Neuromuscular electrical stimulation to improve exercise capacity in patients with severe COPD: a randomised double-blind, placebo-controlled trial

BACKGROUND

Skeletal muscle dysfunction and exercise intolerance are common in severe chronic obstructive pulmonary disease (COPD). We assessed the effectiveness of neuromuscular electrical stimulation (NMES) as a home-based exercise therapy.

METHODS

In this double-blind, placebo-controlled trial, undertaken across three UK National Health Service sites, we randomly assigned (1:1) adults with COPD, a forced expiratory volume in 1 s (FEV1) less than 50% predicted, and incapacitating breathlessness (Medical Research Council dyspnoea scale ≥4) to receive active or placebo NMES, daily over a 6-week period. Randomisation was by an independent system using minimisation to balance age, GOLD stage, and quadriceps strength. Participants and outcome assessors were masked to group allocation. The primary endpoint was change in 6-min walk test (6MWT) distance at 6 weeks. Analysis was by intention to treat. The trial was registered as ISRCTN15985261 and is now closed.

FINDINGS

Between June 29, 2012, and July 4, 2014, we enrolled 73 participants, of whom 52 participants were randomly assigned; 25 to receive active NMES and 27 to placebo NMES. Change in 6MWT distance was greater in the active NMES group (mean 29·9 [95% CI 8·9 to 51·0]) compared with in the placebo group (-5·7 [-19·9 to 8·4]; mean difference at 6 weeks 35·7 m [95% CI 10·5 to 60·9]; p=0·005). Sensitivity analyses for complete-cases and adjustment for baseline values showed similar results. 6 weeks after stopping the intervention the effect waned (7·3 m [95% CI -32·5 to 47·0]; p=0·50). The proportion of participants who had adverse events was similar between groups (five [20%] in the active NMES group and nine [33%] in the placebo group). Two participants, one from each group, reported persistent erythema, which was considered to be possibly related to NMES and the use of adhesive electrodes.

INTERPRETATION

NMES improves functional exercise capacity in patients with severe COPD by enhancing quadriceps muscle mass and function. These data support the use of NMES in the management of patients unable to engage with conventional pulmonary rehabilitation. More work is needed to study how to maintain the effect.

FUNDING

National Institute for Health Research.

Acute Dietary Nitrate Supplementation and Exercise Performance in COPD: A Double-Blind, Placebo-Controlled, Randomised Controlled Pilot Study

BACKGROUND

Dietary nitrate supplementation can enhance exercise performance in healthy people, but it is not clear if it is beneficial in COPD. We investigated the hypotheses that acute nitrate dosing would improve exercise performance and reduce the oxygen cost of submaximal exercise in people with COPD.

METHODS

We performed a double-blind, placebo-controlled, cross-over single dose study. Subjects were randomised to consume either nitrate-rich beetroot juice (containing 12.9 mmoles nitrate) or placebo (nitrate-depleted beetroot juice) 3 hours prior to endurance cycle ergometry, performed at 70% of maximal workload assessed by a prior incremental exercise test. After a minimum washout period of 7 days the protocol was repeated with the crossover beverage.

RESULTS

21 subjects successfully completed the study (age 68 ± 7 years; BMI 25.2 ± 5.5 kg/m2; FEV1 percentage predicted 50.1 ± 21.6%; peak VO2 18.0 ± 5.9 ml/min/kg). Resting diastolic blood pressure fell significantly with nitrate supplementation compared to placebo (-7 ± 8 mmHg nitrate vs. -1 ± 8 mmHg placebo; p = 0.008). Median endurance time did not differ significantly; nitrate 5.65 (3.90-10.40) minutes vs. placebo 6.40 (4.01-9.67) minutes (p = 0.50). However, isotime oxygen consumption (VO2) was lower following nitrate supplementation (16.6 ± 6.0 ml/min/kg nitrate vs. 17.2 ± 6.0 ml/min/kg placebo; p = 0.043), and consequently nitrate supplementation caused a significant lowering of the amplitude of the VO2-percentage isotime curve.

CONCLUSIONS

Acute administration of oral nitrate did not enhance endurance exercise performance; however the observation that beetroot juice caused reduced oxygen consumption at isotime suggests that further investigation of this treatment approach is warranted, perhaps targeting a more hypoxic phenotype.

TRIAL REGISTRATION

ISRCTN Registry ISRCTN66099139.

The PROactive instruments to measure physical activity in patients with chronic obstructive pulmonary disease

No current patient-centred instrument captures all dimensions of physical activity in chronic obstructive pulmonary disease (COPD). Our objective was item reduction and initial validation of two instruments to measure physical activity in COPD.Physical activity was assessed in a 6-week, randomised, two-way cross-over, multicentre study using PROactive draft questionnaires (daily and clinical visit versions) and two activity monitors. Item reduction followed an iterative process including classical and Rasch model analyses, and input from patients and clinical experts.236 COPD patients from five European centres were included. Results indicated the concept of physical activity in COPD had two domains, labelled "amount" and "difficulty". After item reduction, the daily PROactive instrument comprised nine items and the clinical visit contained 14. Both demonstrated good model fit (person separation index >0.7). Confirmatory factor analysis supported the bidimensional structure. Both instruments had good internal consistency (Cronbach's α>0.8), test-retest reliability (intraclass correlation coefficient ≥0.9) and exhibited moderate-to-high correlations (r>0.6) with related constructs and very low correlations (r<0.3) with unrelated constructs, providing evidence for construct validity.Daily and clinical visit "PROactive physical activity in COPD" instruments are hybrid tools combining a short patient-reported outcome questionnaire and two activity monitor variables which provide simple, valid and reliable measures of physical activity in COPD patients.

The Impact of Homogeneous Versus Heterogeneous Emphysema on Dynamic Hyperinflation in Patients With Severe COPD Assessed for Lung Volume Reduction

Dynamic hyperinflation (DH) is a pathophysiologic hallmark of Chronic Obstructive Pulmonary Disease (COPD). The aim of this study was to investigate the impact of emphysema distribution on DH during a maximal cardiopulmonary exercise test (CPET) in patients with severe COPD.

This was a retrospective analysis of prospectively collected data among severe COPD patients who underwent thoracic high-resolution computed tomography, full lung function measurements and maximal CPET with inspiratory manouvers as assessment for a lung volume reduction procedure. ΔIC was calculated by subtracting the end-exercise inspiratory capacity (eIC) from resting IC (rIC) and expressed as a percentage of rIC (ΔIC %). Emphysema quantification was conducted at 3 predefined levels using the syngo PULMO-CT (Siemens AG); a difference >25% between best and worse slice was defined as heterogeneous emphysema.

Fifty patients with heterogeneous (62.7% male; 60.9 ± 7.5 years old; FEV₁% = 32.4 ± 11.4) and 14 with homogeneous emphysema (61.5% male; 62.5 ± 5.9 years old; FEV₁% = 28.1 ± 10.3) fulfilled the enrolment criteria. The groups were matched for all baseline variables. ΔIC% was significantly higher in homogeneous emphysema (39.8% ± 9.8% vs.31.2% ± 13%, p = 0.031), while no other CPET parameter differed between the groups. Upper lobe predominance of emphysema correlated positively with peak oxygen pulse, peak oxygen uptake and peak respiratory rate, and negatively with ΔIC%. Homogeneous emphysema is associated with more DH during maximum exercise in COPD patients.

Bronchoscopic lung volume reduction with endobronchial valves for patients with heterogeneous emphysema and intact interlobar fissures (the BeLieVeR-HIFi study): a randomised controlled trial

BACKGROUND

Lung volume reduction surgery improves survival in selected patients with emphysema, and has generated interest in bronchoscopic approaches that might achieve the same effect with less morbidity and mortality. Previous trials with endobronchial valves have yielded modest group benefits because when collateral ventilation is present it prevents lobar atelectasis.

METHODS

We did a single-centre, double-blind sham-controlled trial in patients with both heterogeneous emphysema and a target lobe with intact interlobar fissures on CT of the thorax. We enrolled stable outpatients with chronic obstructive pulmonary disease who had a forced expiratory volume in 1 s (FEV1) of less than 50% predicted, significant hyperinflation (total lung capacity >100% and residual volume >150%), a restricted exercise capacity (6 min walking distance <450 m), and substantial breathlessness (MRC dyspnoea score ≥3). Participants were randomised (1:1) by computer-generated sequence to receive either valves placed to achieve unilateral lobar occlusion (bronchoscopic lung volume reduction) or a bronchoscopy with sham valve placement (control). Patients and researchers were masked to treatment allocation. The study was powered to detect a 15% improvement in the primary endpoint, the FEV1 3 months after the procedure. Analysis was on an intention-to-treat basis. The trial is registered at controlled-trials.com, ISRCTN04761234.

FINDINGS

50 patients (62% male, FEV1 [% predicted] mean 31·7% [SD 10·2]) were enrolled to receive valves (n=25) or sham valve placement (control, n=25) between March 1, 2012, and Sept 30, 2013. In the bronchoscopic lung volume reduction group, FEV1 increased by a median 8·77% (IQR 2·27-35·85) versus 2·88% (0-8·51) in the control group (Mann-Whitney p=0·0326). There were two deaths in the bronchoscopic lung volume reduction group and one control patient was unable to attend for follow-up assessment because of a prolonged pneumothorax.

INTERPRETATION

Unilateral lobar occlusion with endobronchial valves in patients with heterogeneous emphysema and intact interlobar fissures produces significant improvements in lung function. There is a risk of significant complications and further trials are needed that compare valve placement with lung volume reduction surgery.

FUNDING

Efficacy and Mechanism Evaluation Programme, funded by the Medical Research Council (MRC) and managed by the National Institute for Health Research (NIHR) on behalf of the MRC-NIHR partnership.

Gait speed and readmission following hospitalisation for acute exacerbations of COPD: a prospective study

BACKGROUND

Hospitalisation for acute exacerbations of COPD is associated with high risk of readmission. However, no tool has been validated to stratify patients at discharge for risk of readmission.

AIM

To evaluate the ability of the 4 m gait speed (4MGS), a surrogate marker of frailty, to predict risk of future readmission in hospitalised patients with an acute exacerbation of COPD (AECOPD).

METHODS

213 patients hospitalised with an AECOPD were recruited prospectively. 4MGS was measured on day of discharge. Logistic regression models were used to assess the association between 4MGS and readmission at 90 days after discharge.

RESULTS

Baseline characteristics of the cohort: 52% men; mean age 72 years; median FEV1 35%predicted. Mean (SD) 4MGS at hospital discharge was 0.61 (0.26) ms(-1). Significant increased rates of all-cause readmission at 90 days were seen across quartiles of decreasing 4MGS (Q4 fastest: 11.5%; Q3: 20.4%; Q2: 30.2%; Q1 slowest: 48.2%; p trend<0.001). Compared with Q4, those in the slowest 4MGS quartile had unadjusted ORs (95% CIs) for 90-day readmission of 7.12 (2.61 to 19.44) for the whole cohort and 11.56 (3.08 to 43.35) in those aged 65 or over. A multivariate model incorporating 4MGS, Charlson Index, hospital admission in past year, FEV1%predicted and number of exacerbations in past year in those aged 65 or over predicted 90-day readmission with a C-statistic of 0.86.

CONCLUSIONS

The 4MGS, a surrogate marker of physical frailty, independently predicts the risk of readmission in older patients hospitalised for acute exacerbation of COPD.

TRIAL REGISTRATION NUMBER

NCT01507415.

Neural respiratory drive predicts clinical deterioration and safe discharge in exacerbations of COPD

Rationale

Hospitalised patients with acute exacerbation of COPD may deteriorate despite treatment, with early readmission being common.

Objectives

To investigate whether neural respiratory drive, measured using second intercostal space parasternal muscle electromyography (EMG_para), would identify worsening dyspnoea and physician-defined inpatient clinical deterioration, and predict early readmission.

Methods

Patients admitted to a single-site university hospital with exacerbation of COPD were enrolled. Spirometry, inspiratory capacity (IC), EMG_para, routine physiological parameters, modified early warning score (MEWS), modified Borg scale for dyspnoea and physician-defined episodes of deterioration were recorded daily until discharge. Readmissions at 14 and 28 days post discharge were recorded.

Measurements and main results

120 patients were recruited (age 70±9 years, forced expiratory volume in 1 s (FEV₁) of 30.5±11.2%). Worsening dyspnoea, defined as at least one-point increase in Borg scale, was associated with increases in EMG_para%max and MEWS, whereas an increase in EMG_para%max alone was associated with physician-defined inpatient clinical deterioration. Admission-to-discharge change (Δ) in the normalised value of EMG_para (ΔEMG_para%max) was inversely correlated with ΔFEV₁ (r=−0.38, p<0.001) and ΔIC (r=−0.44, p<0.001). ΔEMG_para%max predicted 14-day readmission (OR 1.13, 95% 1.03 to 1.23) in the whole cohort and 28-day readmission in patients under 85 years (OR 1.09, 95% CI 1.01 to 1.18). Age (OR 1.08, 95% CI 1.03 to 1.14) and 12-month admission frequency (OR 1.29, 1.01 to 1.66), also predicted 28-day readmission in the whole cohort.

Conclusions

Measurement of neural respiratory drive by EMG_para represents a novel physiological biomarker that may be helpful in detecting inpatient clinical deterioration and identifying the risk of early readmission among patients with exacerbations of COPD.

Trial registration

NCT01361451.

Lung Volume Reduction in Emphysema Improves Chest Wall Asynchrony

BACKGROUND

Lung volume reduction (LVR) techniques improve lung function in selected patients with emphysema, but the impact of LVR procedures on the asynchronous movement of different chest wall compartments, which is a feature of emphysema, is not known.

METHODS

We used optoelectronic plethysmography to assess the effect of surgical and bronchoscopic LVR on chest wall asynchrony. Twenty-six patients were assessed before and 3 months after LVR (surgical [n = 9] or bronchoscopic [n = 7]) or a sham/unsuccessful bronchoscopic treatment (control subjects, n = 10). Chest wall volumes were divided into six compartments (left and right of each of pulmonary ribcage [Vrc,p], abdominal ribcage [Vrc,a], and abdomen [Vab]) and phase shift angles (θ) calculated for the asynchrony between Vrc,p and Vrc,a (θRC), and between Vrc,a and Vab (θDIA).

RESULTS

Participants had an FEV₁ of 34.6 ± 18% predicted and a residual volume of 217.8 ± 46.0% predicted with significant chest wall asynchrony during quiet breathing at baseline (θRC, 31.3° ± 38.4°; and θDIA, -38.7° ± 36.3°). Between-group difference in the change in θRC and θDIA during quiet breathing following treatment was 44.3° (95% CI, -78 to -10.6; P = .003) and 34.5° (95% CI, 1.4 to 67.5; P = .007) toward 0° (representing perfect synchrony), respectively, favoring the LVR group. Changes in θRC and θDIA were statistically significant on the treated but not the untreated sides.

CONCLUSIONS

Successful LVR significantly reduces chest wall asynchrony in patients with emphysema.

Neural Respiratory Drive and Arousal in Patients with Obstructive Sleep Apnea Hypopnea

STUDY OBJECTIVES

It has been hypothesized that arousals after apnea and hypopnea events in patients with obstructive sleep apnea are triggered when neural respiratory drive exceeds a certain level, but this hypothesis is based on esophageal pressure data, which are dependent on flow and lung volume. We aimed to determine whether a fixed threshold of respiratory drive is responsible for arousal at the termination of apnea and hypopnea using a flow independent technique (esophageal diaphragm electromyography, EMGdi) in patients with obstructive sleep apnea.

SETTING

Sleep center of state Key Laboratory of Respiratory Disease.

PATIENTS

Seventeen subjects (two women, mean age 53 ± 11 years) with obstructive sleep apnea/hypopnea syndrome were studied.

METHODS

We recorded esophageal pressure and EMGdi simultaneously during overnight full polysomnography in all the subjects.

MEASUREMENTS AND RESULTS

A total of 709 hypopnea events and 986 apnea events were analyzed. There was wide variation in both esophageal pressure and EMGdi at the end of both apnea and hypopnea events within a subject and stage 2 sleep. The EMGdi at the end of events that terminated with arousal was similar to those which terminated without arousal for both hypopnea events (27.6% ± 13.9%max vs 29.9% ± 15.9%max, P = ns) and apnea events (22.9% ± 11.5%max vs 22.1% ± 12.6%max, P = ns). The Pes at the end of respiratory events terminated with arousal was also similar to those terminated without arousal. There was a small but significant difference in EMGdi at the end of respiratory events between hypopnea and apnea (25.3% ± 14.2%max vs 21.7% ± 13.2%max, P < 0.05].

CONCLUSIONS

Our data do not support the concept that there is threshold of neural respiratory drive that is responsible for arousal in patients with obstructive sleep apnea.

Does pulmonary rehabilitation reduce peripheral blood pressure in patients with chronic obstructive pulmonary disease?

Pulmonary rehabilitation (PR) can improve aerobic exercise capacity, health-related quality of life and dyspnoea in patients with chronic obstructive pulmonary disease (COPD). Recent studies have suggested that exercise training may improve blood pressure and arterial stiffness, albeit in small highly selected cohorts. The aim of the study was to establish whether supervised outpatient or unsupervised home PR can reduce peripheral blood pressure. Resting blood pressure was measured in 418 patients with COPD before and after outpatient PR, supervised by a hospital-based team (HOSP). Seventy-four patients with COPD undergoing an unsupervised home-based programme acted as a comparator group (HOME). Despite significant improvements in mean (95% confidence interval) exercise capacity in the HOSP group (56 (50-60) m, p < 0.001) and HOME group (30 (17-42) m, p < 0.001) systolic blood pressure (SBP), diastolic blood pressure (DBP) and mean arterial blood pressure (MAP) did not change in either the HOSP (SBP: p = 0.47; DBP: p = 0.06; MAP: p = 0.38) or HOME group (SBP: p = 0.67; DBP: p = 0.38; MAP: p = 0.76). Planned subgroup analysis of HOSP patients with known hypertension and/or cardiovascular disease showed no impact of PR upon blood pressure. PR is unlikely to reduce blood pressure, and by implication, makes a mechanism of action in which arterial stiffness is reduced, less likely.

MiR-181a: a potential biomarker of acute muscle wasting following elective high-risk cardiothoracic surgery

Introduction

Acute muscle wasting in the critically ill is common and associated with significant morbidity and mortality. Although some aetiological factors are recognised and muscle wasting can be detected early with ultrasound, it not possible currently to predict in advance of muscle loss those who will develop muscle wasting. The ability to stratify the risk of muscle wasting associated with critical illness prior to it becoming clinically apparent would provide the opportunity to predict prognosis more accurately and to intervene at an early stage. MicroRNAs are small non-coding RNAs that modulate post-transcriptional regulation of translation, some are tissue specific and can be detected and quantified in plasma. We hypothesised that certain plasma microRNAs could be biomarkers of ICU acquired muscle weakness.

Methods

Plasma levels of selected microRNAs were measured in pre- and post-operative samples from a previously reported prospective observational study of 42 patients undergoing elective high-risk cardiothoracic surgery, 55% of whom developed muscle wasting.

Results

The rise in miR-181a was significantly higher on the second post-operative day in those who developed muscle wasting at 1 week compared to those who did not (p = 0.03). A rise in miR-181a of greater than 1.7 times baseline had 91% specificity and 56% sensitivity for subsequent muscle wasting. Other microRNAs did not show significant differences between the groups.

Conclusion

Plasma miR-181a deserves further investigation as a potential biomarker of muscle wasting. Additionally, since mir-181a is involved in both regulation of inflammation and muscle regeneration and differentiation; our observation therefore also suggests directions for future research.

Dynamic laryngeal narrowing during exercise: a mechanism for generating intrinsic PEEP in COPD?

INTRODUCTION

Patients with COPD commonly exhibit pursed-lip breathing during exercise, a strategy that, by increasing intrinsic positive end-expiratory pressure, may optimise lung mechanics and exercise tolerance. A similar role for laryngeal narrowing in modulating exercise airways resistance and the respiratory cycle volume-time course is postulated, yet remains unstudied in COPD. The aim of this study was to assess the characteristics of laryngeal narrowing and its role in exercise intolerance and dynamic hyperinflation in COPD.

METHODS

We studied 19 patients (n=8 mild-moderate; n=11 severe COPD) and healthy age and sex matched controls (n=11). Baseline physiological characteristics and clinical status were assessed prior to an incremental maximal cardiopulmonary exercise test with continuous laryngoscopy. Laryngeal narrowing measures were calculated at the glottic and supra-glottic aperture at rest and peak exercise.

RESULTS

At rest, expiratory laryngeal narrowing was pronounced at the glottic level in patients and related to FEV1 in the whole cohort (r=-0.71, p<0.001) and patients alone (r=-0.53, p=0.018). During exercise, glottic narrowing was inversely related to peak ventilation in all subjects (r=-0.55, p=0.0015) and patients (r=-0.71, p<0.001) and peak exercise tidal volume (r=-0.58, p=0.0062 and r=-0.55, p=0.0076, respectively). Exercise glottic narrowing was also inversely related to peak oxygen uptake (% predicted) in all subjects (r=-0.65, p<0.001) and patients considered alone (r=-0.58, p=0.014). Exercise inspiratory duty cycle was related to exercise glottic narrowing for all subjects (r=-0.69, p<0.001) and patients (r=-0.62, p<0.001).

CONCLUSIONS

Dynamic laryngeal narrowing during expiration is prevalent in patients with COPD and is related to disease severity, respiratory duty cycle and exercise capacity.

Bioelectrical impedance phase angle relates to function, disease severity and prognosis in stable chronic obstructive pulmonary disease

BACKGROUND & AIMS

Bioelectrical impedance analysis (BIA) provides a simple method to assess changes in body composition. Raw BIA variables such as phase angle provide direct information on cellular mass and integrity, without the assumptions inherent in estimating body compartments, e.g. fat-free mass (FFM). Phase angle is a strong functional and prognostic marker in many disease states, but data in COPD are lacking. Our aims were to describe the measurement of phase angle in patients with stable COPD and determine the construct and discriminate validity of phase angle by assessing its relationship with established markers of function, disease severity and prognosis.

METHODS

502 outpatients with stable COPD were studied. Phase angle and FFM by BIA, quadriceps strength (QMVC), 4-m gait speed (4MGS), 5 sit-to-stand time (5STS), incremental shuttle walk (ISW), and composite prognostic indices (ADO, iBODE) were measured. Patients were stratified into normal and low phase angle and FFM index.

RESULTS

Phase angle correlated positively with FFM and functional outcomes (r = 0.35-0.66, p < 0.001) and negatively with prognostic indices (r = -0.35 to -0.48, p < 0.001). In regression models, phase angle was independently associated with ISW, ADO and iBODE whereas FFM was removed. One hundred and seventy patients (33.9% [95% CI, 29.9-38.1]) had a low phase angle. Phenotypic characteristics included lower QMVC, ISW, and 4MGS, higher 5STS, ADO and iBODE scores, and more exacerbations and hospital days in past year. The proportion of patients to have died was significantly higher in patients with low phase angle compared to those with normal phase angle (8.2% versus 3.6%, p = 0.02).

CONCLUSION

Phase angle relates to markers of function, disease severity and prognosis in patients with COPD. As a directly measured variable, phase angle offers more useful information than fat-free mass indices.

Sarcopenia in COPD: prevalence, clinical correlates and response to pulmonary rehabilitation

BACKGROUND

Age-related loss of muscle, sarcopenia, is recognised as a clinical syndrome with multiple contributing factors. International European Working Group on Sarcopenia in Older People (EWGSOP) criteria require generalised loss of muscle mass and reduced function to diagnose sarcopenia. Both are common in COPD but are usually studied in isolation and in the lower limbs.

OBJECTIVES

To determine the prevalence of sarcopenia in COPD, its impact on function and health status, its relationship with quadriceps strength and its response to pulmonary rehabilitation (PR).

METHODS

EWGSOP criteria were applied to 622 outpatients with stable COPD. Body composition, exercise capacity, functional performance, physical activity and health status were assessed. Using a case-control design, response to PR was determined in 43 patients with sarcopenia and a propensity score-matched non-sarcopenic group.

RESULTS

Prevalence of sarcopenia was 14.5% (95% CI 11.8% to 17.4%), which increased with age and Global Initiative for Chronic Obstructive Pulmonary Disease (GOLD) stage, but did not differ by gender or the presence of quadriceps weakness (14.9 vs 13.8%, p=0.40). Patients with sarcopenia had reduced exercise capacity, functional performance, physical activity and health status compared with patients without sarcopenia (p<0.001), but responded similarly following PR; 12/43 patients were no longer classified as sarcopenic following PR.

CONCLUSIONS

Sarcopenia affects 15% of patients with stable COPD and impairs function and health status. Sarcopenia does not impact on response to PR, which can lead to a reversal of the syndrome in select patients.