Skeletal Muscle Dysfunction in Chronic Obstructive Pulmonary Disease: A Statement of the American Thoracic Society and European Respiratory Society

Effects of photobiomodulation as an adjunctive treatment in chronic obstructive pulmonary disease: a narrative review

Chronic obstructive pulmonary disease (COPD) is a disease characterized by chronic airway inflammation and remodeling and lung parenchymal inflammation and destruction, which result in many pulmonary and extrapulmonary manifestations. The anti-inflammatory effect of photobiomodulation (PBM) has been reported in previous studies. This review was conducted to evaluate the direct effect of PBM on lung inflammation in COPD. The other effects of PBM on modulation of peripheral and respiratory muscle metabolism and angiogenesis in lung tissues were also discussed. The databases of PubMed, Cochrane Library, and Google Scholar were searched to find the relevant studies. Keywords included PBM and related terms, COPD-related signs, and lung inflammation. A total of 12 articles were selected and reviewed in this study. Based on the present review, PBM is helpful in reducing lung inflammation through decreasing the inflammatory cytokines and chemokines at multiple levels and increasing anti-inflammatory cytokines. In addition, PBM also improves both peripheral and respiratory muscle metabolism and promote angiogenesis. This review demonstrated that PBM is a promising adjunctive treatment modality for COPD management which merits further validation.

Air Pollution Exposure as a Relevant Risk Factor for Chronic Obstructive Pulmonary Disease Exacerbations in Male and Female Patients

Chronic obstructive pulmonary disease (COPD) is a multifactorial lung inflammatory disease that affects 174 million people worldwide, with a recently reported increased incidence in female patients. Patients with COPD are especially vulnerable to the detrimental effects of environmental exposures, especially from air particulate and gaseous pollutants; exposure to air pollution severely influences COPD outcomes, resulting in acute exacerbations, hospitalisations, and death. Here, a literature review of the recent work addressing air pollution-induced acute exacerbations of COPD (AECOPD) was conducted in order to determine whether sex was considered as a biological variable in these studies, and whether air pollution exposure affected patients with COPD in a sex-specific manner. It was found that, while the majority of studies enrolled both male and female patients, only a few reported results were disaggregated by sex. Most studies had a higher enrolment of male patients, only four compared AECOPD outcomes between sexes, and only one study identified sex differences in AECOPD, with females displaying higher rates. Overall, this analysis of the literature confirmed that air pollution exposure is a trigger for AECOPD hospitalisations and revealed a significant gap in the knowledge of sex-specific effects of air pollutants on COPD outcomes, highlighting the need for more studies to consider sex as a biological variable.

Pulmonary Rehabilitation is Improved by In-Shoe Foot Orthosis Intervention

Some studies have found that patients with asthma have bilateral foot dorsal flexion limitations, contributing to impaired quality of life. The authors hypothesised that foot misalignments could also occur in patients with chronic obstructive pulmonary disease (COPD), and that foot orthoses could increase the motor benefits of their pulmonary rehabilitation (PR). Presented herein are the results from a nonrandomised controlled study in 40 patients with COPD. Twenty patients had foot misalignment (Group 1) and wore foot orthoses for a 1-month PR period. Their data were compared to those obtained in 20 other patients with COPD who had no foot misalignment and did not wear foot orthoses (Group 2). Bodily fatigue, 6-minute walk test (6MWT) distance, peak plantar flexion force (PFF), and oscillations of the centre of pressure (CoP) were measured. Measurements were performed prior to and following completion of PR (Groups 1 and 2), immediately after wearing the foot orthosis (Group 1), and after completion of PR plus foot orthoses (Group 1). In Group 2, PR increased the 6MWT distance, but did not increase PFF nor reduce CoP oscillations and fatigue scale. Wearing the foot orthosis for the first time significantly increased the 6MWT distance (+98+12 m). Following PR with foot orthoses (Group 1), a further increase in 6MWT distance occurred (+120+13 m), bodily fatigue was reduced, PFF increased, and CoP oscillations decreased. In patients with COPD and foot misalignment, foot orthoses enhanced the functional capacity and improved the postural control.

Elastic Tubing Resistance Training and Autonomic Modulation in Subjects with Chronic Obstructive Pulmonary Disease

This study addresses evidence concerning elastic tubing resistance training (ET) on autonomic modulation in patients with chronic obstructive pulmonary disease (COPD). Autonomic dysfunction is common in COPD and contributes to the development of arrhythmias and sudden death. Along with autonomic dysfunction, muscle dysfunction is related to functional limitations and prognosis of the disease. This study investigated the effects of ET on autonomic modulation, muscle strength, and walking distance in COPD. Subjects were divided into two groups, ET (n = 20; 66,5 ± 8,9 y; 25,5 ± 3,5 kg/m2; FEV1/FVC: 50,3 ± 11,0) and conventional training (n = 19; 66,0 ± 6,9; 27,1 ± 4,3; FEV1/FVC: 55,05 ± 9,56). Both groups undertook 24 sessions for 60 minutes, 3 times in a week. The significance level was p ≤ 0,05. Autonomic modulation was evaluated using heart rate variability in the time (rMSSD, ms) and frequency domain (HF, ms). Strength for upper and lower limbs was measured using dynamometry and walking distance was measured using a 6-minute walking test. There were no significant differences in the outcomes between groups. There was an increment to rMSSD [(16,7 ± 11,0 versus 20,8 ± 14,9) versus (14,2 ± 10,0 versus 17,4 ± 12,1)], HF [(141,9 ± 191,3 versus 234,9 ± 335,7) versus (94,1 ± 123,5 versus 177,6 ± 275,5)], shoulder abduction [(50,1 ± 19,6 versus 56,9 ± 20,4) versus (50,5 ± 19,0 versus 56,9 ± 19,3)], knee flexion [(101,9 ± 34,0 versus 116,8 ± 43,3) versus (98,6 ± 21,5 versus 115,1 ± 30,8)], and walking test [(433,0 ± 84,8 versus 468,9 ± 90,8) versus (397,4 ± 99,8 versus 426,3 ± 101,6)] after training for ET and conventional training, respectively. In conclusion, ET improves autonomic modulation in COPD with additional benefits for strength and cardiorespiratory capacity similar to conventional training.

Both pulmonary and extra-pulmonary factors predict the development of disability in chronic obstructive pulmonary disease

BACKGROUND

Although chronic obstructive pulmonary disease (COPD) is a major cause of disability worldwide, its determinants remain poorly defined.

OBJECTIVE

We hypothesized that both pulmonary and extra-pulmonary factors would predict prospective disablement across a hierarchy of activities in persons with COPD.

METHODS

Six hundred and nine participants were studied at baseline (T0) and 2.5 years later (T1). The Valued Life Activities (VLA) scale quantified disability (10-point scale: 0 = no difficulty and 10 = unable to perform), defining disability as any activity newly rated 'unable to perform' at T1. Predictors included pulmonary (lung function, 6-minute walk distance and COPD severity score) and extra-pulmonary (quadriceps strength and lower extremity function) factors. Prospective disability risk was tested by separate logistic regression models for each predictor (baseline value and its change, T0-T1; odds ratios were scaled at 1 standard deviation per factor. Incident disability across a hierarchy of obligatory, committed and discretionary VLA subscales was compared.

RESULTS

Subjects manifested a 40% or greater increased odds of developing disability for each predictor (baseline and change over time). Disability in discretionary activities developed at a rate 2.2-times higher than observed in committed activities, which was in turn 2.5-times higher than the rate observed in obligatory activities (p < 0.05 for each level).

CONCLUSIONS

Disability is common in COPD. Both pulmonary and extra-pulmonary factors are important in predicting its development.

[Diaphragm and skeletal muscle dysfunction in COPD]

INTRODUCTION

Chronic obstructive pulmonary disease (COPD) is often accompanied by skeletal muscle alterations, resulting in enhanced morbidity and mortality.

STATE OF THE ART

Many studies have highlighted important structural and biochemical modifications in limb and respiratory muscles in COPD. Reviewing the similarities and differences between the two most studied muscles in COPD, the quadriceps and the diaphragm, may provide important clues about the mechanisms dictating muscle changes that occur in this disease.

PERSPECTIVES

Though these two muscle groups share a common systemic environment, discrepancies are observed in their respective alterations. These phenotypic differences suggest that, in addition to systemic factors, the local microenvironment must participate in the reorganization seen in these two muscles in COPD.

CONCLUSIONS

The current review introduces the alterations observed in the quadriceps and diaphragm in the context of COPD and suggests possible signaling pathways involved in the development of muscle dysfunction.

Development and characterization of a rat model of chronic obstructive pulmonary disease (COPD) induced by sidestream cigarette smoke

Cigarette smoke (CS) induced chronic obstructive pulmonary disease (COPD) has been emerging as a great health problem in China. However, lack of appropriate animal model slows down the progress in understanding pathogenesis of the disease. The aim of current study is to establish and evaluate a more adequate rat model of COPD. Study was performed with rats exposed to sidestream cigarette smoke 2h/d and 7d/wk for 2, 4, 6, 8, 10, 12, 24 and 36 wk in a CS chamber (carbon monoxide concentration was 231+/-11ppm). The lung function was determined by using the forced oscillation technique. Pathologic changes were determined by using histological analyses and mucin measurement. Following 36-wk exposure, airway resistance (Raw) and respiratory system elastance (Ers) in CS group rats was elevated by 28.5% and 37.5%, respectively. Up to 4.1-, 2.3- and 1.4-fold increase in the number of neutrophils, macrophages and lymphocytes was observed in the BALF of CS rats. Using quantitative histomorphology techniques, it was found that mean linear intercept (MLI) and mean alveolar airspace (MAA) of CS rats increased by 44.8% and 43.7%, respectively, indicating the occurrence of emphysema. The characteristics of chronic bronchitis including hyperplasia of bronchial epithelial cells, hypersecretion of mucus and development of peribronchial fibrosis were also found in rat lungs. CS group rats showed 43% body weight gain reduction. To conclude, a more adequate sidestream cigarette smoke rat COPD model was established, which will be beneficial for understanding the pathogenesis of the disease and for evaluation of drug effectiveness.

Falls in patients with chronic obstructive pulmonary disease: a call for further research

Chronic obstructive pulmonary disease (COPD) is a respiratory disease that results in airflow limitation and respiratory distress. The effects of COPD, however, are not exclusively limited to respiratory function and people with COPD face many non-respiratory manifestations that affect both function and mobility. Deficits in function and mobility have been associated with an increased risk for falling in older adults. The purpose of this study was to provide a theoretical framework to identify risks factors for falls in people with COPD. We have analyzed the literature to identify possible relationships between pathophysiological changes observed in COPD and common risk factors for falls. Well-established fall risk factors in people with COPD include lower limb muscle weakness and impaired activities of daily living. Other intrinsic risk factors such as gait and balance deficits, nutritional depletion, malnutrition, depression, cognitive impairments and medications are possible risk factors that need to be confirmed with more studies. There is no evidence that visual deficits are common in COPD. The role that precipitating factors such as syncope and postural hypotension may have on fall risk is unclear. Exacerbations and dyspnea do not have a precipitating effect on fall risk but they contribute to the progressive physical deterioration that may theoretically increase the risk for falls. While these results suggest that people with COPD might have an increased susceptibility to fall compared to their healthy peers, further research is needed to determine the prevalence of falls and specific risk factors for falls in people living with COPD.

Vitamin D receptor genotypes influence quadriceps strength in chronic obstructive pulmonary disease

BACKGROUND

Quadriceps weakness is an important complication of chronic obstructive pulmonary disease (COPD) and is associated with impaired exercise capacity and greater mortality. Its etiology is multifactorial, and evidence is growing that it is partly determined by genetic susceptibility.

OBJECTIVE

Using an established cohort, we tested whether quadriceps weakness in patients with COPD is influenced by common variations in the gene for the vitamin D receptor.

DESIGN

Vitamin D receptor FokI and BsmI genotypes and the (I/D) angiotensin-converting enzyme (ACE) and bradykinin receptor (+9/-9) genotypes were identified in 107 patients with stable COPD [x +/- SD forced expiratory volume in 1 s (FEV(1)): 34.5 +/- 16.5] and 104 healthy, age-matched control subjects. Quadriceps maximum voluntary contraction force and fat-free mass assessed by bioelectrical impedance analysis were measured.

RESULTS

After adjustment for covariables, both patients and control subjects who were homozygous for the C allele of the FokI polymorphism had less quadriceps strength than did those with > or =1 T allele [41.0 +/- 11.8 compared with 46.0 +/- 13.2 kg (P = 0.01) and 32.5 +/- 11.2 compared with 36.2 +/- 13.1 kg (P = 0.005), respectively]. The b allele of the BsmI polymorphism was associated with greater quadriceps strength in patients-37.0 +/- 13.3, 33.8 +/- 11.6, and 33.8 +/- 11.6 kg for bb, bB, and BB, respectively (P = 0.0005)-but had no effect in healthy control subjects. The effect of BsmI on quadriceps strength was least apparent in patients with the ACE II genotype (P = 0.003).

CONCLUSIONS

The FokI common variants in the VDR gene are associated with skeletal muscle strength in both patients and control subjects, whereas the BsmI polymorphism is associated with strength only in patients.

Strength and endurance of the respiratory and handgrip muscles after the use of flunisolide in normal subjects

OBJECTIVE

To evaluate the effects of the inhaled flunisolide upon the strength and endurance of the respiratory and peripheral muscles of normal subjects.

DESIGN

A randomized, double blind and placebo-controlled study.

SETTING

A university-affiliated teaching hospital.

PARTICIPANTS

Thirteen normal volunteers selected from a graduation course.

INTERVENTION

Subjects were randomly allocated to receive a placebo or corticosteroid (flunisolide) to be inhaled twice a day for 4 weeks. After 2 weeks of a washout period, subjects who were receiving the placebo, received flunisolide and vise versa for another 4-week period.

MEASUREMENTS AND RESULTS

Spirometry was used to define the volunteers as being normal in terms of pulmonary function. During the study, subjects performed tests of respiratory muscle function (strength and endurance), measurements of handgrip strength and endurance and anthropometric measurements. Muscle strength was measured each week while muscle endurance was measured every 2 weeks. There was no significant difference in the maximal inspiratory and expiratory pressure and handgrip strength during weeks 1-4 when the subjects used either flunisolide or placebo. However, we observed an increase in the endurance time of the respiratory and handgrip muscles in the 4th week of both flunisolide and placebo use, what may be considered due to a learning effect.

CONCLUSION

Inhalation of flunisolide by normal subjects for 1 month does not cause any acute or clinically perceived effect in the peripheral or respiratory muscles.

A prospective study of decline in fat free mass and skeletal muscle strength in chronic obstructive pulmonary disease

BACKGROUND

Skeletal muscle depletion is an important complication of chronic obstructive pulmonary disease (COPD) but little prospective data exists about the rate at which it occurs and the factors that promote its development. We therefore prospectively investigated the impact of disease severity, exacerbation frequency and treatment with corticosteroids on change in body composition and maximum isometric quadriceps strength (QMVC) over one year.

METHODS

64 patients with stable COPD (FEV1 mean (SD) 35.8(18.4) %predicted) were recruited from clinic and studied on two occasions one year apart. Fat free mass was determined using bioelectrical impedance analysis and a disease specific regression equation.

RESULTS

QMVC fell from 34.8(1.5) kg to 33.3(1.5) kg (p = 0.04). The decline in quadriceps strength was greatest in those with the highest strength at baseline (R -0.28 p = 0.02) and was not correlated with lung function, exacerbation frequency or steroid treatment. Decline in fat free mass was similarly higher in those with largest FFM at baseline (R = -0.31 p = 0.01) but was more strongly correlated with greater gas trapping (R = -0.4 p = 0.001). Patients with frequent exacerbations (>1 per year) (n = 36) experienced a greater decline in fat free mass compared to infrequent exacerbators (n = 28) -1.3(3.7)kg vs. +1.2(3.1)kg (p = 0.005), as did patients on maintenance oral steroids (n = 8) -2.8(3.3) kg vs. +0.2(3.5) kg (p = 0.024) whereas in those who stopped smoking (n = 7) fat free mass increased; +2.7(3.1) kg vs. -0.51(3.5) kg (p = 0.026).

CONCLUSION

Decline in fat free mass in COPD is associated with worse lung function, continued cigarette consumption and frequent exacerbations. Factors predicting progression of quadriceps weakness could not be identified from the present cohort.

Skeletal muscle structure and function in response to electrical stimulation in moderately impaired COPD patients

STUDY OBJECTIVE

To determine the structural and functional consequences of high-frequency neuromuscular electrical stimulation (hf-NMES) in a group of moderately impaired outpatients with chronic obstructive pulmonary disease (COPD).

DESIGN

A prospective, cross-over randomized trial.

SETTING

An university-based, tertiary center.

PATIENTS AND MATERIALS

Seventeen patients (FEV(1)=49.6+/-13.4% predicted, Medical Research Council dyspnoea grades II-III) underwent 6-weeks hf-NMES (50Hz) and sham stimulation of the quadriceps femoris in a randomized, cross-over design. Knee strength was measured by isokinetic dynamometry (peak torque) and leg muscle mass (LMM) by DEXA; in addition, median cross-sectional area (CSA) of type I and II fibres and capillary-fibre ratio were evaluated in the vastus lateralis. The 6-min walking distance (6MWD) was also determined.

RESULTS

At baseline, patients presented with well-preserved functional capacity, muscle strength and mass: there was a significant relationship between strength and type II CSA (P<0.05). NMES was not associated with significant changes in peak torque, LMM or 6MWD as compared to sham (P>0.05). At micro-structural level, however, electrical stimulation increased type II, but decreased type I, CSA; no change, however, was found in the relative fibre distribution or capillary:fibre ratio (P<0.05). There was no significant association between individual changes in structure and function with training (P>0.05). Post-NMES increase in type II CSA was inversely related to baseline mass and strength (P<0.05).

CONCLUSION

NMES may promote a modest degree of type II muscle fibre hypertrophy in COPD patients with well-preserved functional status. These micro-structural changes, however, were not translated into increased volitional strength in this sub-population.

Peripheral muscle composition and health status in patients with COPD

STUDY OBJECTIVE

The present study evaluated the relationship between health status (HS) and peripheral muscle histochemical characteristics in chronic obstructive pulmonary disease (COPD), and identified selected independent respiratory and extrapulmonary variables that predicted the HS of these patients.

DESIGN

Cross-sectional study.

SETTING

Outpatient respiratory clinic of a university hospital.

PATIENTS AND METHODS

We studied 29 patients (63+/-10 yrs) with a forced expiratory volume in 1s (FEV1) of 39+/-12%. All patients underwent vastus lateralis muscle biopsies for histochemical analysis. They also had spirometry, arterial blood gas analysis, body mass index (BMI), dyspnea determined with the MMRC scale and responded to the St. George's Respiratory Questionnaire (SGRQ) for HS assessment.

RESULTS

SGRQ total score correlated with fiber type distribution. A stepwise multiple regression identified three independent predictors of SGRQ total score: type I fiber proportion, BMI, and FEV1; r = 0.78 and r2 = 0.61.

CONCLUSIONS

These results indicate that impaired HS in COPD is related to the peripheral muscle changes characterized by less type I fibers proportion. The findings argue in favor of an important contribution of the systemic consequences on the HS in COPD independently from the airflow limitation severity, and help to explain the observation of the poor correlation between the degree of airflow limitation and SGRQ total score.

+9/+9 Homozygosity of the bradykinin receptor gene polymorphism is associated with reduced fat-free mass in chronic obstructive pulmonary disease

BACKGROUND

The etiology of muscle wasting in chronic obstructive pulmonary disease (COPD) is incompletely understood. We previously showed that the D rather than the I polymorphic variant of the angiotensin-converting enzyme (ACE) gene is associated with preserved quadriceps strength in COPD. If the ACE D allele influences skeletal muscle through increased ACE-related kinin degradation [and reduced activity at the bradykinin type 2 receptor (BK(2)R)], we might expect a similar association with the +9 BK(2)R genotype in this population as well.

OBJECTIVE

The objective was to test the hypothesis that the BK(2)R gene polymorphism is a determinant of fat-free mass and quadriceps strength in patients with COPD.

DESIGN

In a cross-sectional design we determined BK(2)R genotype, fat-free mass, and quadriceps strength in 110 COPD patients with a mean (+/-SD) predicted forced expiratory volume in 1 s of 34.3 +/- 16.4% and in 104 healthy age-matched control subjects.

RESULTS

The mean (+/-SD) fat-free mass index (in kg/m(2)) was significantly lower in 37 patients homozygous for the +9 allele than in carriers of the -9 allele (15.7 +/- 1.8 compared with 16.7 +/- 2.3; P = 0.038); the same pattern was true for quadriceps maximal voluntary force (30.8 +/- 10.4 and 36.4 +/- 12.8 kg; P = 0.02), respectively. No significant effect of BK(2)R genotype on inspiratory muscle strength or on any variable in control subjects was observed. There was no interaction between the effect of the BK(2)R and ACE genotypes on quadriceps strength.

CONCLUSIONS

The genotype associated with reduced BK(2)R expression is associated with reduced fat-free mass and quadriceps strength in COPD. However, alterations in the activity at the BK(2)R do not seem to account for the previously identified association of quadriceps strength with ACE genotype.

Diminution de la fonction musculaire dynamique dans la BPCO : étude préliminaire

BACKGROUND

The aim of the study was to investigate dynamic muscle function during all-out exercise in patients with chronic obstructive pulmonary disease (COPD) and to observe the relationship between body composition and skeletal muscle function.

MATERIAL AND METHODS

Eight patients (FEV1: 53.0 +/- 9.3%) performed three tests i) three maximal sprints on a specialised cycle ergometer to assess individual Velocity-Power relationship, and measure of maximal anaerobic power (Pmax), optimal velocity (Vopt), ii) assessment of whole-body and subregional fat-free mass (FFM) by dual-energy X-ray absorptiometry, iii) determination of maximal oxygen consumption.

RESULTS

Maximal anaerobic power and corresponding optimal velocity were 3.9 +/- 1.6 W x kg(-1) et 85.4 +/- 17.0 rpm, respectively. COPD showed a 30% decrease of Pmax, compared to healthy older subjects (5.6 +/- 1.1 W x kg(-1)). No such difference was observed with Vopt (85.4 +/- 13.0 rpm vs 86.8 +/- 9.5 rpm). Pmax and Vopt were highly significantly correlated with lower extremities FFM, but not with airflow obstruction parameters.

CONCLUSION

Our results showed that skeletal muscle function parameters such as Pmax and Vopt could characterise peripheral muscle weakness of COPD.

Interval exercise versus continuous exercise in patients with moderate to severe chronic obstructive pulmonary disease--study protocol for a randomised controlled trial [ISRCTN11611768]

BACKGROUND

Physical exercise has become a cornerstone of management of chronic obstructive pulmonary disease (COPD) because it leads to clinically relevant improvements of exercise capacity and health-related quality of life (HRQL). Despite the scarcity of randomised trials directly comparing exercise protocols, current guidelines recommend high intensity continuous exercise for lower extremities as the probably most effective exercise modality. However, for patients admitted to inpatient respiratory rehabilitation programmes, it is often difficult to initiate such an exercise programme because they are severely limited by dyspnoea and leg fatigue and therefore unable to perform continuous exercise at higher intensities and for periods longer than 30 minutes. Interval exercise may be an attractive alternative for these COPD patients because it allows high intensity exercise with recovery periods. The aim of this study is to assess if interval exercise compared to high intensity continuous exercise is not of inferior effectiveness in terms of HRQL and exercise capacity improvements but associated with better exercise tolerance in patients with moderate to severe COPD at the beginning of a respiratory rehabilitation.

METHODS/DESIGN

We will assign patients with moderately severe to severe COPD to either continuous exercise or interval exercise using a stratified randomisation. Patients will follow 12-15 exercise sessions during a comprehensive inpatient respiratory rehabilitation. Primary end point for effectiveness is HRQL as measured by the Chronic Respiratory Questionnaire (CRQ) two weeks after the end of rehabilitation and secondary endpoints include additional clinical outcomes such as functional exercise capacity, other HRQL measures, patients' experience of physical exercise as well as physiological measures of the effects of physical exercise such as cardiopulmonary exercise testing. Including expected drop-outs, we will need 52 patients per group to show differences corresponding to the minimal clinically important difference of the CRQ. Outcome assessors and investigators involved in data analysis will be blinded to group assignment until analyses have been carried out.

DISCUSSION

Clinicians and the scientific community need evidence on the benefits and tolerance of exercise protocols available in clinical practice. The proposed trial will provide important and needed data on interval and continuous exercise for decision making in clinical practice.

Does Oxidative Stress Alter Quadriceps Endurance in Chronic Obstructive Pulmonary Disease?

The role of exercise-induced oxidative stress in the reduced quadriceps endurance of chronic obstructive pulmonary disease (COPD) patients has never been shown. We conducted a randomized, double-blind, and crossover study in which nine severe patients performed localized dynamic quadriceps endurance tests at 40% of maximal strength after oral treatment with the antioxidant, N-acetylcysteine (NAC), and placebo. Venous blood was sampled before, immediately after exercise, and 6 hours later. Endurance time improved by 25% after NAC treatment compared with placebo (p < 0.05). Superoxide anion (oxidant) release by stimulated phagocytes decreased after treatment (p < 0.05). No change in the antioxidant system was observed. Lipid peroxidation, an index of oxidative stress, was significantly increased 6 hours after exercise in the placebo condition (p < 0.05) but not after treatment. Advanced oxidized protein products, another index of oxidative stress, were also increased 6 hours after exercise by 139 +/- 27% in the placebo condition but only by 54 +/- 19% after treatment (p < 0.05). This study shows that NAC treatment in COPD reduced basal disturbance in the prooxidant system, improved endurance time, and prevented exercise-induced oxidative stress. Oxidative stress thus seems to be implicated in the reduced quadriceps endurance of patients with COPD.

Le réentraînement à l’effort des BPCO : bases physiologiques et résultats

INTRODUCTION

In the last decade pulmonary rehabilitation has become a well accepted treatment for patients with chronic obstructive pulmonary disease (COPD) suffering from persistent dyspnea and fatigue, despite appropriate medical treatment.

STATE OF ART

Patients with COPD frequently have muscular dysfunction that can be corrected by appropriate exercise training programmes. Muscle function as measured by strength and endurance tests exercise capacity and also the health status and quality of life are improved by exercise and endurance training. However, integration of exercise training in a multidisciplinary management programme is necessary to take account of all aspects of the illness.

PERSPECTIVES

Methods of exercise training need to be adapted for patients with severe COPD who are unable to undertake endurance training and for patients who obtain little benefit.

CONCLUSIONS

Pulmonary rehabilitation, thanks to its multidisciplinary nature, seems to be an effective modality of management for patients with COPD. However, the improvements in physical ability, quality of life and general health require an exercise training programme that is adapted for the individual patient.

Exercise training during rehabilitation of patients with COPD: a current perspective

Patients with chronic obstructive pulmonary disease (COPD) suffer frequently from physiologic and psychological impairments, such as dyspnea, peripheral muscle weakness, exercise intolerance, decreased health-related quality of life (HRQOL) and emotional distress. Rehabilitation programmes have shown to result in significant changes in perceived dyspnea and fatigue, utilisation of healthcare resources, exercise performance and HRQOL. Exercise training, which consists of whole-body exercise training and local resistance training, is the cornerstone of these programmes. Regrettably, the positive effects of respiratory rehabilitation deteriorate over time, especially after short programmes. Hence, attention should be given to the aftercare of these patients to prevent them to revert again to a sedentary lifestyle. On empirical basis three possibilities seem to be clinically feasible: (1) continuous outpatient exercise training; (2) exercise training in a home-based or community-based setting; or (3) exercise training sessions in a group of asthma and COPD patients.

Management of stable COPD

Chronic obstructive pulmonary disease (COPD) is a systemic disease with major impact worldwide. In the treatment of COPD a holistic approach should be taken. In order to reach this, an individual treatment plan should be made which includes at least elements of smoking cessation, optimisation of pulmonary status by pharmacotherapy and exercise embedded in a new lifestyle. Furthermore, more research on nutritional and metabolic intervention strategies for COPD patients is needed. With the availability of all these treatment options, a nihilistic attitude toward the patient with COPD is no longer justified.

Efeitos de programa de exercícios físicos direcionado ao aumento da mobilidade torácica em pacientes portadores de doença pulmonar obstrutiva crônica

INTRODUÇÃO: A doença pulmonar obstrutiva crônica acarreta prejuízos na mecânica pulmonar e musculatura periférica. O treinamento físico dos pacientes com doença pulmonar obstrutiva crônica é geralmente voltado à melhora das condições aeróbias e são raros os programas que abordam especificamente as alterações da caixa e musculatura torácicas. OBJETIVO: Avaliar o efeito de um programa de exercícios físicos direcionados ao aumento da mobilidade da caixa torácica sobre a capacidade funcional e psicossocial de pacientes portadores de doença pulmonar obstrutiva crônica moderada e grave. MÉTODO: Foram estudados 30 pacientes portadores de doença pulmonar obstrutiva crônica moderada e grave, divididos aleatoriamente em dois grupos: controle (GC) e tratado (GT). O GC foi submetido a um programa de educação e o GT foi submetido ao mesmo programa educacional e a um programa de exercícios físicos objetivando o aumento da mobilidade torácica. Os efeitos dos programas foram avaliados pela espirometria, mobilidade torácica, qualidade de vida, níveis de ansiedade e depressão e teste da caminhada de seis minutos (TC6). RESULTADOS: Após dois meses de treinamento, somente o GT apresentou aumento na expansibilidade torácica (de 4,20 ± 0,58cm para 5,27 ± 0,58cm; p = 0,05) e no TC6 (de 469,73 ± 31,99m para 500,60 ± 27,38m; p = 0,01). Foi observado também que o GT apresentou melhora na qualidade de vida avaliada pelo St. George's Respiratory Questionnaire (SGRQ) e Chronic Respiratory Questionnaire (CRQ), bem como nos níveis de depressão após dois meses de tratamento. Não houve melhora da função pulmonar em nenhum dos dois grupos estudados. CONCLUSÃO: Exercícios direcionados ao aumento da mobilidade da caixa torácica melhoram a expansibilidade torácica, a qualidade de vida e a capacidade submáxima de exercício, bem como reduzem a dispnéia e os níveis de depressão nos pacientes portadores de doença pulmonar obstrutiva crônica.

Symptoms and quadriceps fatigability after walking and cycling in chronic obstructive pulmonary disease

Patients with chronic obstructive pulmonary disease (COPD) may stop cycling due to leg effort rather than breathlessness. However, cycling is not relevant to many patients, although walking may be more familiar. A total of 84 patients with COPD were asked to name the predominant symptom limiting incremental shuttle walking, endurance shuttle walking, incremental cycle ergometry, and endurance cycle ergometry, performed to exhaustion on four separate days. Furthermore, quadriceps fatigability was evaluated in 12 patients by measuring unpotentiated and potentiated twitch quadriceps tensions before and 30 minutes after incremental walking and cycling. Breathlessness alone was a more commonly cited limiting symptom after incremental walking compared with incremental cycling (81 vs. 34%; p < 0.001) and after endurance walking compared with endurance cycling (75 vs. 29%; p < 0.001). In addition, there was no significant change in mean pre- and postwalking twitch quadriceps tensions. However, cycling produced a significant reduction (unpotentiated 7.42 +/- 2.22 vs. 6.48 +/- 2.09 kg [p < 0.001]; potentiated 10.19 +/- 3.99 vs. 8.45 +/- 3.18 kg [p < 0.001]). Pre- to postexercise changes were significantly greater during cycling compared with walking (unpotentiated p = 0.01; potentiated p = 0.003). Leg effort is an infrequent symptom after walking in COPD, and low frequency fatigue of the quadriceps is an infrequent feature of incremental walking.

ROS in the local and systemic pathogenesis of COPD

An imbalance between oxidants and antioxidants is proposed in the pathogenesis of COPD. Potential alterations responsible for an imbalance in oxidant production and intra- and extracellular antioxidant defense systems are discussed with respect to COPD-related changes in the pulmonary compartment. In line with the current view of COPD as a disease with multiple systemic consequences, there is increasing evidence that imbalances in the redox milieu extend beyond the diseased lung in COPD patients. Skeletal muscle dysfunction is often observed in COPD and may result from imbalances in the redox environment of skeletal muscle. Potential triggers of oxidative stress in the muscle compartment include inflammation and hypoxia, and local sources of reactive oxygen and nitrogen species are discussed, as well the mechanisms by which skeletal muscle trophical state, contractility and fatigability may be affected by oxidative stress, resulting in skeletal muscle dysfunction.

Dual morphometrical changes of the deltoid muscle in patients with COPD

The present study was specifically aimed at evaluating if the structure of the deltoid muscles is modified in patients with chronic obstructive pulmonary disease (COPD). Twenty-eight male volunteers (61+/-13 yr) were assigned, according to pulmonary function, to either the COPD (n=14, FEV(1)=22-74%pred) or control group (n=14, FEV(1)=83-121%pred). Biopsies from non-dominant deltoid muscle were obtained and processed for morphometric analysis of the fibre types. Both type I and type II muscle fibres were distributed in the typical mosaic pattern. The mean value of the fibre size was within the normal range. However, three differentiated modes were observed in the deltoid from COPD patients: a central mode of normal sized fibres, a mode of atrophic fibres and a mode of hypertrophic fibres. This observation was evident even within single fascicles and especially prevalent in the most severe COPD patients. We conclude that factors with opposite effect (promotion of either atrophy or hypertrophy) exert relevant roles in the histomorphometrical characteristics of the deltoid muscles in COPD patients.

Respiratory and limb muscle weakness induced by tumor necrosis factor-alpha: involvement of muscle myofilaments

The respiratory and limb skeletal muscles become weakened in sepsis, congestive heart failure, and other inflammatory diseases. A potential mediator of muscle weakness is tumor necrosis factor (TNF)-alpha, a cytokine that can stimulate muscle wasting and also can induce contractile dysfunction without overt catabolism. This study addressed the latter process. Murine diaphragm and limb muscle (flexor digitorum brevis [FDB]) preparations were used to determine the relative sensitivities of these muscles to TNF-alpha. Intact muscle fibers were isolated from FDB and microinjected with indo-1 to measure changes in sarcoplasmic calcium regulation. We found that TNF-alpha depressed tetanic force of the diaphragm and FDB to comparable degrees across a range of stimulus frequencies. In isolated muscle fibers, TNF-alpha decreased tetanic force without altering tetanic calcium transients or resting calcium levels. We conclude that (1) TNF-alpha compromises contractile function of diaphragm and limb muscle similarly, and (2) TNF-alpha decreases force by blunting the response of muscle myofilaments to calcium activation.