderate-to-severe AECOPDs in the year before treatment), high peripheral blood eosinophil counts (≥250 cells/µL in the previous year), all on inhaled triple therapy, and only 1 patient with a diagnosis of asthma prior to smoking. There was a statistically significant decrease in the exacerbation rate compared with baseline after 8 and 12 months of anti-IL-5 treatment, respectively, yielding the equivalent of a 2-3x reduction in exacerbation rate. Absolute FEV1 decreased, and the decline in FEV1 % of predicted reached statistical significance (p<0.05); CAT score improved (p<0.05). Discussion: This real-world evidence data aligns with existing studies suggesting the potential benefit of anti-IL-5 treatment for specific patients with COPD and therefore advocates for further investigation of RCTs on the use of anti-IL-5 biologics for well-characterized patients with COPD.

Dysanapsis is not associated with exertional dyspnoea in healthy male and female never-smokers aged 40 years and older.

In healthy adults, airway-to-lung (i.e., dysanapsis) ratio is lower and dyspnoea during exercise at a given minute ventilation (V̇E) is higher in females than in males. We investigated the relationship between dysanapsis and sex on exertional dyspnoea in healthy adults. We hypothesized that females would have a smaller airway-to-lung ratio than males and that exertional dyspnoea would be associated with airway-to-lung ratio in males and females. We analyzed data from n = 100 healthy never-smokers aged ≥40 years enrolled in the Canadian Cohort Obstructive Lung Disease (CanCOLD) study who underwent pulmonary function testing, a chest computed tomography scan, and cardiopulmonary exercise testing. The luminal area of the trachea, right main bronchus, left main bronchus, right upper lobe, bronchus intermedius, left upper lobe, and left lower lobe were 22%-37% smaller (all p < 0.001) and the airway-to-lung ratio (i.e., average large conducting airway diameter relative to total lung capacity) was lower in females than in males (0.609 ± 0.070 vs. 0.674 ± 0.082; p < 0.001). During exercise, there was a significant effect of V̇E, sex, and their interaction on dyspnoea (all p < 0.05), indicating that dyspnoea increased as a function of V̇E to a greater extent in females than in males. However, after adjusting for age and total lung capacity, there were no significant associations between airway-to-lung ratio and measures of exertional dyspnoea, regardless of sex (all r < 0.34; all p > 0.05). Our findings suggest that sex differences in airway size do not contribute to sex differences in exertional dyspnoea.

Respiratory health and its determinants among Nunavimmiut: results from the Qanuilirpitaa? 2017 Nunavik Health Survey.

OBJECTIVES: Respiratory diseases are the leading cause of hospitalization in Nunavik (northern Québec, Canada) and contribute to disparities in life expectancy with the rest of Canada. As part of Qanuilirpitaa? 2017, a cross-sectional population-based health survey, we sought to describe the prevalence of respiratory health indicators, including the first estimate of airway obstruction based on spirometry in an Inuit population, and explore their associated characteristics. METHODS: We analyzed data from 1296 participants aged 16 years and older, using multivariate logistic regression to assess characteristics associated with spirometry-determined airway obstruction and self-reported respiratory symptoms, i.e., wheezing in the last year and chronic cough during at least 3 months. RESULTS: In this relatively young population (83% aged 16 to 54), the prevalences of wheezing, chronic cough, and airway obstruction were, respectively, 27% (95% CI 24-30), 21% (18-23), and 17% (14-20). These estimates are prone to biases due to the relatively low participation rate (about 37%). The most consistent associations were with smoking (≥ 15 pack-years; odds ratio [OR] 3.13, 3.39, and 2.86 for the three indicators, respectively) and food security (OR 0.55 with wheezing and OR 0.26 with chronic cough), as defined in the Household Food Security Survey Module. Wheezing was also associated with allergic sensitization to dogs (2.60) and obesity (2.18). Chronic cough was associated with respiratory infections during childhood (2.12), housing in need of major repairs (1.72), and housing crowding (1.50), and was negatively associated with participation to traditional activities (0.62) and going on the land (0.64). Airway obstruction was associated with being underweight (3.84) and post-secondary education (0.40). Among young adults and women, wheezing was also associated with any inhalation of solvents for recreational purposes during their lifetime (2.62 and 1.56, respectively), while airway obstruction was associated with regular marijuana use (2.22 and 1.84, respectively). CONCLUSION: Smoking and food insecurity are both highly prevalent and strongly associated with respiratory symptoms in Nunavik. Together with essential smoking prevention and cessation programs, our findings suggest that solving food security and housing crises, improving socioeconomic conditions, and promoting traditional lifestyle may improve respiratory health in Nunavik.

RéSUMé: OBJECTIFS: Les maladies respiratoires sont la première cause d'hospitalisation au Nunavik (Nord-du-Québec, Canada) et contribuent aux écarts d'espérance de vie avec le reste du Canada. Dans le cadre de l'enquête transversale et populationnelle Qanuilirpitaa? 2017, cette étude décrit la prévalence d'indicateurs de santé respiratoire et explore les caractéristiques qui leur sont associées. Elle fournit le premier estimé de la prévalence d'obstruction respiratoire par spirométrie dans la population inuite. MéTHODES: Les données de 1 296 participants âgés de 16 ans et plus ont été analysées par régression logistique multivariée pour évaluer les caractéristiques associées avec le wheezing (dans la dernière année), la toux chronique (durant au moins 3 mois) et l'obstruction bronchique (mesurée par spirométrie). RéSULTATS: Dans cette population relativement jeune (83 % entre 16 et 54 ans), les prévalences de wheezing, de toux chronique et d'obstruction bronchique étaient de 27 % (IC95% 24-30), 21 % (18-23) et 17 % (14-20). Ces estimés pourraient être biaisés puisque le taux de participation à l'enquête était relativement faible (environ 37 %). Les associations les plus fortes et consistantes sont observées avec le tabagisme (≥ 15 paquets-années; RC 3,13, 3,39 et 2,86 pour les trois indicateurs, respectivement) et avec la sécurité alimentaire (RC 0,55 avec le wheezing et 0,26 avec la toux chronique), définie à partir du Module d'enquête sur la sécurité alimentaire des ménages. Le wheezing était notamment associé avec la sensibilisation allergique aux chiens (2,60) et l'obésité (2,18). La toux chronique était associée avec les infections respiratoires sévères dans l'enfance (2,12), un logement ayant besoin de réparations majeures (1,72) et un logement surpeuplé (1,50); tandis que participer aux activités traditionnelles (0,62) et aller souvent dans la nature (0,64) semblaient protecteurs. L'obstruction bronchique était associée avec un faible indice de masse corporelle (3,84) et un niveau de scolarité postsecondaire (0,40). Le wheezing était aussi associé avec le fait d'avoir déjà inhalé des solvants chez les jeunes adultes (2,62) et chez les femmes (1,56), tandis que l'obstruction bronchique était associée avec la consommation régulière de cannabis chez les jeunes adultes (2,22) et chez les femmes (1,84). CONCLUSION: Le tabagisme et l'insécurité alimentaire sont fort prévalents et fortement associés avec des symptômes respiratoires au Nunavik. En plus de rappeler l'importance de la prévention du tabagisme, ces résultats supportent la pertinence des efforts communautaires et gouvernementaux pour résoudre les crises de l'insécurité alimentaire et du logement, améliorer les conditions socioéconomiques et promouvoir la culture inuite afin d'améliorer la santé respiratoire au Nunavik.

Normative Reference Equations for Breathlessness Intensity during Incremental Cardiopulmonary Cycle Exercise Testing.

Rationale: Cardiopulmonary exercise testing (CPET) is the gold standard to evaluate exertional breathlessness, a common and disabling symptom. However, the interpretation of breathlessness responses to CPET is limited by a scarcity of normative data. Objectives: We aimed to develop normative reference equations for breathlessness intensity (Borg 0-10 category ratio) response in men and women aged ⩾40 years during CPET, in relation to power output (watts), oxygen uptake, and minute ventilation. Methods: Analysis of ostensibly healthy people aged ⩾40 years undergoing symptom-limited incremental cycle CPET (10 W/min) in the CanCOLD (Canadian Cohort Obstructive Lung Disease) study. Participants had smoking histories <5 pack-years and normal lung function and exercise capacity. The probability of each Borg 0-10 category ratio breathlessness intensity rating by power output, oxygen uptake, and minute ventilation (as an absolute or a relative value [percentage of predicted maximum]) was predicted using ordinal multinomial logistic regression. Model performance was evaluated by fit, calibration, and discrimination (C statistic) and externally validated in an independent sample (n = 86) of healthy Canadian adults. Results: We included 156 participants (43% women) from CanCOLD; the mean age was 65 (range, 42-91) years, and the mean body mass index was 26.3 (standard deviation, 3.8) kg/m2. Reference equations were developed for women and men separately, accounting for age and/or body mass. Model performance was high across all equations, including in the validation sample (C statistic for men = 0.81-0.92, C statistic for women = 0.81-0.96). Conclusions: Normative reference equations are provided to compare exertional breathlessness intensity ratings among individuals or groups and to identify and quantify abnormal breathlessness responses (scores greater than the upper limit of normal) during CPET.

Distinctive features of the oropharyngeal microbiome in Inuit of Nunavik and correlations of mild to moderate bronchial obstruction with dysbiosis.

Inuit of Nunavik are coping with living conditions that can influence respiratory health. Our objective was to investigate associations between respiratory health in Inuit communities and their airway microbiome. Oropharyngeal samples were collected during the Qanuilirpitaa? 2017 Inuit Health Survey and subjected to metagenomic analyses. Participants were assigned to a bronchial obstruction group or a control group based on their clinical history and their pulmonary function, as monitored by spirometry. The Inuit microbiota composition was found to be distinct from other studied populations. Within the Inuit microbiota, differences in diversity measures tend to distinguish the two groups. Bacterial taxa found to be more abundant in the control group included candidate probiotic strains, while those enriched in the bronchial obstruction group included opportunistic pathogens. Crossing taxa affiliation method and machine learning consolidated our finding of distinct core microbiomes between the two groups. More microbial metabolic pathways were enriched in the control participants and these were often involved in vitamin and anti-inflammatory metabolism, while a link could be established between the enriched pathways in the disease group and inflammation. Overall, our results suggest a link between microbial abundance, interactions and metabolic activities and respiratory health in the Inuit population.

2023 Canadian Thoracic Society Guideline on Pharmacotherapy in Patients With Stable COPD.

Chronic obstructive pulmonary disease patient care must include confirming a diagnosis with postbronchodilator spirometry. Because of the clinical heterogeneity and the reality that airflow obstruction assessed by spirometry only partially reflects disease severity, a thorough clinical evaluation of the patient should include assessment of symptom burden and risk of exacerbations that permits the implementation of evidence-informed pharmacologic and nonpharmacologic interventions. This guideline provides recommendations from a comprehensive systematic review with a meta-analysis and expert-informed clinical remarks to optimize maintenance pharmacologic therapy for individuals with stable COPD, and a revised and practical treatment pathway based on new evidence since the 2019 update of the Canadian Thoracic Society (CTS) Guideline. The key clinical questions were developed using the Patients/Population (P), Intervention(s) (I), Comparison/Comparator (C), and Outcome (O) model for three questions that focuses on the outcomes of symptoms (dyspnea)/health status, acute exacerbations, and mortality. The evidence from this systematic review and meta-analysis leads to the recommendation that all symptomatic patients with spirometry-confirmed COPD should receive long-acting bronchodilator maintenance therapy. Those with moderate to severe dyspnea (modified Medical Research Council ≥ 2) and/or impaired health status (COPD Assessment Test ≥ 10) and a low risk of exacerbations should receive combination therapy with a long-acting muscarinic antagonist/long-acting ẞ2-agonist (LAMA/LABA). For those with a moderate/severe dyspnea and/or impaired health status and a high risk of exacerbations should be prescribed triple combination therapy (LAMA/LABA/inhaled corticosteroids) azithromycin, roflumilast or N-acetylcysteine is recommended for specific populations; a recommendation against the use of theophylline, maintenance systemic oral corticosteroids such as prednisone and inhaled corticosteroid monotherapy is made for all COPD patients.

The modified Borg/6-min walk distance ratio: a method to assess exertional breathlessness and leg discomfort using the 6-min walk test.

Background: The 6-min walk test (6MWT) is widely used to assess exercise capacity across chronic health conditions, but is currently not useful to assess symptoms, as the scores do not account for the 6-min walk distance (6MWD). We aimed to 1) develop normative reference equations for breathlessness and leg discomfort intensity expressed as modified Borg (mBorg)/6MWD ratios; and 2) validate the equations in people with COPD. Methods: Analysis of people aged ≥40 years who performed two 6MWTs (on a 20-m course) in the Canadian Cohort Obstructive Lung Disease (CanCOLD) study: a healthy cohort (n=291; mean±sd age 67.5±9.4 years; 54% male) with normal 6MWD and lung function, and a COPD cohort (n=156; age 66.2±9.0 years; 56% male; forced expiratory volume in 1 s (FEV1)/forced vital capacity 56.6±8.2%; FEV1 74.4±18.6% pred). The mBorg score was calculated as the Borg 0-10 category ratio intensity rating of breathlessness or leg discomfort recorded at the end of the 6MWT +1 (range 1-11), to avoid zeros and yield ratios proportional to the symptom score and 6MWD-1. Results: Using data from the healthy cohort, sex-specific normative reference equations for breathlessness and leg discomfort mBorg/6MWD ratios were developed using multivariable linear regression, accounting for age, and body mass or body mass index. In the COPD cohort, abnormal breathlessness and leg discomfort (mBorg/6MWD>upper limit of normal) showed strong concurrent validity with worse airflow limitation, Medical Research Council breathlessness and COPD Assessment Test scores. Conclusion: Normative references for the mBorg/6MWD ratio are presented to assess breathlessness and leg discomfort responses to the 6MWT in COPD.

Pulmonary Rehabilitation for Adults with Chronic Respiratory Disease: An Official American Thoracic Society Clinical Practice Guideline.

Background: Despite the known benefits of pulmonary rehabilitation (PR) for patients with chronic respiratory disease, this treatment is underused. Evidence-based guidelines should lead to greater knowledge of the proven benefits of PR, highlight the role of PR in evidence-based health care, and in turn foster referrals to and more effective delivery of PR for people with chronic respiratory disease. Methods: The multidisciplinary panel formulated six research questions addressing PR for specific patient groups (chronic obstructive pulmonary disease [COPD], interstitial lung disease, and pulmonary hypertension) and models for PR delivery (telerehabilitation, maintenance PR). Treatment effects were quantified using systematic reviews. The Grading of Recommendations, Assessment, Development and Evaluation approach was used to formulate clinical recommendations. Recommendations: The panel made the following judgments: strong recommendations for PR for adults with stable COPD (moderate-quality evidence) and after hospitalization for COPD exacerbation (moderate-quality evidence), strong recommendation for PR for adults with interstitial lung disease (moderate-quality evidence), conditional recommendation for PR for adults with pulmonary hypertension (low-quality evidence), strong recommendation for offering the choice of center-based PR or telerehabilitation for patients with chronic respiratory disease (moderate-quality evidence), and conditional recommendation for offering either supervised maintenance PR or usual care after initial PR for adults with COPD (low-quality evidence). Conclusions: These guidelines provide the basis for evidence-based delivery of PR for people with chronic respiratory disease.

Mortality in individuals with COPD on long-term home non-invasive ventilation.

BACKGROUND: Real-world evidence regarding survival of patients with chronic obstructive pulmonary disease (COPD) using chronic non-invasive ventilation (NIV) is scarce. RESEARCH QUESTION: How do obesity and other factors relate to mortality in patients with COPD on chronic NIV? STUDY DESIGN: and Methods: We retrospectively analyzed data from COPD patients enrolled in a home ventilation program between 2014 and 2018. Survival was compared between obese and non-obese groups using the Kaplan-Meier method. Factors associated with mortality were identified using multivariable Cox proportional regression analyses with Least Absolute Selection and Shrinkage Operator (LASSO) regularization. Univariable analyses were also done stratified by obesity. RESULTS: Median survival was 80.0 (95% CI: 71.0-NA) months among obese (n = 205) and 30.0 (95%CI: 19.0-42.0) months in non-obese (n = 61) patients. NIV adherence was high in both groups. Mortality was associated with male gender [HR 1.44], chronic opioids or benzodiazepines use [HR 1.07], home oxygen use [HR 1.82], fixed pressure mode of ventilation [HR 1.55], NIV inspiratory pressure [HR 1.05], and thoracic cancer [HR 1.27]; obesity [HR: 0.43], age [HR 0.99] and NIV expiratory pressure [HR 0.94] were associated with decreased mortality. In the obese, univariable analyses revealed that chest wall disease, thoracic cancer, home oxygen use, FEV1% predicted, and ventilation parameters were associated with mortality. In the non-obese, male gender and respiratory comorbidities were related to mortality. INTERPRETATION: Obesity is associated with improved survival in COPD patients highly adherent to NIV. Other factors associated with mortality reflect disease severity and ventilator parameters, with differences between obese and non-obese patients.

CT Imaging With Machine Learning for Predicting Progression to COPD in Individuals at Risk.

BACKGROUND: Identifying individuals at risk of progressing to COPD may allow for initiation of treatment to potentially slow the progression of the disease or the selection of subgroups for discovery of novel interventions. RESEARCH QUESTION: Does the addition of CT imaging features, texture-based radiomic features, and established quantitative CT scan to conventional risk factors improve the performance for predicting progression to COPD in individuals who smoke with machine learning? STUDY DESIGN AND METHODS: Participants at risk (individuals who currently or formerly smoked, without COPD) from the Canadian Cohort Obstructive Lung Disease (CanCOLD) population-based study underwent CT imaging at baseline and spirometry at baseline and follow-up. Various combinations of CT scan features, texture-based CT scan radiomics (n = 95), and established quantitative CT scan (n = 8), as well as demographic (n = 5) and spirometry (n = 3) measurements, with machine learning algorithms were evaluated to predict progression to COPD. Performance metrics included the area under the receiver operating characteristic curve (AUC) to evaluate the models. DeLong test was used to compare the performance of the models. RESULTS: Among the 294 at-risk participants who were evaluated (mean age, 65.6 ± 9.2 years; 42% female; mean pack-years, 17.9 ± 18.7), 52 participants (23.7%) in the training data set and 17 participants (23.0%) in the testing data set progressed to spirometric COPD at follow-up (2.5 ± 0.9 years from baseline). Compared with machine learning models with demographics alone (AUC, 0.649), the addition of CT imaging features to demographics (AUC, 0.730; P < .05) or CT imaging features and spirometry to demographics (AUC, 0.877; P < .05) significantly improved the performance for predicting progression to COPD. INTERPRETATION: Heterogeneous structural changes occur in the lungs of individuals at risk that can be quantified using CT imaging features, and evaluation of these features together with conventional risk factors improves performance for predicting progression to COPD.