Lack of correlation between the ventilatory response to CO2 and lung function impairment in myotonic dystrophy patients: Evidence for a dysregulation at central level

Role of respiratory characteristics in treatment adherence with noninvasive home mechanical ventilation in myotonic dystrophy type 1, a retrospective study

Chronic respiratory insufficiency is common in patients with myotonic dystrophy type 1 (DM1) and can be treated with noninvasive home mechanical ventilation (HMV). HMV is not always tolerated well resulting in low treatment adherence. We aimed to analyze if baseline respiratory characteristics such as pulmonary function, level of pCO2 and presence of sleep apnea are associated with HMV treatment adherence in DM1 patients. Pulmonary function testing, polysomnography and blood gas measurement data of DM1 patients were retrospectively collected. Initiation of HMV and treatment adherence after one year was documented. Patients with low treatment adherence (average daily use of HMV <5 h) were grouped with patients that discontinued HMV and compared with patients with high treatment adherence (average daily use of HMV >5 h). HMV was initiated in 101 patients. After one year, 58 patients had low treatment adherence. There were no differences between the low and high treatment adherence group regarding the respiratory characteristics. None of the included predictors (gender, age, body mass index, cytosine-thymine-guanine repeat length, FVC, daytime pCO2, bicarbonate, nighttime pCO2, nighttime base excess, apnea-hypopnea index and mean saturation during sleep) was able to significantly predict high treatment adherence. In conclusion, the respiratory characteristics are not associated with treatment adherence with HMV in DM1 patients and cannot be used to identify patients at risk for low HMV treatment adherence.

Obstructive Sleep Apnea Treatment with Oral Appliance in a Myotonic Dystrophy Type I Subject: A Case Report

Objective  to report a myotonic dystrophy type 1 (MD1) subject with obstructive sleep apnea syndrome treated with oral appliance. Methods  A review of individual's history and records, associated with a photographic register of all diagnostic methods and literature research about the topic were done. Final Statements  This case depicts the therapeutical choices disposable to treat subjects with obstructive sleep apnea and DM1. Although considered an uncommon treatment, the oral appliances, if well indicated in adequately selected cases, can satisfactorily improve respiratory parameters, symptoms and quality of life.

Retraction: Ferrari Aggradi, CR, Falcier, E, Lizio, A, et al. Assessment of respiratory function and need for non-invasive ventilation in a cohort of patients with myotonic dystrophy type 1 followed at one single expert centre. The Clinical Respiratory Journal. 2022; 1- 13. (https://doi.org/10.1111/crj.13516)

The above article, published online on 27 June 2022 in Wiley Online Library (wileyonlinelibrary.com), has been retracted by agreement between the authors, the journal Editors in Chief, Professor Paul Jones and Professor Yuanlin Song and John Wiley and Sons Ltd. The retraction has been agreed due to an error with the publisher and author which caused a duplicate of the article to be published on 27 June 2022. The correct version of the article is to be found at: Carola R. Ferrari Aggradi, Elisa Falcier, Andrea Lizio, Alice Pirola, Jacopo Casiraghi, Alice Zanolini, Elena Carraro, Luca Mauro, Fabrizio Rao, Elisabetta Roma, Antonino Iannello, Elisa De Mattia, Andrea Barp, Sara Lupone, Valentina Gatti, Cristina Italiano, Valeria A. Sansone, "Assessment of Respiratory Function and Need for Noninvasive Ventilation in a Cohort of Patients with Myotonic Dystrophy Type 1 Followed at One Single Expert Center", Canadian Respiratory Journal, vol. 2022, Article ID 2321909, 11 pages, 2022. https://doi.org/10.1155/2022/2321909.

Central Bradypnea and Ataxic Breathing in Myotonic Dystrophy Type 1 - A Clinical Case Report

BACKGROUND

The occurrence of obstructive and central sleep apnea syndromes, ventilator pump failure and reduced hypercapnic ventilatory drive in myotonic dystrophy type 1 (DM1) is well established, and there are indications for an impairment of the hypoxic ventilator drive, too. Yet, it is still unknown, to which extent the respiratory rhythm is affected by DM1, thus if a central bradypnea, cluster breathing or ataxic ("Biot's") breathing can occur. Additionally, the causes of the impairment of the central respiratory drive in DM1 are not known.

CASE PRESENTATION

We present the case of a tracheotomized female patient with DM 1 with central bradypnea and ataxic breathing. A 57-year-old woman with DM1 was admitted to our Neurointensive Care Unit (NICU) due to refractory tracheobronchial retention of secretions resulting from aspiration of saliva. Due to a combination of chronic hypercapnic respiratory failure, severe central bradypnea with a minimal breathing frequency of 3 per minute and ataxic breathing a pressure-controlled home ventilation was initiated.

CONCLUSIONS

In our patient central bradypnea and ataxic breathing possibly were respiratory sequale of DM1, that may have been caused by pontine white matter lesions affecting the pontine respiratory nuclei. From a clinical viewpoint, polygraphy is a suitable tool to objectify disorders of the respiratory rhythm in DM1 even in tracheotomized patients. Clinical studies combining respiratory diagnostics as polygraphy, transcutaneous capnometry and blood gas analysis with brain magnetic resonance imaging (MRI) are required to better understand disorders of respiratory regulation in DM1, and to identify their anatomical correlates.

Respiratory function and sleep in children with myotonic dystrophy type 1

Myotonic dystrophy type 1 (DM1) is a rare neuromuscular disease in children causing sleep and respiratory disorders that are poorly described in the literature compared to adult forms. This retrospective observational study was performed at the Armand Trousseau University Hospital, Assistance Publique-Hôpitaux de Paris (APHP), Paris, France. We retrospectively collected data from lung function tests, nocturnal gas exchange recordings, and polysomnography of 24 children with DM1. 39% of the children with DM1 reported respiratory symptoms indicative of sleep disordered breathing. Three patients (12%) presented with a restrictive respiratory pattern, 10 (42%) with a sleep apnoea syndrome, mainly of obstructive origin (2/10 with severe obstructive sleep apnea syndrome), and 11 (45%) with nocturnal alveolar hypoventilation. Non-invasive ventilation (NIV) was indicated in 9 (37.5%) children, although tolerance was poor. No significant deterioration in respiratory function or nocturnal gas exchange was observed during the NIV-free period. This study provides new and useful insights into DM1 disease evolution in children to better adapt for respiratory follow-up and management. This highlights the need for future research to better understand the origin of respiratory and sleep disorders in patients with DM1.

Development of prediction models based on respiratory assessments to determine the need for non-invasive ventilation in patients with myotonic dystrophy type 1

INTRODUCTION

Myotonic dystrophy type 1 is a slowly progressive, multisystem, autosomal dominant disorder, in which the impairments of respiratory systems represent one of the main causes of death.

OBJECTIVE

The aim of our study is to develop prediction models to identify the most appropriate test(s) providing indication for NIV.

METHODS

DM1 patients attending the NEMO Clinical Center (Milan) between January 2008 and July 2020, who had been subjected to a complete battery of respiratory tests, were retrospectively recruited. Demographic, clinical, and anthropometric characteristics were collected, as well as arterial blood gas (ABG) analysis, spirometry, respiratory muscle strength, cough efficacy, and nocturnal oximetry as respiratory assessments. Patients were stratified in those requiring NIV and those with normal respiratory function.

RESULTS

Out of 151 DM1 patients (median age: 44 years [35.00-53.00]; male/female ratio: 0.80 (67/84)), 76 had an indication for NIV initiation (50.33%). ABG, spirometry, and nocturnal oximetry prediction models resulted in an excellent discriminatory ability in distinguishing patients who needed NIV from those who did not (AUC of 0.818, 0.808, and 0.935, respectively). An easy-to-use calculator was developed to automatically determine a score of NIV necessity based on the prediction equations generated from each aforementioned prediction model.

CONCLUSIONS

The proposed prediction models may help to identify which patients are at a higher risk of requiring ventilator support and therefore help in defining individual management plans and criteria for specific interventions early in the disease course.

Assessment of Respiratory Function and Need for Noninvasive Ventilation in a Cohort of Patients with Myotonic Dystrophy Type 1 Followed at One Single Expert Center

Introduction

Respiratory insufficiency is one of the main causes of death in myotonic dystrophy type 1 (DM1). Although there is general consensus that these patients have a restrictive ventilatory pattern, hypoventilation, chronic hypercapnia, and sleep disturbances, the prevalence of respiratory disease and indication for the effects of noninvasive ventilation (NIV) need to be further explored.

Objectives

To describe respiratory function and need for NIV at baseline and over time in a cohort of adult patients with DM1.

Methods

A total of 151 adult patients with DM1 were subjected to arterial blood gas analysis, sitting and supine forced vital capacity (FVC), peak cough expiratory flow (PCEF), nocturnal oximetry, and maximal inspiratory pressure and expiratory pressure (MIP/PEP).

Results

On first assessment, 84 of 151 had normal respiratory function (median age: 38 years, median BMI: 23.9, and median disease duration: 11 years); 67 received an indication to use NIV (median age: 49 years, median BMI: 25,8, and median disease duration: 14 years). After a median time of 3.85 years, 43 patients were lost to follow-up; 9 of 84 required NIV; only 17 of 67 with the new NIV prescription were adherent.

Conclusions

We provide additional data on the natural history of respiratory function decline and treatment adherence in a relatively large cohort of well-characterized patients with DM1. A high proportion (28%) was lost to follow-up. A minority (11%) required NIV, and only 25% were treatment adherent, irrespective of specific demographics and respiratory features. Our results also confirm previous findings, showing that age, disease duration, and higher BMIs are predisposing factors for respiratory impairment.

Outcome measures frequently used to assess muscle strength in patients with myotonic dystrophy type 1: a systematic review

Measurement of muscle strength is fundamental for the management of patients with myotonic dystrophy type 1 (DM1). Nevertheless, guidance on this topic is somewhat limited due to heterogeneous outcome measures used. This systematic literature review aimed to summarize the most frequent outcome measures to assess muscle strength in patients with DM1. We searched on Pubmed, Web of Science and Embase databases. Observational studies using measures of muscle strength assessment in adult patients with DM1 were included. From a total of 80 included studies, 24 measured cardiac, 45 skeletal and 23 respiratory muscle strength. The most common method and outcome measures used to assess cardiac muscle strength were echocardiography and ejection fraction, for skeletal muscle strength were quantitative muscle test, manual muscle test and maximum isometric torque and medical research council and for respiratory muscle strength were manometry and maximal inspiratory and expiratory pressure. We successfully gathered the more consensual methods and measures to evaluate muscle strength in future clinical studies, particularly to test muscle strength response to treatments in patients with DM1. Future consensus on a set of measures to evaluate muscle strength (core outcome set), is important for these patients.

The role of noninvasive ventilation in the management of type II respiratory failure in patients with myotonic dystrophy

Type 1 myotonic dystrophy (DM1) causes sleep disordered breathing and respiratory failure due to a combination of obstructive sleep apnoea, reduced central drive and respiratory muscle weakness. Noninvasive ventilation (NIV) is commonly used for treating respiratory failure in neuromuscular disease; however, there have been few studies assessing the role of NIV in DM1. The aim of this retrospective service evaluation was to investigate the impact of NIV adherence on hypercapnia and symptoms of hypoventilation in patients with DM1. Data on capillary carbon dioxide tension (P_CO2), lung function, adherence to NIV and symptoms of hypoventilation were obtained from the records of 40 patients with DM1. Mean capillary P_CO2 significantly reduced from 6.81±1.17 kPa during supervised inpatient set-up to 5.93±0.82 kPa after NIV set-up (p<0.001). NIV adherence reduced from 7.8 (range: 1.0–11.0) h per 24 h during supervised inpatient set-up to 2.9 (0–10.4) h per 24 h in the community. Overall 72% of patients used NIV <5 h per 24 h during follow-up, including 11% who discontinued NIV completely. There was no correlation between adherence to NIV and changes in capillary P_CO2. Patients who reported symptomatic benefit (50%) had higher adherence than those who did not feel benefit (p<0.05). In conclusion, in patients with myotonic dystrophy with Type II respiratory failure maintaining adherence is challenging.

Commencing patients with myotonic dystrophy on noninvasive ventilation appears to reverse respiratory failure despite poor adherence to ventilationhttps://bit.ly/343XUGK

New developments in myotonic dystrophies from a multisystemic perspective

PURPOSE OF REVIEW

The multisystemic involvement of myotonic dystrophies (DMs) intricates disease monitoring, patients' care and trial design. This update of the multifaceted comorbidities observed in DMs aims to assist neurologists in the complex management of patients and to encourage further studies for still under-investigated aspects of the disease.

RECENT FINDINGS

We reviewed the most recent studies covering pathogenesis and clinical aspects of extra-muscular involvement in DM1 and DM2. The largest body of evidence regards the cardiac and respiratory features, for which experts' recommendations have been produced. Gastrointestinal symptoms emerge as one of the most prevalent complaints in DMs. The alteration of insulin signaling pathways, involved in gastrointestinal manifestations, carcinogenesis, muscle function, cognitive and endocrinological aspects, gain further relevance in the light of recent evidence of metformin efficacy in DM1. Still, too few studies are performed on large DM2 cohorts, so that current recommendations mainly rely on data gathered in DM1 that cannot be fully translated to DM2.

SUMMARY

Extra-muscular manifestations greatly contribute to the overall disease burden. A multidisciplinary approach is the key for the management of patients. Consensus-based recommendations for DM1 and DM2 allow high standards of care but further evidence are needed to implement these recommendations.

Noninvasive Home Mechanical Ventilation in Adult Myotonic Dystrophy Type 1: A Systematic Review

INTRODUCTION

Chronic hypercapnic respiratory failure induces considerable morbidity and mortality in patients with myotonic dystrophy type 1 (DM1). This study systematically reviews the effects of noninvasive home mechanical ventilation (HMV) on gas exchange, quality of life, survival, and compliance in DM1 patients.

METHODS

A systematic Medline and Embase search was performed (January 1995 to January 2020). Records were screened for eligibility criteria, data were extracted from included studies, and risk of bias was assessed. We present findings mainly using a narrative synthesis.

RESULTS

Twenty-eight relevant full-text articles were screened for eligibility criteria. Nine studies were included. Randomized controlled trials were not found. Studies had either an observational (n = 8) or interventional (n = 1) design. In the pooled data analysis, HMV showed to improve mean oxygen saturation with 4.8% and decreased mean carbon dioxide values with 3 mm Hg. Compliance varied widely between studies, from no use to more than 12 h per day. Quality of life was not studied extensively, but some studies reported positive effects of HMV on symptoms of chronic respiratory failure. HMV may improve survival in DM1 patients with chronic hypercapnic respiratory failure.

CONCLUSION

This review shows that HMV can improve gas exchange and relieve symptoms with a possible survival benefit in DM1 patients with chronic hypercapnic respiratory failure. Future studies should focus on developing strategies to optimize the timing of HMV initiation and to promote compliance.

Factors Influencing the Severity and Progression of Respiratory Muscle Dysfunction in Myotonic Dystrophy Type 1

Respiratory complications are the most common cause of death among patients with Myotonic Dystrophy type 1 (DM1), but the natural history of respiratory decline in DM1 patients is incompletely characterized and few predictors of the progression of respiratory dysfunction have been identified. To identify factors influencing the progression of respiratory dysfunction electronic medical records from 110 adult patients diagnosed with DM1 were reviewed along with data for respiratory symptoms and pulmonary function obtained from routine respiratory therapist clinical evaluations. At baseline, 70.9% had evidence of restrictive respiratory impairment. We examined various parameters of respiratory functional status, and found FVC (% predicted) correlated best with other measures of disease severity. Annual change in FVC was −1.42 (std error = 0.381). Greater CTG repeat size, higher MIRS rating, and longer disease duration were all correlated with lower baseline FVC but not with annual rate of change. Wide variability in clinical phenotype made determination of disease measures directly related to respiratory functional decline challenging.

Management of respiratory complications and rehabilitation in individuals with muscular dystrophies: 1st Consensus Conference report from UILDM - Italian Muscular Dystrophy Association (Milan, January 25-26, 2019)

Respiratory complications are common in the patient with muscular dystrophy. The periodic clinical and instrumental respiratory evaluation is extremely important. Despite the presence in the literature of updated guidelines, patient associations often report lack of knowledge of these pathologies, particularly in peripheral hospitals. The purpose of this work, inspired by the Italian Muscular Dystrophy Association (UILDM) is to improve management of respiratory problems necessary for the management of these patients complex. To this end, the main items that the specialist can meet in the follow-up of these pathologies have been analyzed and discussed, among which the respiratory basal evaluation, the criteria of adaptation to non-invasive ventilation, management of bronchial secretions, situations of respiratory emergency, indications for tracheostomy and the subject of advance directives of treatment (DAT).

Predictors of respiratory decline in myotonic dystrophy type 1 (DM1): a longitudinal cohort study

We studied 33 patients affected by juvenile and adult myotonic dystrophy type 1 (DM1). The aim of the study was to assess clinical and laboratory parameters that could predict the requirement of noninvasive ventilation (NIV) in DM1. Secondary outcome was to assess the interplay between genetic profile, muscle impairment severity and presence of cardiac comorbidities.Patients with genetic diagnosis of DM1 were recruited. An abnormal trinucleotide repeat (CTG) expansion of dystrophy protein kinase gene (DMPK) on chromosome 19q13.3 was the prerequisite for inclusion. The number of triplet repeats was measured in genomic DNA to classify subjects. A multidisciplinary team evaluated the patients every 6-8 months up to 18 years with serial cardiological and respiratory function assessments. Neurological progression was monitored using a validated DM1-specific rating scale (MIRS). Independent variables considered for the study outcomes were gender, genetic status, age of presentation, MIRS scores, and results of pulmonary function tests (PFTs).Patients were 17 males (51.5%) and 16 females (48.5%). 16 cases were younger than mean age of 31.4 years, the remaining 17 were up to 65. 12 subjects (36.4%) underwent NIV during follow up. Cardiac comorbidities were detected in 63.6% of cases and in 91% of patients in NIV. Among PFTs, forced vital capacity (FVC) was a reliable indicator of respiratory decline. FVC values were significantly associated with clinical muscle severity assessed by MIRS.Severity of muscular impairment, CTG expansion size, age and presence of cardiac comorbidities predict respiratory impairment in DM1.

New Insights in Adherence and Survival in Myotonic Dystrophy Patients Using Home Mechanical Ventilation

BACKGROUND

Non-invasive home mechanical ventilation (HMV) is a complex treatment in myotonic dystrophy type 1 (DM1) patients, due to a presumed poor adherence, variable symptom improvement, and uncertainty regarding survival benefits.

OBJECTIVES

We aimed to investigate indications, adherence to HMV and its effects on mortality in a large cohort of DM1 patients.

METHODS

In this retrospective cohort study, we evaluated 224 DM1 patients. Different groups based on hypercapnia and HMV treatment were compared. Cox regression analyses were performed to compare mortality between different defined groups.

RESULTS

224 patients were analysed of whom 111 started non-invasive HMV. Indications were daytime hypercapnia (n = 75), only nocturnal hypercapnia (n = 33), or other reasons (n = 3). Adequate adherence (≥4 h/night) was found in 84.9% of patients. Adequate ventilation was reached in 86.5% of patients. In 33 patients (29.7%), HMV was stopped prematurely due to not reaching patients' expectations on symptom relief or treatment burden (n = 22), or intolerance (n = 8), or other reasons (n = 3). HMV did not improve survival in daytime hypercapnic patients (p = 0.61) nor in nocturnal hypercapnia patients compared to daytime hypercapnia (p = 0.21). Significant survival benefits after starting HMV were found for patients with HMV adherence ≥5 h/24 h compared to patients who used HMV less.

CONCLUSION

In this large cohort, daytime hypercapnia is the main reason for starting HMV, which is well tolerated and used. Mortality is not associated with the reason why HMV was started, but once started, patients with ≥5 h/24 h adherence have significantly better survival compared to patients who use it less.

Central Nervous System Involvement as Outcome Measure for Clinical Trials Efficacy in Myotonic Dystrophy Type 1

Increasing evidences indicate that in Myotonic Dystrophy type 1 (DM1 or Steinert disease), an autosomal dominant multisystem disorder caused by a (CTG)n expansion in DMPK gene on chromosome 19q13. 3, is the most common form of inherited muscular dystrophy in adult patients with a global prevalence of 1/8000, and involvement of the central nervous system can be included within the core clinical manifestations of the disease. Variable in its severity and progression rate over time, likely due to the underlying causative molecular mechanisms; this component of the clinical picture presents with high heterogeneity involving cognitive and behavioral alterations, but also sensory-motor neural integration, and in any case, significantly contributing to the disease burden projected to either specific functional neuropsychological domains or quality of life as a whole. Principle manifestations include alterations of the frontal lobe function, which is more prominent in patients with an early onset, such as in congenital and childhood onset forms, here associated with severe intellectual disabilities, speech and language delay and reduced IQ-values, while in adult onset DM1 cognitive and neuropsychological findings are usually not so severe. Different methods to assess central nervous system involvement in DM1 have then recently been developed, these ranging from more classical psychometric and cognitive functional instruments to sophisticated psycophysic, neurophysiologic and especially computerized neuroimaging techniques, in order to better characterize this disease component, at the same time underlining the opportunity to consider it a suitable marker on which measuring putative effectiveness of therapeutic interventions. This is the reason why, as outlined in the conclusive section of this review, the Authors are lead to wonder, perhaps in a provocative and even paradoxical way to arise the question, whether or not the myologist, by now the popular figure in charge to care of a patient with the DM1, needs to remain himself a neurologist to better appreciate, evaluate and speculate on this important aspect of Steinert disease.

Predictors of prognosis in type 1 myotonic dystrophy (DM1): longitudinal 18-years experience from a single center

The aim of the study was to identify possible predictors of neurological worsening and need of non-invasive ventilation (NIV) in individuals affected by myotonic dystrophy type 1 (DM1), the most common form of adult-onset muscular dystrophy.

METHODS

A retrospective observational cohort study was undertaken. Thirty-three patients with genetic diagnosis of DM1 were followed at our Neuromuscular unit in Modena. Abnormal trinucleotide repeat (CTG) expansion of dystrophy protein kinase gene (MDPK) on chromosome 19q 13.3 was the prerequisite for inclusion. The number of CTG repeats was determined. All the participants were older than 14 at the time of enrolment, therefore they could be included into the juvenile or adult form of the disease. Participants were neurologically evaluated every 6-8 months up to 18 years. Neurological impairment was assessed by Muscular Impairment Rating (MIRS), Medical Research Council (MRC), and modified Rankin (mRS) scales. The independent variables considered for prognosis were age at first evaluation, duration of the disease, CTG repeat number, gender, and presence of cardiac and vascular morbidities.Male patients were 51.5% and female patients 48.5%. Sixteen patients were younger than the mean age of 30.1 years, while the remaining 17 were up to 65. Twelve subjects (36.4%) underwent NIV before the end of follow-up. Muscle force and disability scores showed statistically significant deterioration (p < 0.001) during follow-up. The worsening was significantly higher among patients carrying higher number of CTG repeats and of younger age. The presence of cardio-vascular involvement has significant impact on neurological and respiratory progression.Neurological worsening is predicted by CTG expansion size, young age and presence of cardio-vascular morbidities.

Consensus-Based Care Recommendations for Pulmonologists Treating Adults with Myotonic Dystrophy Type 1

PURPOSE OF REVIEW

Myotonic dystrophy type 1 (DM1) is a severe, progressive genetic disease that affects approximately 1 in 2,500 individuals globally [Ashizawa et al.: Neurol Clin Pract 2018;8(6):507-20]. In patients with DM1, respiratory muscle weakness frequently evolves, leading to respiratory failure as the main cause of death in this patient population, followed by cardiac complications [de Die-Smulders et al.: Brain 1998;121(Pt 8):1557-63], [Mathieu et al.: Neurology 1999;52(8):1658-62], [Groh et al.: Muscle Nerve 2011;43(5):648-51]. This paper provides a more detailed outline on the diagnostic and management protocols, which can guide pulmonologists who may not have experience with DM1 or who are not part of a neuromuscular multidisciplinary clinic. A group of neuromuscular experts in DM1 including pulmonologists, respiratory physiotherapists and sleep specialists discussed respiratory testing and management at baseline and during follow-up visits, based on their clinical experience with patients with DM1. The details are presented in this report.

RECENT FINDINGS

Myotonic recruited 66 international clinicians experienced in the treatment of people living with DM1 to develop and publish consensus-based care recommendations targeting all body systems affected by this disease [Ashizawa et al.: Neurol Clin Pract. 2018;8(6):507-20]. Myotonic then worked with 12 international respiratory therapists, pulmonologists and neurologists with long-standing experience in DM respiratory care to develop consensus-based care recommendations for pulmonologists using a methodology called the Single Text Procedure. This process generated a 7-page document that provides detailed respiratory care recommendations for the management of patients living with DM1. This consensus is completely based on expert opinion and not backed up by empirical evidence due to limited clinical care data available for respiratory care management in DM patients. Nevertheless, we believe it is of relevance for professionals treating adults with myotonic dystrophy because it addresses practical issues related to respiratory management and care, which have been adapted to meet the specific issues in patients with DM1.

SUMMARY

The resulting recommendations are intended to improve respiratory care for the most vulnerable of DM1 patients and lower the risk of untoward respiratory complications and mortality by providing pulmonologist who are less experienced with DM1 with practical indications on which tests and when to perform them, adapting the general respiratory knowledge to specific issues related to this multiorgan disease.

Beatmung bei neuromuskulären Erkrankungen

Neuromuskuläre Erkrankungen betreffen das erste und zweite Motoneuron, die peripheren Nerven, die neuromuskulären Übertragung und die Muskelzelle. Es handelt sich um eine heterogene Gruppe von erblichen, degenerativen und autoimmunen Erkrankungen. Eine korrekte diagnostische Einordnung ist erforderlich, da zentralnervöse, kardiale, endokrine und weitere Begleitsymptome vorliegen können und für einige Erkrankungen bereits medikamentöse Therapien zur Verfügung stehen. Neuromuskuläre Erkrankungen haben eine große Bedeutung in der neuromuskulären Beatmungsmedizin. Die respiratorische Symptomatik resultiert in der Regel aus Paresen der am Atmen, Schlucken oder Husten beteiligten Muskulatur mit konsekutiver ventilatorischer Insuffienz, Dysphagie bis hin zur Speichelaspiration und Sekretretention. Mittels eines strukturierte Sekretmanagements und einer effektive nichtinvasive oder invasive Beatmungstherapie können neuromuskuläre Patienten viele Jahre mit guter Lebensqualität überleben. Themen dieses Kapitels sind ein Überblick über die neuromuskulären Erkrankungen, die Indikationen und Strategien der nichtinvasiven und der invasiven Beatmung und eine ausführliche Darstellung beatmungsmedizinisch besonders relevanter neuromuskulärer Erkrankungen wie der amyotrophe Lateralsklerose, des Guillain-Barré-Syndroms, der Myasthenia gravis und der Critical-Illness-Polyneuropathie/-Myopathie.

Two Adult Siblings With Myotonic Dystrophy Type 1 With Different Phenotypes Presenting With Chronic Respiratory Insufficiency and Sleep Apnea Syndrome

Myotonic dystrophy type 1 (DM1) is an autosomal dominant disease characterized by progressive muscle weakness and myotonia along with multiple organ system involvements. Overall, DM1 patients show reduced life expectancy, mainly due to respiratory or cardiac abnormalities. Chronic respiratory impairment is associated with increased morbidity in DM1. The main ventilatory dysfunction etiology in DM1 is complex, consisting of both peripheral respiratory dysfunction and central respiratory drive dysfunction as well as upper airway muscle dysfunction leading to obstructive sleep apnea syndrome (SAS) and aspiration. Advancements in early diagnosis of DM1 and management with non-invasive therapeutic tools have improved life expectancy for DM1 patients. We present herein two siblings with DM1, a thin elder brother and an obese younger sister with visceral fat accumulation. Although neither had voluntary symptoms related to respiratory dysfunction, their apnea-hypopnea indices revealed severe SAS and subsequent arterial blood gases studies showed hypercapnia as well as hypoxia, suggesting central nervous system involvement with peripheral respiratory dysfunction. Non-invasive positive pressure ventilation during sleep was started following pulmonary assessment. Respiratory function should be assessed in DM1 patients, even those free of respiratory symptoms, because respiratory muscle weakness occurs in a high percentage of these patients and will shorten their lives.

Clinical implication of maximal voluntary ventilation in myotonic muscular dystrophy

Patients with myotonic muscular dystrophy type 1 (DM1) tend to exhibit earlier respiratory insufficiency than patients with other neuromuscular diseases at similar or higher forced vital capacity (FVC). This study aimed to analyze several pulmonary function parameters to determine which factor contributes the most to early hypercapnia in patients with DM1.We analyzed ventilation status monitoring, pulmonary function tests (including FVC, maximal voluntary ventilation [MVV], and maximal inspiratory and expiratory pressure), and polysomnography in subjects with DM1 who were admitted to a single university hospital. The correlation of each parameter with hypercapnia was determined. Subgroup analysis was also performed by dividing the subjects into 2 subgroups according to usage of mechanical ventilation.Final analysis included 50 patients with a mean age of 42.9 years (standard deviation = 11.1), 46.0% of whom were male. The hypercapnia was negatively correlated with MVV, FVC, forced expiratory volume in 1 second (FEV1), and their ratios to predicted values in subjects with myotonic muscular dystrophy type 1. At the same partial pressure of carbon dioxide, the ratio to the predicted value was lowest for MVV, then FEV1, followed by FVC. Moreover, the P values for differences in MVV and its ratio to the predicted value between ventilator users and nonusers were the lowest.When screening ventilation failure in patients with DM1, MVV should be considered alongside other routinely measured parameters.

A model to predict ventilator requirement in myotonic dystrophy type 1

INTRODUCTION

Respiratory failure is one of the most common causes of mortality in myotonic dystrophy type 1 (DM1). The variation in the DM1 phenotype causes difficulty in clinically predicting the severity of respiratory involvement, and variables such as daytime somnolence are insensitive for identifying patients who require continuous or bilevel nocturnal positive airway pressure (NPAP).

METHODS

We retrospectively analyzed a cohort of 126 adult onset patients with DM1 at the point of their first respiratory assessment to identify significant factors in predicting ventilator requirement.

RESULTS

Triplet repeat years score and Muscle Impairment Rating Scale were significantly linearly related to NPAP and, thus, formed the model.

DISCUSSION

We devised a simple model to aid clinicians in predicting at first visit those patients with DM1 who are likely to require NPAP. We also describe the causes of failure to tolerate NPAP in DM1. Muscle Nerve 59:683-687, 2019.

Massive abscess with prolonged respiratory failure due to newly diagnosed myotonic dystrophy: A case report

RATIONALE

Myotonic dystrophy is a progressive multisystem genetic heterogeneous disorder. General anesthesia with opioids increases the risk of prolonged postanesthetic respiratory recovery in myotonic dystrophy patients.

PATIENT CONCERNS

A 20-year-old previously healthy woman was transferred to our emergency department for further workup of respiratory failure, and massive ascites with abscess caused by endometriosis. Hypercapnic respiratory failure persisted under intensive care unit (ICU) management, but finally improved after cessation of fentanyl as a sedative agent.

DIAGNOSIS

Myotonic dystrophy type 1.

INTERVENTIONS

Massive ascites with abscess was accordingly managed by drainage, antibiotics, and an antifungal agent. Myotonic dystrophy type 1 was confirmed after molecular genetic testing revealed a cytosine-thymine-guanine repeat length of 400 to 450 in the DMPK gene.

OUTCOMES

The patient was discharged without complications on hospital day 69.

LESSONS

Myotonic dystrophy should be considered when hypercapnic respiratory failure persists in sedated ICU patients. Opioids should not be used for perioperative management of patients with myotonic dystrophy.

How to Interpret Abnormal Findings of Spirometry and Manometry in Myotonic Dystrophies?

BACKGROUND/AIM

Pulmonary function tests are used for screening respiratory insufficiency in patients with myotonic dystrophy (DM). We analysed the agreement between two different approaches in assessment of abnormal findings of forced vital capacity (FVC), forced expiratory volume in the first second (FEV1), maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP), in DM patients.

METHODS

We used Cohen's κ- and Bangdiwala's B- statistic to compare the agreement between different cut-off values recommended by experts (ENMC) and the cut-off values based on the reference range (RR). We further analysed their sensitivity (Sn) and specificity (Sp) in detecting symptoms associated with respiratory insufficiency.

RESULTS

The observed agreement was: 1) for FVC: κ= -0.002, B = 0.406; 2) for FEV1: κ= 0.944, B = 0.946; 3) for MIP: κ= 0.625, B = 0.674; and 4) for MEP: κ= 0.241, B = 0.373. Overall, RR cut-off values showed higher sensitivity, whereas the ENMC values showed higher specificity in detecting symptoms of respiratory involvement.

CONCLUSIONS

The two approaches showed perfect agreement in assessment of FEV1, substantial agreement for MIP, and weak agreement for FVC and MEP. RR is an established method of assessment for spirometry and should be favoured because it takes variability within the population into account. Further development and validation of regression equations for RR calculations of predicted maximal respiratory pressures, with corresponding lower limits of normal, is required.The B statistic is more robust in assessing agreement between two diagnostic methods, resolving the issue of the κ paradox.

Respiratory dysfunction in myotonic dystrophy type 1: A systematic review

Myotonic dystrophy type 1 (DM1) is one of the most common muscular dystrophies in adults. This review summarises the current literature regarding the natural history of respiratory dysfunction in DM1, the role of central respiratory drive and peripheral respiratory muscle involvement and its significance in respiratory function, and investigates the relationship between genetics (CTG repeat length) and respiratory dysfunction. The review included all articles that reported spirometry on 10 or more myotonic dystrophy patients. The final review included 55 articles between 1964 and 2017. The major conclusions of this review were (1) confirmation of the current consensus that respiratory dysfunction, predominantly a restrictive ventilatory pattern, is common in myotonic dystrophy and is associated with alveolar hypoventilation, chronic hypercapnia, and sleep disturbance in the form of sleep apnoea and sleep related disordered breathing; (2) contrary to commonly held belief, there is no consensus in the literature regarding the relationship between CTG repeat length and severity of respiratory dysfunction and a relationship has not been established; (3) the natural history and time-course of respiratory functional decline is very poorly understood in the current literature; (4) there is a consensus that there is a significant involvement of central respiratory drive in this alveolar hypoventilation however the current literature does not identify the mechanism for this.

Myotonic Dystrophies: Targeting Therapies for Multisystem Disease

Myotonic dystrophy is an autosomal dominant muscular dystrophy not only associated with muscle weakness, atrophy, and myotonia but also prominent multisystem involvement. There are 2 similar, but distinct, forms of myotonic dystrophy; type 1 is caused by a CTG repeat expansion in the DMPK gene, and type 2 is caused by a CCTG repeat expansion in the CNBP gene. Type 1 is associated with distal limb, neck flexor, and bulbar weakness and results in different phenotypic subtypes with variable onset from congenital to very late-onset as well as variable signs and symptoms. The classically described adult-onset form is the most common. In contrast, myotonic dystrophy type 2 is adult-onset or late-onset, has proximal predominant muscle weakness, and generally has less severe multisystem involvement. In both forms of myotonic dystrophy, the best characterized disease mechanism is a RNA toxic gain-of-function during which RNA repeats form nuclear foci resulting in sequestration of RNA-binding proteins and, therefore, dysregulated splicing of premessenger RNA. There are currently no disease-modifying therapies, but clinical surveillance, preventative measures, and supportive treatments are used to reduce the impact of muscular impairment and other systemic involvement including cataracts, cardiac conduction abnormalities, fatigue, central nervous system dysfunction, respiratory weakness, dysphagia, and endocrine dysfunction. Exciting preclinical progress has been made in identifying a number of potential strategies including genome editing, small molecule therapeutics, and antisense oligonucleotide-based therapies to target the pathogenesis of type 1 and type 2 myotonic dystrophies at the DNA, RNA, or downstream target level.

Flow and airway pressure analysis for detecting ineffective effort during mechanical ventilation in neuromuscular patients

Ineffective efforts (IEs) are among the most common types of patient–ventilator asynchrony. The objective of this study is to validate IE detection during expiration using pressure and flow signals, with respiratory effort detection by esophageal pressure (Pes) measurement as the reference, in patients with neuromuscular diseases (NMDs). We included 10 patients diagnosed with chronic respiratory failure related to NMD. Twenty-eight 5-minute recordings of daytime ventilation were studied for IE detection. Standard formulas were used to calculate sensitivity, specificity, positive predictive value (PPV), and negative predictive value (NPV) of IE detection using pressure and flow signals compared to Pes measurement. Mean sensitivity and specificity of flow and pressure signal-based IE detection versus Pes measurement were 97.5% ± 5.3% and 91.4% ± 13.7%, respectively. NPV was 98.1% ± 8.2% and PPV was 67.6% ± 33.8%. Spearman’s rank correlation coefficient indicated a moderately significant correlation between frequencies of IEs and controlled cycles (ρ = 0.50 and p = 0.01). Among respiratory cycles, 311 (11.2%) were false-positive IEs overall. Separating false-positive IEs according to their mechanisms, we observed premature cycling in 1.2% of cycles, delayed ventilator triggering in 0.1%, cardiac contraction in 9.2%, and upper airway instability during expiration in 0.3%. Using flow and pressure signals to detect IEs is a simple and rapid method that produces adequate data to support clinical decisions.

Effect and impact of mechanical ventilation in myotonic dystrophy type 1: a prospective cohort study

Few studies have assessed the impact of home ventilation in patients with myotonic dystrophy type 1 (DM1) and no specific recommendations are available. We assessed the survival associated with category of home ventilation adherence of patients with DM1 followed up at a home ventilation unit using a Cox proportional hazards model. 218 patients were included; those who refused or delayed their acceptance of non-invasive ventilation were at higher risk for severe events (invasive ventilation or death) (P=0.03). Risk of death was associated with orthopnoea (HR 2.37; 95% CI 1.17 to 4.80; P<0.02) and adherence category (100 to 90% vs >75%: HR 3.26; 95% CI 1.32 to 8.04; P<0.03). Failure to use home ventilation as prescribed may be associated with increased mortality in patients with DM1.

Sleepiness and Sleep-related Breathing Disorders in Myotonic Dystrophy and Responses to Treatment: A Prospective Cohort Study

OBJECTIVE

We conducted prospective assessments in people with myotonic dystrophy type 1 (DM1) with daytime sleepiness, provided targeted therapies and assessed response.

METHODS

Patients had overnight sleep assessments. Treatment with continuous positive airway pressure (CPAP) for OSA, non-invasive ventilation (NIV) for respiratory failure, modafinil for excessive daytime sleepiness were commenced.

RESULTS

120 people were studied: mean age 46.9 years (SD 13.2, range 18-74), body mass index 27.9 kg/m2 (7.2, 16-53), Epworth Sleepiness Score (ESS) 13.1 (4.7, 2-24). Twenty one people (18% of group) had OSA: mean age 49.6, BMI 31.1, ESS 14.3, ODI 22, pO2 11.3, pCO2 5.4. All were offered CPAP; seven continued with benefit but 14 had intolerance or no benefit. Thirty-three people (27%) had respiratory failure and abnormal sleep study: mean age 51.5, BMI 31.3, ESS 13.9, ODI 22.9, pO2 8.7, pCO2 6.8. All were offered NIV; 12 continued with benefit but 18 had intolerance or no benefit, 1 died and 2 declined commencement. Thirty-six people (30%) had predominantly sleepiness: mean age 44.8, BMI 24.6, ESS 14.1, ODI 9.2, pO2 11.7, pCO2 5.4. All were offered modafinil; 12 continued this with benefit but 10 had intolerance or no benefit, one was unkeen to start, 11 did not attend further clinic and two had other sleep disorders. Comparing means of treatment responders to non-responders showed no significant difference in any variable, except ESS: 15.9 vs.11.9 respectively, p < 0.0001.

CONCLUSIONS

Causes of sleepiness are variable in DM1, but include obstructive sleep apnoea, respiratory failure and sleepiness with a normal sleep study; 29% of this studied cohort benefited from targeted sleep therapies.

[Update on the respiratory management of patients with chronic neuromuscular disease]

BACKGROUND

Neuromuscular diseases include a wide range of conditions that may involve potentially life-threatening respiratory complications (infection, respiratory failure).

SURVEILLANCE AND PULMONARY FUNCTION TESTS

For patients with neuromuscular diseases, clinical assessment of respiratory function and regular pulmonary function tests are needed to screen for nocturnal respiratory disorders, weakness of the diaphragm and potential restrictive disorders and/or chronic hypercapnic respiratory insufficiency, possibly with couch deficiency. MANAGEMENT OF NOCTURNAL RESPIRATORY DISORDERS AND CHRONIC RESPIRATORY FAILURE: Nocturnal respiratory assistance is an important phase of care for nocturnal respiratory disorders and chronic respiratory failure. This may involve continuous positive airway pressure, adaptative servo-ventilation or non-invasive ventilation with a facial or nasal mask. As needed, diurnal assistance may be proposed by mouthpiece ventilation. Should non-invasive ventilation prove insufficient, or if significant swallowing disorders or recurrent bronchial obstruction develop, or in case of prolonged intubation, tracheotomy may be required.

LOWER AIRWAY OBSTRUCTION

In case of lower airway infection with ineffective cough, physical therapy, associated with air stacking, intermittent positive pressure breathing or mechanical in-exsufflation may be proposed.

PATIENT-CENTERED MANAGEMENT

Care for swallowing disorders, nutritional counseling (cachexia, obesity), vaccinations and therapeutic education are integral elements of patient-centered management aiming to prevent the negative impact of infection and to manage respiratory failure of chronic neuromuscular disease.

Noninvasive assessment of respiratory muscle strength and activity in Myotonic dystrophy

OBJECTIVE

To evaluate sensitivity/specificity of the maximum relaxation rate (MRR) of inspiratory muscles, amplitude of electromyographic activity of the sternocleidomastoid (SCM), scalene (SCA), parasternal (2ndIS) and rectus abdominis (RA) muscles; lung function and respiratory muscle strength in subjects with Myotonic dystrophy type 1 (DM1) compared with healthy subjects.

DESIGN AND METHODS

Quasi-experimental observational study with control group. MRR of inspiratory muscles, lung function and amplitude of the electromyographic activity of SCM, SCA, 2ndIS and RA muscles during maximum inspiratory pressure (PImax), maximum expiratory pressure (PEmax) and sniff nasal inspiratory pressure (SNIP) tests were assessed in eighteen DM1 subjects and eleven healthy.

RESULTS

MRR was lower in DM1 group compared to healthy (P = 0.001) and was considered sensitive and specific to identify disease in DM1 and discard it in controls, as well as SNIP% (P = 0.0026), PImax% (P = 0.0077) and PEmax% (P = 0.0002). Contraction time of SCM and SCA was higher in DM1 compared to controls, respectively, during PImax (P = 0.023 and P = 0.017) and SNIP (P = 0.015 and P = .0004). The DM1 group showed lower PImax (P = .0006), PEmax (P = 0.0002), SNIP (P = 0.0014), and higher electromyographic activity of the SCM (P = 0.002) and SCA (P = 0.004) at rest; of 2ndIS (P = 0.003) during PEmax and of SCM (P = 0.02) and SCA (P = 0.03) during SNIP test.

CONCLUSIONS

MD1 subjects presented restrictive pattern, reduced respiratory muscle strength, muscular electrical activity and MRR when compared to higher compared to controls. In addition, the lower MRR found in MD1 subjects showed to be reliable to sensitivity and specificity in identifying the delayed relaxation of respiratory muscles.

Definition, discrimination, diagnosis and treatment of central breathing disturbances during sleep

The complexity of central breathing disturbances during sleep has become increasingly obvious. They present as central sleep apnoeas (CSAs) and hypopnoeas, periodic breathing with apnoeas, or irregular breathing in patients with cardiovascular, other internal or neurological disorders, and can emerge under positive airway pressure treatment or opioid use, or at high altitude. As yet, there is insufficient knowledge on the clinical features, pathophysiological background and consecutive algorithms for stepped-care treatment. Most recently, it has been discussed intensively if CSA in heart failure is a “marker” of disease severity or a “mediator” of disease progression, and if and which type of positive airway pressure therapy is indicated. In addition, disturbances of respiratory drive or the translation of central impulses may result in hypoventilation, associated with cerebral or neuromuscular diseases, or severe diseases of lung or thorax. These statements report the results of an European Respiratory Society Task Force addressing actual diagnostic and therapeutic standards. The statements are based on a systematic review of the literature and a systematic two-step decision process. Although the Task Force does not make recommendations, it describes its current practice of treatment of CSA in heart failure and hypoventilation.