Pathways associated with reduced quadriceps oxidative fibres and endurance in COPD

Reduced quadriceps endurance in chronic obstructive pulmonary disease (COPD) is associated with a predominance of type II glycolytic fibres over type I oxidative fibres (fibre shift) and reduced muscle energy stores. The molecular mechanisms responsible for this remain unknown. We hypothesised that expression of known regulators of type I fibres and energy production in quadriceps muscle would differ in COPD patients with and without fibre shift. We measured lung function, physical activity, exercise performance, quadriceps strength and endurance (nonvolitionally) in 38 Global Initiative for Chronic Obstructive Lung Disease stage I-IV COPD patients and 23 healthy age-matched controls. Participants underwent a quadriceps biopsy: type I and II fibre proportions were determined using immunohistochemistry and fibre shift defined using published reference ranges. Calcineurin A, phosphorylated AMP kinase (phospho-AMPK)-α, protein kinase A-α catalytic subunits, modulators of calcineurin activity and calmodulin, 14-3-3 proteins were measured by Western blotting, and myocyte-enriched calcineurin-interacting protein-1 mRNA measured by quantitative PCR. Downstream, nuclear myocyte enhancer factor-2 capable of DNA binding was quantified by transcription factor ELISA. Unexpectedly, calcineurin expression was higher, while phospho-AMPK was lower, in COPD patients with fibre shift compared to COPD patients without fibre shift. Phospho-AMPK levels correlated with quadriceps endurance in patients. Reduced phospho-AMPK may contribute to reduced quadriceps oxidative capacity and endurance in COPD.

High pressure versus high intensity noninvasive ventilation in stable hypercapnic chronic obstructive pulmonary disease: a randomized crossover trial

BACKGROUND

High-intensity (high-pressure and high backup rate) noninvasive ventilation has recently been advocated for the management of stable hypercapnic chronic obstructive pulmonary disease (COPD). However, the relative contributions of high inspiratory pressure and high backup rate to ventilator adherence and physiological outcome have not been investigated.

METHODS

Patients with stable hypercapnic COPD (daytime PaCO(2) > 6 kPa) and nocturnal hypoventilation were enrolled. Patients were randomly allocated to high-pressure and high backup rate (high-intensity) and high-pressure and low backup rate (high-pressure) for a 6-week period. At the end of the first treatment period, patients were switched to the alternative treatment. The primary outcome measure was mean nightly ventilator usage.

RESULTS

Twelve patients were recruited, with seven completing the 12-week trial protocol. The mean patient age was 71 ± 8 years, with a forced expiratory volume in one second (FEV(1))/forced vital capacity (FVC) of 50% ± 13% and FEV(1) of 32% ± 12%. The baseline PaCO(2) and PaO(2) were 8.6 ± 1.7 kPa and 7.3 ± 1.4 kPa, respectively. There was no significant difference demonstrated in mean nightly ventilator usage between the high-intensity and high-pressure groups (difference of 4 minutes; 95% confidence interval -45 to 53; P = 0.9). Furthermore, there were no differences in any of the secondary endpoints, with the exception of the respiratory domain of the Severe Respiratory Insufficiency questionnaire, which was lower in the high-intensity arm than in the high-pressure arm (57 ± 11 versus 69 ± 16; P < 0.05).

CONCLUSION

There was no additional benefit, in terms of night-time ventilator adherence or any of the other measured parameters, demonstrated by addition of a high backup rate to high-pressure noninvasive ventilation. These data suggest that it is the high-pressure component of the high-intensity noninvasive ventilation approach that plays the important therapeutic role in the management of hypercapnic respiratory failure in COPD patients.

Reliability and validity of 4-metre gait speed in COPD

In community-dwelling older adults, usual gait speed over 4 m (4MGS) consistently predicts greater risk of adverse health outcomes. The aims of the present study were to assess the reliability of the 4MGS and the relationship with established health outcome measures in chronic obstructive pulmonary disease (COPD). Test-retest and interobserver reliability of the 4MGS were measured in 80 and 58 COPD patients, respectively. In 586 COPD patients, the 4MGS, as well as forced expiratory volume in 1 s (FEV1), the incremental shuttle walk (ISW), Medical Research Council (MRC) dyspnoea scale and St George's Respiratory Questionnaire (SGRQ) were measured. Participants were stratified according to "slow" (<0.8 m·s(-1)) or "normal" 4MGS (≥0.8 m·s(-1)). Intra-class correlation coefficients for test-retest and interobserver reliability were 0.97 and 0.99, respectively. There was a significant positive correlation between 4MGS with ISW (ρ = 0.78; p<0.001) and a negative correlation with MRC dyspnoea scale and SGRQ (ρ = -0.55 and -0.44; p<0.001 for both). COPD patients with slow 4MGS had significantly reduced ISW and higher MRC dyspnoea scale and SGRQ than those with preserved walking speed, despite similar FEV1 % predicted. The 4MGS is reliable in COPD, correlates with exercise capacity, dyspnoea and health-related quality of life, and has potential as a simple assessment tool in COPD.

Quadriceps and ankle dorsiflexor strength in chronic obstructive pulmonary disease

INTRODUCTION

Quadriceps strength and size are commonly reduced in chronic obstructive pulmonary disease (COPD). We wished to assess volitional and nonvolitional ankle dorsiflexor strength in COPD.

METHODS

Quadriceps and ankle dorsiflexor strength were measured by maximum voluntary contraction (MVC) and by twitch responses to supramaximal femoral and fibular nerve stimulation. Cross-sectional areas of the tibialis anterior (TA(CSA)) and rectus femoris muscles (RF(CSA)) were measured by ultrasound.

RESULTS

Eighteen elderly subjects and 20 COPD patients [mean(SD) %predictedFEV(1) 50(20)%] participated. No significant difference in fat-free mass index, ankle dorsiflexor strength, or TA(CSA) were observed in the presence of reduced quadriceps strength and size in COPD [mean MVC difference: -10.9 kg (95% confidence interval {CI}: -17.1 kg to -4.8 kg, P < 0.01; mean RF(CSA) difference -119 mm(2), 95% CI: -180 mm(2) to -58 mm(2), P < 0.01)].

CONCLUSIONS

Ankle dorsiflexor strength is less attenuated than quadriceps strength in COPD patients with moderate airflow obstruction. Direct quadriceps assessment may be more relevant than measurement of lower limb fat-free mass.

Singing classes for chronic obstructive pulmonary disease: a randomized controlled trial

BACKGROUND

There is some evidence that singing lessons may be of benefit to patients with chronic obstructive pulmonary disease (COPD). It is not clear how much of this benefit is specific to singing and how much relates to the classes being a group activity that addresses social isolation.

METHODS

Patients were randomised to either singing classes or a film club for eight weeks. Response was assessed quantitatively through health status questionnaires, measures of breathing control, exercise capacity and physical activity and qualitatively, through structured interviews with a clinical psychologist.

RESULTS

The singing group (n=13 mean(SD) FEV1 44.4(14.4)% predicted) and film group (n=11 FEV1 63.5(25.5)%predicted) did not differ significantly at baseline. There was a significant difference between the response of the physical component score of the SF-36, favouring the singing group +12.9(19.0) vs -0.25(11.9) (p=0.02), but no difference in response of the mental component score of the SF-36, breathing control measures, exercise capacity or daily physical activity. In the qualitative element, positive effects on physical well-being were reported in the singing group but not the film group.

CONCLUSION

Singing classes have an impact on health status distinct from that achieved simply by taking part in a group activity.

TRIALS REGISTRATION

Registration Current Controlled Trials - ISRCTN17544114.

Muscle function in COPD: a complex interplay

The skeletal muscles play an essential role in life, providing the mechanical basis for respiration and movement. Skeletal muscle dysfunction is prevalent in all stages of chronic obstructive pulmonary disease (COPD), and significantly influences symptoms, functional capacity, health related quality of life, health resource usage and even mortality. Furthermore, in contrast to the lungs, the skeletal muscles are potentially remedial with existing therapy, namely exercise-training. This review summarizes clinical and laboratory observations of the respiratory and peripheral skeletal muscles (in particular the diaphragm and quadriceps), and current understanding of the underlying etiological processes. As further progress is made in the elucidation of the molecular mechanisms of skeletal muscle dysfunction, new pharmacological therapies are likely to emerge to treat this important extra-pulmonary manifestation of COPD.

Respiratory muscle fatigue following exercise in patients with interstitial lung disease

BACKGROUND

It is not known whether respiratory muscle fatigue occurs as a consequence of exercise in patients with interstitial lung disease (ILD) and, if so, to what extent it is related to changes in dynamic lung volumes.

OBJECTIVES

To assess the development of respiratory muscle fatigue in patients with ILD and relate it to the respiratory pattern during exercise.

METHODS

Sixteen ILD patients (11 women) performed incremental, symptom-limited cycle ergometry with inspiratory capacity manoeuvres used to measure changes in end-expiratory lung volume (EELV). Twitch transdia-phragmatic pressure (TwPdi) and twitch gastric pressure (TwT10Pga), in response to magnetic stimulation, were used to assess the development of fatigue.

RESULTS

TwPdi did not differ significantly before and after exercise (21.8 ± 8 vs. 20.2 ± 8 cm H2O; p = 0.10), while TwT10Pga fell from 28.6 ± 18 to 25.2 ± 14 cm H2O (p = 0.02). EELV fell from 2.18 ± 0.65 to 1.91 ± 0.59 liters following exercise (p = 0.04). The fall in TwT10Pga correlated with peak oxygen uptake at peak of exercise (r = -0.52, p = 0.041), increase in heart rate (r = 0.53, p = 0.032) and with the decrease of EELV during exercise (r = 0.57, p = 0.021). Abdominal muscle fatiguers (n = 9, 56%), defined as having a ≥10% fall in TwT10Pga, had a fall in EELV of 22 ± 22% compared to 0.7 ± 8% in non-fatiguers (p = 0.016).

CONCLUSION

Abdominal muscle fatigue develops during exercise in some ILD patients in association with increased expiratory muscle activity manifested by reduced EELV.

Central and peripheral quadriceps fatigue in congestive heart failure

AIMS

The clinical syndrome of heart failure includes exercise limitation that is not directly linked to measures of cardiac function. Quadriceps fatigability may be an important component of this and this may arise from peripheral or central factors.

METHODS AND RESULTS

We studied 10 men with CHF and 10 healthy age-matched controls. Compared with a rest condition, 10 min after incremental maximal cycle exercise, twitch quadriceps force in response to supramaximal magnetic femoral nerve stimulation fell in both groups (CHF 14.1% ± 18.1%, p=0.037;

CONTROL

20.8 ± 11.0%, p<0.001; no significant difference between groups). There was no significant change in quadriceps maximum voluntary contraction voluntary force. The difference in the motor evoked potential (MEP) response to transcranial magnetic stimulation of the motor cortex between rest and exercise conditions at 10 min, normalised to the peripheral action potential, also fell significantly in both groups (CHF: 27.3 ± 38.7%, p=0.037;

CONTROL

41.1 ± 47.7%, p=0.024). However, the fall in MEP was sustained for a longer period in controls than in patients (p=0.048).

CONCLUSIONS

The quadriceps is more susceptible to fatigue, with a similar fall in TwQ occurring in CHF patients at lower levels of exercise. This is associated with no change in voluntary activation but a lesser degree of depression of quadriceps motor evoked potential.

Anemia and survival in chronic obstructive pulmonary disease: a dichotomous rather than a continuous predictor

BACKGROUND

Chronic obstructive pulmonary disease (COPD) is a disorder characterized by high mortality. Hemoglobin (Hb) concentration has a prognostic impact on COPD patients receiving long-term oxygen treatment, but its value as an independent predictor of survival among stable COPD outpatients has not been fully clarified by previous studies.

OBJECTIVES

To investigate the potential association between anemia and survival in a cohort of stable COPD outpatients.

METHODS

A cohort of stable COPD patients, who had had their first spirometry, blood count and serum chemistry profile done between October 1999 and November 2010 were retrospectively analyzed. Patients with heart failure, renal impairment, malignancy, recent hemorrhage and other causes of anemia were excluded. Variables that were found to be univariately associated with survival entered a multivariate stepwise Cox regression analysis model, to allow independent predictors of survival to be identified.

RESULTS

Of 294 patients (67.9 ± 9.8 years old, 64.6% male) 15.6% were anemic (Hb <13 g/dl). The median survival differed significantly between anemic [68.7 (18.1-91.5) months] and nonanemic [79.8 (57.5-98.4) months, p = 0.035] individuals. Independent predictors of mortality in the total population were anemia [hazard ratio (HR) 1.87, 95% confidence interval (CI) 1.06-3.29], age (HR 1.08, 95% CI 1.04-1.12) and forced expiratory volume in 1 s (FEV(1)) % predicted (HR 0.94, 95% CI 0.92-0.97); the Hb concentration was neither univariately nor multivariately associated with mortality.

CONCLUSION

This is the first study to indicate that anemia (but not the Hb value) is independently associated with survival in stable COPD outpatients. It would be better to treat this as a categorical variable in future scoring systems.

The effect of acute non-invasive ventilation on corticospinal pathways to the respiratory muscles in chronic obstructive pulmonary disease

Chronic obstructive pulmonary disease is associated with altered cortical excitability. The relevance of this to the need for non-invasive ventilation is not known. We assessed the diaphragm response to transcranial magnetic stimulation in terms of motor threshold and latency as well as assessing intracortical excitability using paired stimulation in eight long-term users and six non-users of home ventilation with COPD. Overall, intracortical facilitation was strongly correlated with inspiratory muscle strength (r² 0.72, p < 0.001) whereas intracortical inhibition was correlated with PaCO₂ (r² 0.51, p = 0.01). The two groups did not differ in motor evoked potential or latency, nor in the excitability of intracortical inhibitory or facilitatory circuits assessed using paired stimulation. The acute effect of isocapnic non-invasive ventilation was studied in six established ventilator users. Diaphragm motor evoked potential fell but there was no effect on intracortical facilitation or inhibition, implying an effect of neuromechanical feedback at brainstem or spinal level.

The COPD Assessment Test (CAT): short- and medium-term response to pulmonary rehabilitation

BACKGROUND

The COPD Assessment Test (CAT) is a recently introduced instrument to assess health-related quality of life in COPD. We aimed to evaluate the longitudinal change in CAT following Pulmonary Rehabilitation (PR), and test the relationship between CAT and CRQ-Self Report (SR) over time. We hypothesised that the CAT would show similar responsiveness to PR as the CRQ-SR both in the short and medium-term.

METHODS

118 COPD patients completed an eight-week outpatient multidisciplinary PR programme. CAT, CRQ-SR and the incremental shuttle walk (ISW) were measured prior to starting PR (T1), completion of PR (T2) and 6 months after completion of PR (T3).

RESULTS

There was a significant improvement in CAT, CRQ-SR and ISW immediately following PR (p < 0.001). Although there was decline between T2 and T3, CAT, CRQ-SR and ISW remained significantly better at T3 compared with T1 (ANOVA p < 0.001). Both between T1-T2 and between T2-T3, change in CAT correlated significantly with change in CRQ (both r = -0.44 and p < 0.001). The slope of the relationship between CAT change and CRQ-SR change at T1-T2 and T2-T3 was not significantly different (ANCOVA: intercept p = 0.79, interaction effect p = 0.95).

CONCLUSIONS

In COPD, the CAT score is immediately responsive to PR and remains improved at 6 months. There is no significant difference in the short and medium term changes in the CAT and CRQ-SR following PR. We propose that for most clinical indications for assessing health-related quality of life in COPD, the CAT is a robust and practical alternative to longer-established instruments such as the CRQ-SR.

Health status assessment in routine clinical practice: the chronic obstructive pulmonary disease assessment test score in outpatients

BACKGROUND

The chronic obstructive pulmonary disease (COPD) assessment test (CAT) is a simple, self-completion questionnaire developed to measure health status in patients with COPD, which is potentially suitable for routine clinical use.

OBJECTIVES

The purpose of this study was to establish the determinants of the CAT score in routine clinical practice.

METHODS

Patients attending the clinic completed the CAT score before being seen. Clinical data, including, where available, plethysmographic lung volumes, transfer factor and arterial blood gas analysis, were recorded on a pro forma in the clinic.

RESULTS

In 224 patients (36% female), mean forced expiratory volume in 1 s (FEV₁) was 40.1% (17.9) of predicted (%pred); CAT score was associated with exacerbation frequency [0-1/year 20.1 (7.6); 2-4/year 23.5 (7.8); >4/year 28.5 (7.3), p < 0.0001; 41/40/19% in each category] and with Medical Research Council (MRC) dyspnoea score (r² = 0.26, p < 0.0001) rising approximately 4 points with each grade. FEV(1) %pred had only a weak influence. Using stepwise regression, CAT score = 2.48 + 4.12 [MRC (1-5) dyspnoea score] + 0.08 (FEV(1) %pred) + 1.06 (exacerbation rate/year)] (r² = 0.36, p < 0.0001). The CAT score was higher in patients (n = 54) with daily sputum production [25.9 (7.5) vs. 22.2 (8.2); p = 0.004]. Detailed lung function (plethysmography and gas transfer) was available in 151 patients but had little influence on the CAT score.

CONCLUSION

The CAT score is associated with clinically important variables in patients with COPD and enables health status measurement to be performed in routine clinical practice.

Lack of association between impaired glucose tolerance and appetite regulating hormones in patients with obstructive sleep apnea

STUDY OBJECTIVES

Understanding the etiologic mechanisms underlying impaired glucose tolerance in obstructive sleep apnea (OSA) would assist development of therapies against this comorbidity. We hypothesized that in patients with OSA impaired glucose tolerance (IGT) would be associated with elevated levels of hormones associated with appetite regulation (leptin, ghrelin, neuropeptide Y [NPY] and peptide tyrosine-tyrosine [PYY]).

METHOD

We studied 68 OSA patients (mean AHI 22 events/h) and 37 age and weight matched healthy controls recruited by advertisement. All participants received a standardized evening meal, attended polysomnography and an oral glucose tolerance test (OGTT) on waking. Hormones were measured in blood taken before sleep (22:30) and at the start of the OGTT.

RESULTS

Impaired glucose tolerance was present in 54% of patients and 32% of controls (p = 0.05). The only differences between groups was that leptin was significantly higher at 22:30 in OSA patients compared to controls (9.6 ng/L vs 7.9 ng/L, p = 0.05). OSA patients had marginally elevated plasma NPY levels at 22:30 (56.6 [52, 67] pmol/L vs 51.1[47.3, 61] pmol/L; p = 0.04). No differences in ghrelin, PYY or NPY were observed between patients with IGT and those without. However OSA patients with IGT had significantly higher value of leptin at both 22:30 (10.9 [7.7, 15.9] ng/mL vs 7.4 [5.6, 12.3] ng/mL, p = 0.02) and 07:00 (11.6 [7.6, 16.2] ng/mL vs 6.9 [5.4, 12.6] ng/mL, p = 0.024) than those without. In multivariate analysis the only major association of leptin was body mass index.

CONCLUSION

Clinically significant abnormalities of appetite regulating hormones are not present in OSA. Appetite regulating hormones did not differ in OSA patients with and without impaired glucose tolerance.

Quadriceps wasting and physical inactivity in patients with COPD

Quadriceps weakness is an important complication of advanced chronic obstructive pulmonary disease (COPD) but few data exist concerning muscle bulk in early disease. We hypothesised that quadriceps bulk, measured by ultrasound rectus femoris cross-sectional area (USRF(CSA)), would be reduced in mild, as well as advanced, COPD compared with controls, and would correlate with physical activity. 161 patients with stable COPD and 40 healthy subjects had a measurement of USRF(CSA) and wore a multisensor armband to record physical activity. USRF(CSA) was reduced in Global Initiative for Chronic Obstructive Lung Disease (GOLD) stage I patients compared with healthy subjects (p=0.0002). Stage II-IV patients had reduced USRF(CSA) (p<0.0001) compared with controls but were not significantly different from those with stage I disease. Physical activity level was reduced in stage I (p=0.002) and stage II-IV disease compared with controls. Using regression analysis, physical activity level was independently associated with USRF(CSA) in stage I (p=0.01) but not stage II-IV disease, where residual volume to total lung capacity ratio was the only independent predictor of physical activity level. Quadriceps wasting exists in patients with mild, as well as advanced, COPD, and is independently associated with physical inactivity in GOLD stage I disease. The identification of these patients may guide early lifestyle and therapeutic interventions.

Effect of acute exacerbations on skeletal muscle strength and physical activity in cystic fibrosis

BACKGROUND

Skeletal muscle weakness is an important complication of chronic respiratory disease. The effect of acute exacerbations on strength in patients with cystic fibrosis is not known.

METHODS

Quadriceps (QMVC) and respiratory muscle strength were measured in patients at the time of acute admission, at discharge and one month later. Patients wore an activity monitor during admission and at one month. Convalescent values were compared to the stable clinic population.

RESULTS

Data were available for 13 acute admissions and 25 stable CF outpatients. Strength and other parameters including daily step count did not differ significantly between the stable and one month post-admission groups. At admission, QMVC was 16.7 (8.3)% lower than at convalescence, whereas inspiratory muscle strength did not change significantly. Reduction in QMVC did not correlate with activity levels or with markers of systemic inflammation.

CONCLUSION

Further research is needed to identify the mechanisms responsible for the reduction in QMVC.

Melatonin concentration as a marker of the circadian phase in patients with obstructive sleep apnoea

OBJECTIVE

The effects of obstructive sleep apnoea (OSA) on the markers of glucose metabolism and other hormones are of interest, particularly since there is growing evidence that OSA may be a risk factor for disorders such as insulin resistance. However, interpreting these studies depends on the target hormone not having a diurnal rhythm and the circadian rhythm not being altered by the sleep fragmentation that occurs in OSA. Therefore, the aim of our study was to test the hypothesis that OSA displaces the circadian rhythm.

METHODS

We carried out a prospective, observational, controlled, parallel study in 22 OSA patients (mean [SD] age: 45.1 [8.8]years; apnoea/hypopnoea index (AHI): 37 [24] events/h) and 22 age matched healthy subjects (age: 47.9 [7.9]years; AHI: 3 [1] events/h). Saliva samples for the measurement of melatonin were collected from participants resting in dim light at 30 min intervals between 19:30 and 22:30 h. Dim light melatonin onset (DLMO), a marker of the circadian phase, was taken at the end of the 30 min interval in which the greatest rise in melatonin occurred.

RESULTS

The group median (interquartile range) DLMO did not differ in OSA patients compared to healthy subjects (OSA patients: 90 [60-150]min; healthy subjects: 135 [90-150]min, p=0.19).

CONCLUSION

The circadian phase is the same in OSA patients and healthy subjects using salivary melatonin concentration as a marker of the circadian phase.

Non-invasive ventilation (NIV) as an aid to rehabilitation in acute respiratory disease

Background

Non-invasive ventilation (NIV) can increase exercise tolerance, reduce exercise induced desaturation and improve the outcome of pulmonary rehabilitation in patients with chronic respiratory disease. It is not known whether it can be applied to increase exercise capacity in patients admitted with non-hypercapnic acute exacerbations of COPD (AECOPD). We investigated the acceptability and feasibility of using NIV for this purpose.

Methods

On a single occasion, patients admitted with an acute exacerbation of chronic respiratory disease who were unable to cycle for five minutes at 20 watts attempted to cycle using NIV and their endurance time (T_lim) was recorded. To determine feasibility of this approach in clinical practice patients admitted with AECOPD were screened for participation in a trial of regular NIV assisted rehabilitation during their hospital admission.

Results

In 12 patients tested on a single occasion NIV increased T_lim from 184(65) seconds to 331(229) seconds (p = 0.04) and patients desaturated less (median difference = 3.5%, p = 0.029). In the second study, 60 patients were admitted to hospital during a three month period of whom only 18(30)% were eligible to participate and of these patients, only four (7%) consented to participate.

Conclusion

NIV improves exercise tolerance in patients with acute exacerbations of chronic respiratory disease but the applicability of this approach in routine clinical practice may be limited.

Trial registration

http://www.controlled-trials.com/ISRCTN35692743

Physical activity monitoring in COPD: compliance and associations with clinical characteristics in a multicenter study

BACKGROUND

Little is known about COPD patients' compliance with physical activity monitoring and how activity relates to disease characteristics in a multi-center setting.

METHODS

In a prospective study at three Northern European sites physical activity and clinical disease characteristics were measured in 134 COPD patients (GOLD-stage II-IV; BODE index 0-9) and 46 controls. Wearing time, steps per day, and the physical activity level (PAL) were measured by a multisensory armband over a period of 6 consecutive days (in total, 144 h). A valid measurement period was defined as ≥22 h wearing time a day on at least 5 days.

RESULTS

The median wearing time was 142 h:17 min (99%), 141 h:1 min (98%), and 142 h:24 min (99%), respectively in the three centres. A valid measurement period was reached in 94%, 97%, and 94% of the patients and did not differ across sites (P = 0.53). The amount of physical activity did not differ across sites (mean steps per day, 4725 ± 3212, P = 0.58; mean PAL, 1.45 ± 0.20, P = 0.48). Multivariate linear regression analyses revealed significant associations of FEV1, 6-min walk distance, quadriceps strength, fibrinogen, health status, and dyspnoea with both steps per day and PAL. Previously unrecognized correlates of activity were grade of fatigue, degree of emphysema, and exacerbation rate.

CONCLUSIONS

The excellent compliance with wearing a physical activity monitor irrespective of study site and consistent associations with relevant disease characteristics support the use of activity monitoring as a valid outcome in multi-center studies.

Downregulation of the serum response factor/miR-1 axis in the quadriceps of patients with COPD

RATIONALE

Muscle atrophy confers a poor prognosis in patients with chronic obstructive pulmonary disease (COPD), yet the molecular pathways responsible are poorly characterised. Muscle-specific microRNAs and serum response factor (SRF) are important regulators of muscle phenotype that contribute to a feedback system to regulate muscle gene expression. The role of these factors in the skeletal muscle dysfunction that accompanies COPD is unknown.

METHODS

31 patients with COPD and 14 healthy age-matched controls underwent lung and quadriceps function assessments, measurement of daily activity and a percutaneous quadriceps muscle biopsy. The expression of muscle-specific microRNAs, myosin heavy chains and components of the serum response factor signalling pathway were determined by qPCR.

RESULTS

A reduction in expression of miR-1 (2.5-fold, p=0.01) and the myocardin-related transcription factors (MRTFs) A and B was observed in patients compared with controls (MRTF-A mRNA: twofold, p=0.028; MRTF-B mRNA: fourfold, p=0.011). miR-1 expression was associated with smoking history, lung function, fat-free mass index, 6 min walk distance and percentage of type 1 fibres. miR-133 and miR-206 were negatively correlated with daily physical activity. Insulin-like growth factor 1 mRNA was increased in the patients and miR-1 was negatively correlated with phosphorylation of the kinase Akt. Furthermore, the protein levels of histone deacetylase 4, another miR-1 target, were increased in the patients.

CONCLUSIONS

Downregulation of the activity of the MRTF-SRF axis and the expression of muscle-specific microRNAs, particularly miR-1, may contribute to COPD-associated skeletal muscle dysfunction.

Attacking the disease spiral in chronic obstructive pulmonary disease: an update

In chronic obstructive pulmonary disease (COPD) a pathophysiological cycle occurs such that locomotor muscle weakness and fatiguabilty exist, which in turn limit exercise performance both because of leg discomfort and also because anaerobic metabolism leads to lactic acid production. Since the lactic acid is buffered by bicarbonate there is consequent carbon dioxide (CO2) production. Patients with advanced COPD are flow limited and cannot excrete the CO2 by raising ventilation and thus these patients experience breathlessness which discourages exercise and, in turn, prompts further deconditioning. Structured exercise, termed pulmonary rehabilitation is at the core of reversing the cycle but novel strategies should be employed for patients with advanced disease and alternative therapeutic opportunities may soon be available to improve pulmonary mechanics.

Predicting outcomes from 6-minute walk distance in chronic obstructive pulmonary disease

BACKGROUND

Exercise tolerance is an important clinical aspect of chronic obstructive pulmonary disease that can be easily and reliably measured with the 6-minute walking test (6MWT). To improve the utility of the 6MWT for patient and health care system management, the interpretation of the functional status measure in relation to death and hospitalization should be elucidated.

METHODS

Three-year, prospective, multicenter observational study to evaluate the predictive power of 6MWD for death or exacerbation-related hospitalization and to evaluate the factors that help determine 6MWD.

RESULTS

We measured 6MWD at baseline and annually in 2110 patients with clinically stable Global Initiative for Obstructive Lung Disease (GOLD) stage II-IV COPD and recorded exacerbation-related hospitalizations and all-cause mortality. During the study, 200 patients died and 650 were hospitalized. Using receiver operating characteristics, the best predictive thresholds of the 6MWD were 334 m for increased risk of death and 357 m for exacerbation-related hospitalization (area under the curve 0.67 and 0.60 respectively); however, the discriminatory thresholds, especially for mortality, were influenced by age. The mean (SE) 6MWD declined by 1.6 (1.2) m per year in GOLD II, 9.8 (1.3) m per year in GOLD III, and 8.5 (2.4) m per year in GOLD IV.

CONCLUSION

The 6MWD provides prognostic information that may be useful for identifying high-risk patients with COPD.

Neural respiratory drive as a physiological biomarker to monitor change during acute exacerbations of COPD

BACKGROUND

Acute exacerbations of chronic obstructive pulmonary disease have a significant negative impact on both patients and healthcare systems. Currently, there are no physiological biomarkers that effectively monitor clinical change or predict respiratory readmission. Acute exacerbations impose a change in the respiratory muscle load-capacity-drive relationship. It was hypothesised that lack of a fall in neural respiratory drive would identify patients at risk of treatment failure and early hospital readmission.

METHODS

An observational study was performed at two UK teaching hospitals. Routine clinical physiological parameters and neural respiratory drive index (NRDI), calculated as the product of second intercostal space parasternal electromyography (EMG) activity normalised to the peak EMG activity during a maximum inspiratory sniff manoeuvre and respiratory rate, were recorded daily from admission to discharge.

RESULTS

30 acutely unwell patients of mean (SD) age 72 (10) years, forced expiratory volume in 1 s 0.60 (1.65) l, NRDI 455 (263) AU and median length of stay 6 days were studied. Changes in NRDI correlated with changes in Borg score (r=+0.60; p<0.001), discriminated between patients deemed to have clinically improved rather than deteriorated (mean difference 339 AU; 95% CI 234 to 444; p<0.001) and identified those patients readmitted within 14 days (mean difference 203 AU; 95% CI 39 to 366; p=0.017).

CONCLUSIONS

NRDI is a feasible clinical physiological parameter in patients with an acute exacerbation of chronic obstructive pulmonary disease and can provide useful information on treatment response and risk of readmission.

Nocturnal asthma monitoring by chest wall electromyography

RATIONALE

Patients with suboptimal asthma control often have nocturnal symptoms which wake them, causing sleep fragmentation.

OBJECTIVES

It was hypothesised that symptomatic patients were more accurately identified by measuring respiratory effort using chest wall electromyography than by pulmonary function testing.

METHODS

Nocturnal electrical activity of the parasternal intercostal muscles (EMG(para)) in the second intercostal space was measured in subjects with controlled (diurnal peak expiratory flow (PEF) variability <20%, n=12) and uncontrolled (diurnal PEF variability >20%, n=12) asthma, and it was compared with that in normal subjects (n=12).

RESULTS

Subjects with controlled and uncontrolled asthma did not differ significantly in age (mean (SD) 42 (17) vs 46 (17) years, p=0.64), body mass index (BMI; 26.6 (2.9) vs 27.5 (3.5) kg/m(2), p=0.48) or gender distribution (males:females, 6:6 vs 7:5, p=0.68); the normal subject group was younger (27 (11) years, p=0.011) and slimmer (BMI 21.1 (2.9) kg/m(2), p<0.001). An elevated respiratory disturbance index (RDI) was associated with poor asthma control (RDI in normals 0.5 (0.9), in controlled asthma 4.0 (1.9), p<0.001, and in poorly controlled asthma 7.4 (4.3) h(-1); p<0.021). Similarly, EMG(para)%max (normals 4.9 (3.2)%max evening, 4.9 (3.5)%max morning) was higher in controlled asthma (7.2 (2.3)%max evening, 8.1 (4.0)%max morning, p=0.049) and higher still in uncontrolled asthma (16.8 (14.2)%max in the evening, 18.4 (11.6)%max in the morning, p<0.008).

CONCLUSIONS

Nocturnal respiratory effort is increased in those with asthma and neural respiratory drive is more variable in patients with poorly controlled asthma. Changes in the EMG(para) inversely reflect changes in pulmonary function tests. Measuring the EMG(para) offers a method to monitor asthma breath-by-breath while subjects are asleep, which could be adapted for home use.

The COPD assessment test (CAT): response to pulmonary rehabilitation. A multicentre, prospective study

BACKGROUND

The COPD (chronic obstructive pulmonary disease) assessment test (CAT) is a recently introduced, simple to use patient-completed quality of life instrument that contains eight questions covering the impact of symptoms in COPD. It is not known how the CAT score performs in the context of clinical pulmonary rehabilitation (PR) programmes or what the minimum clinically important difference is.

METHODS

The introduction of the CAT score as an outcome measure was prospectively studied by PR programmes across London. It was used alongside other measures including the St George's Respiratory Questionnaire, the Chronic Respiratory Disease Questionnaire, the Clinical COPD Questionnaire, the Hospital Anxiety and Depression score, the Medical Research Council (MRC) dyspnoea score and a range of different walking tests. Patients completed a 5-point anchor question used to assess overall response to PR from 'I feel much better' to 'I feel much worse'.

RESULTS

Data were available for 261 patients with COPD participating in seven programmes: mean (SD) age 69.0 (9.0) years, forced expiratory volume in 1 s (FEV(1)) 51.1 (18.7) % predicted, MRC score 3.2 (1.0). Mean change in CAT score after PR was 2.9 (5.6) points, improving by 3.8 (6.1) points in those scoring 'much better' (n=162), and by 1.3(4.5) in those who felt 'a little better' (n=88) (p=0.002). Only eight individuals reported no difference after PR and three reported feeling 'a little worse', so comparison with these smaller groups was not possible.

CONCLUSION

The CAT score is simple to implement as an outcome measure, it improves in response to PR and can distinguish categories of response.

Neural respiratory drive, pulmonary mechanics and breathlessness in patients with cystic fibrosis

BACKGROUND

Neural respiratory drive (NRD) measured from the diaphragm electromyogram (EMGdi) reflects the load/capacity balance of the respiratory muscle pump and is a marker of lung disease severity. EMGdi measurement is invasive, but recording the EMG from the parasternal intercostal muscles using surface electrodes (sEMGpara) could provide a non-invasive method of assessing NRD and disease severity. Objectives To test the hypothesis that NRD measured by sEMGpara correlates with EMGdi, to provide an index of disease severity in cystic fibrosis (CF) and to relate to exercise-induced breathlessness.

METHODS

15 patients with CF (mean forced expiratory volume in 1&emsp14;s (FEV(1)) 53.5% predicted) and 15 age-matched healthy controls were studied. sEMGpara and EMGdi were recorded at rest and during exercise. sEMGpara was recorded using surface electrodes and EMGdi using a multipair oesophageal electrode catheter. Signals were normalised using the peak EMG recorded during maximum respiratory manoeuvres and expressed as EMG%max. The respiratory pattern, metabolic data, oesophageal and gastric pressures and Borg scores were also recorded.

RESULTS

Mean (SD) resting sEMGpara%max and EMGdi%max were higher in patients with CF than in controls (13.1 (7)% and 18.5 (7.5)% vs 5.8 (3)% and 7.5 (2)%, respectively, p<0.001). In the patients with CF, resting sEMGpara%max and EMGdi%max were related to the degree of airways obstruction (FEV(1)) (r = -0.91 and r = -0.82, both p<0.001), hyperinflation (r = 0.63 and r = 0.56, both p<0.001) and dynamic lung compliance (r = -0.53 and r = -0.59, both p<0.001). During exercise, sEMGpara%max and EMGdi%max were strongly correlated with breathlessness in the patients with CF before (r = 0.906, p<0.001) and after (r = 0.975, p<0.001) the onset of neuromechanical dissociation.

CONCLUSION

sEMGpara%max provides a non-invasive marker of neural drive, which reflects disease severity and exercise-induced breathlessness in CF.

Atelectasis and survival after bronchoscopic lung volume reduction for COPD

Bronchoscopic therapies to reduce lung volumes in chronic obstructive pulmonary disease are intended to avoid the risks associated with lung volume reduction surgery (LVRS) or to be used in patient groups in whom LVRS is not appropriate. Bronchoscopic lung volume reduction (BLVR) using endobronchial valves to target unilateral lobar occlusion can improve lung function and exercise capacity in patients with emphysema. The benefit is most pronounced in, though not confined to, patients where lobar atelectasis has occurred. Few data exist on their long-term outcome. 19 patients (16 males; mean±sd forced expiratory volume in 1 s 28.4±11.9% predicted) underwent BLVR between July 2002 and February 2004. Radiological atelectasis was observed in five patients. Survival data was available for all patients up to February 2010. None of the patients in whom atelectasis occurred died during follow-up, whereas eight out of 14 in the nonatelectasis group died (Chi-squared p=0.026). There was no significant difference between the groups at baseline in lung function, quality of life, exacerbation rate, exercise capacity (shuttle walk test or cycle ergometry) or computed tomography appearances, although body mass index was significantly higher in the atelectasis group (21.6±2.9 versus 28.4±2.9 kg·m(-2); p<0.001). The data in the present study suggest that atelectasis following BLVR is associated with a survival benefit that is not explained by baseline differences.

Singing teaching as a therapy for chronic respiratory disease--a randomised controlled trial and qualitative evaluation

Background

Despite optimal pharmacological therapy and pulmonary rehabilitation, patients with COPD continue to be breathless. There is a need to develop additional strategies to alleviate symptoms. Learning to sing requires control of breathing and posture and might have benefits that translate into daily life.

Methods

To test this hypothesis we performed a randomised controlled trial, comparing a six week course of twice weekly singing classes to usual care, in 28 COPD patients. The experience of singing was assessed in a qualitative fashion, through interviews with a psychologist. In addition, we surveyed patients with chronic respiratory conditions who participated in a series of open singing workshops.

Results

In the RCT, the physical component score of the SF36 improved in the singers (n = 15) compared to the controls (n = 13); +7.5(14.6) vs. -3.8(8.4) p = 0.02. Singers also had a significant fall in HAD anxiety score; -1.1(2.7) vs. +0.8(1.7) p = 0.03. Singing did not improve single breath counting, breath hold time or shuttle walk distance. In the qualitative element, 8 patients from the singing group were interviewed. Positive effects on physical sensation, general well-being, community/social support and achievement/efficacy emerged as common themes. 150 participants in open workshops completed a questionnaire. 96% rated the workshops as "very enjoyable" and 98% thought the workshop had taught them something about breathing in a different way. 81% of attendees felt a "marked physical difference" after the workshop.

Conclusion

Singing classes can improve quality of life measures and anxiety and are viewed as a very positive experience by patients with respiratory disease; no adverse consequences of participation were observed.

Trial Registration

Current Controlled Trials - ISRCTN17544114.

Acute ischaemic hemispheric stroke is associated with impairment of reflex in addition to voluntary cough

Cough function is impaired after stroke; this may be important for protection against chest infection. Reflex cough (RC) intensity indices have not been described after stroke. RC, voluntary cough (VC) and respiratory muscle strength were studied in patients within 2 weeks of hemispheric infarct. The null hypotheses were that patients with cortical hemisphere stroke would show the same results as healthy controls on: 1) objective indices of RC and VC intensity; and 2) respiratory muscle strength tests. Peak cough flow rate (PCFR) and gastric pressure (P(ga)) were measured during maximum VC and RC. Participants also underwent volitional and nonvolitional respiratory muscle testing. Nonvolitional expiratory muscle strength was assessed by measuring P(ga) increase after magnetic stimulation over the T₁₀ nerve roots (twitch T₁₀ P(ga)). Stroke severity was scored using the National Institutes of Health Stroke Scale (NIHSS; maximum = 31). 18 patients (mean ± sd age 62 ± 15 yrs and NIHSS score 14 ± 8) and 20 controls (56 ± 16 yrs) participated. VC intensity was impaired in patients (PCFR 287 ± 171 versus 497 ± 122 L·min⁻¹) as was VC P(ga) (98.5 ± 61.6 versus 208.5 ± 61.3 cmH₂O; p < 0.001 for both). RC PCFR was reduced in patients (204 ± 111 versus 379 ± 110 L·min⁻¹; p < 0.001), but RC P(ga) was not significantly different from that of controls (179.0 ± 78.0 versus 208.0 ± 77.4 cmH₂O; p = 0.266). Patients exhibited impaired volitional respiratory muscle tests, but twitch T₁₀ P(ga) was normal. VC and RC are both impaired in hemispheric stroke patients, despite preserved expiratory muscle strength. Cough coordination is probably cortically modulated and affected by hemispheric stroke.