Clinical Characteristics of COPD Patients According to COPD Assessment Test (CAT) Score Level: Cross-Sectional Study

Impact of Fluticasone Propionate and Salmeterol Combined with Pulmonary Rehabilitation on Pulmonary Function, Exercise Tolerance, and Quality of Life in Elderly Patients with Stable Chronic Obstructive Pulmonary Disease

Aims/Background Chronic obstructive pulmonary disease (COPD) is a common respiratory disease characterized by persistent respiratory problems. COPD has become a major public health concern worldwide as the population ages. Therefore, we investigated the impact of fluticasone propionate and salmeterol inhalation combined with pulmonary rehabilitation on pulmonary function, exercise tolerance, and quality of life in elderly patients with stable COPD. Methods This retrospective study included 102 elderly patients with stable COPD who were treated between January 2021 and October 2023. Based on previous treatment regimens, patients were divided into a fluticasone propionate and salmeterol inhalation combined with a pulmonary rehabilitation group (n = 58) and a pulmonary rehabilitation alone group (n = 44). We collected baseline data upon admission and other relevant data after 3 months of follow-up. Furthermore, we evaluated pulmonary function [forced expiratory volume in the first second (FEV1), forced vital capacity (FVC), peak expiratory flow (PEF)], inflammatory markers [interleukin-8 (IL-8), interleukin-6 (IL-6), tumour necrosis factor-α (TNF-α), tumour necrosis factor-β (TNF-β)], exercise tolerance [6-minute walk test (6MWT)], and quality of life [COPD Assessment Test (CAT), and St. George's Respiratory Questionnaire (SGRQ)] between the two experimental groups. Additionally, the recurrence rate and adverse events during the 3-month follow-up were examined. Results Compared to baseline, FEV1, FVC, PEF, and 6MWT levels were significantly improved in both groups at the 3-month follow-up, with the combined treatment group performing better than the pulmonary rehabilitation alone group (p < 0.05). CAT and SGRQ scores decreased significantly, with the combined treatment group scoring lower than the pulmonary rehabilitation alone group (p < 0.05). Inflammatory markers, such as IL-8, IL-6, TNF-α, and TNF-β were significantly reduced in the combined treatment group and were lower than in the pulmonary rehabilitation alone group (p < 0.05). The recurrence rate in the combined treatment group was significantly lower than in the pulmonary rehabilitation alone group (p = 0.018), with no significant difference in the incidence of adverse events between the two groups (p > 0.05). Conclusion Fluticasone propionate and salmeterol inhalation combined with pulmonary rehabilitation can reduce recurrence rates, and improve pulmonary function, inflammatory status, and exercise tolerance, thereby significantly enhancing the quality of life for elderly patients with stable COPD.

Addressing inhaler technique challenges in cognitively impaired chronic obstructive pulmonary disease patients: the impact of customized training programs

Individuals with chronic obstructive pulmonary disease (COPD) and cognitive impairment (CI) often face difficulties accurately administering inhalers, which are essential for managing their respiratory condition. Many elderly individuals make major errors that prevent proper medicine administration. Maintaining proper inhaler use skills is critical in controlling COPD. Our goal was to examine and evaluate the inhaler use skills of CI patients with COPD during both the initial evaluation and subsequent appointments. The Respiratory Department of KLEs Dr. Prabhakar Kore Hospital and Medical Research Centre, Nehru Nagar, Belagavi, Karnataka, India, was the site of this prospective interventional study. Based on the Montreal Cognitive Assessment Scale (MoCA), a subset of patients with COPD exhibited mild CI. Patients exhibiting improper inhaler-using skills were detected, corrected, and trained. Inhaler techniques were reassessed immediately and at follow-up visits. The modified Medical Research Council scale score (mMRC), COPD assessment test (CAT) score, St. George Respiratory Questionnaire (SGRQ), and pulmonary function tests were reassessed. A total of 56 COPD and CI patients who had made at least one significant mistake when using an inhaler device were added to the study. The mean age was 66.89±9.85 years. When evaluated with MoCA, the mean score was 17.02±3.91. At baseline, the mean number of mistakes was 1.38±0.93, which decreased to 0.54±0.57 after face-to-face demonstration of correct inhaler techniques. Correlational analysis revealed MoCA scores were negatively associated with the number of mistakes (r=-0.344). At follow-up, CAT score (25±5.61 vs. 18.48±5.24 p=0.001), SGRQ score (53.82±20.59 vs. 37.61±22.17 p=0.001), mMRC score (3.21±0.76 vs. 3.20±0.75 p=0.001), and forced expiratory volume in 1 second/forced vital capacity score (66.86±9.35 vs. 70.08±9.07 p=0.001) had significantly improved in patients demonstrating the correct technique. Pharmacist-led interventions demonstrated improvements in health-associated quality of life and therapeutic outcomes for individuals with COPD and CI. The study highlighted the importance of cognitive evaluation in routine COPD therapy, identifying potential impediments to effective therapy, and offering face-to-face presentations of inhaler techniques. The best inhalers and methods for COPD patients experiencing CI should be further investigated, according to the study.

Assessment of Metabolic Syndrome in Patients with Chronic Obstructive Pulmonary Disease: A 6-Month Follow-Up Study

BACKGROUND/OBJECTIVES

The association between chronic obstructive pulmonary disease (COPD) and metabolic syndrome (MetS) is a common one, with long-term therapeutic and prognostic impact. In view of the high pulmonary and cardiovascular morbidity and mortality, self-management contributes to decreasing the risk of an acute cardiac event or pulmonary decompensation.

METHODS

We conducted a prospective cohort study on 100 patients admitted to Iasi Clinical Rehabilitation Hospital who were divided into two groups according to the presence (67 patients) or absence (33 patients) of MetS. All patients benefited from multidisciplinary counseling sessions on their active role in improving modifiable cardiovascular risk factors and thus increasing quality of life. The aim of this study was to examine the impact of metabolic syndrome on lung function and the role of self-management in a 6-month follow-up period. The demographic, anthropometric, cardiovascular risk factors, and respiratory function were analyzed at baseline and at 6 months.

RESULTS

The presence of MetS was associated with higher fasting blood glucose (p = 0.004) and triglycerides (p = 0.003) but not with higher levels of interleukins or TNF-alpha. At the 6-month follow-up, abdominal circumference, forced expiratory volume in one second (FEV1), dyspnea severity, and blood pressure values improved in male patients with COPD. Systolic and diastolic blood pressure decreased in the COPD group as a whole, but especially in male patients with and without associated MetS. BMI was positively correlated with FEV1 (r = 0.389, p = 0.001) and the FEV1/forced vital capacity (FVC) ratio (r = 0.508, p < 0.001) in all COPD patients and in the MetS subgroup. In the COPD group as a whole. the six-minute walk test (6MWT) results (m) were positively correlated with FEV1 and FVC. The correlation remained significant for FVC in COPD patients with and without MetS. An increase in BMI by one unit led to an increase in TG values by 3.358 mg/dL, and the presence of metabolic syndrome led to an increase in TG values by 17.433 mg/dL.

CONCLUSIONS

In our study, MetS is a common comorbidity in patients with COPD and is associated with higher BMI, fasting glucose, and triglycerides but not with the inflammatory parameters. A mixed pulmonary-cardiovascular rehabilitation intervention leads to improvement in various parameters in both female and male COPD patients.

In vitro evidence of antioxidant and anti-inflammatory effects of a new nutraceutical formulation explains benefits in a clinical setting of COPD patients

Background and Aim: Increased oxidative stress within the airways is associated to epithelial damage and amplification of inflammatory responses that in turn contribute to Chronic Obstructive Pulmonary Disease (COPD) progression. This study was aimed to identify whether a new formulation of N-acetylcisteine (NAC), carnitine, curcumin and B2 vitamin could counteract oxidative stress and downstream pro-inflammatory events promoted by cigarette smoke extract (CSE) exposure in primary bronchial epithelial cells (PBEC), both submerged/undifferentiated (S-PBEC) and cultured at the air-liquid interface (ALI-PBEC). Methods: PBEC were exposed to CSE with/without the new formulation or NAC alone and ROS production, IL-8 and IL-6 gene expression and protein release were evaluated. Results: CSE increased ROS, IL-8 and IL-6 gene expression and protein release and the new formulation counteracted these effects. NAC alone was not effective on IL-8 and IL-6 release. The effects of a similar nutraceutical formulation were evaluated in COPD patients treated for six months. The results showed that the treatment reduced the concentration of IL-8 in nasal wash and improved quality of life. Conclusion: The tested formulation, exerting antioxidant and anti-inflammatory effects, can preserve airway epithelial homeostasis and improve clinical symptoms in COPD.

Consideration points in the decision making in chronic respiratory diseases

Objective: Even though dynamic multidisciplinary team discussions are crucial for end-of-life care management and decisions concerning chronic obstructive pulmonary disease (COPD), the details of the discussion contents remain poorly understood. This study aimed to identify essential considerations in decision-making for patients with chronic respiratory diseases to enhance a consensus-based approach. Materials and Methods: A qualitative content analysis of focus group conversations on published clinical case reports in the Japanese community about end-of-life care for patients with chronic respiratory disorders was conducted. The cases were searched through Igaku Chuo Zasshi (ICHUSHI) and Google in February 2021, using the keywords: "COPD", "chronic respiratory diseases", and "end-of-life care". A total of 41 healthcare professionals participated in the focus group discussions. Results: Four major themes evolved from the qualitative content analysis: unpredictable disease prognosis and stages, low awareness of patients on disease severity, acute exacerbations, and home oxygen therapy (HOT). The participants perceived that assessment of severity and prognosis in chronic respiratory diseases such as COPD was a core discussion point to enhance patients' decision-making. The study's findings also indicated that healthcare providers evaluate the influence of acute aggravation of the condition on patients' perceived health status and decision-making. Conclusion: The study reaffirms the significance of informed consent in patients with chronic respiratory disease. It details how, after a thorough assessment of disease severity, patients are given personalized explanations of standardized HOT. This approach ensures they fully understand the unpredictable nature and various stages of their condition resulting from acute exacerbations.

Clinical utilization of airway inflammatory biomarkers in the prediction and monitoring of clinical outcomes in patients with chronic obstructive pulmonary disease

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) accounts for 545 million people living with chronic respiratory disorders and is the third leading cause of morbidity and mortality around the world. COPD is a progressive disease, characterized by episodes of acute worsening of symptoms such as cough, dyspnea, and sputum production.

AREAS COVERED

Airway inflammation is a prominent feature of COPD. Chronic airway inflammation results in airway structural remodeling and emphysema. Persistent airway inflammation is a treatable trait of COPD and plays a significant role in disease development and progression. In this review, the authors summarize the current and emerging biomarkers that reveal the heterogeneity of airway inflammation subtypes, clinical outcomes, and therapeutic response in COPD.

EXPERT OPINION

Airway inflammation can be broadly categorized as eosinophilic (type 2 inflammation) and non-eosinophilic (non-type 2 inflammation) in COPD. Currently, blood eosinophil counts are incorporated in clinical practice guidelines to identify COPD patients who are at a higher risk of exacerbations and lung function decline, and who are likely to respond to inhaled corticosteroids. As new therapeutics are being developed for the chronic management of COPD, it is essential to identify biomarkers that will predict treatment response.

Components of the Chronic Obstructive Pulmonary Disease Assessment Test Associated with the Exacerbation of Severe Chronic Obstructive Pulmonary Disease Patients

INTRODUCTION

The chronic obstructive pulmonary disease (COPD) Assessment Test (CAT) score is widely used for evaluating the health status of patients diagnosed with COPD. The aim of this study was to identify which components of the CAT are associated with exacerbations in severe COPD patients.

METHODS

Using data from the Korean COPD Subgroup Study (KOCOSS), we identified 3,440 COPD patients, among which 1,027 patients are classified as having severe COPD based on spirometry results. The CAT scores on 8 items were evaluated and classified into respiratory and non-respiratory categories. We analyzed the association between CAT item scores and moderate-to-severe exacerbations during study enrollment and the following years.

RESULTS

Patients with a history of moderate-to-severe exacerbations had higher scores on non-respiratory CAT components. Longitudinal CAT scores on all items after enrollment were higher in the moderate-to-severe exacerbation group. Additionally, the frequency of severe exacerbations was associated with specific CAT components related to limited activities, confidence leaving home, sleeplessness, and energy.

CONCLUSIONS

This study revealed that the non-respiratory CAT component scores were statistically significant factors for predicting the moderate-to-severe exacerbation of severe COPD patients. Non-respiratory symptoms and functional limitations should be considered in patients with severe COPD. Interventions, such as pulmonary rehabilitation, may be needed to improve patients' overall well-being and prevent exacerbations.

Serum levels of HMW adiponectin and its receptors are associated with cytokine levels and clinical characteristics in chronic obstructive pulmonary disease

We aimed to investigate the changes in the levels of high-molecular-weight (HMW) adiponectin, adiponectin receptors, and cytokines in patients with chronic obstructive pulmonary disease (COPD), as well as their potential relationships. Forty-one patients who underwent lobectomy for lung lesions and had a clear postoperative pathological diagnosis were divided into the non-COPD (N = 23) and COPD (N = 18) groups. HMW adiponectin, cytokine, and T-cadherin levels in serum and tissues were detected by enzyme-linked immunosorbent assay. The levels of HMW adiponectin and cytokine (interleukin [IL]-6, IL-10, surfactant protein D, 4-hydroxynonenal, tumor necrosis factor-α, and C reactive protein) in the serum and tissues increased in the COPD group compared to those in the non-COPD group. Patients with COPD exhibited AdipoR1 upregulation and AdipoR2 downregulation. Although T-cadherin did not differ significantly between patients with and those without COPD, its expression was elevated during the progression from COPD with benign lung lesions to combined lung cancer. Furthermore, the HMW adiponectin levels were significantly correlated with the cytokine levels and the clinical characteristics of COPD. HMW adiponectin and its receptors affect the inflammatory process in COPD and may further contribute to the progression of the disease to malignancy.

Prediction value of neutrophil and eosinophil count at risk of COPD exacerbation

INTRODUCTION

Predicting acute exacerbations (AEs) in chronic obstructive pulmonary disease (COPD) is crucial. This study aimed to identify blood biomarkers for predicting COPD exacerbations by inflammatory phenotypes.

MATERIALS AND METHODS

We analyzed blood cell counts and clinical outcomes in 340 COPD patients aged 20-90 years. Patients were categorized into eosinophilic inflammation (EOCOPD) and non-eosinophilic inflammation (N-EOCOPD) groups. Blood cell counts, eosinophil-to-lymphocyte ratio (ELR), neutrophil-to-lymphocyte ratio (NLR) and neutrophil-to-eosinophil ratio (NER) were calculated. Linear and logistic regression models assessed relationships between health outcomes and blood cell counts.

RESULTS

EOCOPD patients had distinct characteristics compared to N-EOCOPD patients. Increased neutrophil % and decreased lymphocyte % were associated with reduced pulmonary function, worse quality of life and more exacerbations, but they did not show statistical significance after adjusting by age, sex, BMI, smoking status, FEV1% and patient's medication. Subgroup analysis revealed a 1.372-fold increase in the OR of AE for every 1 unit increase in NLR in EOCOPD patients (p < .05). In N-EOCOPD patients, every 1% increase in blood eosinophil decreased the risk of exacerbation by 59.6%.

CONCLUSIONS

Our study indicates that distinct white blood cell profiles in COPD patients, with or without eosinophilic inflammation, can help assess the risk of AE in clinical settings.

Effects of whey protein complex combined with low-intensity exercise in elderly inpatients with COPD at a stable stage

BACKGROUND AND OBJECTIVES

Previous literature mostly has demonstrated the efficacy of pulmonary rehabilitation (PR) combined with whole nutrition powder in patients with chronic obstructive pulmonary disease (COPD). However, the benefits of whey protein as an oral nutritional supplement (ONS) during PR are not clear.

METHODS AND STUDY DESIGN

It took 12 weeks to complete the trial, we divided 90 elderly patients with stable-stage COPD into a low-intensity exercise group (n= 30, PR group), PR plus whey proteins complex group (n= 30, PRWP group), and a control group (n= 30) randomly, and assessed index such as exercise capacity, mental health status, lung function, and body composition. Eventually, 84 people persisted until the end of the trial.

RESULTS

Compared with the control group, hand grip strength (HGS)(1.4 ± 0.6 kg, and 1.0 ± 0.2 kg respectively, p< 0.05) in the PRWP and PR group, 6 minutes of walking distance (6MWD)(14.1 ± 3.8m, p< 0.05) in PRWP group improved. Furthermore, compared with the PR group, Medical Research Council Dyspnea Scale (MRC)(-0.2 ± 0.1, p< 0.01), anxiety score (-1.2 ± 0.4, p< 0.01), and body weight (2.0 ± 0.8kg, p< 0.05) improved in the PRWP group. There were no inter-group differences in a fat-free mass index or appendicular skeletal muscle mass index.

CONCLUSIONS

Muscle strength could be enhanced in both intervention models. Adding whey protein complex was additionally successful in rectifying dyspnea, anxiety, and weight loss caused by exercise. This rehabilitation pattern might be valuable in elderly patients with COPD.

Airborne Particulate Matter Size and Chronic Obstructive Pulmonary Disease Exacerbations: A Prospective, Risk-Factor Analysis Comparing Global Initiative for Obstructive Lung Disease 3 and 4 Categories

Current research primarily emphasizes the generalized correlations between airborne pollution and respiratory diseases, seldom considering the differential impacts of particular particulate matter sizes on chronic obstructive pulmonary disease (COPD) exacerbations in distinct Global Initiative for Obstructive Lung Disease (GOLD) categories. This study hypothesizes a critical association between particulate matter sizes (PM 1.0, PM 2.5, and PM 10) and exacerbation frequency in COPD patients categorized under GOLD 3 and GOLD 4, with a potential augmenting role played by proximity to main roads and industrial areas. This research aspires to offer a nuanced perspective on the exacerbation patterns in these groups, setting the stage for targeted intervention strategies. Utilizing a prospective design, this study followed 79 patients divided into GOLD 3 (n = 47) and GOLD 4 (n = 32) categories. The participants were monitored for ten days for daily activity levels, symptoms, living conditions, and airborne particulate matter concentrations, with spirometric evaluations employed to measure lung function. Statistical analyses were used to identify potential risk factors and significant associations. The analysis revealed substantial disparities in airborne particulate matter sizes between the two groups. The mean PM 1.0 concentration was notably higher in GOLD 4 patients (26 µg/m3) compared to GOLD 3 patients (18 µg/m3). Similarly, elevated PM 2.5 levels were observed in the GOLD 4 category (35 µg/m3) in contrast to the GOLD 3 category (24 µg/m3). A vital finding was the increased frequency of exacerbations in individuals residing within 200 m of main roads compared to those living further away (OR = 2.5, 95% CI: 1.5-4.1). Additionally, patients residing in homes smaller than 50 square meters demonstrated a greater frequency of exacerbations. Spirometry results corroborated the exacerbated condition in GOLD 4 patients, indicating a significant decline in lung function parameters compared to the GOLD 3 group. This study substantiates a significant association between airborne particulate matter sizes and exacerbation frequencies in COPD patients, particularly accentuating the increased risk in GOLD 4 patients. Our findings underscore the pivotal role of environmental factors, including the size of living areas and proximity to main roads, in influencing COPD exacerbations. These results suggest the need for personalized healthcare strategies and interventions, which account for environmental risk factors and the distinctions between GOLD 3 and GOLD 4 categories of COPD patients.

Development and Validation of a Multivariable Prediction Model to Identify Acute Exacerbation of COPD and Its Severity for COPD Management in China (DETECT Study): A Multicenter, Observational, Cross-Sectional Study

Purpose

There is an unmet clinical need for an accurate and objective diagnostic tool for early detection of acute exacerbation of chronic obstructive pulmonary disease (AECOPD). DETECT (NCT03556475) was a multicenter, observational, cross-sectional study aiming to develop and validate multivariable prediction models for AECOPD occurrence and severity in patients with chronic obstructive pulmonary disease (COPD) in China.

Patients and Methods

Patients aged ≥40 years with moderate/severe COPD, AECOPD, or no COPD were consecutively enrolled between April 22, 2020, and January 18, 2021, across seven study sites in China. Multivariable prediction models were constructed to identify AECOPD occurrence (primary outcome) and AECOPD severity (secondary outcome). Candidate variables were selected using a stepwise procedure, and the bootstrap method was used for internal model validation.

Results

Among 299 patients enrolled, 246 were included in the final analysis, of whom 30.1%, 40.7%, and 29.3% had COPD, AECOPD, or no COPD, respectively. Mean age was 64.1 years. Variables significantly associated with AECOPD occurrence (P<0.05) and severity (P<0.05) in the final models included COPD disease-related characteristics, as well as signs and symptoms. Based on cut-off values of 0.374 and 0.405 for primary and secondary models, respectively, the performance of the primary model constructed to identify AECOPD occurrence (AUC: 0.86; sensitivity: 0.84; specificity: 0.77), and of the secondary model for AECOPD severity (AUC: 0.81; sensitivity: 0.90; specificity: 0.73) indicated high diagnostic accuracy and clinical applicability.

Conclusion

By leveraging easy-to-collect patient and disease data, we developed identification tools that can be used for timely detection of AECOPD and its severity. These tools may help physicians diagnose AECOPD in a timely manner, before further disease progression and possible hospitalizations.

Change in individual chronic obstructive pulmonary disease assessment test item scores after short-term bronchodilator therapy and its impact on exacerbation in treatment-naïve patients with chronic obstructive pulmonary disease

Background:

The chronic obstructive pulmonary disease (COPD) assessment test (CAT) measures the health status of patients with COPD. We aimed to investigate the change in individual CAT scores after short-term bronchodilator therapy among treatment-naïve patients with COPD.

Methods:

Data from 148 patients newly diagnosed with COPD between January 2016 and April 2020 were retrospectively analyzed. We compared the CAT score, modified Medical Research Council (mMRC) dyspnea grade, and forced expiratory volume in 1 s (FEV1) before and after short-term (6 ± 2 months) bronchodilator therapy. We analyzed the change trends using generalized estimating equations.

Results:

The mean patient age was 70.9 years, and 92.6% were male. The total CAT score did not significantly improve. However, among the CAT items, phlegm [adjusted difference: –0.22 (–0.48, –0.002)], chest tightness [–0.30 (–0.56, –0.05)], and breathlessness [–0.45 (–0.66, –0.23)] scores significantly improved after bronchodilator therapy. The patients were divided into two groups: CAT score improved ( n = 69) and not improved group ( n = 79). The development of moderate-to-severe exacerbations during follow-up was significantly lower (2.9% versus 17.7%, p = 0.004) in the CAT score improved group.

Conclusion:

The improvement in CAT items indicating respiratory symptoms was more evident than the CAT total score after short-term bronchodilator therapy. Despite the significant increase in FEV1 after bronchodilator therapy, fewer than half of the patients achieved meaningful improvement in CAT, and this group showed significantly lower development of exacerbation during follow-up.

Value of Cardiopulmonary Exercise Testing in the Prognosis Assessment of Chronic Obstructive Pulmonary Disease Patients: A Retrospective, Multicentre Cohort Study

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is one of the most common chronic diseases associated with high mortality. Previous studies suggested a prognostic role for peak oxygen uptake (VO2peak) assessed during cardiopulmonary exercise testing (CPET) in patients with COPD. However, most of these studies had small sample sizes or short follow-up periods, and despite their relevance, CPET parameters are not included in the Global Initiative for Chronic Obstructive Lung Disease (GOLD) tool for assessment of severity.

OBJECTIVES

We therefore aimed to assess the prognostic value of CPET parameters in a large cohort of outpatients with COPD.

METHODS

In this retrospective, multicentre cohort study, medical records of patients with COPD who underwent CPET during 2004-2017 were reviewed and demographics, smoking habits, GOLD grade and category, exacerbation frequency, dyspnoea score, lung function measurements, and CPET parameters were documented. Relationships with survival were evaluated using Kaplan-Meier analysis, Cox regression, and receiver operating characteristic (ROC) curves.

RESULTS

Of a total of 347 patients, 312 patients were included. Five-year and 10-year survival probability was 75% and 57%, respectively. VO2peak significantly predicted survival (hazard ratio: 0.886 [95% confidence interval: 0.830; 0.946]). The optimal VO2peak threshold for discrimination of 5-year survival was 14.6 mL/kg/min (area under ROC curve: 0.713). Five-year survival in patients with VO2peak <14.6 mL/kg/min versus ≥ 14.6 mL/kg/min was 60% versus 86% in GOLD categories A/B and 64% versus 90% in GOLD categories C/D.

CONCLUSIONS

We confirm that VO2peak is a highly significant predictor of survival in COPD patients and recommend the incorporation of VO2peak into the assessment of COPD severity.