Dyspnoea and symptom burden in mild-moderate COPD: the Canadian Cohort Obstructive Lung Disease Study

Maternal smoking around birth as a risk factor for offspring chronic obstructive pulmonary disease: Evidence from Mendelian randomization

INTRODUCTION

Previous observational studies suggested that exposure of the fetus to maternal smoking during pregnancy may increase the likelihood of chronic obstructive pulmonary disease (COPD). Hence, following the STROBE-MR guidelines, we carried out a two-sample MR analysis to explore the association between maternal smoking around birth and offspring COPD.

METHODS

We used independent single nucleotide polymorphisms (SNPs) related to maternal smoking around birth, obtained from genome-wide association study summary data, as instrumental variables (IVs). The dataset included 121634 controls and 276098 cases. The selected outcome was chronic obstructive pulmonary disease (COPD) in offspring, with 454945 controls and 13530 cases. We performed analyses using inverse variance weighting (IVW), weighted median, and MR-Egger regression methods. Multivariate MR included maternal illnesses (high blood pressure and heart disease) as covariates to address potential mediators. Sensitivity analysis was conducted using leave-one-out analysis, Cochran's Q test, and MR-Egger intercept test.

RESULTS

In the univariate MR analysis, it was found that maternal smoking around birth significantly increased the likelihood of offspring COPD (IVW, OR=35.13; 95% CI: 10.18-121.20; p<0.001). Furthermore, after adjusting the variates for maternal illnesses, the relationship between maternal smoking around birth and offspring COPD remained statistically significant (adjusted odds ratio, AOR= 62.11; 95% CI: 16.60-232.46; p<0.001).

CONCLUSIONS

The study provides MR evidence of a potential association between maternal smoking around birth and increased COPD risk in offspring.

Beyond Spirometry: Linking Wasted Ventilation to Exertional Dyspnea in the Initial Stages of COPD

Exertional dyspnea, a key complaint of patients with chronic obstructive pulmonary disease (COPD), ultimately reflects an increased inspiratory neural drive to breathe. In non-hypoxemic patients with largely preserved lung mechanics - as those in the initial stages of the disease - the heightened inspiratory neural drive is strongly associated with an exaggerated ventilatory response to metabolic demand. Several lines of evidence indicate that the so-called excess ventilation (high ventilation-CO2 output relationship) primarily reflects poor gas exchange efficiency, namely increased physiological dead space. Pulmonary function tests estimating the extension of the wasted ventilation and selected cardiopulmonary exercise testing variables can, therefore, shed unique light on the genesis of patients' out-of-proportion dyspnea. After a succinct overview of the basis of gas exchange efficiency in health and inefficiency in COPD, we discuss how wasted ventilation translates into exertional dyspnea in individual patients. We then outline what is currently known about the structural basis of wasted ventilation in "minor/trivial" COPD vis-à-vis the contribution of emphysema versus a potential impairment in lung perfusion across non-emphysematous lung. After summarizing some unanswered questions on the field, we propose that functional imaging be amalgamated with pulmonary function tests beyond spirometry to improve our understanding of this deeply neglected cause of exertional dyspnea. Advances in the field will depend on our ability to develop robust platforms for deeply phenotyping (structurally and functionally), the dyspneic patients showing unordinary high wasted ventilation despite relatively preserved FEV1.

A Multi-Specialty Delphi Consensus on Assessing and Managing Cardiopulmonary Risk in Patients with COPD

Background

In Canada, COPD represents a significant burden to the patient and health system, as it is often under or misdiagnosed and sub-optimally treated. Cardiovascular disease (CVD) is a common co-morbidity in COPD and there is significant interplay between these two chronic conditions. Across all stages of COPD disease severity, deaths can be attributed not only to respiratory causes but also to cardiovascular-related factors. The established links between COPD and CVD suggest the need for a greater degree of collaboration between respirologists and cardiologists. This modified Delphi consensus was initiated to consider how optimal COPD care can be delivered within Canada, with specific consideration of reducing cardiopulmonary risk and outcomes in COPD patients.

Methods

A steering group with interest in the management of COPD and CVD from primary care, cardiology, and respirology identified 40 statements formed from four key themes. A 4-point Likert scale questionnaire was sent to healthcare professionals working in COPD across Canada by an independent third party to assess agreement (consensus) with these statements. Consensus was defined as high if ≥75% and very high if ≥90% of respondents agreed with a statement.

Results

A total of 100 responses were received from respirologists (n=30), cardiologists (n=30), and primary care physicians (n=40). Consensus was very strong (≥90%) in 28 (70%) statements, strong (≥75 and <90%) in 7 (17.5%) statements and was not achieved (<75%) in 5 (12.5%) of statements.

Conclusion

Based on the consensus scores, 9 key recommendations were proposed by the steering group. These focus on the need to comprehensively risk stratify and manage COPD patients to help prevent exacerbations. Consensus within this study provides a call to action for the expeditious implementation of the latest COPD guidelines from the Canadian Thoracic Society.

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 (Canadian Cohort Obstructive Lung Disease) 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 control participants, and 170 ever-smokers with chronic obstructive pulmonary disease (COPD), at rest and during cardiopulmonary exercise testing. Measurements and Main Results: Individuals with PRISm had lower total lung, vital, and inspiratory capacities than healthy controls (all P < 0.05) and minimal small airway, pulmonary gas exchange, and radiographic parenchymal lung abnormalities. Compared with healthy controls, individuals with PRISm had higher dyspnea/[Formula: see text]o2 ratio at peak exercise (4.0 ± 2.2 vs. 2.9 ± 1.9 Borg units/L/min; P < 0.001) and lower [Formula: see text]o2peak (74 ± 22% predicted vs. 96 ± 25% predicted; P < 0.001). At standardized submaximal work rates, individuals with PRISm had greater Vt/inspiratory capacity (Vt%IC; P < 0.001), reflecting inspiratory mechanical constraint. In contrast to participants with PRISm, those with COPD had characteristic small airways dysfunction, dynamic hyperinflation, and pulmonary gas exchange abnormalities. Despite these physiological differences among the three groups, the relationship between increasing dyspnea and Vt%IC during cardiopulmonary exercise testing was similar. Resting IC significantly correlated with [Formula: see text]o2peak (r = 0.65; P < 0.001) in the entire sample, even after adjusting for airflow limitation, gas trapping, and diffusing capacity. Conclusions: In individuals with 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. Clinical trial registered with www.clinicaltrials.gov (NCT00920348).

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.

Mild airways obstruction: spirometric diagnostic pitfalls and solutions

PURPOSE OF REVIEW

Spirometry is a validated tool in the diagnosis of obstructive airways disease. However, it may be insufficiently sensitive in detecting airflow limitation in the small airways. This review highlights common clinical scenarios wherein airflow limitation may be missed or overlooked.

RECENT FINDINGS

This article covers recent literature on the interpretation of lung function test, focusing on detection of mild obstructive airways disease. It also sheds light on the contextual difficulties of defining mild airflow limitation on spirometry.

SUMMARY

We highlight the consensus definition of mild obstructive airways disease and emphasize that this definition does not necessarily mean mild in certain disease-specific contexts. Several spirometric findings outside of a reduced forced expiratory volume in one second/forced vital capacity ratio should raise suspicion of mild obstruction.

An investigation of the risk factors of chronic obstructive pulmonary disease in natural population-based cohorts in China - a nested case-control study

Background

Chronic obstructive pulmonary disease (COPD) has become one of the most significant chronic diseases in China. According to conventional wisdom, smoking is the pathogenic factor. However, current research indicates that the pathophysiology of COPD may be associated with prior respiratory system events (e.g., childhood hospitalization for pneumonia, chronic bronchitis) and environmental exposure (e.g., dust from workplace, indoor combustion particles). Dyspnea, persistent wheezing, and other respiratory symptoms further point to the need for pulmonary function tests in this population. Reducing the burden of chronic diseases in China requires a thorough understanding of the various factors that influence the occurrence of COPD.

Methods

Using a cohort from the natural population, this study used nested case-control analysis. We carried out a number of researches, including questionnaire surveys and pulmonary function testing, in the Northwest and Southeast cohorts of China between 2014 and 2021. After removing any variations in the baseline data between patients and control subjects using propensity score matching analysis, the risk factors were examined using univariate or multivariate regression.

Result

It was discovered that prior history of chronic bronchitis, long-term wheezing symptoms, and environmental exposure-including smoking and biofuel combustion-were risk factors for COPD. Dyspnea, symptoms of mobility limitation, organic matter, and a history of hospitalization for pneumonia at an early age were not significant in the clinical model but their incidence in COPD group is higher than that in healthy population.

Discussion

COPD screening effectiveness can be increased by looking for individuals with chronic respiratory symptoms. Smokers should give up as soon as they can, and families that have been exposed to biofuels for a long time should convert to clean energy or upgrade their ventilation. Individuals who have previously been diagnosed with emphysema and chronic bronchitis ought to be extra mindful of the prevention or advancement of COPD.

Physical Activity and Symptom Burden in COPD: The Canadian Obstructive Lung Disease Study

Background

The relationship between symptom burden and physical activity (PA) in chronic obstructive pulmonary disease (COPD) remains poorly understood with limited data on undiagnosed individuals and those with mild to moderate disease.

Objective

The primary objective was to evaluate the relationship between symptom burden and moderate-to-vigorous intensity PA (MVPA) in individuals from a random population-based sampling mirroring the population at large.

Methods

Baseline participants of the Canadian Cohort Obstructive Lung Disease (n=1558) were selected for this cross-sectional sub-study. Participants with mild COPD (n=406) and moderate COPD (n=331), healthy individuals (n=347), and those at risk of developing COPD (n=474) were included. The Community Healthy Activities Model Program for Seniors (CHAMPS) questionnaire was used to estimate MVPA in terms of energy expenditure. High symptom burden was classified using the COPD Assessment Test ([CAT] ≥10).

Results

Significant associations were demonstrated between high symptom burden and lower MVPA levels in the overall COPD sample (β=-717.09; 95% confidence interval [CI]=-1079.78, -354.40; p<0.001) and in the moderate COPD subgroup (β=-694.1; 95% CI=-1206.54, -181.66; p=0.006). A total of 72% of the participants with COPD were previously undiagnosed. The undiagnosed participants had significantly higher MVPA than those with physician diagnosed COPD (β=-592.41 95% CI=-953.11, -231.71; p=0.001).

Conclusion

MVPA was found to be inversely related to symptom burden in a large general population sample that included newly diagnosed individuals, most with mild to moderate COPD. Assessment of symptom burden may help identify patients with lower MVPA, especially for moderate COPD and for relatively inactive individuals with mild COPD.

Cardiovascular Risk in Patients with COPD: Cardiovascular Comorbidities in Patients with COPD Increase CAT and mMRC Dyspnea Scores

BACKGROUND: Chronic obstructive pulmonary disease (COPD) is associated with a number of different comorbidities. Cardiovascular diseases (CVD) are the most frequent comorbidities in COPD. The economic burden associated with cardiovascular comorbidity (CVC) in this population of patients is considerable. The COPD patients are related to the increased systemic inflammation, reduced capacity for physical activity, and airflow obstruction. AIM: The aim of our investigation was to evaluate the dyspnea as a disabling symptom in COPD patients with cardiovascular comorbidity (CVC) especially heart failure. The main aim of this study is to evaluate its intensity in patients with COPD in stages II according to GOLD. METHODS: The investigation was conducted from December 2019 to January 2020, on pulmonology and allergology clinic and cardiology clinic of medical faculty in Skopje. We investigated 65 outpatients with COPD, 44 with different type of CVD, Group I, and 21 without CVD, Group II. All patients were with partial chronic respiratory failure (In type 1 respiratory failure hypoxemic). Patients, according GOLD initiative, were in COPD stadium II, 70% < forced expiratory volume in 1 s (FEV1)>50%. Heart condition was diagnosed on the basis of clinical examination, electrocardiography, and echocardiography of the heart. Included patients with CVD were with ejection fraction (EF) <65%. Dyspnea was measured with modified MRC (mMRC) dyspnea scale. RESULTS: The forced vital capacity and forced expiratory volume in 1 s were statically significantly higher in Group II with CVD. Dyspnea measured with Modified Medical Research Council (MRC) dyspnea scale showed statistically significantly higher values in Group I COPD patients with CVC (2.9 ± 1.4) versus Group II without CVC (1.7 ± 1.4), (p < 0.05). The perception of the higher dyspnea in Group I was associated with increased COPD assessment test-scores, in Group I: Group I (19.8 ± 9.1) versus Group II: (9.8 ± 9.1), (p < 0.001). The number of exacerbations and what is more important the number of severe exacerbation leading to hospitalizations was statistically higher in patients of Group I with CVC than in Group II without CVC (3.0 ± 1.1 vs. 1.0 ± 2.1), (p < 0.001) and the number of hospitalizations (1.0 ± 1.1 vs. 0.3 ± 2.1) (p < 0.001). CONCLUSION: We can conclude that patients with COPD who have CVC have an increased risk of high symptoms, which mean poor quality of life and increased morbidity.

Mechanisms of Exertional Dyspnea in Patients with Mild COPD and a Low Resting DLCO

Patients with mild chronic obstructive pulmonary disease (COPD) and lower resting diffusing capacity for carbon monoxide (DL_CO) often report troublesome dyspnea during exercise although the mechanisms are not clear. We postulated that in such individuals, exertional dyspnea is linked to relatively high inspiratory neural drive (IND) due, in part, to the effects of reduced ventilatory efficiency. This cross-sectional study included 28 patients with GOLD I COPD stratified into two groups with (n = 15) and without (n = 13) DL_CO less than the lower limit of normal (<LLN; Global Lung Function Initiative criteria) and 16 healthy controls. We compared dyspnea (Borg scale), IND (by diaphragm electromyography), ventilatory equivalent for CO₂ (V̇_E/V̇CO₂), and respiratory mechanics during incremental cycle exercise in the three groups. Spirometry and resting lung volumes were similar between COPD groups. During exercise, dyspnea, IND and V̇_E/V̇CO₂ were higher at equivalent work rates (WR) in the DL_CO<LLN group compared with the other two groups (all p < 0.05). In patients with DL_CO<LLN, severe respiratory mechanical constraints, indicated by end-inspiratory lung volume of approximately 90% of total lung capacity, occurred at a lower WR than the other two groups (p < 0.05). The dyspnea/IND relationship was similar across groups; therefore, the increased dyspnea at a standardized WR in the low DL_CO<LLN group reflected the higher corresponding IND. Higher dyspnea ratings in patients with mild COPD and DL_CO<LLN were associated with higher IND and V̇_E/V̇CO₂ at a given work rate. Higher ventilatory requirements in the DL_CO<LLN group accelerated dynamic mechanical abnormalities earlier in exercise, further increasing IND and dyspnea.