[Comorbidities in COPD: a new challenge in clinical practice]

Today it is a recognised fact that chronic obstructive pulmonary disease (COPD) is a real systemic disease that is respiratory-based. Recently, the focus has been on the importance of the comorbidities that are associated with COPD, such as all the cardiovascular diseases, lung cancer, diabetes, metabolic syndrome, peripheral muscular dysfunction, depression, anxiety, osteoporosis and anaemia, etc. These comorbidities constitute a new medical and therapeutic challenge with regard to COPD; their high frequency and considerable impact on the quality of life and the prognosis for survival of the patients make them a key element. The aims of this focus are to present the spectrum and prevalence of comorbidities in COPD, to obtain an objective view as to why and how these comorbidities should be systematically assessed and treated in patients, and subsequently to discuss the impact of this new data in clinical practice and in research. This recent data is another positive step in understanding the disease, optimising the diagnosis, and assessing and caring for COPD patients.

Skeletal muscle effects of electrostimulation after COPD exacerbation: a pilot study

Muscle dysfunction is a major problem in chronic obstructive pulmonary disease (COPD), particularly after exacerbations. We thus asked whether neuromuscular electrostimulation (NMES) might be directly useful following an acute exacerbation and if such a therapy decreases muscular oxidative stress and/or alters muscle fibre distribution. A pilot randomised controlled study of NMES lasting 6 weeks was carried out in 15 in-patients (n=9 NMES; n=6 sham) following a COPD exacerbation. Stimulation was delivered to the quadriceps and hamstring muscles (35 Hz). Primary outcomes were quadriceps force and muscle oxidative stress. At the end of the study, quadriceps force improvement was statistically different between groups (p=0.02), with a significant increase only in the NMES group (median (interquartile range) 10 (4.7-11.5) kg; p=0.01). Changes in the 6-min walking distance were statistically different between groups (p=0.008), with a significant increase in the NMES group (165 (125-203) m; p=0.003). NMES did not lead to higher muscle oxidative stress, as indicated by the decrease in total protein carbonylation (p=0.02) and myosin heavy chain carbonylation (p=0.01) levels. Finally, we observed a significant increase in type I fibre proportion in the NMES group. Our study shows that following COPD exacerbation, NMES is effective in counteracting muscle dysfunction and decreases muscle oxidative stress.

[Oxygen therapy by a portable concentrator with a demand valve: a randomised controlled study of its effectiveness in patients with COPD]

INTRODUCTION

There is doubt concerning the clinical effectiveness of portable oxygen concentrators with a control valve (PCDV) and their appreciation by patients. Objectives. To compare the effectiveness and appreciation of oxygen therapy by PCDV and liquid oxygen by continuous f low (O(2)Liq).

METHODS

Nineteen patients with COPD were randomised to receive PCDV or O(2)Liq at rest and during a 6 minute walk test (6MWT). For each mechanism they assessed, by visual analogue scales, the convenience and portability, the noise, and the discomfort of the nasal oxygen delivery.

RESULTS

The 6MW distance was 315 ± 120 m with PCDV and 325 ± 114 m with O(2)Liq (P>0.05). Dyspnoea and the desaturation induced by the 6MWT were identical with both systems (P>0.05). The time spent with a SaO(2)<90 % was 289 ± 69 s with PCDV and 242 ± 130 s with O(2)Liq (P=0.08). PCDV was noisier than O(2)Liq (P<0.05); there was no difference in convenience and portability or in nasal discomfort.

CONCLUSION

The PCDV model that we tested was equally effective to O(2)Liq. However, the prescription of this type of system is a matter of personal choice.

Comparison of total antioxidant capacity of salivary, capillary and venous samplings: interest of the salivary total antioxidant capacity on triathletes during training season

AIM

Total antioxidant capacity (TAC) is an essential parameter to watch over defense system of athletes exposed to an oxidant stress during intensive periods of training. To control this parameter throughout the training period, repetitive biological samples are required. The TAC is usually investigated in venous blood which needs invasive withdrawings. Thus, we proposed to find alternatives to venous blood analysis by venepuncture, which is invasive, stressful and not allow a regular follow-up on athletes during annual training season.

METHODS

We measured capillary and salivary TAC in 65 physically active subjects at rest and compared them to the venous TAC. We followed the evolution of venous and salivary TAC in 7 triathletes throughout an annual training period (March and June) corresponding to two different types of training.

RESULTS

There was a good correlation between plasma venous and capillary TAC values (r=0.77; P<0.0001), but salivary TAC were significantly lower than the plasma ones and did not correlate. Venous and saliva TAC of triathletes were significantly higher in March compared to June. The variations of plasma and salivary TAC between the two periods of training were correlated (r=0.96; P<0.01).

CONCLUSION

The capillary sampling can replace the venous one for TAC evaluation in routine assays for the follow-up of athletes. Even if saliva TAC did not reflect plasma TAC, it could be used in the follow-up of athletes since a strong correlation is found between the variation of saliva and plasma TAC during the training season.

From muscle disuse to myopathy in COPD: potential contribution of oxidative stress

Evidence has been accumulating that chronic inactivity leading to muscle disuse is unlikely to be the only explanation for the peripheral muscle dysfunction of chronic obstructive pulmonary disease (COPD) patients. Although a new concept of myopathy was recently proposed, the question of disuse and/or a form of myopathy is still being debated. This review proposes definitions for the terms used in this debate, discusses the relevant studies and concludes that the evidence points to a myopathy associated with muscle disuse in COPD. COPD myopathy implies pharmacological and/or pathophysiological mechanisms that need to be identified in order to optimally orient therapeutic strategies. The literature indicates that corticosteroids, inflammation, hypoxaemia and oxidative stress are among the factors contributing to COPD muscle dysfunction, but their relative contributions have not been fully elucidated. This review presents the advances in understanding each of these mechanisms, especially the data showing that muscle oxidative stress occurs and contributes to muscle dysfunction in chronic obstructive pulmonary disease. The current review also reports the studies that have elucidated the molecular mechanisms underlying this stress in chronic obstructive pulmonary disease by demonstrating alterations in oxidant and/or antioxidant systems. Finally, the review considers how inflammation and hypoxaemia may trigger oxidative stress in chronic obstructive pulmonary disease muscles and presents the therapeutic modalities that should be proposed to prevent it.

Does systemic inflammation trigger local exercise-induced oxidative stress in COPD?

Inflammatory abnormalities may be involved in the inadequate basal oxidant/antioxidant balance and local exercise-induced oxidative stress in chronic obstructive pulmonary disease (COPD) patients. The time course of oxidative stress and inflammation was investigated in 10 COPD patients and seven healthy subjects before and after local dynamic quadriceps endurance exercise at 40% of maximal strength. Venous samples were collected before, immediately after and up to 48 h after exercise. At rest, levels of an oxidant released by stimulated phagocytes, the superoxide anion, were significantly higher in patients, as were plasma levels of C-reactive protein, tumour necrosis factor-alpha and interleukin-6, inflammatory markers. An inverse relationship was found between baseline C-reactive protein levels and endurance time in patients. Six hours after exercise, superoxide anion release and levels of protein oxidation products, an index of oxidative stress, increased similarly in both groups, whereas thiobarbituric acid reactive substance levels, another index of oxidative stress, increased significantly only in patients. Plasma nonenzymatic antioxidant and inflammatory cytokine levels were unchanged by the exercise protocol. The increased baseline systemic inflammation in chronic obstructive pulmonary disease patients could be related to disturbed oxidant/antioxidant balance, and, together, these may have triggered the exercise-induced oxidative stress. The absence, however, of local exercise-induced systemic inflammation suggests that additional mechanisms explain local exercise-induced oxidative stress.

Evidence of local exercise-induced systemic oxidative stress in chronic obstructive pulmonary disease patients

Chronic inactivity may not be the sole factor involved in the myopathy of chronic obstructive pulmonary disease (COPD) patients. One hypothesis is that exercise-induced oxidative stress that leads to muscle alterations may also be involved. This study investigated whether exercise localised to a peripheral muscle group would induce oxidative stress in COPD patients. Eleven COPD patients (FEV1 1.15+/-0.4 L (mean+/-SD)) and 12 healthy age-matched subjects with a similar low quantity of physical activity performed endurance exercise localised to a peripheral muscle group, the quadriceps of the dominant leg. The authors measured plasma levels of thiobarbituric reactive substances (TBARs) as an index of oxidative stress, the release in superoxide anion (O2*-) by stimulated phagocytes as an oxidant, and blood vitamin E as one antioxidant. Quadriceps endurance was significantly lower in the COPD patients compared with healthy subjects (136+/-16 s versus 385+/-69 s (mean+/-SEM), respectively). A significant increase in TBARs 6 h after quadriceps exercise was only found in the COPD patients. In addition, significantly higher O2*- release and lower blood vitamin E levels were found in COPD patients than in controls at rest. This blood vitamin E level was significantly correlated with the resting level of plasma TBARs in the COPD patients. This study mainly showed that quadriceps exercise induced systemic oxidative stress in chronic obstructive pulmonary disease patients and that vitamin E levels were decreased in these patients at rest. The exact relevance of these findings to chronic obstructive pulmonary disease myopathy needs to be elucidated.

[Local exercise and oxidative stress in chronic obstructive broncho-pneumopathies: preliminary results]

The role of altered peripheral muscle function in exercise intolerance of chronic obstructive pulmonary disease (COPD) is now well established. However, the mechanisms underlying this phenomen, have not been determined. One hypothesis is that the oxidative stress, that leads to tissue injury may be involved. A recent study has shown that general exercise caused systemic oxidative stress in COPD patients. However, the origin of this stress was not absolutely clear: airways, muscle, both, or other? The aim of this study was first to determine with a systemic approach, whether systemic oxidative stress occur in patients who perform local exercise and then with a muscular needle biopsy approach, to confirm the muscular origin of this oxidative stress.

METHODS

In each approach, 7 COPD patients moderate to severe and 7 age-matched subjects performed an endurance test consisting of dynamic strength of the quadriceps against 40% (systemic approach) or 30% (biopsy approach) of maximal voluntary strength at an imposed regular pace until exhaustion.

RESULTS

The results showed in each approach, that endurance test duration was significantly decreased in the COPD patients (p < 0.05). In systemic approach, the results showed that blood vitamin E at rest was significantly decreased in the COPD (p < 0.001), with a significant increase in superoxide anion release by stimulated phagocytes (p < 0.001). Local exercise induced, only in COPD, a significant increase in serum MDA (p < 0.05), which is an index of oxidative stress. In the biopsy approach, the results showed that local exercise induced in COPD an increase in muscular levels of MDA. A significant increase in muscular peroxidase glutathion activity (antioxidant) occurred after exercise only in normal subjects (p < 0.05). In conclusion, this study in COPD, confirms the altered peripheral muscle function, reveals a deficit in blood vitamin E and suggest that local muscular exercise causes a muscular oxidative stress in these patients. Further studies are needed to confirm these results and evaluate the implication of this oxidative stress in the myopathy of COPD.