Respiratory management of patients with neuromuscular disease: current perspectives

Future Directions for Respiratory Muscle Training in Neuromuscular Disorders: A Scoping Review

BACKGROUND

Respiratory muscle training (RMT) aims to improve inspiratory and/or expiratory muscle function in neuromuscular disorders (NMDs). A comprehensive overview of the available literature is lacking. This scoping review explores methodological characteristics, (adverse) effects, and adherence of RMT studies in NMDs. Moreover, it identifies limitations and research gaps in the literature and provides future research directions.

SUMMARY

Eligible studies were identified using MEDLINE, Embase, Cochrane Database of Systematic Reviews, and Cochrane Central Register of Controlled Trials databases. Three reviewers independently selected articles. Inclusion criteria were English language, original research articles on RMT using a device, patients with an NMD, and pulmonary function tests or respiratory muscle strength as outcome measures. We included NMDs with slow, intermediate and fast progression. Exclusion criteria were critically ill patients, weaning from mechanical ventilation, other neurological disorders, and RMT combined with non-respiratory interventions. One reviewer extracted the data on patients' characteristics, methodological characteristics, results of outcome measures, adverse events, and patient adherence. Forty-five studies were identified. We found a large diversity in study designs and training protocols. The effects of RMT on respiratory muscle strength and/or endurance are variable. Patient adherence was high and no serious adverse events were reported.

KEY MESSAGES

The diversity in studies across the available literature precludes definitive conclusions regarding the effects of RMT on respiratory muscle function and clinically relevant outcomes in NMDs. Therefore, well-powered and -designed studies that focus on clinically relevant outcomes and assess whether RMT can improve or offset deterioration of respiratory muscle weakness in NMDs are needed.

Responsiveness of respiratory function in Parkinson's Disease to an integrative exercise programme: A prospective cohort study

INTRODUCTION

Respiratory disorders are the most common cause of death in Parkinson's Disease (PD). Conflicting data exist on the aetiology of respiratory dysfunction in PD and few studies examine the effects of exercise-based interventions on respiratory measures. This study was conducted to better understand respiratory dysfunction in PD and to identify measures of dysfunction responsive to an integrative exercise programme.

OBJECTIVES

The objectives were to compare baseline respiratory measures with matched, published population norms and to examine immediate and longer-term effects of a 12-week integrated exercise programme on these measures.

DESIGN

Twenty-three people with mild PD (median Hoehn & Yahr = 2) self-selected to participate in this exploratory prospective cohort study. Evaluation of participants occurred at three time points: at baseline; following the 12-week exercise programme and at 4-month follow-up.

OUTCOME MEASURES

Outcome measures included: Forced Vital Capacity (FVC), Forced Expiratory Volume in 1 second (FEV1), FEV1/FVC ratio, Peak Expiratory Flow (PEF), Inspiratory Muscle Strength (MIP), Expiratory Muscle Strength (MEP), Peak Cough Flow (PCF), and Cardiovascular Fitness measures of estimated VO2 max and 6-Minute Walk Test (6MWT).

RESULTS

Compared to published norms, participants had impaired cough, reduced respiratory muscle strength, FEV, FVC, PEF and cardiovascular fitness. Post exercise intervention, statistically significant improvements were noted in MEP, cardiovascular fitness, and PEF. However only gains in PEF were maintained at 4-month follow-up.

CONCLUSIONS

Significant respiratory dysfunction exists, even in the early stages of PD. Metrics of respiratory muscle strength, peak expiratory flow and cardiovascular fitness appear responsive to an integrative exercise programme.

Respiratory Muscle Strength Is Related to Handgrip Performance in Community-Dwelling Persons Aged 80+ from the BUTTERFLY Study

INTRODUCTION

This study aimed to evaluate the association of respiratory muscle strength with sarcopenia and its indicators in the oldest old.

METHODS

Maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), and sarcopenia-related factors (handgrip strength and appendicular lean mass) were evaluated in a cohort of n = 286 (45.5% female) non-frail, community-dwelling persons aged 83.6 ± 3.0 years (age range 80-97 years).

RESULTS

The sample presented a sarcopenia prevalence of 32.2%. Sarcopenic subjects showed comparable MIP and MEP as non-sarcopenic ones (female: MIP 43.9 ± 18.9 vs. 50.3 ± 19.5, p = 0.053; MEP 63.0 ± 23.0 vs. 69.2 ± 19.1, p = 0.067; male: MIP, 65.1 ± 24.4 vs. 64.4 ± 23.9, p = 0.433; MEP 87.7 ± 33.3 vs. 93.8 ± 30.9, p = 0.124). Statistically significant but very low associations were found between grip strength and MIP (r = 0.193 for male, p < 0.05 and r = 0.257 for female participants, p < 0.01) and MEP (r = 0.200 for male, p < 0.01 and r = 0.191 for female participants, p < 0.05). Lean mass was significantly correlated to MIP and MEP in female (r = 0.253, p < 0.01 and r = 0.343, p < 0.01, respectively), whereas this association was not found in male participants. Grip strength was the only statistically significant predictor of MEP (r2 = 0.212, p < 0.001), while MIP was independently predicted by age, male sex, and grip strength (r2 = 0.177, p < 0.001).

CONCLUSIONS

Peripheral muscle strength is a statistically significant, albeit weak predictor for respiratory muscle strength in well-functioning, community-dwelling persons aged 80+. When confronted to a low grip strength, one should be aware of concomitant respiratory muscle weakness, as this is a known risk factor for atelectasis and pneumonia. Given the relatively low association with handgrip strength, respiratory muscle strength testing might be indicated.

Exploring Factors That Prolong the Diagnosis of Myasthenia Gravis

Background and Objectives

Myasthenia gravis (MG) is a condition with significant phenotypic variability, posing a diagnostic challenge to many clinicians worldwide. Prolonged diagnosis can lead to reduced remission rates and morbidity. This study aimed to identify factors leading to a longer time to diagnosis in MG that could be addressed in future to optimize diagnosis time.

Methods

One hundred and ten patients from 3 institutions in Melbourne, Australia, were included in this retrospective cohort study. Demographic and clinical data were collected for these patients over the first 5 years from diagnosis and at 10 years. Nonparametric statistical analysis was used to identify factors contributing to a longer diagnosis time.

Results

The median time for MG diagnosis was 102 (345) days. 90% of patients were diagnosed before 1 year. Female patients took longer than male patients to be diagnosed (p = 0.013). The time taken for first presentation after symptom onset contributed most to diagnosis time (median 17 [141] days), with female patients and not working as contributory factors. Neurology referral took longer if patients had diplopia (p = 0.022), respiratory (p = 0.026) symptoms, or saw an ophthalmologist first (p < 0.001). Outpatient management compared with inpatient was associated with a longer time to be seen by a neurologist from referral (p < 0.001), for the first diagnostic result to return (p = 0.001), and for the result to be reviewed (p < 0.001). Ocular MG had a median greater time to neurologist review than generalized MG (median 5 [25] days vs 1 [13] days, p = 0.035). Electrophysiology tests took longer for outpatients than inpatients (median 21 [35] days vs 2 [8] days, p < 0.001). Outpatients were also started on treatment later than inpatients (p < 0.001). There was no association of MG severity, ethnicity, age, medical and ocular comorbidities, and public or private health service on diagnosis time. There was also no impact of time to diagnosis on Myasthenia Gravis Foundation of America outcomes, number of follow-ups or hospitalizations, or prevalence of treatments used. This study is limited by low patient numbers and its retrospective nature.

Discussion

This study identified several factors that can contribute to a prolonged diagnosis time of MG. Patient and clinician education about MG and outpatient diagnostic efficiency needs emphasis. Further studies are also needed to explore the delayed presentation time of women and nonworking patients in MG.

Expanded central role of the respiratory physiotherapists in the community setting

The development of community hubs through the Slaintecare initiative will rely on respiratory physiotherapists and clinical nurse specialists for the management of chronic respiratory diseases. The role of the respiratory physiotherapist has evolved dramatically over the last decade. We review the increasing scope of practice of the physiotherapist and the evidence base for same. We pay particular attention to the role of the physiotherapist in areas such as pulmonary rehabilitation, sputum clearance, neuromuscular disease, chronic respiratory failure, ambulatory oxygen assessments and dysfunctional breathing. We give an in depth review of sputum clearance techniques. We also address areas of potential future expansion for the role of the physiotherapist such as prescription and initiation of non-invasive ventilation.

Provisional practice recommendation for the management of myopathy in VCP-associated multisystem proteinopathy

Valosin-containing protein (VCP)-associated multisystem proteinopathy (MSP) is a rare genetic disorder with abnormalities in the autophagy pathway leading to various combinations of myopathy, bone diseases, and neurodegeneration. Ninety percent of patients with VCP-associated MSP have myopathy, but there is no consensus-based guideline. The goal of this working group was to develop a best practice set of provisional recommendations for VCP myopathy which can be easily implemented across the globe. As an initiative by Cure VCP Disease Inc., a patient advocacy organization, an online survey was initially conducted to identify the practice gaps in VCP myopathy. All prior published literature on VCP myopathy was reviewed to better understand the different aspects of management of VCP myopathy, and several working group sessions were conducted involving international experts to develop this provisional recommendation. VCP myopathy has a heterogeneous clinical phenotype and should be considered in patients with limb-girdle muscular dystrophy phenotype, or any myopathy with an autosomal dominant pattern of inheritance. Genetic testing is the only definitive way to diagnose VCP myopathy, and single-variant testing in the case of a known familial VCP variant, or multi-gene panel sequencing in undifferentiated cases can be considered. Muscle biopsy is important in cases of diagnostic uncertainty or lack of a definitive pathogenic genetic variant since rimmed vacuoles (present in ~40% cases) are considered a hallmark of VCP myopathy. Electrodiagnostic studies and magnetic resonance imaging can also help rule out disease mimics. Standardized management of VCP myopathy will optimize patient care and help future research initiatives.

Disruption of cardio-pulmonary coupling in myopathies: Pathophysiological and mechanistic characterization with special emphasis on nemaline myopathy

The heart and lung are in continuous reciprocal interaction that creates a functional and anatomical reserve referred to as cardiopulmonary coupling (CPC). Disruption of CPC can occur due to various cardiac or pulmonary pathologies but also can occur in patients with myopathies. Nemaline myopathy (NM) is a skeletal muscle heterogeneous disorder due to contractile proteins' gene mutations that impact lung and cardiac mechanics and thus is expected to adversely affect CPC in a complex manner. We present a case of NM and we review the literature on cardiac and pulmonary effects of myopathy-related disruption of CPC.

Long-Term Ventilation in Children with Medical Complexity: A Challenging Issue

Children with medical complexity (CMCs) represent a subgroup of children who may have congenital or acquired multisystemic disease. CMCs are frequently predisposed to respiratory problems and often require long-term mechanical ventilation (LTMV). The indications for LTMV in CMCs are increasing, but gathering evidence about indications, titration, and monitoring is currently the most difficult challenge due to the absence of validated data. The aim of this review was to examine the clinical indications and ethical considerations for the initiation, continuation, or withdrawal of LTMV among CMCs. The decision to initiate long-term ventilation should always be based on clinical and ethical considerations and should be shared with the parents.

Clinical Characteristics and Outcome of MDR/XDR Bacterial Infections in a Neuromuscular Semi-Intensive/Sub-Intensive Care Unit

(1) Background: The aim of this study was to assess the clinical and microbiological characteristics of multidrug-resistant infections in a neuromuscular semi-intensive/sub-intensive care unit; (2) Methods: Retrospective analysis on data from 18 patients with NMD with proven MDRO/XDRO colonisation/infection from August 2021 to March 2022 was carried out; (3) Results: Ten patients were males (55.6%), with a median age of 54 years, and there were fourteen patients (77.8%) with amyotrophic lateral sclerosis. All patients had at least one invasive device. Ten (55.6%) patients developed MDRO/XDRO infection (with a median time of 24 days) while six (33.3%) were colonised. The Charlson comorbidity index was >2 in both groups but higher in the infected compared with the colonised (4.5 vs. 3). Infected patients were mostly females (seven patients) with a median age of 62 years. The most common pathogens were Acinetobacter baumannii and Pseudomonas aeruginosa, infecting four (28.6%) patients each. Of eighteen infectious episodes, nine were pneumonia (hospital-acquired in seven cases). Colistin was the most commonly active antibiotic while carbapenems were largely inactive. Eradication of infection occurred in seven infectious episodes (38.9%). None of those with infection died; (4) Conclusions: MDRO/XDRO infections are common in patients with neuromuscular diseases, with carbapenem-resistant non-fermenting Gram-negative bacilli prevailing. These infections were numerically associated with the female sex, greater age, and comorbidities. Both eradication and infection-related mortality appeared low. We highlight the importance of infection prevention in this vulnerable population.

Neuromuscular Complications of SARS-CoV-2 and Other Viral Infections

In this article we review complications to the peripheral nervous system that occur as a consequence of viral infections, with a special focus on complications of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). We discuss neuromuscular complications in three broad categories; the direct consequences of viral infection, autoimmune neuromuscular disorders provoked by viral infections, and chronic neurodegenerative conditions which have been associated with viral infections. We also include discussion of neuromuscular disorders that are treated by immunomodulatory therapies, and how this affects patient susceptibility in the current context of the coronavirus disease 2019 (COVID-19) pandemic. COVID-19 is associated with direct consequences to the peripheral nervous system via presumed direct viral injury (dysgeusia/anosmia, myalgias/rhabdomyolysis, and potentially mononeuritis multiplex) and autoimmunity (Guillain Barré syndrome and variants). It has important implications for people receiving immunomodulatory therapies who may be at greater risk of severe outcomes from COVID-19. Thus far, chronic post-COVID syndromes (a.k.a: long COVID) also include possible involvement of the neuromuscular system. Whether we may observe neuromuscular degenerative conditions in the longer term will be an important question to monitor in future studies.

Multisystem Proteinopathy Due to VCP Mutations: A Review of Clinical Heterogeneity and Genetic Diagnosis

In this work, we review clinical features and genetic diagnosis of diseases caused by mutations in the gene encoding valosin-containing protein (VCP/p97), the functionally diverse AAA-ATPase. VCP is crucial to a multitude of cellular functions including protein quality control, stress granule formation and clearance, and genomic integrity functions, among others. Pathogenic mutations in VCP cause multisystem proteinopathy (VCP-MSP), an autosomal dominant, adult-onset disorder causing dysfunction in several tissue types. It can result in complex neurodegenerative conditions including inclusion body myopathy, frontotemporal dementia, amyotrophic lateral sclerosis, or combinations of these. There is also an association with other neurodegenerative phenotypes such as Alzheimer-type dementia and Parkinsonism. Non-neurological presentations include Paget disease of bone and may also include cardiac dysfunction. We provide a detailed discussion of genotype-phenotype correlations, recommendations for genetic diagnosis, and genetic counselling implications of VCP-MSP.

Non-Invasive Optical Motion Tracking Allows Monitoring of Respiratory Dynamics in Dystrophin-Deficient Mice

Duchenne muscular dystrophy (DMD) is the most common x-chromosomal inherited dystrophinopathy which leads to progressive muscle weakness and a premature death due to cardiorespiratory dysfunction. The mdx mouse lacks functional dystrophin protein and has a comparatively human-like diaphragm phenotype. To date, diaphragm function can only be inadequately mapped in preclinical studies and a simple reliable translatable method of tracking the severity of the disease still lacks. We aimed to establish a sensitive, reliable, harmless and easy way to assess the effects of respiratory muscle weakness and subsequent irregularity in breathing pattern. Optical respiratory dynamics tracking (ORDT) was developed utilising a camera to track the movement of paper markers placed on the thoracic-abdominal region of the mouse. ORDT successfully distinguished diseased mdx phenotype from healthy controls by measuring significantly higher expiration constants (k) in mdx mice compared to wildtype (wt), which were also observed in the established X-ray based lung function (XLF). In contrast to XLF, with ORDT we were able to distinguish distinct fast and slow expiratory phases. In mdx mice, a larger part of the expiratory marker displacement was achieved in this initial fast phase as compared to wt mice. This phenomenon could not be observed in the XLF measurements. We further validated the simplicity and reliability of our approach by demonstrating that it can be performed using free-hand smartphone acquisition. We conclude that ORDT has a great preclinical potential to monitor DMD and other neuromuscular diseases based on changes in the breathing patterns with the future possibility to track therapy response.

BAG3-related myofibrillar myopathy: a further observation with cardiomyopathy at onset in pediatric age

Myofibrillar myopathies are a heterogeneous group of neuromuscular disorders characterized by degeneration of Z-disk, causing the disintegration of myofibrils. They may be caused by mutations in different genes, among these, the BAG3 gene (Bcl-2 associed-athanogene-3) encodes a multidomain protein that plays an important role in many cellular processes. We report the case of a 16-year-old male who at 4 years of age presented with a hypertrophic obstructive cardiomyopathy, then developed axonal sensory motor polyneuropathy, muscle weakness, rigid spine, severe kyphoscoliosis and respiratory failure. Muscle biopsy showed the typical hallmark of myofibrillar myopathy with abnormal cytoplasmic expression of multiple proteins. Ade novo heterozygous common mutation in the BAG3 gene with a c.626C > T (p.Pro209Leu) was discovered on NGS genetic analysis. Mutations in the BAG3 gene are causes of a severe and progressive condition and natural history data are important to be collected. An early diagnosis is critical for prognostic implications in cardiomyopathy and respiratory failure treatment.

Digital Biomarkers for Neuromuscular Disorders: A Systematic Scoping Review

Biomarkers play a vital role in clinical care. They enable early diagnosis and treatment by identifying a patient's condition and disease course and act as an outcome measure that accurately evaluates the efficacy of a new treatment or drug. Due to the rapid development of digital technologies, digital biomarkers are expected to grow tremendously. In the era of change, this scoping review was conducted to see which digital biomarkers are progressing in neuromuscular disorders, a diverse and broad-range disease group among the neurological diseases, to discover available evidence for their feasibility and reliability. Thus, a total of 10 studies were examined: 9 observational studies and 1 animal study. Of the observational studies, studies were conducted with amyotrophic lateral sclerosis (ALS), Duchenne muscular dystrophy (DMD), and spinal muscular atrophy (SMA) patients. Non-peer reviewed poster presentations were not considered, as the articles may lead to erroneous results. The only animal study included in the present review investigated the mice model of ALS for detecting rest disturbances using a non-invasive digital biomarker.

Does respiratory muscle training improve respiratory function compared to sham training, no training, standard treatment or breathing exercises in children and adults with neuromuscular disease? A Cochrane Review summary with commentary

BACKGROUND

Progressive muscle weakness is a feature of neuromuscular diseases (NMDs), a heterogeneous group of conditions with variable onset, presentation and prognosis that affect both children and adults. Respiratory muscle weakness compromises respiratory function and may lead to respiratory failure.

OBJECTIVE

To assess the effects of respiratory muscle training (RMT) in adults and children with NMD.

METHODS

A Cochrane Review by Silva et al. was summarized with comments.

RESULTS

Eleven studies involving 250 randomized participants with NMD were included. While the studies showed that RMT may lead to improvements in lung function and respiratory muscle strength in people with ALS and DMD, this was not a consistent finding. The evidence from all the included trials was of low or very low certainty.

CONCLUSIONS

There may be some improvement in lung capacity and respiratory muscle strength following RMT in some NMD. There appears to be no clinically meaningful effect of RMT on physical functioning and quality of life in ALS. The low certainty of the evidence means that the results need to be interpreted with caution.

Peak In- and Expiratory Flow Revisited: Reliability and Reference Values in Adults

BACKGROUND

While peak in- and expiratory flow rates offer valuable information for diagnosis and monitoring in respiratory disease, these indices are usually considered too variable to be routinely used for quantification in clinical practice.

OBJECTIVES

The aim of the study was to obtain reproducible measurements of maximal inspiratory flow rates and to construct reference equations for peak in- and expiratory flows (PIF and PEF).

METHOD

With coaching for maximal effort, 187 healthy Caucasian subjects (20-80 years) performed at least 3 combined forced inspiratory and expiratory manoeuvres, until at least 2 peak inspiratory flow measurements were within 10% of each other. The effect on PIF preceded by a slow expiration instead of a forced expiration and PIF repeatability over 3 different days was also investigated in subgroups. Reference values and limits of normal for PIF, mid-inspiratory flow, and PEF were obtained according to the Lambda-Mu-Sigma statistical method.

RESULTS

A valid PIF could be obtained within 3.3 ± 0.6(SD) attempts, resulting in an overall within-test PIF variability of 4.6 ± 3.2(SD)%. A slow instead of a forced expiration prior to forced inspiration resulted in a significant (p < 0.001) but small PIF increase (2.5% on average). Intraclass correlation coefficient for between-day PIF was 0.981 (95% CI: 0.960-0.992). Over the entire age range, inter-subject PIF variability was smaller than in previous reports, and PIF could be predicted based on its determinants gender, age, and height (r2 = 0.53).

CONCLUSIONS

When adhering to similar criteria for the measurement of effort-dependent portions of inspiratory and expiratory flow-volume curves, performed according to current ATS/ERS standards, it is possible to obtain reproducible PIF and PEF values for use in routine clinical practice.

Comparison of Diaphragmatic Breathing Exercises, Volume, and Flow-Oriented Incentive Spirometry on Respiratory Function in Stroke Subjects: A Non-randomized Study

Abstract.

BACKGROUND

Reduced respiratory muscle strength leads to reduced pulmonary function, chest wall movements in the affected side, and increased chest infections, which thereby reduces oxygenation and ventilation. Respiratory muscle training can be used in acute stroke subjects to increase their pulmonary function.

PURPOSE

To compare the short-term effects of diaphragmatic breathing exercise, flow, and volume-oriented incentive spirometry on respiratory function following stroke.

METHODS

A non-randomized hospital-based study was conducted at Kasturba Medical College Hospitals, Mangalore, India. Forty-two sub-acute subjects of either gender, with the first episode of stroke within six months, were assigned to three groups by the consultant, i.e., diaphragmatic breathing group (DBE), Flow oriented-incentive spirometry group (FIS), and volume oriented-incentive spirometry group (VIS; N = 14) each. All subjects received intervention thrice daily, along with conventional stroke rehabilitation protocols throughout the study period. Pre- and post-intervention values were taken on alternate days until day 5 for all the three groups.

RESULTS

The pulmonary function and maximal respiratory pressures were found to be significantly increased by the end of intervention in all three groups, but FIS and DBE groups had better results than VIS (FVC = FIS group, 13.71%; VIS group, 14.89%; DBE group, 21.27%, FEV1 = FIS group, 25.97%; VIS group, 22.52%; DBE group, 19.38%, PEFR = FIS group, 38.76%; VIS group,9.75%; DBE group, 33.16%, MIP = FIS group, 28.23%; VIS group, 19.36%; DBE group, 52.14%, MEP = FIS group, 43.00%; VIS group, 22.80%; DBE group, 28.68%).

CONCLUSION

Even though all interventions had positive outcomes in all variables, flow incentive spirometry had better results across all outcomes (pulmonary function and maximal respiratory pressures) when compared to the other two interventions making it a valuable tool for stroke rehabilitation.

ERS International Congress, Madrid, 2019: highlights from the Sleep and Clinical Physiology Assembly

The 2019 European Respiratory Society (ERS) International Congress took place in Madrid, Spain, and served as a platform to find out the latest advances in respiratory diseases research. The research aims are to understand the physiology and consequences of those diseases, as well as the improvement in their diagnoses, treatments and patient care. In particular, the scientific sessions arranged by ERS Assembly 4 provided novel insights into sleep-disordered breathing and new knowledge in respiratory physiology. This article, divided by session, will summarise the most relevant studies presented at the ERS International Congress. Each section has been written by Early Career Members specialising in the different fields of this interdisciplinary assembly.

Colchicine Myopathy: A Case Series Including Muscle MRI and ABCB1 Polymorphism Data

Colchicine is a medication most commonly used in the treatment of gout and familial mediterannean fever. A rare complication of therapy is toxicity causing proximal myopathy and polyneuropathy. Colchicine myopathy has been associated with the coadministration of other medications with colchicine, such as statins or tacrolimus, and is more common in patients with renal impairment. Otherwise, it is unclear which patients are at greatest risk of developing this adverse drug reaction. ABCB1 is important to the metabolism of colchicine, so we speculated that it was possible that colchicine myopathy patients may have a particular genotype that is associated with this side effect. We describe two cases of colchicine myopathy which occurred with co-administration of rosuvastatin. From one case, we present the first published data on muscle MRI in this condition. We additionally present an analysis of four genetic polymorphisms in ABCB1 and transcript levels in muscle tissue, and demonstrate the descriptive finding of reduced ABCB1 transcript levels in the colchicine myopathy patients.