Effect of pulmonary rehabilitation on peripheral muscle fiber remodeling in patients with COPD in GOLD stages II to IV

Differentially co-expressed myofibre transcripts associated with abnormal myofibre proportion in chronic obstructive pulmonary disease

BACKGROUND

Skeletal muscle dysfunction is a common extrapulmonary manifestation of chronic obstructive pulmonary disease (COPD). Alterations in skeletal muscle myosin heavy chain expression, with reduced type I and increased type II myosin heavy chain expression, are associated with COPD severity when studied in largely male cohorts. The objectives of this study were (1) to define an abnormal myofibre proportion phenotype in both males and females with COPD and (2) to identify transcripts and transcriptional networks associated with abnormal myofibre proportion in COPD.

METHODS

Forty-six participants with COPD were assessed for body composition, strength, endurance and pulmonary function. Skeletal muscle biopsies from the vastus lateralis were assayed for fibre-type distribution and cross-sectional area via immunofluorescence microscopy and RNA-sequenced to generate transcriptome-wide gene expression data. Sex-stratified k-means clustering of type I and IIx/IIax fibre proportions was used to define abnormal myofibre proportion in participants with COPD and contrasted with previously defined criteria. Single transcripts and weighted co-expression network analysis modules were tested for correlation with the abnormal myofibre proportion phenotype.

RESULTS

Abnormal myofibre proportion was defined in males with COPD (n = 29) as <18% type I and/or >22% type IIx/IIax fibres and in females with COPD (n = 17) as <36% type I and/or >12% type IIx/IIax fibres. Half of the participants with COPD were classified as having an abnormal myofibre proportion. Participants with COPD and an abnormal myofibre proportion had lower median handgrip strength (26.1 vs. 34.0 kg, P = 0.022), 6-min walk distance (300 vs. 353 m, P = 0.039) and forced expiratory volume in 1 s-to-forced vital capacity ratio (0.42 vs. 0.48, P = 0.041) compared with participants with COPD and normal myofibre proportions. Twenty-nine transcripts were associated with abnormal myofibre proportions in participants with COPD, with the upregulated NEB, TPM1 and TPM2 genes having the largest fold differences. Co-expression network analysis revealed that two transcript modules were significantly positively associated with the presence of abnormal myofibre proportions. One of these co-expression modules contained genes classically associated with muscle atrophy, as well as transcripts associated with both type I and type II myofibres, and was enriched for genetic loci associated with bone mineral density.

CONCLUSIONS

Our findings indicate that there are significant transcriptional alterations associated with abnormal myofibre proportions in participants with COPD. Transcripts canonically associated with both type I and type IIa fibres were enriched in a co-expression network associated with abnormal myofibre proportion, suggesting altered transcriptional regulation across multiple fibre types.

Efficacy of exercise treatments for chronic obstructive pulmonary disease: A systematic review

OBJECTIVE

To review the efficacy of exercise treatments on chronic obstructive pulmonary disease (COPD).

DATA SOURCES

PubMed, Scopus, Science Direct, Ebscohost, SPORTDiscus, ProQuest, Web of Science.

REVIEW METHODS

A systematic review was performed to identify the relevant studies published from 2011 to 2023. Studies were selected using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 5170 articles were retrieved and assessed using the Physiotherapy Evidence Database (PEDro) scale. The risk of bias in individual studies was assessed with the Cochrane risk of bias tool.

RESULTS

A total of 38 eligible studies were included. Eight studies evaluated the effects of Tai Chi, followed by Liuzijue (five studies) and yoga (three studies). The duration of the exercise programmes ranged from 8 weeks to 3 years, and the frequency was between 2 and 7 times a week. Exercise sessions lasted between 20 and 90 min. Low-intensity exercise improved lung function after six months. Whole-body exercise improved dyspnea more than local exercise. Water-based exercise improved physical endurance more than land exercise, and quality of life was unaffected by long-term exercise.

CONCLUSION

This systematic review highlights the benefit of exercise treatments as a potential adjunct treatment for COPD patients.

Metabolomic, oxidative, and inflammatory responses to acute exercise in chronic obstructive pulmonary disease

BACKGROUND

There is currently a need to identify metabolomic responses to acute exercise in chronic obstructive pulmonary disease (COPD).

OBJECTIVE

We investigated the metabolomic, oxidative, and inflammatory responses to constant (CE) and intermittent (IE) work rate exercises in COPD.

METHODS

Sixteen males with COPD performed a symptom-limited incremental cycle exercise test (ICE). Metabolomic, oxidative, and inflammatory responses to CE and IE (based on the performance of ICE) were analyzed in the plasma.

RESULTS

Fructose-6-phosphate, 3-phosphoglyceric acid, l-carnitine, and acylcarnitines levels were significantly decreased, whereas alpha-ketoglutaric, malic, 2-hydroxybutyric, and 3-hydroxybutyric acids were increased, after CE and IE (p<0.05). Increases in citric, isocitric, and lactic acids, as well as decreases in pyruvic and oxalic acids, were only present with IE (p<0.05). Isoleucine was decreased after both exercises (p<0.05). We observed an increase in inosine-5'-diphosphate, uric acid, ascorbic acid, and pantothenic acid, as well as a decrease in 5-hydroxymethyluridine, threonic acid, and dehydroascorbic acid, after IE (p<0.05). Catalase, reduced glutathione, and total antioxidant status difference values for both exercises were similar (p>0.05). The change in glutathione peroxidase (GPx) with CE was more significant than that with IE (p = 0.004). The superoxide dismutase change was greater with IE than with CE (p = 0.015). There were no significant changes in inflammatory markers after exercise (p>0.05).

CONCLUSION

CE and IE cause isoleucine, l-carnitine, and acylcarnitine levels to decrease, whereas ketone bodies were increased, thus indicating the energy metabolism shift from carbohydrates to amino acid utilization and lipid metabolism in COPD. Compared with CE, IE produces significant changes in more metabolomics in terms of carbohydrates, lipids, amino acids, nucleotides, and vitamins. Acute CE and IE alter circulating GPx levels in COPD.

Association Between Anthropometric Indices and Skeletal-Muscle Atrophy in Chinese Patients with Stable Chronic Obstructive Pulmonary Disease: A Cross-Sectional Study

Purpose

Anthropometric indices are simple indicators of patient nutritional status. However, the association between these indices and skeletal-muscle atrophy in patients with stable chronic obstructive pulmonary disease (COPD) has not been fully investigated. In this study, we evaluated this association.

Patients and Methods

We recruited 123 outpatients with stable COPD from a general hospital in China from 2020 to 2021. We recorded their demographic characteristics, including age, sex, course of illness, dyspnea score, body mass index (BMI), force expiratory volume in 1 second (FEV₁), forced vital capacity (FVC), smoking status, and severity grading. In addition, patients' anthropometric indices, including fat-free mass index (FFMI) and appendicular skeletal-muscle mass index (ASMI), were measured using a body composition analyzer, and measurements were taken of the triceps skinfold (TSF), midarm circumference (MAC), and calf circumference (CC). We drew and analyzed a receiver operating characteristic (ROC) curve to identify the best intercept point value for the assessment of skeletal-muscle atrophy.

Results

The TSF, MAC, CC, FFMI, and ASMI of COPD patients were 1.08 ± 0.44 cm, 26.39 ± 2.92 cm, 34.5 ± 3.06 cm, 17.49 ± 1.86 kg/m², and 8.17 ± 0.90 kg/m², respectively. These anthropometric indices had a significant positive correlation with skeletal-muscle mass (correlation values, 0.481-0.820). CC was strongly correlated with both FFMI and ASMI. The ROC curve showed an area-under-the-curve (AUC) value of 0.873-0.959.

Conclusion

Anthropometric indices were correlated with skeletal-muscle mass. CC showed the best diagnostic value in COPD patients, suggesting its effectiveness as a simple method for assessing skeletal-muscle atrophy and identifying patients with a noticeable reduction in muscle mass. Such patients require early, multidisciplinary intervention.

Whole-body and muscle responses to aerobic exercise training and withdrawal in ageing and COPD

BACKGROUND

Chronic obstructive pulmonary disease (COPD) patients exhibit lower peak oxygen uptake (V'_{O2 peak}), altered muscle metabolism and impaired exercise tolerance compared with age-matched controls. Whether these traits reflect muscle-level deconditioning (impacted by ventilatory constraints) and/or dysfunction in mitochondrial ATP production capacity is debated. By studying aerobic exercise training (AET) at a matched relative intensity and subsequent exercise withdrawal period we aimed to elucidate the whole-body and muscle mitochondrial responsiveness of healthy young (HY), healthy older (HO) and COPD volunteers to whole-body exercise.

METHODS

HY (n=10), HO (n=10) and COPD (n=20) volunteers were studied before and after 8 weeks of AET (65% V'_{O2 peak}) and after 4 weeks of exercise withdrawal. V'_{O2 peak}, muscle maximal mitochondrial ATP production rate (MAPR), mitochondrial content, mitochondrial DNA (mtDNA) copy number and abundance of 59 targeted fuel metabolism mRNAs were determined at all time-points.

RESULTS

Muscle MAPR (normalised for mitochondrial content) was not different for any substrate combination in HO, HY and COPD at baseline, but mtDNA copy number relative to a nuclear-encoded housekeeping gene (mean±sd) was greater in HY (804±67) than in HO (631±69; p=0.041). AET increased V'_{O2 peak} in HO (17%; p=0.002) and HY (21%; p<0.001), but not COPD (p=0.603). Muscle MAPR for palmitate increased with training in HO (57%; p=0.041) and HY (56%; p=0.003), and decreased with exercise withdrawal in HO (-45%; p=0.036) and HY (-30%; p=0.016), but was unchanged in COPD (p=0.594). mtDNA copy number increased with AET in HY (66%; p=0.001), but not HO (p=0.081) or COPD (p=0.132). The observed changes in muscle mRNA abundance were similar in all groups after AET and exercise withdrawal.

CONCLUSIONS

Intrinsic mitochondrial function was not impaired by ageing or COPD in the untrained state. Whole-body and muscle mitochondrial responses to AET were robust in HY, evident in HO, but deficient in COPD. All groups showed robust muscle mRNA responses. Higher relative exercise intensities during whole-body training may be needed to maximise whole-body and muscle mitochondrial adaptation in COPD.

Übersicht zur pneumologischen Rehabilitation

Die pneumologische Rehabilitation (PR) ist eine evidenzbasierte interdisziplinäre Behandlung für Patienten mit chronischen Erkrankungen der Atmungsorgane. Die Indikation für die Beantragung einer PR ist gegeben, wenn eine Reha-Fähigkeit, Reha-Bedürftigkeit und eine günstige Reha-Prognose bestehen. Ziele einer PR sind es, die Symptome zu verringern und die Lebensqualität sowie die körperliche Belastbarkeit der Patienten zu steigern. Die Effektivität ist für COPD(„chronic obstructive pulmonary disease“)-Patienten mit dem höchsten und für Non-COPD-Patienten mit einem zunehmend guten Evidenzgrad durch randomisiert kontrollierte Studien und Metaanalysen gesichert. Die Therapieinhalte einer PR werden durch ein multimodales und multidisziplinäres Behandlungsteam individuell an die Bedürfnisse der Patienten angepasst. Um den Rehabilitationserfolg einer PR nachhaltig zu gestalten, besteht die Möglichkeit, an ambulanten Nachsorgeprogrammen (z. B. Lungensport) teilzunehmen sowie digitale Technologien als unterstützende Maßnahme einzusetzen.

Does branched-chain amino acid supplementation improve pulmonary rehabilitation effect in COPD?

BACKGROUND

Muscle wasting is frequent in chronic obstructive lung disease (COPD) and associated with low branched-chain amino acids (BCAA). We hypothesized that BCAA supplementation could potentiate the effect of a pulmonary rehabilitation program (PRP) by inducing muscular change.

MATERIALS AND METHODS

Sixty COPD patients (GOLD 2-3) were involved in an ambulatory 4-week PRP either with BCAA oral daily supplementation or placebo daily supplementation in a randomized double-blind design. Maximal exercise test including quadriceps oxygenation measurements, functional exercise test, muscle strength, lung function tests, body composition, dyspnea and quality of life were assessed before and after PRP.

RESULTS

Fifty-four patients (64.9 ± 8.3 years) completed the protocol. In both groups, maximal exercise capacity, functional and muscle performances, quality of life and dyspnea were improved after 4-week PRP (p ≤ 0.01). Changes in muscle oxygenation during the maximal exercise and recovery period were not modified after 4-week PRP in BCAA group. Contrarily, in the placebo group the muscle oxygenation kinetic of recovery was slowed down after PRP.

CONCLUSION

This study demonstrated that a 4-week PRP with BCAA supplementation is not more beneficial than PRP alone for patients. A longer duration of supplementation or a more precise targeting of patients would need to be investigated to validate an effect on muscle recovery and to demonstrate other beneficial effects.

Is the Power Spectrum of Electromyography Signal a Feasible Tool to Estimate Muscle Fiber Composition in Patients with COPD?

A greater proportion of glycolytic muscle fibers is a manifestation of skeletal muscle dysfunction in Chronic Obstructive Pulmonary Disease (COPD). Here, we propose to use the spectral analysis of the electromyographic signal as a non-invasive approach to investigate the fiber muscle composition in COPD. We recorded the electromyographic activity of Rectus Femoris (RF), Vastus Lateralis (VL), Vastus Medialis (VM) and Biceps Femoris (BF) muscles, in ten patients and ten healthy individuals, during non-fatiguing, flexion–extension leg movements. The mean (MNF) and median frequencies (MDF) were calculated, and the most common profiles of electromyographic power spectrum were characterized by using the principal component analysis. Frequency parameters showed higher values in patients with COPD than in the control group for the RF (+25% for MNF; +21% for MNF), VL (+16% for MNF; 16% for MNF) and VM (+22% for MNF; 22% for MNF) muscles during the extension movements and for the BF (+26% for MNF; 34% for MNF) muscle during flexion movements. Spectrum profiles of the COPD patients shifted towards the higher frequencies, and the changes in frequency parameters were correlated with the level of disease severity. This shift of frequencies may indicate an increase in glycolytic muscle fibers in patients with COPD. These results, along with the non-fatigable nature of the motor task and the adoption of a non-invasive method, encourage to use electromyographic spectral analysis for estimating muscle fiber composition in patients with COPD.

[Rehabilitation in pneumology]

Die pneumologische Rehabilitation (PR) ist eine evidenzbasierte interdisziplinäre Behandlung für Patienten mit chronischen Erkrankungen der Atmungsorgane. Die Indikation für ihre Beantragung ist bei entsprechender Rehabilitationsfähigkeit, -bedürftigkeit und günstigen -prognose gegeben. Ziele einer PR sind die Reduktion der Symptome sowie die Steigerung der Lebensqualität und körperlichen Belastbarkeit. Die Effektivität ist für COPD-Patienten (COPD: chronisch obstruktive Lungenerkrankung) mit dem höchsten und für Nicht-COPD-Patienten mit zunehmend gutem Evidenzgrad durch randomisiert kontrollierte Studien und Metaanalysen gesichert. Die Therapieinhalte einer PR werden durch ein multidisziplinäres Behandlungsteam individuell an die Bedürfnisse der Patienten angepasst. Um den Rehabilitationserfolg nachhaltig zu gestalten, besteht die Möglichkeit, an ambulanten Nachsorgeprogrammen (z. B. Lungensport) teilzunehmen sowie digitale Technologien als unterstützende Maßnahme einzusetzen.

Succinate Dehydrogenase (SDH)-subunit C Regulates Muscle Oxygen Consumption and Fatigability in an Animal Model of Pulmonary Emphysema

Patients with pulmonary emphysema often develop locomotor muscle dysfunction, which is independently associated with disability and higher mortality in that population. Muscle dysfunction entails reduced force-generation capacity which partially depends on fibers' oxidative potential, yet very little mechanistic research has focused on muscle respiration in pulmonary emphysema. Using a recently established animal model of pulmonary emphysema-driven skeletal muscle dysfunction, we found downregulation of succinate dehydrogenase (SDH) subunit C in association with lower oxygen consumption and fatigue-tolerance in locomotor muscles. Reduced SDH activity has been previously observed in muscles from patients with pulmonary emphysema and we found that SDHC is required to support respiration in cultured muscle cells. Moreover, in-vivo gain of SDH function in emphysema animals muscles resulted in better oxygen consumption rate (OCR) and fatigue tolerance. These changes correlated with a larger number of relatively more oxidative type 2-A and 2X fibers, and a reduced amount of 2B fibers. Our data suggests that SDHC is a key regulator of respiration and fatigability in pulmonary emphysema-driven skeletal muscles, which could be impactful to develop strategies aimed at attenuating this comorbidity.

The role of peripheral muscle fatigability on exercise intolerance in COPD

INTRODUCTION

Exercise limitation in chronic obstructive pulmonary disease (COPD) is multi-factorial; however, growing evidence indicates that muscle dysfunction may contribute in some patients.

AREAS COVERED

This work outlines current evidence for and against increased peripheral muscle fatigability in COPD through a comprehensive review of relevant literature available on PubMed/MEDLINE until May 2020. The authors first discuss key methodological issues relative to muscle fatigue assessment by non-volitional techniques, particularly magnetic stimulation. The authors then provide a detailed discussion of critical studies to have objectively measured skeletal muscle fatigue in individuals with COPD.

EXPERT OPINION

Current evidence indicates that localized (knee extension) and cycling exercise are associated with increased quadriceps fatigability in most COPD patients. Increased fatigability, however, has not been consistently found in response to walking, likely reflecting the tendency of 'central' respiratory constraints to overshadow potential functional impairments in the appendicular muscles in this form of exercise. Thus, addressing skeletal muscle abnormalities may be critical to translate improvements in lung mechanics (e.g., due to bronchodilator therapy) into better exercise tolerance. The positive effects of pulmonary rehabilitation on muscle fatigability are particularly encouraging and suggest a role for these measurements to test the efficacy of emerging adjunct training strategies focused on the peripheral muscles.

Hypercapnia-Driven Skeletal Muscle Dysfunction in an Animal Model of Pulmonary Emphysema Suggests a Complex Phenotype

Patients with chronic pulmonary conditions such as chronic obstructive pulmonary disease (COPD) often develop skeletal muscle dysfunction, which is strongly and independently associated with poor outcomes including higher mortality. Some of these patients also develop chronic CO₂ retention, or hypercapnia, which is also associated with worse prognosis. While muscle dysfunction in these settings involve reduction of muscle mass and disrupted fibers’ metabolism leading to suboptimal muscle work, mechanistic research in the field has been limited by the lack of adequate animal models. Over the last years, we have established a rodent model of COPD-induced skeletal muscle dysfunction that allowed a disaggregated interrogation of the cellular and physiological effects driven by COPD from the ones unique to hypercapnia. We found that while COPD and hypercapnia synergistically contribute to muscle atrophy, they are antagonistic processes regarding fibers respiratory capacity. We propose that AMP-activated protein kinase (AMPK) is a crucial regulator of CO₂ signaling in hypercapnic muscles, which leads to both net protein catabolism and improved mitochondrial respiration to support a transition into a substrate-rich, fuel-efficient metabolic mode that allows muscle cells cope with the CO₂ toxicity.

Greater exercise tolerance in COPD during acute interval, compared to equivalent constant-load, cycle exercise: physiological mechanisms

KEY POINTS

Exercise intolerance is common in chronic obstructive pulmonary disease (COPD) patients. In patients with COPD, we compared an interval exercise (IE) protocol (alternating 30 s at 100% peak work rate (WR_peak ) with 30 s at 50% WR_peak ) with moderate-intensity constant-load exercise (CLE) at 75% WR_peak , which yielded the same work rate. Exercise endurance time and total work output were almost twice as high for IE than CLE. At exercise isotime (when work completed was the same between IE and CLE), IE was associated with less dynamic hyperinflation, lower blood lactate concentration, and greater respiratory and locomotor muscle oxygenation, but there were no differences in ventilation or cardiac output. However, at the limit of tolerance for each modality, dynamic hyperinflation was not different between IE and CLE, while blood lactate remained lower and muscle oxygenation higher with IE. Taken together, these findings suggest that dynamic hyperinflation and not muscle-based factors dictate the limits of tolerance in these COPD patients.

ABSTRACT

The relative importance of ventilatory, circulatory and peripheral muscle factors in determining tolerance to exercise in patients with chronic obstructive pulmonary disease (COPD) is not known. In 12 COPD patients (forced expiratory volume in one second: 58 ± 17%pred.) we measured ventilation, cardiac output, dynamic hyperinflation, local muscle oxygenation, blood lactate and time to exhaustion during (a) interval exercise (IE) consisting of 30 s at 100% peak work rate alternating with 30 s at 50%, and (b) constant-load exercise (CLE) at 75% peak work rate, designed to produce the same average work rate. Exercise time was substantially longer during IE than CLE (19.5 ± 4.8 versus 11.4 ± 2.1 min, p = 0.0001). Total work output was therefore greater during IE than CLE (81.3 ± 27.7 versus 48.9 ± 23.8 kJ, p = 0.0001). Dynamic hyperinflation (assessed by changes from baseline in inspiratory capacity, ΔIC) was less during IE than CLE at CLE exhaustion time (isotime, p = 0.009), but was similar at exhaustion (ΔIC_CLE : -0.38 ± 0.10 versus ΔIC_IE : -0.33 ± 0.12 l, p = 0.102). In contrast, at isotime, minute ventilation, cardiac output and systemic oxygen delivery did not differ between protocols (P > 0.05). At exhaustion in both protocols, the vastus lateralis and intercostal muscle oxygen saturation were higher in IE than CLE (p = 0.014 and p = 0.0002, respectively) and blood lactate concentrations were lower (4.9 ± 2.4 mmol l^-1 versus 6.4 ± 2.2 mmol l^-1 , p = 0.039). These results suggest that (1) exercise tolerance with COPD is limited by dynamic hyperinflation; and (2) cyclically lower (50%) effort intervals in IE help to preserve muscle oxygenation and reduce metabolic acidosis compared with CLE at the same average work rate; but these factors do not appear to determine time to exhaustion.

Cigarette Smoking Exacerbates Skeletal Muscle Injury without Compromising Its Regenerative Capacity

Skeletal muscle dysfunction in patients with chronic obstructive pulmonary disease negatively impacts quality of life and survival. Cigarette smoking (CS) is the major risk factor for chronic obstructive pulmonary disease and skeletal muscle dysfunction; however, how CS affects skeletal muscle function remains enigmatic. To examine the impact of CS on skeletal muscle inflammation and regeneration, male BALB/c mice were exposed to CS for 8 weeks before muscle injury was induced by barium chloride injection, and were maintained on the CS protocol for up to 21 days after injury. Barium chloride injection resulted in architectural damage to the tibialis anterior muscle, resulting in a decrease contractile function, which was worsened by CS exposure. CS exposure caused muscle atrophy (reduction in gross weight and myofiber cross-sectional area) and altered fiber type composition (31% reduction of oxidative fibers). Both contractile function and loss in myofiber cross-sectional area by CS exposure gradually recovered over time. Satellite cells are muscle stem cells that confer skeletal muscle the plasticity to adapt to changing demands. CS exposure blunted Pax7⁺ centralized nuclei within satellite cells and thus prevented the activation of these muscle stem cells. Finally, CS triggered muscle inflammation; in particular, there was an exacerbated recruitment of F4/80⁺ monocytic cells to the site of injury along with enhanced proinflammatory cytokine expression. In conclusion, CS exposure amplified the local inflammatory response at the site of skeletal muscle injury, and this was associated with impaired satellite cell activation, leading to a worsened muscle injury and contractile function without detectable impacts on the recovery outcomes.

Effect of high-flow nasal therapy during early pulmonary rehabilitation in patients with severe AECOPD: a randomized controlled study

Background

Chronic obstructive pulmonary disease (COPD) is airway inflammation characterized and low daily physical activity. Most pulmonary rehabilitation (PR) programs are often provided to stable patients, but fewer training programs are specific for hospitalized patients with acute exacerbation (AE). Patients with AECOPD experience increased dyspnea sensations and systemic inflammation during exercise training. High-flow nasal therapy (HFNT) reduces the minute volume, lowers the respiratory rate, and decreases the work of breathing. However, it is not clear whether HFNT is efficient during exercise training. In this study, we investigated the effects of HFNT during exercise training in an early PR program among hospitalized patients with severe AECOPD.

Methods

We enrolled COPD patients hospitalized due to AE. They were randomized into two groups according to their status into HFNT PR and non-HFNT PR groups. This study collected basic data, and also assessed a pulmonary function test, 6-min walking test, blood inflammatory biomarkers, and arterial gas analysis at the baseline, and at 4 and 12 weeks of the intervention. Data were analyzed using SPSS statistical software.

Result

We recruited 44 AECOPD patients who completed the 12-week PR program. The HFNT PR program produced significant improvements in exercise tolerance as assessed by the 6-min walking distance (6MWD), reduced dyspnea sensations in the modified Medical Research Council (mMRC), and decreased systemic inflammation as evidenced by the a lower C-reactive protein (CRP) level. A reduction in the length of hospitalization was achieved with PR in the 1-year follow-up in the two groups. The HFNT PR group showed better trends of reduced air trapping in the delta inspiration capacity (IC) and an increased quality of life according to the COPD assessment test (CAT) than did the non-HFNT PR group.

Conclusions

HFNT during exercise training in early PR increases exercise tolerance and reduces systemic inflammation in hospitalized patients with severe AECOPD.

Exercise training increases respiratory muscle strength and exercise capacity in patients with chronic obstructive pulmonary disease and respiratory muscle weakness

BACKGROUND

How respiratory muscle strength influences the effectiveness of pulmonary rehabilitation (PR) in patients with chronic obstructive pulmonary disease (COPD) is unclear.

OBJECTIVE

To investigate the benefits of PR in subjects with COPD according to respiratory muscle strength.

METHODS

Ninety-seven subjects with COPD were evaluated using maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), pulmonary function tests, the cardiopulmonary exercise test (CPET), and the St. George's Respiratory Questionnaire (SGRQ). Subjects were divided into four groups: 1 (normal MIP and MEP); 2 (low MIP); 3 (low MEP); and 4 (low MIP and MEP). Subjects underwent PR for 3 months; MIP, MEP, SGRQ, and CPET were evaluated post-PR.

RESULTS

Subjects with both poor MIP and MEP had the highest dyspnea score, lowest exercise capacity, and poorest health-related quality of life (HRQoL). PR improved exercise capacity and HRQoL in all groups, with more improvement in MIP, MEP, tidal volume (on exercise), and dyspnea (at rest) in subjects with both low MIP and MEP.

CONCLUSIONS

Patients with respiratory muscle weakness had worse dyspnea, lower exercise capacity, and poorer HRQoL at baseline. Exercise training improved respiratory muscle strength with concurrent improvement of exercise capacity, HRQoL, and dyspnea score. Subjects with both poor baseline MIP and MEP showed greater benefits of PR.

Change in V˙O2peak in Response to Aerobic Exercise Training and the Relationship With Exercise Prescription in People With COPD: A Systematic Review and Meta-analysis

BACKGROUND

Despite the wide-ranging benefits of pulmonary rehabilitation, conflicting results remain regarding whether people with COPD can improve their peak oxygen uptake (V˙O_2peak) with aerobic training.

RESEARCH QUESTION

The goal of this study was to investigate the effect of aerobic training and exercise prescription on V˙O_2peak in COPD.

STUDY DESIGN AND METHODS

A systematic review was performed by using MEDLINE, Embase, Cumulative Index to Nursing and Allied Health Literature, and Cochrane databases for all studies measuring V˙O_2peak prior to and following supervised lower-limb aerobic training in COPD. A random effects meta-analysis limited to randomized controlled trials comparing aerobic training vs usual care was conducted. Other study designs were included in a secondary meta-analysis and meta-regression to investigate the influence of program and patient factors on outcome.

RESULTS

A total of 112 studies were included (participants, N = 3,484): 21 controlled trials (n = 489), of which 13 were randomized (n = 288) and 91 were uncontrolled (n = 2,995) studies. Meta-analysis found a moderate positive change in V˙O_2peak (standardized mean difference, 0.52; 95% CI, 0.34-0.69) with the intervention. The change in V˙O_2peak was positively associated with target duration of exercise session (P = .01) and, when studies > 1 year duration were excluded, greater total volume of exercise training (P = .01). Similarly, the change in V˙O_2peak was greater for programs > 12 weeks compared with those 6 to 12 weeks when adjusted for age and sex. However, reported prescribed exercise intensity (P = .77), training modality (P > .35), and mode (P = .29) did not affect V˙O_2peak. Cohorts with more severe airflow obstruction exhibited smaller improvements in V˙O_2peak (P < .001).

INTERPRETATION

Overall, people with COPD achieved moderate improvements in V˙O_2peak through supervised aerobic training. There is sufficient evidence to show that programs with greater total exercise volume, including duration of exercise session and program duration, are more effective. Reduced effects in severe disease suggest alternative aerobic training methods may be needed in this population.

CLINICAL TRIAL REGISTRATION

PROSPERO; No.: CRD42018099300; URL: https://www.crd.york.ac.uk/prospero/.

Locomotor Muscles in COPD: The Rationale for Rehabilitative Exercise Training

Exercise training as part of pulmonary rehabilitation is arguably the most effective intervention to improve tolerance to physical exertion in patients with chronic obstructive pulmonary disease (COPD). Owing to the fact that exercise training has modest effects on exertional ventilation, operating lung volumes and respiratory muscle performance, improving locomotor muscle structure and function are key targets for pulmonary rehabilitation in COPD. In the current concise review, we initially discuss whether patients’ muscles are exposed to deleterious factors. After presenting corroboratory evidence on this regard (e.g., oxidative stress, inflammation, hypoxemia, inactivity, and medications), we outline their effects on muscle macro- and micro-structure and related functional properties. We then finalize by addressing the potential beneficial consequences of different training strategies on these muscle-centered outcomes. This review provides, therefore, an up-to-date outline of the rationale for rehabilitative exercise training approaches focusing on the locomotor muscles in this patient population.

Baseline Exercise Tolerance and Perceived Dyspnea to Identify the Ideal Candidate to Pulmonary Rehabilitation: A Risk Chart in COPD Patients

Background

The appropriate criteria for patient selection are still a key issue in the clinical management of patients referred to pulmonary rehabilitation (PR).

Methods

We retrospectively analyzed the records of a wide population of 1470 outpatient or inpatients with chronic obstructive pulmonary disease (COPD) referred to standard PR at two specialized Italian centers. Two models of multivariate logistic regression were developed to test the predictive powers of baseline exercise tolerance, namely the distance walked in 6 mins (6MWD), and of baseline dyspnea on exertion, measured by the modified Medical Research Council scale (mMRC), versus the minimal clinically important difference (MCID) for the same outcomes.

Results

Compared to the category of individuals with 6MWD >350 meters, those patients with 201-350 meters and ≤200 meters showed a higher probability (p<0.001) of predicting a MCID change. Compared to the category of individuals with mMRC 0-1point, all the other categories (2, 3, and 4) also showed a higher probability (p<0.001) of predicting a MCID change. The incorporation of baseline categories of 6MWD and mMRC in a risk chart showed that the percentage of patients reaching MCID in both variables increased as the baseline level of 6MWD decreased and of mMRC increased.

Conclusion

This study demonstrates that lower levels of exercise tolerance and greater perceived dyspnea on exertion predict achieving clinically meaningful changes for both these treatment outcomes following PR. A specific risk chart that integrates these two variables may help clinicians to select ideal candidates and best responders to PR.

Are the Effects of High-Intensity Exercise Training Different in Patients with COPD Versus COPD+Asthma Overlap?

PURPOSE

This study aimed to investigate whether patients with chronic obstructive pulmonary disease (COPD) presenting asthma overlap (ACO) benefit similarly in comparison to patients with only COPD after a 12-week high-intensity exercise training (ET) program.

METHODS

Subjects with a diagnosis of COPD alone or ACO were evaluated and compared before and after a high-intensity ET program composed of walking and cycling plus strengthening exercises of the upper and lower limbs (3 days/week, 3 months, 36 sessions). Assessments included spirometry, bioelectrical impedance, 6-min walk test (6MWT), London Chest Activity of Daily Living Scale (LCADL), Hospital anxiety and depression Scale, modified Medical Research Council Scale (mMRC), Saint George Respiratory Questionnaire (SGRQ), and respiratory and peripheral muscle strength [manovacuometry and 1-repetition maximum test (quadriceps femoris, biceps and triceps brachialis), respectively]. ACO was defined according to Sin et al. (Eur Respir J 48(3):664-673, 2016).

RESULTS

The sample was composed of 74 subjects (57% male, age 67 ± 8 years, BMI 26 (21-32) kg/m², FEV₁ 47 ± 17%predicted), and 12 (16%) of them were classified as presenting ACO. Both groups improved pulmonary function, 6MWT, peripheral and inspiratory muscle strength, LCADL, and SGRQ after ET (p < 0.005 for all). There were no significant interactions between ACO and COPD on ET effects (p > 0.05 for all). Likewise, there was no difference in the proportion of patients achieving the minimum clinical important difference for 6MWT and mMRC.

CONCLUSION

High-intensity exercise training generates similar benefits in patients with COPD regardless of whether presenting asthma overlap or not.

Exercise Training Modalities for People with Chronic Obstructive Pulmonary Disease

Exercise training confers health benefits for people with chronic obstructive pulmonary disease (COPD). This article reviews the evidence for several exercise training modalities shown to be beneficial among individuals with COPD. These modalities include aerobic, resistance, nonlinear periodized, upper limb and balance training, as well as yoga, Tai Chi, inspiratory muscle training, whole body vibration training and neuromuscular electrical stimulation. The literature pertaining to each modality was critically reviewed, and information on the rationale, mechanism(s) of action (where known), benefits, and exercise prescription is described to facilitate easy implementation into clinical practice.

Comprehensive care for chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease (COPD) is a common chronic disease worldwide and incurs heavy utilization of healthcare resources. Many COPD patients have comorbidities and experience exacerbations in the course of the disease. Correct diagnosis and appropriate disease assessment are essential for clinical management. Comprehensive care for patients with different severity of disease aims to offer personalized treatment to suit individual needs. Patients with recent exacerbations also need extra care for the post-acute and rehabilitation phases. Comprehensive care consists of self-management and pulmonary rehabilitation and involves multiple healthcare providers working together closely to provide formal structured programmes for patients. The setting, professionals involved, content and the duration of programme vary a lot among different comprehensive care models. Some randomized controlled trials suggested there was improvement in quality of life, exercise capacity and reduced hospital admissions for participants in comprehensive care programmes compared with controls. However, other studies showed that such programmes might not confer benefits and might even bring harm. The reason for the differences in clinical effect of programmes might be due to differences in study design, components and subjects involved in the studies. Careful evaluation of each programme is thus mandatory. Further research is needed to evaluate the safety and effectiveness of comprehensive care management for COPD patients, both at the stable and post-acute exacerbation state.

Skeletal Muscle Dysfunction in Chronic Obstructive Pulmonary Disease. What We Know and Can Do for Our Patients

Skeletal muscle dysfunction occurs in patients with chronic obstructive pulmonary disease (COPD) and affects both ventilatory and nonventilatory muscle groups. It represents a very important comorbidity that is associated with poor quality of life and reduced survival. It results from a complex combination of functional, metabolic, and anatomical alterations leading to suboptimal muscle work. Muscle atrophy, altered fiber type and metabolism, and chest wall remodeling, in the case of the respiratory muscles, are relevant etiological contributors to this process. Muscle dysfunction worsens during COPD exacerbations, rendering patients progressively less able to perform activities of daily living, and it is also associated with poor outcomes. Muscle recovery measures consisting of a combination of pulmonary rehabilitation, optimized nutrition, and other strategies are associated with better prognosis when administered in stable patients as well as after exacerbations. A deeper understanding of this process' pathophysiology and clinical relevance will facilitate the use of measures to alleviate its effects and potentially improve patients' outcomes. In this review, a general overview of skeletal muscle dysfunction in COPD is offered to highlight its relevance and magnitude to expert practitioners and scientists as well as to the average clinician dealing with patients with chronic respiratory diseases.

Distinct skeletal muscle molecular responses to pulmonary rehabilitation in chronic obstructive pulmonary disease: a cluster analysis

BACKGROUND

Pulmonary rehabilitation (PR) is a cornerstone in the management of chronic obstructive pulmonary disease (COPD), targeting skeletal muscle to improve functional performance. However, there is substantial inter-individual variability in the effect of PR on functional performance, which cannot be fully accounted for by generic phenotypic factors. We performed an unbiased integrative analysis of the skeletal muscle molecular responses to PR in COPD patients and comprehensively characterized their baseline pulmonary and physical function, body composition, blood profile, comorbidities, and medication use.

METHODS

Musculus vastus lateralis biopsies were obtained from 51 COPD patients (age 64 ± 1 years, sex 73% men, FEV₁ , 34 (26-41) %pred.) before and after 4 weeks high-intensity supervised in-patient PR. Muscle molecular markers were grouped by network-constrained clustering, and their relative changes in expression values-assessed by qPCR and western blot-were reduced to process scores by principal component analysis. Patients were subsequently clustered based on these process scores. Pre-PR and post-PR functional performance was assessed by incremental cycle ergometry and 6 min walking test (6MWT).

RESULTS

Eight molecular processes were discerned by network-constrained hierarchical clustering of the skeletal muscle molecular rehabilitation responses. Based on the resulting process scores, four clusters of patients were identified by hierarchical cluster analysis. Two major patient clusters differed in PR-induced autophagy (P < 0.001), myogenesis (P = 0.014), glucocorticoid signalling (P < 0.001), and oxidative metabolism regulation (P < 0.001), with Cluster 1 (C1; n = 29) overall displaying a more pronounced change in marker expression than Cluster 2 (C2; n = 16). General baseline characteristics did not differ between clusters. Following PR, both 6 min walking distance (+26.5 ± 8.3 m, P = 0.003) and peak load on the cycle ergometer test (+9.7 ± 1.9 W, P < 0.001) were improved. However, the functional improvement was more pronounced in C1, as a higher percentage of patients exceeded the minimal clinically important difference in peak workload (61 vs. 21%, P = 0.022) and both peak workload and 6 min walking test (52 vs. 8%, P = 0.008) upon PR.

CONCLUSIONS

We identified patient groups with distinct skeletal muscle molecular responses to rehabilitation, associated with differences in functional improvements upon PR.

Pathobiological mechanisms underlying metabolic syndrome (MetS) in chronic obstructive pulmonary disease (COPD): clinical significance and therapeutic strategies

Chronic obstructive pulmonary disease (COPD) is a major incurable global health burden and is currently the 4th largest cause of death in the world. Importantly, much of the disease burden and health care utilisation in COPD is associated with the management of its comorbidities (e.g. skeletal muscle wasting, ischemic heart disease, cognitive dysfunction) and infective viral and bacterial acute exacerbations (AECOPD). Current pharmacological treatments for COPD are relatively ineffective and the development of effective therapies has been severely hampered by the lack of understanding of the mechanisms and mediators underlying COPD. Since comorbidities have a tremendous impact on the prognosis and severity of COPD, the 2015 American Thoracic Society/European Respiratory Society (ATS/ERS) Research Statement on COPD urgently called for studies to elucidate the pathobiological mechanisms linking COPD to its comorbidities. It is now emerging that up to 50% of COPD patients have metabolic syndrome (MetS) as a comorbidity. It is currently not clear whether metabolic syndrome is an independent co-existing condition or a direct consequence of the progressive lung pathology in COPD patients. As MetS has important clinical implications on COPD outcomes, identification of disease mechanisms linking COPD to MetS is the key to effective therapy. In this comprehensive review, we discuss the potential mechanisms linking MetS to COPD and hence plausible therapeutic strategies to treat this debilitating comorbidity of COPD.

Comprehensive Lung Function Assessment Does not Allow to Infer Response to Pulmonary Rehabilitation in Patients with COPD

The degree of lung function is frequently used as referral criterion for pulmonary rehabilitation. The efficacy of pulmonary rehabilitation was assessed in 518 chronic obstructive pulmonary disease (COPD) patients, after clustering based on a comprehensive pre-rehabilitation lung function assessment. Mean improvements in dyspnea, exercise performance, health status, mood status and problematic activities of daily life after pulmonary rehabilitation were mostly comparable between the seven clusters, despite significant differences in the degree of lung function. The current study demonstrates no significant relationship between the seven lung-function-based clusters and response to pulmonary rehabilitation. Therefore, baseline lung function cannot be used to identify those who will respond well to pulmonary rehabilitation, and moreover, cannot be used as a criterion for referral to pulmonary rehabilitation in patients with COPD.

Management of severe acute exacerbations of COPD: an updated narrative review

Background

Patients with chronic obstructive pulmonary disease (COPD) may experience an acute worsening of respiratory symptoms that results in additional therapy; this event is defined as a COPD exacerbation (AECOPD). Hospitalization for AECOPD is accompanied by a rapid decline in health status with a high risk of mortality or other negative outcomes such as need for endotracheal intubation or intensive care unit (ICU) admission. Treatments for AECOPD aim to minimize the negative impact of the current exacerbation and to prevent subsequent events, such as relapse or readmission to hospital.

Main body

In this narrative review, we update the scientific evidence about the in-hospital pharmacological and non-pharmacological treatments used in the management of a severe AECOPD. We review inhaled bronchodilators, steroids, and antibiotics for the pharmacological approach, and oxygen, high flow nasal cannulae (HFNC) oxygen therapy, non-invasive mechanical ventilation (NIMV) and pulmonary rehabilitation (PR) as non-pharmacological treatments. We also review some studies of non-conventional drugs that have been proposed for severe AECOPD.

Conclusion

Several treatments exist for severe AECOPD patients requiring hospitalization. Some treatments such as steroids and NIMV (in patients admitted with a hypercapnic acute respiratory failure and respiratory acidosis) are supported by strong evidence of their efficacy. HFNC oxygen therapy needs further prospective studies. Although antibiotics are preferred in ICU patients, there is a lack of evidence regarding the preferred drugs and optimal duration of treatment for non-ICU patients. Early rehabilitation, if associated with standard treatment of patients, is recommended due to its feasibility and safety. There are currently few promising new drugs or new applications of existing drugs.

Can muscle protein metabolism be specifically targeted by exercise training in COPD?

Patients with stable chronic obstructive pulmonary disease (COPD) frequently exhibit unintentional accentuated peripheral muscle loss and dysfunction. Skeletal muscle mass in these patients is a strong independent predictor of morbidity and mortality. Factors including protein anabolism/catabolism imbalance, hypoxia, physical inactivity, inflammation, and oxidative stress are involved in the initiation and progression of muscle wasting in these patients. Exercise training remains the most powerful intervention for reversing, in part, muscle wasting in COPD. Independently of the status of systemic or local muscle inflammation, rehabilitative exercise training induces up-regulation of key factors governing skeletal muscle hypertrophy and regeneration. However, COPD patients presenting similar degrees of lung dysfunction do not respond alike to a given rehabilitative exercise stimulus. In addition, a proportion of patients experience limited clinical outcomes, even when exercise training has been adequately performed. Consistently, several reports provide evidence that the muscles of COPD patients present training-induced myogenic activity limitation as exercise training induces a limited number of differentially expressed genes, which are mostly associated with protein degradation. This review summarises the nature of muscle adaptations induced by exercise training, promoted both by changes in the expression of contractile proteins and their function typically controlled by intracellular signalling and transcriptional responses. Rehabilitative exercise training in COPD patients stimulates skeletal muscle mechanosensitive signalling pathways for protein accretion and its regulation during muscle contraction. Exercise training also induces synthesis of myogenic proteins by which COPD skeletal muscle promotes hypertrophy leading to fusion of myogenic cells to the myofiber. Understanding of the biological mechanisms that regulate exercise training-induced muscle growth and regeneration is necessary for implementing therapeutic strategies specifically targeting myogenesis and hypertrophy in these patients.

Physiological responses to arm versus leg activity in patients with chronic obstructive pulmonary disease: a systematic review protocol

INTRODUCTION

Compared with healthy older adults, people with chronic obstructive pulmonary disease (COPD) have reduced capacity and increased symptoms during leg and arm activities. While the mechanisms underlying limitations and symptoms during leg activities have been investigated in detail, limitations and symptoms during arm activities are not well understood, and the potential differences between physiological responses of leg and arm activities have not been systematically synthesised. Determining physiological responses and symptoms of arm activities compared with physiological responses and symptoms of leg activities will help us understand the mechanisms behind the difficulties that people with COPD experience when performing physical activities, and determine how exercise training should be prescribed. Thus, the aim of this systematic review is to compare the physiological responses and symptoms during activities involving the arms relative to activities involving the legs in people diagnosed with COPD.

METHODS AND ANALYSES

This protocol is reported in line with the Preferred Reporting Items for Systematic Reviews and Meta-Analyses Protocols. Potentially relevant studies will be identified from CINAHL, EMBASE, PEDro, Cochrane Central Register of Controlled Trials and PubMed databases. The Population, Exposure, Comparator, Outcomes, and Study characteristics framework will be used to systematise the process of selecting and extracting data from relevant studies. Assessment of the methodological quality of the studies will be done by using the 14 most relevant components from the checklist by Downs and Black. The result will be presented with a narrative synthesis, and if appropriate with meta-analyses.

ETHICS AND DISSEMINATION

Ethical approval is not required as this study is a systematic review. It is our intention to submit the results of our review for peer-reviewed publication.

PROSPERO REGISTRATION NUMBER

CRD42017074476.

ERS International Congress 2017: a peek of outstanding abstracts from the clinical assembly

This review highlights a selection of abstracts from the 2017 ERS International Congress in Milan presented by the clinical assembly's groups of interventional pulmonology, general practice and primary care and rehabilitation and chronic care. Attention is brought to the increasing burden of disease of COPD and end-stage emphysema patients in China. The considerable efforts of Chinese pulmonary centers to conduct multicenter, randomized and controlled trials, investigating the possibilities of bronchoscopic lung volume reduction is underlined in the review. Furthermore, the key objectives of asthma management are stressed. We point out presentations emphasizing on achieving good control of daily symptoms and reducing the risk of asthma exacerbations. The findings of a randomized clinical trial evaluating the role of oxygen supplementation in rehabilitation therapy of COPD patients are analyzed. Additionally, another randomized clinical trial researching the influence of whole body vibration training (WBVT) in long-term (>1 year) lung transplant patients are discussed.

Changes in lower limb muscle function and muscle mass following exercise-based interventions in patients with chronic obstructive pulmonary disease: A review of the English-language literature

Chronic obstructive pulmonary disease (COPD) patients often experience lower limb muscle dysfunction and wasting. Exercise-based training has potential to improve muscle function and mass, but literature on this topic is extensive and heterogeneous including numerous interventions and outcome measures. This review uses a detailed systematic approach to investigate the effect of this wide range of exercise-based interventions on muscle function and mass. PUBMED and PEDro databases were searched. In all, 70 studies (n = 2504 COPD patients) that implemented an exercise-based intervention and reported muscle strength, endurance, or mass in clinically stable COPD patients were critically appraised. Aerobic and/or resistance training, high-intensity interval training, electrical or magnetic muscle stimulation, whole-body vibration, and water-based training were investigated. Muscle strength increased in 78%, muscle endurance in 92%, and muscle mass in 88% of the cases where that specific outcome was measured. Despite large heterogeneity in exercise-based interventions and outcome measures used, most exercise-based trials showed improvements in muscle strength, endurance, and mass in COPD patients. Which intervention(s) is (are) best for which subgroup of patients remains currently unknown. Furthermore, this literature review identifies gaps in the current knowledge and generates recommendations for future research to enhance our knowledge on exercise-based interventions in COPD patients.

Eccentric Ergometer Training Promotes Locomotor Muscle Strength but Not Mitochondrial Adaptation in Patients with Severe Chronic Obstructive Pulmonary Disease

Eccentric ergometer training (EET) is increasingly being proposed as a therapeutic strategy to improve skeletal muscle strength in various cardiorespiratory diseases, due to the principle that lengthening muscle actions lead to high force-generating capacity at low cardiopulmonary load. One clinical population that may particularly benefit from this strategy is chronic obstructive pulmonary disease (COPD), as ventilatory constraints and locomotor muscle dysfunction often limit efficacy of conventional exercise rehabilitation in patients with severe disease. While the feasibility of EET for COPD has been established, the nature and extent of adaptation within COPD muscle is unknown. The aim of this study was therefore to characterize the locomotor muscle adaptations to EET in patients with severe COPD, and compare them with adaptations gained through conventional concentric ergometer training (CET). Male patients were randomized to either EET (n = 8) or CET (n = 7) for 10 weeks and matched for heart rate intensity. EET patients trained on average at a workload that was three times that of CET, at a lower perception of leg fatigue and dyspnea. EET led to increases in isometric peak strength and relative thigh mass (p < 0.01) whereas CET had no such effect. However, EET did not result in fiber hypertrophy, as morphometric analysis of muscle biopsies showed no increase in mean fiber cross-sectional area (p = 0.82), with variability in the direction and magnitude of fiber-type responses (20% increase in Type 1, p = 0.18; 4% decrease in Type 2a, p = 0.37) compared to CET (26% increase in Type 1, p = 0.04; 15% increase in Type 2a, p = 0.09). EET had no impact on mitochondrial adaptation, as revealed by lack of change in markers of mitochondrial biogenesis, content and respiration, which contrasted to improvements (p < 0.05) within CET muscle. While future study is needed to more definitively determine the effects of EET on fiber hypertrophy and associated underlying molecular signaling pathways in COPD locomotor muscle, our findings promote the implementation of this strategy to improve muscle strength. Furthermore, contrasting mitochondrial adaptations suggest evaluation of a sequential paradigm of eccentric followed by concentric cycling as a means of augmenting the training response and attenuating skeletal muscle dysfunction in patients with advanced COPD.

Effect of pulmonary rehabilitation on tidal expiratory flow limitation at rest and during exercise in COPD patients

We hypothesized that severe COPD patients who present with the disadvantageous phenomenon of Expiratory Flow Limitation (EFL) may benefit as COPD patients without EFL do after implementation of a Pulmonary Rehabilitation (PR) program. Forty-two stable COPD patients were studied at rest and during exercise. EFL and dynamic hyperinflation (DH) were documented using the negative expiratory pressure (NEP) technique and inspiratory capacity (IC) maneuvers, respectively. Patient centered outcomes were evaluated by the Saint-George's Respiratory Questionnaire (SGRQ) and the mMRC dyspnea scale. Before PR, 16 patients presented with EFL at rest and/or during exercise. After PR, EFL was abolished in 15 out of those 16 EFL patients who exhibited a significant increase in IC values. These were mainly accomplished through a modification of the breathing pattern. In the 26 NFL patients no increase was noted in their IC or a modification of their breathing pattern. However, both NFL and EFL COPD patients improved exercise capacity and patients centered outcomes undergoing the same PR program.

Clinical management of chronic obstructive pulmonary disease patients with muscle dysfunction

Muscle dysfunction is frequently observed in chronic obstructive pulmonary disease (COPD) patients, contributing to their exercise limitation and a worsening prognosis. The main factor leading to limb muscle dysfunction is deconditioning, whereas respiratory muscle dysfunction is mostly the result of pulmonary hyperinflation. However, both limb and respiratory muscles are also influenced by other negative factors, including smoking, systemic inflammation, nutritional abnormalities, exacerbations and some drugs. Limb muscle weakness is generally diagnosed through voluntary isometric maneuvers such as handgrip or quadriceps muscle contraction (dynamometry); while respiratory muscle loss of strength is usually recognized through a decrease in maximal static pressures measured at the mouth. Both types of measurements have validated reference values. Respiratory muscle strength can also be evaluated determining esophageal, gastric and transdiaphragmatic maximal pressures although there is a lack of widely accepted reference equations. Non-volitional maneuvers, obtained through electrical or magnetic stimulation, can be employed in patients unable to cooperate. Muscle endurance can also be assessed, generally using repeated submaximal maneuvers until exhaustion, but no validated reference values are available yet. The treatment of muscle dysfunction is multidimensional and includes improvement in lifestyle habits (smoking abstinence, healthy diet and a good level of physical activity, preferably outside), nutritional measures (diet supplements and occasionally, anabolic drugs), and different modalities of general and muscle training.

Adaptations in limb muscle function following pulmonary rehabilitation in patients with COPD - a review

Even though chronic obstructive pulmonary disease (COPD) is primarily a disease of the respiratory system, limb muscle dysfunction characterized by muscle weakness, reduced muscle endurance and higher muscle fatigability, is a common secondary consequence and a major systemic manifestation of the disease. Muscle dysfunction is especially relevant in COPD because it is related to important clinical outcomes such as mortality, quality of life and exercise intolerance, independently of lung function impairment. Thus, improving muscle function is considered an important therapeutic goal in COPD management. Pulmonary rehabilitation (PR) is a multidisciplinary, evidence-based and comprehensive approach used to promote better self-management of the disease, minimize symptom burden, optimize functional status, and increase participation in activities of daily life. Exercise training, including cardiovascular and muscle exercises, is the cornerstone of PR and is considered the best available strategy to improve exercise tolerance and muscle function among patients with COPD. This paper addresses the various components of exercise training within PR used to improve limb muscle function in COPD, providing clinicians and health-care professionals with an overview and description of these various exercise modalities and of their effects on limb muscle function. Guidance and recommendations to help design optimal limb muscle training regimens for these patients are also presented.

Effect of endurance versus resistance training on quadriceps muscle dysfunction in COPD: a pilot study

Introduction

Exercise is an important countermeasure to limb muscle dysfunction in COPD. The two major training modalities in COPD rehabilitation, endurance training (ET) and resistance training (RT), may both be efficient in improving muscle strength, exercise capacity, and health-related quality of life, but the effects on quadriceps muscle characteristics have not been thoroughly described.

Methods

Thirty COPD patients (forced expiratory volume in 1 second: 56% of predicted, standard deviation [SD] 14) were randomized to 8 weeks of ET or RT. Vastus lateralis muscle biopsies were obtained before and after the training intervention to assess muscle morphology and metabolic and angiogenic factors. Symptom burden, exercise capacity (6-minute walking and cycle ergometer tests), and vascular function were also assessed.

Results

Both training modalities improved symptom burden and exercise capacity with no difference between the two groups. The mean (SD) proportion of glycolytic type IIa muscle fibers was reduced after ET (from 48% [SD 11] to 42% [SD 10], P<0.05), whereas there was no significant change in muscle fiber distribution with RT. There was no effect of either training modality on muscle capillarization, angiogenic factors, or vascular function. After ET the muscle protein content of phosphofructokinase was reduced (P<0.05) and the citrate synthase content tended increase (P=0.08) but no change was observed after RT.

Conclusion

Although both ET and RT improve symptoms and exercise capacity, ET induces a more oxidative quadriceps muscle phenotype, counteracting muscle dysfunction in COPD.

Changes in structural and metabolic muscle characteristics following exercise-based interventions in patients with COPD: a systematic review

Patients with COPD suffer from lower-limb muscle dysfunction characterized by lower muscle oxidative capacity and muscle mass. Exercise-based training is expected to attenuate lower-limb intramuscular characteristics, but a detailed systematic approach to review the available evidence has not been performed yet. PUBMED and PEDro databases were searched. Twenty-five studies that implemented an exercise-based training program (aerobic and/or resistance training, high intensity interval training, electrical or magnetic stimulation) and reported muscle biopsy data of patients with COPD were critically appraised. The coverage of results includes changes in muscle structure, muscle protein turnover regulation, mitochondrial enzyme activity, oxidative and nitrosative stress, and inflammation after exercise-based training interventions. Study design and training modalities varied among studies, which partly explains the observed heterogeneous response in muscle characteristics. Gaps in the current knowledge are identified and recommendations for future research are made to enhance our knowledge on exercise training effects in patients with COPD.

Muscle dysfunction in chronic obstructive pulmonary disease: update on causes and biological findings

Respiratory and/or limb muscle dysfunction, which are frequently observed in chronic obstructive pulmonary disease (COPD) patients, contribute to their disease prognosis irrespective of the lung function. Muscle dysfunction is caused by the interaction of local and systemic factors. The key deleterious etiologic factors are pulmonary hyperinflation for the respiratory muscles and deconditioning secondary to reduced physical activity for limb muscles. Nonetheless, cigarette smoke, systemic inflammation, nutritional abnormalities, exercise, exacerbations, anabolic insufficiency, drugs and comorbidities also seem to play a relevant role. All these factors modify the phenotype of the muscles, through the induction of several biological phenomena in patients with COPD. While respiratory muscles improve their aerobic phenotype (percentage of oxidative fibers, capillarization, mitochondrial density, enzyme activity in the aerobic pathways, etc.), limb muscles exhibit the opposite phenotype. In addition, both muscle groups show oxidative stress, signs of damage and epigenetic changes. However, fiber atrophy, increased number of inflammatory cells, altered regenerative capacity; signs of apoptosis and autophagy, and an imbalance between protein synthesis and breakdown are rather characteristic features of the limb muscles, mostly in patients with reduced body weight. Despite that significant progress has been achieved in the last decades, full elucidation of the specific roles of the target biological mechanisms involved in COPD muscle dysfunction is still required. Such an achievement will be crucial to adequately tackle with this relevant clinical problem of COPD patients in the near-future.

Non-ventilatory approaches to prevent postoperative pulmonary complications

This educational narrative review provides a summary of non-ventilatory strategies to prevent postoperative pulmonary complications (PPCs). It highlights patient- and procedure-related risk factors for PPCs that are non-modifiable, potentially modifiable, or well modifiable. Non-ventilatory strategies, mainly based on the modification of risk factors, play a key role in reducing PPCs. Non-modifiable risk factors, most importantly age, American Society of Anesthesiologists (ASA) class, and risk of the procedure, should be recognized and patients intensively screened for the potential to optimize other, potentially or well-modifiable, risk factors. Potentially modifiable risk factors, mainly comorbidities and the surgical approach, increase the risk of PPCs. Patient-related factors can be improved while procedure-related factors may be adapted in high-risk patients. Well-modifiable risk factors, mainly certain anesthesia techniques, for example, general anesthesia, intravenous opioids or liberal fluid management, and smoking or alcohol abuse, should be avoided as far as possible in order to prevent PPCs.

Guidelines for the evaluation and treatment of muscle dysfunction in patients with chronic obstructive pulmonary disease

In patients with chronic obstructive pulmonary disease (COPD), skeletal muscle dysfunction is a major comorbidity that negatively impacts their exercise capacity and quality of life. In the current guidelines, the most recent literature on the various aspects of COPD muscle dysfunction has been included. The Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) scale has been used to make evidence-based recommendations on the different features. Compared to a control population, one third of COPD patients exhibited a 25% decline in quadriceps muscle strength, even at early stages of their disease. Although both respiratory and limb muscles are altered, the latter are usually more severely affected. Numerous factors and biological mechanisms are involved in the etiology of COPD muscle dysfunction. Several tests are proposed in order to diagnose and evaluate the degree of muscle dysfunction of both respiratory and limb muscles (peripheral), as well as to identify the patients' exercise capacity (six-minute walking test and cycloergometry). Currently available therapeutic strategies including the different training modalities and pharmacological and nutritional support are also described.