Exercise Capacity In COPD Patients Research Articles

Factors limiting exercise capacity in COPD patients

Introduction: Impaired exercise capacity in COPD patients leads to deterioration in their physical activity and quality of life. The aim of our study was to assess the exercise capacity of COPD patients using the 6-minute walk test (6MWT) and to determine the factors limiting their exercise capacity. Methods: Stable COPD patients were included in this study to assess their exercise capacity using the 6-minute walk test (6MWT) and to investigate the relationship between exercise capacity, functional status (FEV1), quadriceps muscle dysfunction (strength and endurance), and fat free mass index (FFMI). Results: 175 COPD patients (166 males and 9 females) aged between 40 and 86 years with a mean age of 67.95 years. The functional stages distribution according to GOLD was GOLDI: 19.43%, GOLDII: 30.29%, GOLDIII: 33.71%, GOLD IV: 16.57%. 25% of patients received long-term oxygen therapy (LTOT). The mean distance covered by COPD patients was 432.26 ± 129.731 meters, corresponding to 64.71 ± 19.04%. 56 (32%) COPD patients had exercise intolerance as assessed by the distance walked over 6 minutes (6MWD). A significant correlation was found between the 6MWD, quadriceps endurance (P<0.000) and FEV1 (p<0.002), whereas no correlation was found with MVC (P<0.039) and (FFMI) (P<0.062). Conclusion: Muscle dysfunction and the severity of bronchial obstruction are the factors most associated with impaired exercise capacity in COPD patients.

Comparison of two thoracic kinesio-taping techniques on pulmonary function, oxygen saturation, and exercise capacity in COPD patients: A randomized clinical trial

Comparison of two thoracic kinesio-taping techniques on pulmonary function, oxygen saturation, and exercise capacity in COPD patients: A randomized clinical trial

Measurement properties of step tests for exercise capacity in COPD: A systematic review

Objective: To determine the level of evidence of the measurement properties (validity, reliability, and responsiveness) and interpretability of the step tests available for assessing the exercise capacity in patients with chronic obstructive pulmonary disease. Data sources: The data sources Web of Science, MEDLINE, PubMed, PEDro, CENTRAL of Cochrane Library, and Scopus were searched up to June 26, 2020. Review methods: Studies of any design that reported results for any measurement property of the step tests for assessing the exercise capacity in COPD patients were selected. One reviewer extracted the data, and two reviewers independently rated the level of evidence by using the Consensus-Based Standards for the Selection of Health Measurements Instruments recommendations. Results: Thirty-one studies were included in the data synthesis. Chester Step Test, Modified Incremental Step Test, two-, three-, four-, and six-Minute Step Test, Paced Step Test, and six-Minute Stepper Test were identified. A step test protocol was also found. The level of evidence of their results for the measurement properties was mostly determined as “low” to “very low.” The best level of evidence found was for the six-minute stepper test: “high” on construct validity (r = 0.56–0.71); and “moderate” on criterion validity (r = 0.36–0.69), and responsiveness (r = 0.26–0.34). Conclusion: The general level of evidence of the measurement properties of the step tests is “low” to “very low” for assessing exercise capacity in patients with chronic obstructive pulmonary disease, which can limit their application in clinical practice. The six-minute Stepper Test is currently the most appropriate step test available.

Efficacy of yoga, tai chi and qi gong on the main symptoms of chronic obstructive pulmonary disease: A systematic review

IntroductionThe aim of this systematic review was to summarize the effects of yoga, qi gong or tai chi in COPD patients. MethodsStudies evaluating effects of the selected complementary therapies on lung function, dyspnea, quality of life or functional exercise capacity in COPD patients were identified and reviewed from three databases. ResultsEighteen studies were included. Six studies evaluated the effects of yoga and the others focused on tai chi or qi gong separately or combined. The duration of the programs ranged from 6 weeks to 6 months and the frequency from 2 to 7 times a week. Each session reached 30 to 90 minutes. Benefits were observed on lung function and functional exercise capacity but benefit was clearly stated neither on quality of life nor on dyspnea. ConclusionThis systematic review highlights the potential of these therapies as complementary therapeutic approach in COPD patients.

Exercise capacity in COPD patients with exercise-induced pulmonary hypertension

BackgroundPulmonary hypertension (PH) in patients with COPD is associated with reduced exercise capacity. A subgroup of COPD patients has normal mean pulmonary artery pressure (mPAP) at rest, but develops high mPAP relative to cardiac output (CO) during exercise, a condition we refer to as exercise-induced pulmonary hypertension (EIPH). We hypothesized that COPD patients with EIPH could be identified by cardiopulmonary exercise test (CPET) and that these patients have lower exercise capacity and more abnormal CPET parameters compared to COPD patients with normal hemodynamic exercise response.MethodsNinety-three stable outpatients with COPD underwent right heart catheterization with the measurement of mPAP, CO, and capillary wedge pressure at rest and during supine exercise. Resting mPAP <25 mmHg with ΔmPAP/ΔCO slope above or below 3 mmHg/L/min were defined as COPD-EIPH and COPD-normal, respectively. Pulmonary function tests and CPET with arterial blood gases were performed. Linear mixed models were fitted to estimate differences between the groups with adjustment for gender, age, and airflow obstruction.ResultsEIPH was observed in 45% of the study population. Maximal workload was lower in COPD-EIPH compared to COPD-normal, whereas other CPET measurements at peak exercise in % predicted values were similar between the two groups. After adjustment for gender, age, and airflow obstruction, patients with COPD-EIPH showed significantly greater increase in oxygen uptake, ventilation, respiratory frequency, heart rate, and lactate with increasing work load, as well as more reduction in pH compared to those with normal hemodynamic responses.ConclusionCOPD-EIPH could not be discriminated from COPD-normal by CPET. However, COPD-EIPH experienced a higher cost of exercise in terms of higher oxygen uptake, ventilation, respiratory frequency, heart rate, and lactate for a given increase in workload compared to COPD-normal.

Physical Inactivity, Functional Status and Exercise Capacity in COPD Patients Receiving Home-Based Oxygen Therapy

ABSTRACTChronic obstructive pulmonary disease (COPD) has systemic consequences that lead to reduced physical activity in daily life (PADL). Little is known about PADL and its associations in individuals with COPD on home-based long-term oxygen therapy (LTOT). The objective of the study was to determine whether there is an association between severe physical inactivity and pulmonary function, fatigue, dyspnea, functional status and exercise capacity in individuals with COPD on home-based LTOT using electric oxygen concentrators and to investigate which of these variables could influence inactivity in these individuals. The population sample included 39 individuals with COPD who were on LTOT (69 ± 8 years, FEV1: 32 ± 14% predicted). They were assessed in terms of PADL (number of steps/day), fatigue (Fatigue Severity Scale – FSS), dyspnea (Medical Research Council – MRC scale), functional status (London Chest ADL scale [LCADL] and Timed Up and Go [TUG] test) and functional exercise capacity (Six-Minute Step test [6MST] and Sit-to-Stand test [STST]). PADL was markedly low (1444 ± 1203 steps/day) and associated with daily duration of LTOT (r = –0.50), fatigue (r = –0.36), LCADL (r = –0.41), 6MST (r = 0.48), and STST (r = 0.53) (p < .05 for all). Multiple linear regression revealed that daily duration of LTOT and STST explained 39% of the variability of PADL. Longer daily duration of LTOT, fatigue, worse functional status and exercise capacity were all associated with physical inactivity in individuals with COPD on LTOT, whereas daily duration of LTOT and the STST were determinants of reduced physical activity.

Long-acting bronchodilators improve exercise capacity in COPD patients: a systematic review and meta-analysis

We carried out a systematic review and meta-analysis with the aim to evaluate the efficacy of longacting bronchodilators on exercise capacity in COPD patients. The endpoints were the efficacy of long-acting bronchodilators (altogether, and by single classes) vs. placebo in modifying endurance time (ET), inspiratory capacity (IC) and dyspnea during exercise, taking into consideration the outcomes according to different patients’ inclusion criteria and exercise methodology. Twenty-two studies were deemed eligible for analysis. Weighted mean increase in ET resulted of 67 s (95% CI ranges from 55 to 79). For isotime IC and dyspnea during exercise, weighted improvements were 195 ml (162–229), and − 0.41 units (− 0.56 to − 0.27), respectively. The increase in trough IC was 157 ml (138–175). We found a trend in favour of LAMA compared to LABA in terms of ET. In the 11 studies which reported a value of functional residual capacity > 120% as inclusion criterion, weighted mean increase in endurance time was 94 s (65 to 123); however we did not find any significant correlation between ET and mean trough IC (P: 0.593). The improvement of ET in the 5 studies using walking as exercise methodology resulted of 58 s (− 4 to 121). Long-acting bronchodilators improve exercise capacity in COPD. The main effect of long-acting bronchodilators seems to be a increase of basal IC rather than a modification of dynamic hyperinflation during exercise. The efficacy in terms of endurance time seems higher in studies which enrolled patients with hyperinflation, with a similar efficacy on walking or cycling.

Heterogeneity of Systemic Oxidative Stress Profiles in COPD: A Potential Role of Gender.

Oxidative stress (OS) plays a key role in the muscle impairment and exercise capacity of COPD patients. However, the literature reveals that systemic OS markers show great heterogeneity, which may hinder the prescription of effective antioxidant supplementation. This study therefore aimed to identify OS markers imbalance of COPD patients, relative to validated normal reference values, and to investigate the possibility of systemic OS profiles. We measured systemic enzymatic/nonenzymatic antioxidant and lipid peroxidation (LP) levels in 54 stable COPD patients referred for a rehabilitation program. The main systemic antioxidant deficits in these patients concerned vitamins and trace elements. Fully 89% of the COPD patients showed a systemic antioxidant imbalance which may have caused the elevated systemic LP levels in 69% of them. Interestingly, two patient profiles (clusters 3 and 4) had a more elevated increase in LP combined with increased copper and/or decreased vitamin C, GSH, and GPx. Further analysis revealed that the systemic LP level was higher in COPD women and associated with exercise capacity. Our present data therefore support future supplementations with antioxidant vitamins and trace elements to improve exercise capacity, but COPD patients will probably show different positive responses.

Dietary nitrate supplementation in COPD: An acute, double-blind, randomized, placebo-controlled, crossover trial☆

BackgroundThe acute consumption of dietary nitrate has been shown to improve exercise capacity in athletes, healthy adults and subjects with peripheral vascular disease. Many COPD patients have reduced exercise capacity. We hypothesized that acute nitrate consumption might increase incremental shuttle walk test (ISWT) distance in COPD subjects. MethodsEleven COPD subjects were randomly assigned to consume either a high nitrate or a matched, low nitrate beverage in a double-blind, randomized, placebo-controlled, crossover design. ISWT distance was measured both before and 3 h after the beverage and change was recorded. After a 7-day washout, ISWT distances were re-measured before and 3 h after the alternate beverage and changes were recorded. ResultsWe observed an increase in ISWT distance after consuming the high nitrate juice (25 m) compared with a reduction after the low nitrate juice (14 m) (p < 0.01). This improvement in exercise capacity was associated with significant increases in serum nitrate (p < 0.000005) and nitrite (p < 0.01) levels and a significant lowering of resting blood pressure (<0.05). ConclusionsIn patients with stable COPD, the acute consumption of dietary nitrate increased serum nitrate/nitrite levels and exercise capacity and was associated with a decrease in resting blood pressure. Nitrate consumption might alter exercise capacity in COPD patients.

Dietary nitrate supplementation improves exercise performance and decreases blood pressure in COPD patients

Dietary nitrate (NO3−) supplementation via beetroot juice has been shown to increase the exercise capacity of younger and older adults. The purpose of this study was to investigate the effects of acute NO3− ingestion on the submaximal constant work rate exercise capacity of COPD patients. Fifteen patients were assigned in a randomized, single-blind, crossover design to receive one of two treatments (beetroot juice then placebo or placebo then beetroot juice). Submaximal constant work rate exercise time at 75% of the patient's maximal work capacity was the primary outcome. Secondary outcomes included plasma NO3− and nitrite (NO2−) levels, blood pressure, heart rate, oxygen consumption (VO2), dynamic hyperinflation, dyspnea and leg discomfort. Relative to placebo, beetroot ingestion increased plasma NO3− by 938% and NO2− by 379%. Median (+interquartile range) exercise time was significantly longer (p = 0.031) following the ingestion of beetroot versus placebo (375.0 + 257.0 vs. 346.2 + 148.0 s, respectively). Compared with placebo, beetroot ingestion significantly reduced iso-time (p = 0.001) and end exercise (p = 0.008) diastolic blood pressures by 6.4 and 5.6 mmHg, respectively. Resting systolic blood pressure was significantly reduced (p = 0.019) by 8.2 mmHg for the beetroot versus the placebo trial. No other variables were significantly different between the beetroot and placebo trials. These results indicate that acute dietary NO3− supplementation can elevate plasma NO3− and NO2− concentrations, improve exercise performance, and reduce blood pressure in COPD patients.

Impaired Carbon Monoxide Diffusing Capacity is the strongest lung function predictor of decline in 12 minute-walking distance in COPD; a 5-year follow-up study

Background: The purpose of this study was to evaluate the longitudinal relationship between functional exercise capacity, assessed through standardized 12-minute walk test (12MWT), and various lung function parameters obtained using spirometry, body plethysmography and diffusing capacity (DLco) measurements in patients with COPD. Methods: Spirometry, body plethysmography and DLco-measurements were performed at baseline in 84 subjects with moderate to very severe COPD and at follow-up visit (n = 34) after 5 years. Functional exercise capacity was determined using standardized 12MWT. Results: Patients were characterized at baseline by FEV1 of 1.2 ± 0.4 L (41 ± 13% predicted), RV of 3.4 ± 1.0 L (187 ± 58% predicted) and DLco of 3.8 ± 1.2 mmol/min/kPa (51 ± 16% predicted). A decrease of 12MWD was found between baseline and follow-up (928 ± 193 m vs. 789 ± 273 m, p < 0.001). DLco and 12MWD at baseline were the only independent predictors of 12MWD at follow-up in a multiple logistic regression model that also included all other lung function parameters, gender, age and BMI. Decline in 12MWD was mainly explained by deterioration in DLco. Furthermore, DLco value at baseline had the highest explanatory value for the loss in 12MWD after 5 years (R2 = 0.18, p = 0.009). Conclusions: In a 5-year longitudinal study, DLco-measurements at baseline were the most important predictors of declining exercise capacity in COPD patients. These results suggest that integration of DLco in the clinical workup provides a more comprehensive assessment in patients with COPD.

Correlations between small airway function, ventilation distribution, and functional exercise capacity in COPD patients.

Interest in using the nitrogen single-breath washout (N2SBW) test to measure ventilation inhomogeneity and small airway function in COPD patients has grown in recent years. Our aim was to assess the correlation of the measures obtained by the N2SBW test and other pulmonary function parameters with the six-minute walk distance (6MWD), the degree of dyspnea score, and health status in COPD patients. In this cross-sectional study, 31 patients with COPD were subjected to the N2SBW test, spirometry, whole-body plethysmography, carbon monoxide diffusing capacity measurement, the six-minute walk test, the modified Medical Research Council (mMRC) scale, and the COPD Assessment Test (CAT). We found a strong correlation between the 6MWD and the phase III slope of the nitrogen single-breath washout (Phase III slopeN2SBW) (r = -0.796; p = 0.0001). We found moderate correlations between the 6MWD and the residual volume (RV) (r = -0.651; p = 0.0001) and RV/total lung capacity (RV/TLC) (r = -0.600; p = 0.0004). We also found moderate correlations between the CAT score and Phase III slopeN2SBW(r = 0.728; p = 0.0001), RV (r = 0.646; p = 0.0001) and RV/TLC (r = 0.603; p = 0.0003). There was a significant difference between the mMRC grades for the following variables: Phase III slopeN2SBW (p = 0.0001), RV (p = 0.0001), and smoking history (p = 0.008). Multivariate analysis showed that Phase III slopeN2SBW was the only independent predictor of the 6MWD (R2 = 0.703; p = 0.0001), CAT score (R2 = 0.586; p = 0.0001), and mMRC scale (relative risk = 1.14; p = 0.0001). In patients with COPD, our findings suggest that the ventilation inhomogeneity impacts the functional exercise capacity, the degree of dyspnea, and health status.

Validity of the six-minute step test of free cadence in patients with chronic obstructive pulmonary disease.

Objectives: to evaluate the concurrent validity of the six-minute step test (6MST) in assessing exercise capacity of COPD patients using the six-minute walk test (6MWT) as a gold-standard. The predictive validity of the 6MST was assessed to determine a cut-off point for identification of low exercise capacity. Method: thirty-two COPD patients (50-87 years old) with mild to very severe obstruction performed the 6MST and 6MWT twice. Results:Concurrent validity: a strong positive correlation (Pearson) between the number of ascents on the first (T1), second (T2) and the best of both (T1 or T2) tests during the 6MWT was observed. Although a moderate negative correlation with BODE index and FEV1 was found, it was considered insufficient to test the validity, therefore ROC curves were not applied. The predictive validity (ROC) of the 6MST to identify low physical capacity (compared with the 6MWT) using the performance of T1 or T2, or solely T1 was considered accurate, and the area under the curve was 0.8 (IC95% 0.62-0.98) and 0.85 (IC95% 0.70-0.99), respectively. To classify patients, the cut-off points of 86 and 78 steps were chosen, with both values showing 90% of sensitivity and specificity of 64% and 68% for T1 or T2, or solely T1, respectively. Conclusion: The number of steps on the 6MST was valid to verify exercise capacity in COPD patients and the cut-off point of 78 steps was able to identify patients with poor exercise tolerance. Values under this cut-off point are considered to identify patients with a poorer prognosis.

Fat-Free Mass Depletion Is Associated With Poor Exercise Capacity Irrespective of Dynamic Hyperinflation in COPD Patients

In patients with COPD, we investigated the effect of the fat-free mass (FFM) on maximal exercise capacity and the relationship with changes in operational lung volumes during exercise. In a cross-sectional study 57 patients (16 females; age 65 ± 8 y) were consecutively assessed by resting lung function, symptom-limited cardiopulmonary exercise test, and body composition by means of bioelectrical impedance analysis to measure the FFM index (FFMI; in kilograms per square meter). Patients were categorized as depleted (n = 14) or nondepleted (n = 43) according to FFMI. No significant difference in gender, age, and resting lung function was found between depleted and nondepleted patients. When compared with nondepleted COPD patients, the depleted COPD patients had a significantly lower O2 uptake at the peak of exercise and at anaerobic threshold as well as at peak oxygen pulse, oxygen uptake efficiency slope (OUES), and heart rate recovery (HRR) (P < .05 for all comparisons), but similar inspiratory capacity/total lung capacity at the peak of exercise. Moreover, they also reported significantly higher leg fatigue (P < .05), but not dyspnea on exertion. In all patients, significant correlations (P < .01) were found between FFMI and peak oxygen pulse, OUES, HRR, and leg fatigue. This study shows that FFM depletion plays a part in the reduction of exercise capacity in COPD patients, regardless of dynamic hyperinflation, and is strictly associated with poor cardiovascular response to exercise and to leg fatigue, but not with dyspnea.

Ventilatory Inefficiency as a Limiting Factor for Exercise in Patients With COPD

Ventilatory inefficiency increases ventilatory demand; corresponds to an abnormal increase in the ratio of minute ventilation (V_dot(E)) to CO(2) production (V_dot(CO(2))); represents increased dead space, deregulation of respiratory control, and early lactic threshold; and is associated with expiratory flow limitation that enhances dynamic hyperinflation and may limit exercise capacity. To evaluate the influence of ventilatory inefficiency over exercise capacity in COPD patients. Prospective study of 35 COPD subjects with different levels of severity, in whom cardiopulmonary stress test was performed. Ventilatory inefficiency was represented by the V_dot(E) /V_dot(CO(2)) relation. Its influence over maximal oxygen consumption (V_dot(O(2))max), power (W), and ventilatory threshold was evaluated. Surrogate parameters of cardiac function, like oxygen pulse (V_dot(O(2))/heart rate) and circulatory power (%V_dot(O(2))max × peak systolic pressure), were also evaluated. Cardiopulmonary stress test was stopped due to dyspnea with elevated V_dot(E) and marked reduction of breathing reserve. A severe increase in V_dot(CO(2)) (mean ± SD 35.9 ± 5.6), a decrease of V_dot(O(2)) (mean ± SD 75.2 ± 20%), and a decrease of W (mean ± SD 68.6 ± 23.3%) were demonstrated. Twenty-eight patients presented dynamic hyperinflation. Linear regression showed a reduction of 2.04% on V_dot(O(2>))max (P < .001), 2.6% on W (P < .001), 1% on V_dot(O(2))/heart rate (P = .049), and 322.7 units on circulatory power (P = .02) per each unit of increment in V_dot(E)/V_dot(CO(2)), respectively. Ventilatory inefficiency correlates with a reduction in exercise capacity in COPD patients. Including this parameter in the evaluation of exercise limitation in this patient population may mean a contribution toward the understanding of its pathophysiology.

P47 The impact of comorbid ischaemic heart disease on exercise capacity in COPD patients

IntroductionComorbid ischaemic heart disease (IHD) is associated with an adverse impact on health status, symptoms (ARJCCM 2011;183:A2614) and exacerbation recovery in COPD patients (ERJ 2010;954s:E5209). Any impact on exercise capacity...

Neuromuscular electrical stimulation improves exercise tolerance in chronic obstructive pulmonary disease patients with better preserved fat-free mass

BACKGROUND:High-frequency neuromuscular electrical stimulation increases exercise tolerance in patients with advanced chronic obstructive pulmonary disease (COPD patients). However, it is conceivable that its benefits are more prominent in patients with better-preserved peripheral muscle function and structure.OBJECTIVE:To investigate the effects of high-frequency neuromuscular electrical stimulation in COPD patients with better-preserved peripheral muscle function. Design: Prospective and cross-over study.METHODS:Thirty COPD patients were randomly assigned to either home-based, high-frequency neuromuscular electrical stimulation or sham stimulation for six weeks. The training intensity was adjusted according to each subject's tolerance. Fat-free mass, isometric strength, six-minute walking distance and time to exercise intolerance (Tlim) were assessed.RESULTS:Thirteen (46.4%) patients responded to high-frequency neuromuscular electrical stimulation; that is, they had a post/pre ΔTlim >10% after stimulation (unimproved after sham stimulation). Responders had a higher baseline fat-free mass and six-minute walking distance than their seventeen (53.6%) non-responding counterparts. Responders trained at higher stimulation intensities; their mean amplitude of stimulation during training was significantly related to their fat-free mass (r = 0.65; p<0.01). Logistic regression revealed that fat-free mass was the single independent predictor of Tlim improvement (odds ratio [95% CI] = 1.15 [1.04-1.26]; p<0.05).CONCLUSIONS:We conclude that high-frequency neuromuscular electrical stimulation improved the exercise capacity of COPD patients with better-preserved fat-free mass because they tolerated higher training stimulus levels. These data suggest that early training with high-frequency neuromuscular electrical stimulation before tissue wasting begins might enhance exercise tolerance in patients with less advanced COPD.

Aerobic exercise capacity in COPD patients with and without pulmonary hypertension

Pulmonary hypertension is a common occurrence in advanced COPD, but its effects on exercise capacity remain undetermined. Exercise testing and an echocardiographic examination were performed in 29 patients with advanced stable COPD. Mean pulmonary artery pressure (mPAP) was calculated from the acceleration time of pulmonary flow. Exercise capacity was evaluated by the distance walked in 6 min (6MWD) and by an incremental cardiopulmonary exercise test (CPET). The patients had a forced expiratory volume in 1s of 1.13+/-0.49 L, and a 6MWD of 305+/-66 m (mean+/-SD). The CPET (n=24) showed a: maximum workload of 52+/-25 W, a peak O(2) uptake of 13.8+/-4.4 mL/kg/min, a peak heart rate of 127+/-22 bpm, a peak respiratory exchange ratio 1.06+/-0.11, a ventilation (V(E))/CO(2) production slope of 37+/-11, and a peak O(2) pulse 7.5+/-2.3 mL. The peak V(E) was 41+/-15 L/min, and the calculated maximum voluntary V(E) 45+/-20 L/min. There was no difference in any of the CPET variables and 6MWD between the patients with a mPAP<30 mm Hg (mPAP 22+/-6 mm Hg, n=15) and those with a mPAP>30 mm Hg (mPAP 38+/-6 mm Hg, n=14). There was no correlation between PAP and any of the exercise measurements. These results suggest that exercise capacity in unselected patients with advanced COPD and mild to moderate pulmonary hypertension is essentially limited by exhaustion of the ventilatory reserve.

Correlação entre hipoxemia moderada e função muscular esquelética periférica na doença pulmonar obstrutiva crónica – Estudo-piloto

Rationale: Exercise capacity in COPD patients depends on the degree of airflow obstruction, the severity of the hypoxaemia and skeletal muscle function. Muscle atrophy and weakness are considered systemic consequences of COPD and are associated with reduced exercise capacity.Aims: To investigate the correlation between mild hypoxaemia and muscular strength, muscular fatigue and functional capacity in COPD patients.Methods: Ten patients enrolled on a PRP at the Hospital Universitário de Brasília – HUB were included in this study. Lung function was evaluated by spirometry and arterial blood gas analysis. Functional evaluation was made using the 6MWT and using isometric contraction of deltoid and quadriceps muscles.Results: There were positive correlations between PaO2, quadriceps strength (r2=0.61 and p=0.007) and PaO2 and the 6MWT (r2=0.96, p=0.001). There were negative correlations between PaO2 and median frequency of quadriceps (r2=-0.42 and p=0.04). We observed significant correlation between quadriceps strength and the 6MWT (r2=0.67 and p=0.001). There was negative correlation between median frequency of quadriceps and the 6MWT (r2=-0.42 and p=0.04). We did not observe any correlation between PaO2 and strength or median frequency of deltoid muscle.Conclusions: PaO2 has important correlations with muscular function variables. The main negative impact of mild hypoxaemia and precocious limb muscular disability on COPD patients is decreased functional capacity.Rev Port Pneumol 2008; XIV (6): 769-785

The major limitation to exercise performance in COPD is inadequate energy supply to the respiratory and locomotor muscles

No doubt dynamic hyperinflation and lack of oxidative capacity of skeletal muscles are important causes of exercise limitation in COPD. O'Donnell and Webb and Debigare and Maltais will convince the reader of this by the elegant experiments they have performed. The thesis we will put forward is that