Corticospinal control of respiratory muscles in chronic obstructive pulmonary disease

Pulmonary rehabilitation in Iranian outpatients with mustard gas lung disease: a randomised controlled trial

OBJECTIVE

People with mustard gas lung disease experience cough, sputum, breathlessness and exercise limitation. We hypothesised that pulmonary rehabilitation (PR) would be beneficial in this condition.

DESIGN

An assessor-blind, two-armed, parallel-design randomised controlled clinical trial.

SETTING

Secondary care clinics in Iran.

PARTICIPANTS

60 men with breathlessness due to respiratory disease caused by documented mustard gas exposure, mean (SD) age 52.7 (4.36) years, MRC dyspnoea score 3.5 (0.7), St. George's Respiratory Questionnaire (SGRQ) 72.3 (15.2).

INTERVENTIONS

Participants were allocated either to a 6-week course of thrice-weekly PR (n=31) or to usual care (n=29), with 6-week data for 28 and 26, respectively.

OUTCOME MEASURES

Primary endpoint was change in cycle endurance time at 70% baseline exercise capacity at 6 weeks. Secondary endpoints included 6 min walk distance, quadriceps strength and bulk, body composition and health status. For logistical reasons, blood tests that had been originally planned were not performed and 12-month follow-up was available for only a small proportion.

RESULTS

At 6 weeks, cycle endurance time increased from 377 (140) s to 787 (343) s with PR vs 495 (171) s to 479 (159) s for usual care, effect size +383 (231) s (p<0.001). PR also improved 6 min walk distance+103.2 m (63.6-142.9) (p<0.001), MRC dyspnoea score -0.36 (-0.65 to -0.07) (p=0.016) and quality of life; SGRQ -8.43 (-13.38 to -3.48) p<0.001, as well as quadriceps strength+9.28 Nm (1.89 to 16.66) p=0.015.

CONCLUSION

These data suggest that PR can improve exercise capacity and quality of life in people with breathlessness due to mustard gas lung disease and support the wider provision of this form of care.

TRIAL REGISTRATION NUMBER

IRCT2016051127848N1.

Assessing the effect of transcranial magnetic stimulation on peak cough flow in patients with supratentorial cerebral infarction: A retrospective cohort study

Respiratory dysfunction following supratentorial cerebral infarction leads to pneumonia and is a major cause of mortality. Decreased voluntary cough function impairs the ability to clear mucus or secretions from the airways and increases the risk of aspiration pneumonia. Peak cough flow (PCF) is one of the objective tools for evaluating voluntary cough function. Repetitive transcranial magnetic stimulation (rTMS) could be applied to the respiratory motor cortex to improve respiratory function. Little is known about the effect of rTMS on PCF in patients with supratentorial cerebral infarction during the subacute period. This study aimed to determine whether rTMS treatment could improve PCF in patients with supratentorial cerebral infarction. We retrospectively recruited patients with subacute supratentorial cerebral infarction who underwent a PCF test. The rTMS group received a combination of rTMS treatment for 2 weeks and conventional rehabilitation for 4 weeks. However, the control group underwent only conventional rehabilitation for 4 weeks. PCF tests were performed before and after treatment and the results were compared between the 2 groups. In total, 145 patients with supratentorial cerebral infarctions were recruited. The PCF parameters before and after treatment increased in both the rTMS and control groups. However, the rTMS group showed a greater increase in PCF values compared with the control group. In patients with supratentorial cerebral infarction, the combination of conventional rehabilitation and rTMS in the subacute period may be helpful in improving voluntary cough function compared with conventional rehabilitation alone.

Oscillatory positive expiratory pressure therapy in COPD (O-COPD): a randomised controlled trial

BACKGROUND

Oscillatory positive expiratory pressure (OPEP) devices are intended to facilitate sputum clearance and reduce cough, but there is limited evidence for their effectiveness in COPD, or to guide patient selection. We aimed to assess the impact of OPEP therapy on quality of life and objective measures of cough and sleep disturbance in patients with COPD with regular sputum production.

METHODS

We enrolled stable patients with COPD, who reported sputum production every day or most days, into an assessor-blind, parallel-group, randomised controlled trial comparing 3 months of using an Acapella device against usual care (including use of the active cycle of breathing technique). The primary outcome was cough-related quality of life measured using the Leicester Cough Questionnaire (LCQ). Secondary outcomes included fatigue (Functional Assessment of Chronic Illness Therapy, FACIT score) and generic quality of life (EuroQol-5 Dimensions, EQ-5D). In a substudy (n=45), objective monitoring of cough and disturbance/movement during sleep were also available.

RESULTS

122 participants (61/61 OPEP/control) were recruited, 40% female, 17% smokers, FEV1 38 (25-56)% predicted, and age 62±10 years. 103 completed the study (55/48 OPEP/control). Use of OPEP was associated with an improvement in LCQ compared with controls; MD (95% CI) 1.03 (0.71 to 2.10); (p=0.03), FACIT score 4.68 (1.34 to 8.02); (p<0.001) and EQ-5D 4.00 (0.49 to 19.75); (p=0.04). There was also an improvement in cough frequency -60 (-43 to -95) coughs/24 hours (p<0.001), but no statistically significant effect on sleep disturbance was identified.

CONCLUSIONS

Regular use of an Acapella device improves symptoms and quality of life in people with COPD who produce sputum daily or most days.

TRIAL REGISTRATION NUMBER

ISRCTN44651852.

Ventilatory neural drive in chronically hypercapnic patients with COPD: effects of sleep and nocturnal noninvasive ventilation

Sleep brings major challenges for the control of ventilation in humans, particularly the regulation of arterial carbon dioxide pressure (P _aCO2 ). In patients with COPD, chronic hypercapnia is associated with increased mortality. Therefore, nocturnal high-level noninvasive positive-pressure ventilation (NIV) is recommended with the intention to reduce P _aCO2 down to normocapnia. However, the long-term physiological consequences of P _aCO2 "correction" on the mechanics of breathing, gas exchange efficiency and resulting symptoms (i.e. dyspnoea) remain poorly understood. Investigating the influence of sleep on the neural drive to breathe and its translation to the mechanical act of breathing is of foremost relevance to create a solid rationale for the use of nocturnal NIV. In this review, we critically discuss the mechanisms by which sleep influences ventilatory neural drive and mechanical consequences in healthy subjects and hypercapnic patients with advanced COPD. We then discuss the available literature on the effects of nocturnal NIV on ventilatory neural drive and respiratory mechanics, highlighting open avenues for further investigation.

Dietary nitrate supplementation to enhance exercise capacity in hypoxic COPD: EDEN-OX, a double-blind, placebo-controlled, randomised cross-over study

RATIONALE

Dietary nitrate supplementation improves skeletal muscle oxygen utilisation and vascular endothelial function. We hypothesised that these effects might be sufficient to improve exercise performance in patients with COPD and hypoxia severe enough to require supplemental oxygen.

METHODS

We conducted a single-centre, double-blind, placebo-controlled, cross-over study, enrolling adults with COPD who were established users of long-term oxygen therapy. Participants performed an endurance shuttle walk test, using their prescribed oxygen, 3 hours after consuming either 140 mL of nitrate-rich beetroot juice (BRJ) (12.9 mmol nitrate) or placebo (nitrate-depleted BRJ). Treatment order was allocated (1:1) by computer-generated block randomisation.

MEASUREMENTS

The primary outcome was endurance shuttle walk test time. The secondary outcomes included area under the curve to isotime for fingertip oxygen saturation and heart rate parameters during the test, blood pressure, and endothelial function assessed using flow-mediated dilatation. Plasma nitrate and nitrite levels as well as FE_NO were also measured.

MAIN RESULTS

20 participants were recruited and all completed the study. Nitrate-rich BRJ supplementation prolonged exercise endurance time in all participants as compared with placebo: median (IQR) 194.6 (147.5-411.7) s vs 159.1 (121.9-298.5) s, estimated treatment effect 62 (33-106) s (p<0.0001). Supplementation also improved endothelial function: NR-BRJ group +4.1% (-1.1% to 14.8%) vs placebo BRJ group -5.0% (-10.6% to -0.6%) (p=0.0003).

CONCLUSION

Acute dietary nitrate supplementation increases exercise endurance in patients with COPD who require supplemental oxygen.Trial registration number ISRCTN14888729.

Contemporary perspectives in COPD: Patient burden, the role of gender and trajectories of multimorbidity

An individual's experience of COPD is determined by many factors in addition to the pathological features of chronic bronchitis and emphysema and the symptoms that derive directly from them. Multimorbidity is the norm rather than the exception, so most people with COPD are living with a range of other medical problems which can decrease overall quality of life. COPD is caused by the inhalation of noxious particles or gases, in particular tobacco smoke, but also by early life disadvantage impairing lung development and by occupations where inhaled exposures are common (e.g. industrial, farming and cleaning work). Wealthy people are therefore relatively protected from developing COPD and people who do develop the condition may have reduced resources to cope. COPD is also no longer a condition that predominantly affects men. The prevalence of COPD among women has equalled that of men since 2008 in many high-income countries, due to increased exposure to tobacco, and in low-income countries due to biomass fuels. COPD is one of the leading causes of death in women in the USA, and death rates attributed to COPD in women in some countries are predicted to overtake those of men in the next decade. Many factors contribute to this phenomenon, but in addition to socioeconomic and occupational factors, there is increasing evidence of a higher susceptibility of females to smoking and pollutants. Quality of life is also more significantly impaired in women. Although most medications (bronchodilators and inhaled corticosteroids) used to treat COPD demonstrate similar trends for exacerbation prevention and lung function improvement in men and women, this is an understudied area and clinical trials frequently have a preponderance of males. A better understanding of gender-based predictors of efficacy of all therapeutic interventions is crucial for comprehensive patient care. There is an urgent need to recognize the increasing burden of COPD in women and to facilitate global improvements in disease prevention and management in this specific population. Many individuals with COPD follow a trajectory of both lung function decline and also multimorbidity. Unfavourable lung function trajectories throughout life have implications for later development of other chronic diseases. An enhanced understanding of the temporal associations underlying the development of coexisting diseases is a crucial first step in unravelling potential common disease pathways. Lessons can be learned from exploring disease trajectories of other NCD as well as multimorbidity development. Further research will be essential to explain how early life risk factors commonly influence trajectories of COPD and other diseases, how different diseases develop in relation to each other in a temporal way and how this ultimately leads to different multimorbidity patterns in COPD. This review integrates new knowledge and ideas pertaining to three broad themes (i) the overall burden of disease in COPD, (ii) an unappreciated high burden in women and (iii) the contrast of COPD trajectories and different multimorbidity patterns with trajectories of other NCD. The underlying pathology of COPD is largely irreversible, but many factors noted in the review are potentially amenable to intervention. Health and social care systems need to ensure that effective treatment is accessible to all people with the condition. Preventive strategies and treatments that alter the course of disease are crucial, particularly for patients with COPD as one of many problems.

Lung volume reduction eligibility in patients with COPD completing pulmonary rehabilitation: results from the UK National Asthma and COPD Audit Programme

OBJECTIVES

To establish what proportion of patients completing a UK pulmonary rehabilitation (PR) programme meet the 2018 National Institute for Health and Care Excellence (NICE) chronic obstructive pulmonary disease (COPD) guideline (NG115) criteria to have a respiratory review to establish whether referral to a lung volume reduction multidisciplinary team would be appropriate. This respiratory review would include evaluation of the presence of hyperinflation and the presence of emphysema on CT scan. The NICE criteria include measures of breathlessness and exercise capacity but these parameters are not completely defined.

DESIGN

Observational study.

SETTING

PR programmes across the UK in 2015 (210 centres) and 2017 (184 centres) entering data into the Royal College of Physicians' National Asthma and COPD Audit Programme.

PARTICIPANTS

8295 (55.7%) of 14 889 patients in programmes using incremental shuttle walk test (ISWT) or 6-minute walk test (6MWT) as an outcome measure completed PR, and 4856 (32.6%) had complete data recorded (6MWT/ISWT, baseline spirometry, Medical Research Council (MRC) dyspnoea score).

RESULTS

Depending on the walking test safety threshold adopted for the ISWT (≥140 m or ≥ 80 m) and the MRC dyspnoea score threshold used (MRC score ≥3 or ≥4 at the end of PR), between 4.9% and 18.1% of PR completers met the NICE criteria for a lung volume reduction-focused respiratory review.

CONCLUSIONS

Lung volume reduction therapies are beneficial in appropriately selected patients with COPD, but few procedures are performed, and treatment pathways are unclear. These data help to inform the feasibility of the approach recommended by NICE and highlight the need for future systematic pathways to reduce inequalities in patients being considered for effective treatments.

Physiological sex differences affect the integrative response to exercise: acute and chronic implications

NEW FINDINGS

What is the topic of this review? We review sex differences within physiological systems implicated in exercise performance; specifically, how they integrate to determine metabolic thresholds and fatigability. Thereafter, we discuss the implications that these sex differences might have for long-term adaptation to exercise. What advances does it highlight? The review collates evidence from recent physiological studies that have investigated sex as a biological variable, demonstrating that the physiological response to equivalent 'dosages' of exercise is not the same in males and females; thus, highlighting the need to research diversity in physiological responses to interventions.

ABSTRACT

The anatomical and physiological differences between males and females are thought to determine differences in the limits of human performance. The notion of studying sex as a biological variable has recently been emphasized in the biosciences as a vital step in enhancing human health. In this review, we contend that the effects of biological sex on acute and chronic responses must be studied and accounted for when prescribing aerobic exercise, much like any intervention targeting the optimization of physiological function. Emerging evidence suggests that the response of physiological systems to exercise differs between males and females, potentially mediating the beneficial effects in healthy and clinical populations. We highlight evidence that integrative metabolic thresholds during exercise are influenced by phenotypical sex differences throughout many physiological systems. Furthermore, we discuss evidence that female skeletal muscle is more resistant to fatigue elicited by equivalent dosages of high-intensity exercise. How the different acute responses affect the long-term trainability of males and females is considered, with discussion about tailoring exercise to the characteristics of the individual presented within the context of biological sex. Finally, we highlight the influence of endogenous and exogenous sex hormones on physiological responses to exercise in females. Sex is one of many mediating influences on the outcomes of exercise, and with careful experimental designs, physiologists can advance the collective understanding of diversity in physiology and optimize outcomes for both sexes.

Use of oscillatory positive expiratory pressure (OPEP) devices to augment sputum clearance in COPD: a systematic review and meta-analysis

Introduction

Oscillating positive expiratory pressure (OPEP) devices are intended to facilitate sputum clearance in chronic obstructive pulmonary disease (COPD), but there is uncertainty as to their place in treatment pathways. We aimed to review the existing literature to establish the evidence base for their use.

Methods

A systematic search of records up to March 2020 was performed on PubMed, CINAHL, Medline (Ovid), Cochrane and Embase to retrieve clinical trials that evaluated the efficacy of OPEP devices in patients with COPD. Two independent reviewers retrieved the titles, abstracts and full texts, and completed the data extraction.

Results

Following full-text review of 77 articles, eight (six randomised control trials and 2 cross-over studies) were eligible for inclusion. Pooled analysis showed low-grade evidence that the use of OPEP devices was associated with decreased COPD symptoms and exacerbations (OR 0.37, 95% CI 0.19 to 0.72), and enhanced exercise capacity; 6 min walk distance (mean difference (95% CI), 49.8 m (14.2 m to 85.5 m); p=0.009]). However, studies were mostly short term with the majority having a high risk of bias. The average acceptance, completion and drop-out rates were 82%, 91% and 8%, respectively.

Conclusion

The use of OPEP devices can have a positive impact in COPD, but confidence in effect sizes is low and there is a need for further, higher quality studies to examine their long-term efficacy in COPD as well as to identify specific patient phenotypes that are more likely to respond.

PROSPERO registration number

CRD 42016041835.

Inhibition of central activation of the diaphragm: a mechanism of weaning failure

During a T-tube trial following disconnection of mechanical ventilation, patients failing the trial do not develop contractile diaphragmatic fatigue despite increases in inspiratory pressure output. Studies in volunteers, patients, and animals raise the possibility of spinal and supraspinal reflex mechanisms that inhibit central-neural output under loaded conditions. We hypothesized that diaphragmatic recruitment is submaximal at the end of a failed weaning trial despite concurrent respiratory distress. Tidal transdiaphragmatic pressure (ΔP_di) and electrical activity (ΔEA_di) were recorded with esophago-gastric catheters during a T-tube trial in 20 critically ill patients. During the T-tube trial, ∆EA_di was greater in weaning failure patients than in weaning success patients (P = 0.049). Despite increases in ΔP_di, from 18.1 ± 2.5 to 25.9 ± 3.7 cm H₂O (P < 0.001), rate of transdiaphragmatic pressure development (from 22.6 ± 3.1 to 37.8 ± 6.7 cm H₂O/s; P < 0.0004), and concurrent respiratory distress, ∆EA_di at the end of a failed T-tube trial was half of maximum, signifying inhibition of central neural output to the diaphragm. The increase in ΔP_di in the weaning failure group, while ∆EA_di remained constant, indicates unexpected improvement in diaphragmatic neuromuscular coupling (from 46.7 ± 6.5 to 57.8 ± 8.4 cm H₂O/%; P = 0.006). Redistribution of neural output to the respiratory muscles characterized by a progressive increase in rib cage and accessory muscle contribution to tidal breathing and expiratory muscle recruitment contributed to enhanced coupling. In conclusion, diaphragmatic recruitment is submaximal at the end of a failed weaning trial despite concurrent respiratory distress. This finding signifies that reflex inhibition of central neural output to the diaphragm contributes to weaning failure.

NEW & NOTEWORTHY Research into pathophysiology of failure to wean from mechanical ventilation has excluded several factors, including contractile fatigue, but the precise mechanism remains unknown. We recorded transdiaphragmatic pressure and diaphragmatic electrical activity in patients undergoing a T-tube trial. Diaphragmatic recruitment was submaximal at the end of a failed trial despite concurrent respiratory distress, signifying that inhibition of central neural output to the diaphragm is an important mechanism of weaning failure.

Oral nitrate supplementation to enhance pulmonary rehabilitation in COPD: ON-EPIC a multicentre, double-blind, placebo-controlled, randomised parallel group study

RATIONALE

Dietary nitrate supplementation has been proposed as a strategy to improve exercise performance, both in healthy individuals and in people with COPD. We aimed to assess whether it could enhance the effect of pulmonary rehabilitation (PR) in COPD.

METHODS

This double-blind, placebo-controlled, parallel group, randomised controlled study performed at four UK centres, enrolled adults with Global Initiative for Chronic Obstructive Lung Disease grade II-IV COPD and Medical Research Council dyspnoea score 3-5 or functional limitation to undertake a twice weekly 8-week PR programme. They were randomly assigned (1:1) to either 140 mL of nitrate-rich beetroot juice (BRJ) (12.9 mmol nitrate), or placebo nitrate-deplete BRJ, consumed 3 hours prior to undertaking each PR session. Allocation used computer-generated block randomisation.

MEASUREMENTS

The primary outcome was change in incremental shuttle walk test (ISWT) distance. Secondary outcomes included quality of life, physical activity level, endothelial function via flow-mediated dilatation, fat-free mass index and blood pressure parameters.

RESULTS

165 participants were recruited, 78 randomised to nitrate-rich BRJ and 87 randomised to placebo. Exercise capacity increased more with active treatment (n=57) than placebo (n=65); median (IQR) change in ISWT distance +60 m (10, 85) vs +30 m (0, 70), estimated treatment effect 30 m (95% CI 10 to 40); p=0.027. Active treatment also impacted on systolic blood pressure: treatment group -5.0 mm Hg (-5.0, -3.0) versus control +6.0 mm Hg (-1.0, 15.5), estimated treatment effect -7 mm Hg (95% CI 7 to -20) (p<0.0005). No significant serious adverse events or side effects were reported.

CONCLUSIONS

Dietary nitrate supplementation appears to be a well-tolerated and effective strategy to augment the benefits of PR in COPD.

TRIAL REGISTRATION NUMBER

ISRCTN27860457.

Effects of Chronic and Acute Pulmonary Hyperinflation on Phrenic Nerve Conduction in Patients with COPD

In patients with moderate-to-severe Chronic Obstructive Pulmonary Disorder (COPD), pulmonary hyperinflation can occur at rest and increase during episodes of exacerbation. Among other mechanical constraints, changes in position and configuration of the diaphragm are also induced by increased end-expiratory lung volume. Both descent and flattening of diaphragm might damage the phrenic nerves by stretching their fibers. The study aimed to investigate the phrenic nerve conduction in COPD patients in stable conditions and during COPD exacerbation. In a group of 11 COPD patients without relevant comorbidities in stable conditions and subsequently in another group of 10 COPD patients during in-hospital COPD exacerbation and recovery, measurements of functional respiratory parameters and assessment of phrenic nerves motor conduction by bilateral electric stimulation were performed concurrently. Significant increase in phrenic nerves latency (p < 0.05), but similar amplitude of motor compound muscle action potential (cMAP) was observed in stable COPD patients vs. matched controls (p < 0.05). However, in COPD patients with resting pulmonary hyperinflation as reliably detected by substantial Inspiratory Capacity reduction (<80% pred.), the mean bilateral latency was longer vs. COPD patients without pulmonary hyperinflation (p < 0.02). During COPD exacerbation, in contrast with mean latency, the mean amplitude of phrenic nerves cMAP improved at discharge when compared with in-hospital admission (p < 0.05). In stable COPD patients the velocity of phrenic nerve conduction was impaired mostly in the presence of pulmonary hyperinflation, while during COPD exacerbation where dynamic pulmonary hyperinflation abruptly occurs, the reversible decrease of cMAP amplitude does suggest a temporary, acute axonal damage of phrenic nerves, potentially contributing to diaphragmatic dysfunction in these circumstances.

Diaphragmatic motor cortex hyperexcitability in patients with chronic obstructive pulmonary disease

Background and objectives

Respiratory muscles dysfunction has been reported in COPD. Transcranial magnetic stimulation (TMS) has been used for assessing the respiratory corticospinal pathways particularly of diaphragm. We aimed to study the cortico-diaphragmatic motor system changes in COPD using TMS and to correlate the findings with the pulmonary function.

Methods

A case control study recruited 30 stable COPD from the out-patient respiratory clinic of Main Alexandria University hospital- Egypt and 17 healthy control subjects who were subjected to spirometry. Cortical conduction of the diaphragm was performed by TMS to all participants followed by cervical magnetic stimulation of the phrenic nerve roots. Diaphragmatic resting motor threshold (DRMT), cortical motor evoked potential latency (CMEPL), CMEP amplitude (CMEPA), peripheral motor evoked potential latency (PMEPL), PMEP amplitude (PMEPA) and central motor conduction time (CMCT) were measured.

Results

66.7% of COPD patients had severe and very severe COPD with median age of 59 (55–63) years. There was statistically significant bilateral decrease in DRMT, CMEPA and PMEPA in COPD group versus healthy subjects and significant increase in CMEPL and PMEPL (p <0.01). Left CMCT was significantly prolonged in COPD group versus healthy subjects (p <0.0001) but not right CMCT. Further, there was significant increase in CMEPL and CMCT of left versus right diaphragm in COPD group (p = 0.003 and 0.001 respectively) that inversely correlated with FEV₁% and FVC% predicted. Right and left DRMT were insignificantly different in COPD group (p >0.05) but positively correlated with FEV₁/FVC, FEV₁% and FVC% predicted.

Conclusion

Central cortico-diaphragmatic motor system is affected in COPD patients with heterogeneity of both sides that is correlated with pulmonary function.

Significance

Coticospinal pathway affection could be a factor for development of diaphragmatic dysfunction in COPD patients accordingly its evaluation could help in personalization of COPD management especially pulmonary rehabilitation programs.

Diaphragm quantitative electromyography in difficult-to-treat asthmatic patients

Quantitative electromyography is an important tool to evaluate myopathies, and some difficult-to-treat asthmatic patients may have a subclinical corticosteroid myopathic process, using only inhaled corticosteroid, according to some studies. In this report, diaphragm quantitative electromyography was used to evaluate asthmatic difficult-to-treat patients, comparing them with a control group. Significant differences were obtained in amplitude, duration and size index of motor unit action potentials, with lower parameters in the asthmatic patients, which may indicate a myopathic process.

ERS statement on respiratory muscle testing at rest and during exercise

Assessing respiratory mechanics and muscle function is critical for both clinical practice and research purposes. Several methodological developments over the past two decades have enhanced our understanding of respiratory muscle function and responses to interventions across the spectrum of health and disease. They are especially useful in diagnosing, phenotyping and assessing treatment efficacy in patients with respiratory symptoms and neuromuscular diseases. Considerable research has been undertaken over the past 17 years, since the publication of the previous American Thoracic Society (ATS)/European Respiratory Society (ERS) statement on respiratory muscle testing in 2002. Key advances have been made in the field of mechanics of breathing, respiratory muscle neurophysiology (electromyography, electroencephalography and transcranial magnetic stimulation) and on respiratory muscle imaging (ultrasound, optoelectronic plethysmography and structured light plethysmography). Accordingly, this ERS task force reviewed the field of respiratory muscle testing in health and disease, with particular reference to data obtained since the previous ATS/ERS statement. It summarises the most recent scientific and methodological developments regarding respiratory mechanics and respiratory muscle assessment by addressing the validity, precision, reproducibility, prognostic value and responsiveness to interventions of various methods. A particular emphasis is placed on assessment during exercise, which is a useful condition to stress the respiratory system.

Is phrenic nerve conduction affected in patients with difficult-to-treat asthma?

Objective The aim of this study was to obtain data on phrenic neuroconduction and electromyography of the diaphragm muscle in difficult-to-treat asthmatic patients and compare the results to those obtained in controls. Methods The study consisted of 20 difficult-to-treat asthmatic patients compared with 27 controls. Spirometry, maximal inspiratory and expiratory pressure, chest X-ray, phrenic neuroconduction and diaphragm electromyography data were obtained. Results The phrenic compound motor action potential area was reduced, compared with controls, and all the patients had normal diaphragm electromyography. Conclusion It is possible that a reduced phrenic compound motor action potential area, without electromyography abnormalities, could be related to diaphragm muscle fiber abnormalities due to overload activity.

Corticospinal excitability during fatiguing whole body exercise

The corticospinal pathway is considered the primary conduit for voluntary motor control in humans. The efficacy of the corticospinal pathway to relay neural signals from higher brain areas to the locomotor muscle, i.e., corticospinal excitability, is subject to alterations during exercise. While the integrity of this motor pathway has historically been examined during single-joint contractions, a small number of investigations have recently focused on whole body exercise, such as cycling or rowing. Although differences in methodologies employed between these studies complicate the interpretation of the existing literature, it appears that the net excitability of the corticospinal pathway remains unaltered during fatiguing whole body exercise. Importantly, this lack of an apparent effect does not designate the absence of change, but a counterbalance of excitatory and inhibitory influences on the two components of the corticospinal pathway, namely the motor cortex and the spinal motoneurons. Specific emphasis is put on group III/IV afferent feedback from locomotor muscle which has been suggested to play a significant role in mediating these changes. Overall, this review aims at summarizing our limited understanding of how fatiguing whole body exercise influences the corticospinal pathway.

Phrenic nerve conduction studies: normative data and technical aspects

OBJECTIVE

The aim of the present study was to define normative data of phrenic nerve conduction parameters of a healthy population.

METHODS

Phrenic nerve conduction studies were performed in 27 healthy volunteers.

RESULTS

The normative limits for expiratory phrenic nerve compound muscle action potential were: amplitude (0.47 mv - 0.83 mv), latency (5.74 ms - 7.10 ms), area (6.20 ms/mv - 7.20 ms/mv) and duration (18.30 ms - 20.96 ms). Inspiratory normative limits were: amplitude (0.67 mv - 1.11 mv), latency (5.90 ms - 6.34 ms), area (5.62 ms/mv - 6.72 ms/mv) and duration (13.77 ms - 15.37 ms).

CONCLUSION

The best point of phrenic nerve stimulus in the neck varies among individuals between the medial and lateral border of the clavicular head of the sternocleidomastoid muscle and stimulation of both sites, then choosing the best phrenic nerve response, seems to be the appropriate procedure.

Endobronchial valves for emphysema: an individual patient-level reanalysis of randomised controlled trials

Introduction

Endobronchial valve placement has potential as a treatment for patients with chronic obstructive pulmonary disease (COPD). However, a robust evidence base will be needed to convince commissioners of healthcare that it is a high-value treatment. We sought to develop the evidence base by performing an individual patient-level analysis of randomised controlled trials in people with heterogeneous emphysema and an absence of collateral ventilation.

Methods

A literature search (PROSPERO register CRD42016048127) identified two trials meeting these criteria, the BelieVeR-HIFi and STELVIO studies. Anonymised individual patient data were obtained from investigators and analysed. The primary outcome measure was a comparison of change in forced expiratory volume in 1 s (FEV₁) from baseline between the treatment and control groups. Secondary end points were change from baseline in 6 min walk distance (6MWD), Medical Research Council dyspnoea score and St George’s Respiratory Questionnaire (SGRQ).

Results

114 individuals were treated with 3-month to 6-month follow-up data available for 101 individuals. FEV₁ improved by 23.1 (±28.3)% in patients treated with valves with a mean (95% CI) difference in response between groups of 17.8 (26.5, 9.2)% (p<0.0001). Relative to controls valve placement was associated with a fall in residual volume of 0.64 (0.43, 0.86) L (p<0.0001), a 9.5 (3.5, 15.6) unit fall in SGRQ (p=0.0022) and a 64.2 (94.0, 34.5) m increase in 6MWD. There were three deaths in the treatment arm and the pneumothorax rate was 15%.

Conclusions

These data strengthen the evidence that endobronchial valve treatment can produce clinically meaningful improvements in appropriately selected COPD patients.

Functional connectivity and information flow of the respiratory neural network in chronic obstructive pulmonary disease

Breathing involves a complex interplay between the brainstem automatic network and cortical voluntary command. How these brain regions communicate at rest or during inspiratory loading is unknown. This issue is crucial for several reasons: (i) increased respiratory loading is a major feature of several respiratory diseases, (ii) failure of the voluntary motor and cortical sensory processing drives is among the mechanisms that precede acute respiratory failure, (iii) several cerebral structures involved in responding to inspiratory loading participate in the perception of dyspnea, a distressing symptom in many disease. We studied functional connectivity and Granger causality of the respiratory network in controls and patients with chronic obstructive pulmonary disease (COPD), at rest and during inspiratory loading. Compared with those of controls, the motor cortex area of patients exhibited decreased connectivity with their contralateral counterparts and no connectivity with the brainstem. In the patients, the information flow was reversed at rest with the source of the network shifted from the medulla towards the motor cortex. During inspiratory loading, the system was overwhelmed and the motor cortex became the sink of the network. This major finding may help to understand why some patients with COPD are prone to acute respiratory failure. Network connectivity and causality were related to lung function and illness severity. We validated our connectivity and causality results with a mathematical model of neural network. Our findings suggest a new therapeutic strategy involving the modulation of brain activity to increase motor cortex functional connectivity and improve respiratory muscles performance in patients. Hum Brain Mapp 37:2736–2754, 2016. © 2016 The Authors Human Brain Mapping Published by Wiley Periodicals, Inc.

Electroencephalographic detection of respiratory-related cortical activity in humans: from event-related approaches to continuous connectivity evaluation

The presence of a respiratory-related cortical activity during tidal breathing is abnormal and a hallmark of respiratory difficulties, but its detection requires superior discrimination and temporal resolution. The aim of this study was to validate a computational method using EEG covariance (or connectivity) matrices to detect a change in brain activity related to breathing. In 17 healthy subjects, EEG was recorded during resting unloaded breathing (RB), voluntary sniffs, and breathing against an inspiratory threshold load (ITL). EEG were analyzed by the specially developed covariance-based classifier, event-related potentials, and time-frequency (T-F) distributions. Nine subjects repeated the protocol. The classifier could accurately detect ITL and sniffs compared with the reference period of RB. For ITL, EEG-based detection was superior to airflow-based detection (P < 0.05). A coincident improvement in EEG-airflow correlation in ITL compared with RB (P < 0.05) confirmed that EEG detection relates to breathing. Premotor potential incidence was significantly higher before inspiration in sniffs and ITL compared with RB (P < 0.05), but T-F distributions revealed a significant difference between sniffs and RB only (P < 0.05). Intraclass correlation values ranged from poor (-0.2) to excellent (1.0). Thus, as for conventional event-related potential analysis, the covariance-based classifier can accurately predict a change in brain state related to a change in respiratory state, and given its capacity for near "real-time" detection, it is suitable to monitor the respiratory state in respiratory and critically ill patients in the development of a brain-ventilator interface.

Neural respiratory drive and breathlessness in COPD

The aim of this study was to test the hypothesis that neural respiratory drive, measured using diaphragm electromyogram (EMGdi) activity expressed as a percentage of maximum (EMGdi%max), is closely related to breathlessness in chronic obstructive pulmonary disease. We also investigated whether neuroventilatory uncoupling contributes significantly to breathlessness intensity over an awareness of levels of neural respiratory drive alone. EMGdi and ventilation were measured continuously during incremental cycle and treadmill exercise in 12 chronic obstructive pulmonary disease patients (forced expiratory volume in 1 s±sd was 38.7±14.5 % pred). EMGdi was expressed both as EMGdi%max and relative to tidal volume expressed as a percentage of predicted vital capacity to quantify neuroventilatory uncoupling. EMGdi%max was closely related to Borg breathlessness in both cycle (r=0.98, p=0.0001) and treadmill exercise (r=0.94, p=0.005), this relationship being similar to that between neuroventilatory uncoupling and breathlessness (cycling r=0.94, p=0.005; treadmill r=0.91, p=0.01). The relationship between breathlessness and ventilation was poor when expansion of tidal volume became limited. In chronic obstructive pulmonary disease the intensity of exertional breathlessness is closely related to EMGdi%max. These data suggest that breathlessness in chronic obstructive pulmonary disease can be largely explained by an awareness of levels of neural respiratory drive, rather than the degree of neuroventilatory uncoupling. EMGdi%max could provide a useful physiological biomarker for breathlessness in chronic obstructive pulmonary disease.

An official American Thoracic Society/European Respiratory Society statement: update on limb muscle dysfunction in chronic obstructive pulmonary disease

BACKGROUND

Limb muscle dysfunction is prevalent in chronic obstructive pulmonary disease (COPD) and it has important clinical implications, such as reduced exercise tolerance, quality of life, and even survival. Since the previous American Thoracic Society/European Respiratory Society (ATS/ERS) statement on limb muscle dysfunction, important progress has been made on the characterization of this problem and on our understanding of its pathophysiology and clinical implications.

PURPOSE

The purpose of this document is to update the 1999 ATS/ERS statement on limb muscle dysfunction in COPD.

METHODS

An interdisciplinary committee of experts from the ATS and ERS Pulmonary Rehabilitation and Clinical Problems assemblies determined that the scope of this document should be limited to limb muscles. Committee members conducted focused reviews of the literature on several topics. A librarian also performed a literature search. An ATS methodologist provided advice to the committee, ensuring that the methodological approach was consistent with ATS standards.

RESULTS

We identified important advances in our understanding of the extent and nature of the structural alterations in limb muscles in patients with COPD. Since the last update, landmark studies were published on the mechanisms of development of limb muscle dysfunction in COPD and on the treatment of this condition. We now have a better understanding of the clinical implications of limb muscle dysfunction. Although exercise training is the most potent intervention to address this condition, other therapies, such as neuromuscular electrical stimulation, are emerging. Assessment of limb muscle function can identify patients who are at increased risk of poor clinical outcomes, such as exercise intolerance and premature mortality.

CONCLUSIONS

Limb muscle dysfunction is a key systemic consequence of COPD. However, there are still important gaps in our knowledge about the mechanisms of development of this problem. Strategies for early detection and specific treatments for this condition are also needed.

Cortical implication in lower voluntary muscle force production in non-hypoxemic COPD patients

Recent studies have shown that muscle alterations cannot totally explain peripheral muscle weakness in COPD. Cerebral abnormalities in COPD are well documented but have never been implicated in muscle torque production. The purpose of this study was to assess the neural correlates of quadriceps torque control in COPD patients. Fifteen patients (FEV1 54.1±3.6% predicted) and 15 age- and sex-matched healthy controls performed maximal (MVCs) and submaximal (SVCs) voluntary contractions at 10, 30 and 50% of the maximal voluntary torque of the knee extensors. Neural activity was quantified with changes in functional near-infrared spectroscopy oxyhemoglobin (fNIRS-HbO) over the contralateral primary motor (M1), primary somatosensory (S1), premotor (PMC) and prefrontal (PFC) cortical areas. In parallel to the lower muscle torque, the COPD patients showed lower increase in HbO than healthy controls over the M1 (p<0.05), PMC (p<0.05) and PFC areas (p<0.01) during MVCs. In addition, they exhibited lower HbO changes over the M1 (p<0.01), S1 (p<0.05) and PMC (p<0.01) areas during SVCs at 50% of maximal torque and altered motor control characterized by higher torque fluctuations around the target. The results show that low muscle force production is found in a context of reduced motor cortex activity, which is consistent with central nervous system involvement in COPD muscle weakness.

Neural mechanisms underlying breathing complexity

Breathing is maintained and controlled by a network of automatic neurons in the brainstem that generate respiratory rhythm and receive regulatory inputs. Breathing complexity therefore arises from respiratory central pattern generators modulated by peripheral and supra-spinal inputs. Very little is known on the brainstem neural substrates underlying breathing complexity in humans. We used both experimental and theoretical approaches to decipher these mechanisms in healthy humans and patients with chronic obstructive pulmonary disease (COPD). COPD is the most frequent chronic lung disease in the general population mainly due to tobacco smoke. In patients, airflow obstruction associated with hyperinflation and respiratory muscles weakness are key factors contributing to load-capacity imbalance and hence increased respiratory drive. Unexpectedly, we found that the patients breathed with a higher level of complexity during inspiration and expiration than controls. Using functional magnetic resonance imaging (fMRI), we scanned the brain of the participants to analyze the activity of two small regions involved in respiratory rhythmogenesis, the rostral ventro-lateral (VL) medulla (pre-Bötzinger complex) and the caudal VL pons (parafacial group). fMRI revealed in controls higher activity of the VL medulla suggesting active inspiration, while in patients higher activity of the VL pons suggesting active expiration. COPD patients reactivate the parafacial to sustain ventilation. These findings may be involved in the onset of respiratory failure when the neural network becomes overwhelmed by respiratory overload We show that central neural activity correlates with airflow complexity in healthy subjects and COPD patients, at rest and during inspiratory loading. We finally used a theoretical approach of respiratory rhythmogenesis that reproduces the kernel activity of neurons involved in the automatic breathing. The model reveals how a chaotic activity in neurons can contribute to chaos in airflow and reproduces key experimental fMRI findings.

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.

Renin-angiotensin system blockade: a novel therapeutic approach in chronic obstructive pulmonary disease

ACE (angiotensin-converting enzyme) inhibitors and ARBs (angiotensin II receptor blockers) are already widely used for the treatment and prevention of cardiovascular disease and their potential role in other disease states has become increasingly recognized. COPD (chronic obstructive pulmonary disease) is characterized by pathological inflammatory processes involving the lung parenchyma, airways and vascular bed. The aim of the present review is to outline the role of the RAS (renin-angiotensin system) in the pathogenesis of COPD, including reference to results from fibrotic lung conditions and pulmonary hypertension. The review will, in particular, address the emerging evidence that ACE inhibition could have a beneficial effect on skeletal muscle function and cardiovascular co-morbidity in COPD patients. The evidence to support the effect of RAS blockade as a novel therapeutic approach in COPD will be discussed.

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.

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.

Inspiratory resistances facilitate the diaphragm response to transcranial stimulation in humans

Background

Breathing in humans is dually controlled for metabolic (brainstem commands) and behavioral purposes (suprapontine commands) with reciprocal modulation through spinal integration. Whereas the ventilatory response to chemical stimuli arises from the brainstem, the compensation of mechanical loads in awake humans is thought to involve suprapontine mechanisms. The aim of this study was to test this hypothesis by examining the effects of inspiratory resistive loading on the response of the diaphragm to transcranial magnetic stimulation.

Results

Six healthy volunteers breathed room air without load (R0) and then against inspiratory resistances (5 and 20 cmH₂O/L/s, R5 and R20). Ventilatory variables were recorded. Transcranial magnetic stimulation (TMS) was performed during early inspiration (I) or late expiration (E), giving rise to motor evoked potentials (MEPs) in the diaphragm (Di) and abductor pollicis brevis (APB). Breathing frequency significantly decreased during R20 without any other change. Resistive breathing had no effect on the amplitude of Di MEPs, but shortened their latency (R20: -0.903 ms, p = 0.03) when TMS was superimposed on inspiration. There was no change in APB MEPs.

Conclusion

Inspiratory resistive breathing facilitates the diaphragm response to TMS while it does not increase the automatic drive to breathe. We interpret these findings as a neurophysiological substratum of the suprapontine nature of inspiratory load compensation in awake humans.

Predictive factors for tracheostomy in neurocritical care patients with spontaneous supratentorial hemorrhage

BACKGROUND

Up to 30% of patients with supratentorial intracerebral hemorrhage (ICH) require mechanical ventilation during the course of treatment. For these patients, tracheostomy is necessary in cases of protracted weaning. As only limited data exist about predictors for a tracheostomy in patients with ICH, the aim of this study was to investigate the frequency of tracheostomy and clinical findings that increase the risk for a tracheostomy in patients with supratentorial hemorrhage.

METHODS

A total of 392 patients with supratentorial ICH were analyzed. The parameters age, gender, chronic obstructive pulmonary disease (COPD), Glasgow Coma Scale on admission, ganglionic or non-ganglionic localization, presence of ventricular hemorrhage, hydrocephalus, hematoma volume, and hematoma evacuation were investigated. The effects on the end-point tracheostomy were analyzed using multivariate regression analyses.

RESULTS

The overall need for tracheostomy was 9.9% (16.3% in patients with ganglionic hemorrhage versus 2.8% in patients with non-ganglionic hemorrhages). 31% of the ventilated patients required tracheostomy. The risk for tracheostomy was increased eightfold in patients who developed hydrocephalus. The presence of ventricular blood, in general, showed no significant impact on the need for tracheostomy, whereas hemorrhage extending into the third and fourth ventricles in conjunction with hydrocephalus increased the risk for tracheostomy. The hematoma volume correlated positively with the risk for tracheostomy.

CONCLUSIONS

Our study demonstrates that approximately 10% of patients with ICH require tracheostomy during the course of their disease. Presence of COPD, hematoma volume, ganglionic location of the hematoma, and the development of hydrocephalus are predisposing factors for tracheostomy.

Motor control of the costal and crural diaphragm – insights from transcranial magnetic stimulation in man

The costal and crural parts of the diaphragm differ in their embryological development and physiological function. It is not known if this is reflected in differences in their motor cortical representation. We compared the response of the costal and crural diaphragms using varying intensities of transcranial magnetic stimulation of the motor cortex at rest and during submaximal and maximal inspiratory efforts. The costal and crural motor evoked potential recruitment curves during submaximal inspiratory efforts were similar. The response to stimulation before, during and at 10 and 30 min after 44 consecutive maximal inspiratory efforts was also the same. Using paired stimulations to investigate intra-cortical facilitatory and inhibitory circuits we found no difference between the costal and crural response with varying interstimulus intervals, or when conditioning and test stimulus intensity were varied. We conclude that supraspinal control of the costal and crural diaphragm is identical during inspiratory tasks.

Excitability of the motor cortical representation of the external anal sphincter

This study was designed to assess the excitability of the motor cortical representation of the external anal sphincter by using transcranial magnetic stimulation (TMS). In six healthy volunteers, the rest motor threshold and the duration of the cortical silent period were determined with single TMS pulses, and the intracortical inhibition and facilitation were measured with paired TMS pulses. Values obtained from the anal sphincter were compared with those obtained from a muscle in the right hand. All subjects completed the study. Rest motor threshold and intracortical facilitation were similar in both muscles. In contrast, cortical silent period duration and intra-cortical inhibition were less for the anal sphincter than for hand muscle. This study has opened new perspectives for the investigation of anal sphincter cortical control in humans.