Sleep-related symptoms and sleep-disordered breathing in adult Pompe disease

Monitoring and Management of Respiratory Function in Pompe Disease: Current Perspectives

Pompe disease (PD) is a neuromuscular disorder caused by a deficiency of acid alpha-glucosidase (GAA) - a lysosomal enzyme responsible for hydrolyzing glycogen. GAA deficiency leads to accumulation of glycogen in lysosomes, causing cellular disruption. The severity of PD is directly related to the extent of GAA deficiency - if no or minimal GAA is produced, symptoms are severe and manifest in infancy, known as infantile onset PD (IOPD). If left untreated, infants with IOPD experience muscle hypotonia and cardio-respiratory failure leading to significant morbidity and mortality in the first year of life. In contrast, late-onset PD (LOPD) patients have more GAA activity and present later in life, but also have significant respiratory function decline. Despite FDA-approved enzyme replacement therapy, respiratory insufficiency remains a major cause of morbidity and mortality, emphasizing the importance of early detection and management of respiratory complications. These complications include impaired cough and airway clearance, respiratory muscle weakness, sleep-related breathing issues, and pulmonary infections. This review aims to provide an overview of the respiratory pathology, monitoring, and management of PD patients. In addition, we discuss the impact of novel approaches and therapies on respiratory function in PD.

Screening data from 19 patients with late-onset Pompe disease for a phase I clinical trial of AAV8 vector-mediated gene therapy

Late-onset Pompe disease (LOPD) is a multisystem disorder with significant myopathy. The standard treatment is enzyme replacement therapy (ERT), a therapy that is lifesaving, yet with limitations. Clinical trials have emerged for other potential treatment options, including adeno-associated virus (AAV) gene therapy. We present clinical parameters and AAV antibody titers for 19 individuals with LOPD undergoing screening for a Phase I clinical trial with an AAV serotype 8 vector targeting hepatic transduction (AAV2/8-LSPhGAA). Reported clinical parameters included GAA genotype, assessments of muscle function, upright and supine spirometry, anti-recombinant human GAA antibody titers, and biomarkers. Variability in measured parameters and phenotypes of screened individuals was evident. Eligibility criteria required that all participants have six-minute walk test (6MWT) and upright forced vital capacity (FVC) below the expected range for normal individuals, and were stably treated with ERT for >2 years. All participants had Pompe disease diagnosed by enzyme deficiency, and all had the common c.-32-13T>G LOPD pathogenic variant. Screening identified 14 patients (74%) with no or minimal detectable neutralizing antibodies against AAV8 (titer ≤1:5). 6MWT distance varied significantly (percent of expected distance ranging from 24% to 91% with an average of 60 and standard deviation of 21). Upright FVC percent predicted ranged from 35% predicted to 91% predicted with an average of 66 and standard deviation of 18. None of the participants had significantly elevated alanine transaminase, which has been associated with LOPD and could complicate screening for hepatitis related to AAV gene therapy. We review the parameters considered in screening for eligibility for a clinical trial of AAV8 vector-mediated gene therapy.

Respiratory Management of Patients With Neuromuscular Weakness: An American College of Chest Physicians Clinical Practice Guideline and Expert Panel Report

BACKGROUND

Respiratory failure is a significant concern in neuromuscular diseases (NMDs). This CHEST guideline examines the literature on the respiratory management of patients with NMD to provide evidence-based recommendations.

STUDY DESIGN AND METHODS

An expert panel conducted a systematic review addressing the respiratory management of NMD and applied the Grading of Recommendations, Assessment, Development, and Evaluations approach for assessing the certainty of the evidence and formulating and grading recommendations. A modified Delphi technique was used to reach a consensus on the recommendations.

RESULTS

Based on 128 studies, the panel generated 15 graded recommendations, one good practice statement, and one consensus-based statement.

INTERPRETATION

Evidence of best practices for respiratory management in NMD is limited and is based primarily on observational data in amyotrophic lateral sclerosis. The panel found that pulmonary function testing every 6 months may be beneficial and may be used to initiate noninvasive ventilation (NIV) when clinically indicated. An individualized approach to NIV settings may benefit patients with chronic respiratory failure and sleep-disordered breathing related to NMD. When resources allow, polysomnography or overnight oximetry can help to guide the initiation of NIV. The panel provided guidelines for mouthpiece ventilation, transition to home mechanical ventilation, salivary secretion management, and airway clearance therapies. The guideline panel emphasizes that NMD pathologic characteristics represent a diverse group of disorders with differing rates of decline in lung function. The clinician's role is to add evaluation at the bedside to shared decision-making with patients and families, including respect for patient preferences and treatment goals, considerations of quality of life, and appropriate use of available resources in decision-making.

Diaphragm pacing and independent breathing in individuals with severe Pompe disease

Introduction

Pompe disease is an inherited disease characterized by a deficit in acid-α-glucosidase (GAA), an enzyme which degrades lysosomal glycogen. The phrenic-diaphragm motor system is affected preferentially, and respiratory failure often occurs despite GAA enzyme replacement therapy. We hypothesized that the continued use of diaphragm pacing (DP) might improve ventilator-dependent subjects' respiratory outcomes and increase ventilator-free time tolerance.

Methods

Six patients (3 pediatric) underwent clinical DP implantation and started diaphragm conditioning, which involved progressively longer periods of daily, low intensity stimulation. Longitudinal respiratory breathing pattern, diaphragm electromyography, and pulmonary function tests were completed when possible, to assess feasibility of use, as well as diaphragm and ventilatory responses to conditioning.

Results

All subjects were eventually able to undergo full-time conditioning via DP and increase their maximal tolerated time off-ventilator, when compared to pre-implant function. Over time, 3 of 6 subjects also demonstrated increased or stable minute ventilation throughout the day, without positive-pressure ventilation assistance.

Discussion

Respiratory insufficiency is one of the main causes of death in patients with Pompe disease. Our results indicate that DP in Pompe disease was feasible, led to few adverse events and stabilized breathing for up to 7 years.

Quality of life in patients with chronic respiratory failure on home mechanical ventilation

Home mechanical ventilation (HMV) is a treatment for chronic respiratory failure that has shown clinical and cost effectiveness in patients with underlying COPD, obesity-related respiratory failure and neuromuscular disease (NMD). By treating chronic respiratory failure with adequate adherence to HMV, improvement in patient-reported outcomes including health-related quality of life (HRQoL) have been evaluated using general and disease-specific quantitative, semi-qualitative and qualitative methods. However, the treatment response in terms of trajectory of change in HRQoL is not uniform across the restrictive and obstructive disease groups. In this review, the effect of HMV on HRQoL across the domains of symptom perception, physical wellbeing, mental wellbeing, anxiety, depression, self-efficacy and sleep quality in stable and post-acute COPD, rapidly progressive NMD (such as amyotrophic lateral sclerosis), inherited NMD (including Duchenne muscular dystrophy) and obesity-related respiratory failure will be discussed.

Home-based enzyme replacement therapy in children and adults with Pompe disease; a prospective study

BACKGROUND

Pompe disease is a lysosomal storage disease treated with life-long enzyme replacement therapy (ERT). Home-based ERT has been provided in the Netherlands since 2008 because it diminishes the burden of treatment, increases patient flexibility and autonomy, and is thus a more patient-centred approach to ERT.

METHODS

All Dutch Pompe patients receiving alglucosidase alfa infusions at home were approached to participate in a questionnaire to validate the safety of home-based ERT. Prospective data on symptoms occurring during or within 48 h after infusion and retrospective data on infusion associated reactions (IARs) in the last three months were collected four times during one year.

RESULTS

In total, 116 out of 120 eligible patients (17 classic infantile, 2 atypical infantile, 15 childhood onset and 82 adult) filled out 423 questionnaires (response rate: 88.1%). Symptoms during or after infusion were reported 27 times in 17 patients. Fatigue was the most commonly reported health complaint (in 9.5% of patients). Four health complaints were judged to be IARs and reported to the Erasmus MC University Medical Center. None of the IARs reported in this study warranted emergency clinical care.

CONCLUSIONS

Our data demonstrate that home-based ERT in Pompe disease can be safely implemented as few, mostly mild, symptoms were reported during or after infusion. Insights from this study can be used as a base for implementing home-based ERT in other countries and to further optimize patient care, as unreported mild symptoms do not pose a health risk but may still be relevant to the patient.

Quality of Life with Late-Onset Pompe Disease: Qualitative Interviews and General Public Utility Estimation in the United Kingdom

Background: Late-onset Pompe disease (LOPD) is a rare, progressive neuromuscular condition typically characterized by weakness of skeletal muscles, including those involved in respiration and diaphragmatic dysfunction. Individuals with LOPD typically eventually require mobility and/or ventilatory support. Objectives: This study aimed to develop health state vignettes and estimate health state utility values for LOPD in the United Kingdom. Methods: Vignettes were developed for 7 health states of LOPD with states defined in terms of mobility and/or ventilatory support. Vignettes were drafted based on patient-reported outcome data from the Phase 3 PROPEL trial (NCT03729362) and supplemented by a literature review. Qualitative interviews with individuals living with LOPD and clinical experts were conducted to explore the health-related quality-of-life (HRQoL) impact of LOPD and to review the draft vignettes. Vignettes were finalized following a second round of interviews with individuals living with LOPD and used in health state valuation exercises with people of the UK population. Participants rated the health states using the EQ-5D-5L, visual analogue scale, and time trade-off interviews. Results: Twelve individuals living with LOPD and 2 clinical experts were interviewed. Following the interviews, 4 new statements were added regarding dependence on others, bladder control problems, balance issues/fear of falling, and frustration. One hundred interviews with a representative UK population sample were completed. Mean time trade-off utilities ranged from 0.754 (SD = 0.31) (no support) to 0.132 (SD = 0.50) (invasive ventilatory and mobility support-dependent). Similarly, EQ-5D-5L utilities ranged from 0.608 (SD = 0.12) to -0.078 (SD = 0.22). Discussion: The utilities obtained in the study are consistent with utilities reported in the literature (0.670-0.853 for nonsupport state). The vignette content was based on robust quantitative and qualitative evidence and captured the main HRQoL impacts of LOPD. The general public rated the health states consistently lower with increasing disease progression. There was greater uncertainty around utility estimates for the severe states, suggesting that participants found it harder to rate them. Conclusion: This study provides utility estimates for LOPD that can be used in economic modeling of treatments for LOPD. Our findings highlight the high disease burden of LOPD and reinforce the societal value of slowing disease progression.

Smartphone-based follow-up of upper airway symptoms in head and neck cancer survivors one year after radiation therapy

BACKGROUND

Improvements in treatment of head-and-neck cancer (HNC) have resulted in improved long-term survival rates so there is a growing interest in long-term consequences.

OBJECTIVE

The aim was to perform a smartphone-based assessment to analyse the upper airway dysfunction-related symptoms in HNC 1 year after radiotherapy (RT) during social distancing due to COVID-19.

METHODS & PROCEDURES

Smartphone-based assessment on upper airway function 1 year after RT was performed. Upper airway functions include perceived impact of voice on quality of life (Voice Handicap Index, VHI-30), swallowing (Functional Oral Intake, FOIS; and Swallowing Quality of Life questionnaire, SWAL-QOL) and sleep-disordered breathing (Pittsburgh Sleep Quality Index, PSQI) assessments. Additionally, quality of life was assessed using the European Organization for Research and Treatment of Cancer Quality of Life Questionnaire.

OUTCOMES & RESULTS

The HNC group presented worse results in the VHI-30 scale, in the three subscales (p < 0.001). Swallowing function also presented worse results in the HNC group, with a lower score in the FOIS questionnaire (p < 0.001) and a poorer score in the SWAL-QOL (p < 0.001). Regarding to the sleep-disordered breathing, the HNC group presented poorer scores in all subscales (p < 0.05). The HNC group also presented worse scores in quality of life.

CONCLUSION

Our findings showed that HNC survivors presented a poorer upper airway function and a worse quality of life. This population needs to be systematically screened for those function impairments.

WHAT THIS PAPER ADDS

What is already known on the subject Head-and-neck cancer radiotherapy treatment is anatomically related to the upper airway, involved in several functions such as breathing, swallowing and speech that could be affected by the treatment. Public health restrictions caused by the COVID-19 pandemic have made it difficult, and in many cases impossible, to see patients in person and complete assessments that are often crucial to improve their approach. Telephone interviews appear to be largely equivalent to face-to-face interviews, which could solve these problems. What this paper adds to existing knowledge The aim of this study was to perform a smartphone-based assessment to analyse the upper airway dysfunction-related symptoms in head-and-neck cancer survivors 1 year after radiotherapy treatment. Our findings showed that head-and-neck cancer survivors who have been treated with radiotherapy presented a poorer upper airway function, with subjective speech and voice problems, swallowing and sleep-disordered breathing compared to a control group matched for age and sex 1 year after the treatment. What are the potential or actual clinical implications of this work? The results of this study will allow a better approach to treatment of head-and-neck cancer survivors.

A Multidisciplinary Perspective Addressing the Diagnostic Challenges of Late-Onset Pompe Disease in the Arabian Peninsula Region Developed From an Expert Group Meeting

Pompe disease is a rare, metabolic, autosomal recessive disorder. Early diagnosis is critical for progressive Pompe disease as delays can significantly alter the clinical course of the disease. Diagnostic modalities, including dried blood spot testing and genetic testing, are available and are effective for diagnosing patients with late-onset Pompe disease (LOPD). However, clinicians face numerous clinical challenges related to the diagnosis of the disease. Two expert group committee meetings, involving 11 experts from the United Arab Emirates, Kuwait, the Kingdom of Saudi Arabia, and Oman, were convened in October 2019 and November 2020 respectively to develop a uniform diagnostic algorithm for the diagnosis of pediatric and adult LOPD in the Arabian Peninsula region. During the first meeting, the specialty-specific clinical presentation of LOPD was defined. During the second meeting, a diagnostic algorithm was developed after a thorough validation of clinical presentation or symptoms, which was performed with the aid of existing literature and expert judgement. A consensus was reached on the diagnostic algorithm for field specialists, such as neurologists, rheumatologists, general practitioners/internal medicine specialists, orthopedic specialists, and pulmonologists. This specialty-specific diagnostic referral algorithm for pediatric and adult LOPD will guide clinicians in the differential diagnosis of LOPD.

A Systematic Review investigating the Effectiveness of Exercise training in Glycogen Storage Diseases

Introduction

Glycogen storage diseases (GSDs) are rare inborn errors of carbohydrate metabolism typically with skeletal muscle and liver involvement. In those with skeletal muscle involvement, the majority display symptoms of exercise intolerance which can cause profound exercise limitation and impair everyday living and quality of life (QoL). There are no curative treatments for GSDs, thus therapeutic options, such as exercise training, are aimed at improving QoL by alleviating signs and symptoms. In order to investigate the effectiveness of exercise training in adults with GSDs, we systematically reviewed the literature.

Methods

In this review we conducted searches within SCOPUS and MEDLINE to identify potential papers for inclusion. These papers were independently assessed for inclusion and quality by two authors. We identified 23 studies which included aerobic training, strength training or respiratory muscle training in patients with McArdles (n = 41) and Pompe disease (n = 139).

Results

In McArdle disease, aerobic exercise training improved aerobic capacity (VO2 peak) by 14-111% with further benefits to functional capacity and well-being. Meanwhile, strength training increased muscle peak power by 100-151% and reduced disease severity. In Pompe disease, a combination of aerobic and strength training improved VO2 peak by 9-10%, muscle peak power by 64%, functional capacity and well-being. Furthermore, respiratory muscle training (RMT) improved respiratory muscular strength [maximum inspiratory pressure (MIP) increased by up to 65% and maximum expiratory pressure (MEP) by up to 70%], with additional benefits shown in aerobic capacity, functional capacity and well-being.

Conclusion

This adds to the growing body of evidence which suggests that supervised exercise training is safe and effective in improving aerobic capacity and muscle function in adults with McArdle or Pompe disease. However, the literature base is limited in quality and quantity with a dearth of literature regarding exercise training in other GSD subtypes.

Respiratory Muscle Function Tests and Diaphragm Ultrasound Predict Nocturnal Hypoventilation in Slowly Progressive Myopathies

Introduction: In slowly progressive myopathies, diaphragm weakness early manifests through sleep-related hypoventilation as reflected by nocturnal hypercapnia. This study investigated whether daytime tests of respiratory muscle function and diaphragm ultrasound predict hypercapnia during sleep.

Methods: Twenty-seven patients with genetic myopathies (myotonic dystrophy type 1 and 2, late-onset Pompe disease, facioscapulohumeral dystrophy; 48 ± 11 years) underwent overnight transcutaneous capnometry, spirometry, measurement of mouth occlusion pressures, and diaphragm ultrasound.

Results: Sixteen out of 27 patients showed nocturnal hypercapnia (peak p_tcCO₂ ≥ 50 mmHg for ≥ 30 min or increase in p_tcCO₂ by 10 mmHg or more from the baseline value). In these patients, forced vital capacity (FVC; % predicted) and maximum inspiratory pressure (MIP; % of lower limit or normal or LLN) were significantly reduced compared to normocapnic individuals. Nocturnal hypercapnia was predicted by reduction in FVC of <60% [sensitivity, 1.0; area under the curve (AUC), 0.82] and MIP (%LLN) <120% (sensitivity, 0.83; AUC, 0.84), the latter reflecting that in patients with neuromuscular disease, pretest likelihood of abnormality is per se higher than in healthy subjects. Diaphragm excursion velocity during a sniff maneuver excluded nocturnal hypercapnia with high sensitivity (0.90) using a cutoff of 8.0 cm/s.

Conclusion: In slowly progressive myopathies, nocturnal hypercapnia is predicted by FVC <60% or MIP <120% (LLN). As a novelty, nocturnal hypercapnia can be excluded with acceptable sensitivity by diaphragm excursion velocity >8.0 cm/s on diaphragm ultrasound.

Quality of life and its contributors among adults with late-onset Pompe disease in China

Background

Pompe disease (PD) is a rare inherited disorder caused by the deficiency of acid-α glucosidase, which leads to the impairment of organ and tissue functions and causes disabilities. As the first national survey on patients with late-onset PD (LOPD) in China, this study investigated the quality of life (QOL) of adult patients with LOPD in China and explored its contributors.

Methods

Data were derived from a nation-based, cross-sectional, self-response survey on rare diseases (RDs) in early 2018. Answers from 68 adult Chinese patients with LOPD were used for data analysis. QOL was measured using the World Health Organization Quality of Life: Brief Version. Covariates included age, gender, education, employment, reliance on assistive devices, medication history, social support, and disease economic burden. Data were analyzed using linear regression in R.

Results

For adult patients with LOPD, the average scores and standard deviations (SD) of the four dimensions of QOL were physical health = 33.77 (SD = 18.28), psychological health = 43.81 (SD = 21.70), environmental health = 39.43 (SD = 16.93), and social relationship = 46.20 (SD = 19.76); the scoring for each dimension was evaluated on a scale of 0 to 100. At the significance level of p < 0.05, with increasing age, the patients experienced a significant decrease in physical health QOL (β = − 0.75) and environmental health QOL (β = − 0.79). Those who relied heavily on assistive devices had lower perceived physical health (β = − 17.8), psychological health (β = − 22.76), environmental health (β = − 17.8), and social relationships (β = − 22.12) than those who did not. A one-unit increase in the amount of social support, as a form of social interaction, led to a significant increase in physical health (β = 0.28), psychological health (β = 0.71), environmental health (β = 0.72), and social relationships (β = 0.70).

Conclusion

Adult Chinese patients with LOPD had a lower physical health and QOL compared to their counterparts with other RDs. Being employed was found to affect the QOL of adult Chinese patients with LOPD in almost all dimensions. Encouraging adult Chinese patients with LOPD to be socially active and help them become more involved in social life might improve their QOL.

Effects of nasal high flow on nocturnal hypercapnia, sleep, and sympathovagal balance in patients with neuromuscular disorders

PURPOSE

In neuromuscular disorders (NMD), inspiratory muscle weakness may cause sleep-related hypoventilation requiring non-invasive ventilation (NIV). Alternatively, nasal high flow therapy (NHF) may ameliorate mild nocturnal hypercapnia (NH) through washout of anatomical dead space and generation of positive airway pressure. Ventilatory support by NIV or NHF might have favourable short-term effects on sympathovagal balance (SVB). This study comparatively investigated the effects of NHF and NIV on sleep-related breathing and SVB in NMD patients with evolving NH.

METHODS

Transcutaneous CO₂ (p_tcCO₂), peripheral oxygen saturation (SpO₂), sleep outcomes and SVB (spectral analysis of heart rate, diastolic blood pressure variability) along with haemodynamic measures (cardiac index, total peripheral resistance index) were evaluated overnight in 17 patients. Polysomnographies (PSG) were randomly split into equal parts with no treatment, NIV and NHF at different flow rates (20 l/min vs. 50 l/min). In-depth analysis of SVB and haemodynamics was performed on 10-min segments of stable N2 sleep taken from each intervention.

RESULTS

Compared with no treatment, NHF20 and NHF50 did not significantly change p_tcCO₂, SpO₂ or the apnea hypopnea index (AHI). NHF50 was poorly tolerated. In contrast, NIV significantly improved both gas exchange and AHI without adversely affecting sleep. During daytime, NHF20 and NHF50 had neutral effects on ventilation and oxygenation whereas NIV improved p_tcCO₂ and SpO₂. Effects of NIV and NHF on SVB and haemodynamics were neutral during both night and daytime.

CONCLUSIONS

NHF does not correct sleep-disordered breathing in NMD patients with NH. Both NHF and NIV exert no immediate effects on SVB.

Respiratory failure and sleep-disordered breathing in late-onset Pompe disease: a narrative review

Late-onset Pompe disease (LOPD) is a rare autosomal recessive glycogen storage disease that results in accumulation of glycogen in muscle cells causing muscular weakness. It causes a progressive proximal myopathy, accompanied by respiratory muscle weakness, which can lead to ventilatory failure. In untreated LOPD, the most common cause of death is respiratory failure. Patients suffering from respiratory compromise may present with symptoms of sleep-disordered breathing (SDB) before overt signs of respiratory failure. Diaphragm weakness leads to nocturnal hypoventilation, which can result in sleep disruption. Both subjective and objective sleep quality can be impaired with associated excessive daytime sleepiness (EDS). Health-related quality of life worsens as sleep disturbance increases. The mainstay of treatment for SDB and respiratory failure in LOPD is non-invasive ventilation (NIV), which aims to ensure adequate ventilation, particularly during sleep, and prevent acute hypercapnic failure. These patients are at risk of acute deterioration due to lower respiratory tract infections; effective secretion clearance and vaccination against common pathogens is an important facet of care. Whilst disease-modifying enzyme replacement therapy (ERT) delays progression of locomotor dysfunction and prolongs life, its effect on respiratory function and SDB remains unclear. There are no data demonstrating the impact of ERT on sleep quality or SDB.

M Mode Ultrasound and Tissue Doppler Imaging to Assess Diaphragm Feature in Late Onset Pompe Disease

Late-onset Pompe disease (LOPD) is an autosomal recessive lysosomal storage disease. Clinical features include skeletal muscle deficiency and diaphragm weakness. Clinical management relies on supportive treatment and mechanical ventilation in patients with chronic respiratory failure. M mode ultrasound and sniff tissue Doppler imaging can be used to assess and follow diaphragm function.

Respiratory muscle training in late-onset Pompe disease: Results of a sham-controlled clinical trial

To address progressive respiratory muscle weakness in late-onset Pompe disease (LOPD), we developed a 12-week respiratory muscle training (RMT) program. In this exploratory, double-blind, randomized control trial, 22 adults with LOPD were randomized to RMT or sham-RMT. The primary outcome was maximum inspiratory pressure (MIP). Secondary and exploratory outcomes included maximum expiratory pressure (MEP), peak cough flow, diaphragm ultrasound, polysomnography, patient-reported outcomes, and measures of gross motor function. MIP increased 7.6 cmH₂O (15.9) in the treatment group and 2.7 cmH₂O (7.6) in the control group (P = 0.4670). MEP increased 14.0 cmH₂O (25.9) in the treatment group and 0.0 cmH₂O (12.0) in the control group (P = 0.1854). The only statistically significant differences in secondary/exploratory outcomes were improvements in time to climb 4 steps (P = 0.0346) and daytime sleepiness (P = 0.0160). The magnitude of changes in MIP and MEP in the treatment group were consistent with our pilot findings but did not achieve statistical significance in comparison to controls. Explanations for this include inadequate power and baseline differences in subject characteristics between groups. Additionally, control group subjects appeared to exhibit an active response to sham-RMT and therefore sham-RMT may not be an optimal control condition for RMT in LOPD.

Potential patient screening for late-onset Pompe disease in suspected sleep apnea: a rationale and study design for a Prospective Multicenter Observational Cohort Study in Japan (PSSAP-J Study)

BACKGROUND

Pompe disease is an autosomal recessive disorder caused by deficiency of the acid α-glucosidase (GAA) enzyme. GAA deficiency induces progressive glycogen accumulation which leads to weakness of the respiratory muscle including the diaphragm. Pompe disease is one of the few myopathies, for which an established therapy is available. Thus, earlier detection of potential late-onset Pompe disease (LOPD) and earlier intervention would have a significant clinical impact.

PURPOSE

Our hypothesis is that sleep problems including sleep disordered breathing (SDB) and clinical symptoms may indicate an early stage of LOPD since decreased respiratory muscle activity generally first presents during sleep. Thus, the aims of this prospective, multicenter observational cohort study in Japan (PSSAP-J) are to demonstrate a higher prevalence of LOPD in a sleep lab-based population (primary outcome), and to identify predictive factors for LOPD from findings in diagnostic polysomnography (PSG) and clinical symptoms (secondary outcomes).

METHODS

The study design is a prospective multicenter observational cohort study. Consecutive patients who present to sleep labs due to suspected SDB for an overnight PSG will be enrolled. All patients will be measured for creatine kinase, GAA activity, and if necessary, genetic analysis of GAA. Furthermore, chest X-ray, pulmonary function test, and arterial blood gas analysis will be collected. Then, prevalence and specific findings of LOPD will be assessed.

RESULT

Congenital myopathy shows a shift from slow-deep to rapid-shallow breathing during transition from wakefulness to sleep accompanying a symptom of waking with gasping (actual further results are pending).

DISCUSSION

The distribution in respiratory physiology between during wakefulness and sleep specific to LOPD may provide insights into early-stage detection.

CLINICAL TRIAL REGISTRATION NUMBER

UMIN000039191, UMIN Clinical Trials Registry ( http://www.umin.ac.jp/ctr ).

Dynamic respiratory muscle function in late-onset Pompe disease

Maximal inspiratory pressure (PI_MAX) reflects inspiratory weakness in late-onset Pompe disease (LOPD). However, static pressure tests may not reveal specific respiratory muscle adaptations to disruptions in breathing. We hypothesized that dynamic respiratory muscle functional tests reflect distinct ventilatory compensations in LOPD. We evaluated LOPD (n = 7) and healthy controls (CON, n = 7) during pulmonary function tests, inspiratory endurance testing, dynamic kinematic MRI of the thorax, and ventilatory adjustments to single-breath inspiratory loads (inspiratory load compensation, ILC). We observed significantly lower static and dynamic respiratory function in LOPD. PI_MAX, spirometry, endurance time, and maximal diaphragm descent were significantly correlated. During single-breath inspiratory loads, inspiratory time and airflow acceleration increased to preserve volume, and in LOPD, the response magnitudes correlated to maximal chest wall kinematics. The results indicate that changes in diaphragmatic motor function and strength among LOPD subjects could be detected through dynamic respiratory testing. We concluded that neuromuscular function significantly influenced breathing endurance, timing and loading compensations.

[Not Available]

INTRODUCTION:

Morbidity and mortality in adults with late-onset Pompe disease (LOPD) results primarily from persistent progressive respiratory muscle weakness despite treatment with enzyme replacement therapy (ERT). To address this need, we have developed a 12-week respiratory muscle training (RMT) program that provides calibrated, individualized, and progressive pressure-threshold resistance against inspiration and expiration. Our previous results suggest that our RMT regimen is safe, well-tolerated, and results in large increases in respiratory muscle strength. We now conduct an exploratory double-blind, randomized control trial (RCT) to determine: 1) utility and feasibility of sham-RMT as a control condition, 2) the clinically meaningful outcome measures for inclusion in a future efficacy trial. This manuscript provides comprehensive information regarding the design and methods used in our trial and will aid in the reporting and interpretation of our future findings.

METHODS:

Twenty-eight adults with LOPD will be randomized (1:1) in blocks of 4 to RMT (treatment) or sham-RMT (control). Assessments will be conducted at pretest, posttest, 3-months detraining, and 6-months detraining. The primary outcome is maximum inspiratory pressure (MIP). Secondary outcomes include maximum expiratory pressure (MEP), 6-minute walk test (6MWT), Gait, Stairs, Gowers, and Chair test (GSGC), peak cough flow (PCF), and patient-reported life activity/social participation (Rasch-built Pompe-specific Activity scale [R-Pact]). Exploratory outcomes include quantitative measures from polysomnography; patient reported measures of fatigue, daytime sleepiness, and sleep quality; and ultrasound measures of diaphragm thickness. This research will use a novel tool to provide automated data collection and user feedback, and improve control over dose.

ETHICS AND DISSEMINATION:

The results of this clinical trial will be promptly analyzed and submitted for publication. Results will also be made available on clinicaltrials.gov.

CLINICALTRIALS.GOV:

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Multisystem late onset Pompe disease (LOPD): an update on clinical aspects

Pompe disease is classified by age of onset, organ involvement, severity, and rate of progression in two main forms: the first one, infantile onset Pompe disease (IOPD), presents before the age of 12 months with generalized muscle weakness, hypotonia, respiratory distress, and hypertrophic cardiomyopathy as main clinical features. The second form, late onset Pompe disease (LOPD), is characterized by an onset at the age of 12 months to adulthood, hyperCKemia, and limb-girdle and axial muscle weakness, often complicated by respiratory muscles degeneration. In the last 10-15 years, an increasing interest in Pompe disease has led to multiple studies in an effort to clarify the emerging clinical aspects, to find out the best diagnostic tools to identify the disease as early as possible, and to offer new therapeutic options apart from enzyme replacement therapy (ERT). Since 2006, ERT-the first treatment for Pompe disease-has been universally accepted in the majority of countries all over the world. Although for years Pompe disease has been primarily considered a muscle disorder, nowadays it is clear that the involvement of several other organs has changed the cultural approach to this entity which is now viewed as a multisystem disorder. The emerging clinical aspects have greatly expanded the spectrum of the disease manifestations. In fact, central, peripheral, and autonomous nervous systems are often involved; vascular malformations and heart involvement are frequently observed; musculoskeletal and bone changes as well as oro-gastrointestinal and urinary tract alterations have been better defined. A great deal of effort has been made to clarify the clinical aspects of Pompe disease, to raise awareness of the LOPD patients' problems and to improve their quality of life.

Early-onset of symptoms and clinical course of Pompe disease associated with the c.-32-13 T > G variant

BACKGROUND

Individuals with late-onset Pompe disease (LOPD) and the common c.-32-13 T > G variant are widely thought to have milder, adult-onset disease. This belief, and the consequent low suspicion of clinical involvement in children, has led to delays in diagnosis and treatment initiation in patients with early onset of symptoms. Previous reports of LOPD in children do not include description of the early-onset phenotype. This description of signs and symptoms, some of which are subtle and less known, is important to facilitate prompt identification and appropriate treatment in symptomatic children.

METHODS

Retrospective chart review of a cohort of 84 LOPD patients with the c.-32-13 T > G variant was conducted to identify patients diagnosed clinically (as opposed to through newborn screening) who had clinically documented symptom-onset within the first two years of life.

RESULTS

Four patients had early onset of symptoms, with age at onset ranging from 10 days to 20 months. Initial symptoms included delay in achievement of gross motor milestones, signs of proximal muscle weakness, swallow and feeding difficulties, and sleep apnea. Early and characteristic alterations in posture and movement were identified in all patients. Age at diagnosis ranged from 10 months to 26 months. Median age at enzyme replacement therapy (ERT) initiation was 23.5 months. Despite ERT, progression of musculoskeletal involvement and residual muscle weakness was evident in all patients, as evidenced by ptosis, myopathic facies, scoliosis, lumbar lordosis, scapular winging, and trunk and lower extremity weakness. Standardized functional assessments showed gross motor function below age level as measured by the Alberta Infant Motor Scales, the Peabody Developmental Motor Scales-2, the Bruininks-Oseretsky Test of Motor Proficiency, Second Edition, and the six-minute walk test.

CONCLUSIONS

Onset of symptoms including delay in achievement of gross motor milestones, signs of proximal muscle weakness, swallow and feeding difficulties, and sleep apnea in the first two years of life is not uncommon in individuals with LOPD and the c.-32-13 T > G variant. Patients with early-onset disease appear to have a more, rapid and severe progression of disease with persistent residual muscle deficits which partially improve with higher doses of ERT. Careful evaluation for specific and characteristic patterns of posture and movement in patients with this variant is necessary to identify those who have early onset of disease. Increased awareness of the early-onset signs and symptoms may also enable early identification of disease onset in children who are diagnosed through newborn screening.

Respiratory involvement in neuromuscular disorders

PURPOSE OF REVIEW

In numerous neuromuscular disorders (NMDs), respiratory muscle weakness is present, and acute or chronic respiratory failure may evolve. Very often, respiratory involvement substantially adds to the burden of disease, impairs quality of life, or reduces life expectancy. This article summarizes new aspects of both diagnosis and management of respiratory muscle weakness in patients with NMDs.

RECENT FINDINGS

Drugs like deflazacort, ataluren, eteplirsen, and nusinersen are now approved treatments for Duchenne Muscular Dystrophy and Spinal Muscular Atrophy, and others are on their way in NMDs. Although observing how innovative drugs will change the natural history of these diseases, including respiratory function over time, adequate symptomatic treatment remains meaningful and is strongly recommended. Physicians should systematically take respiratory involvement into account to improve patients' quality of life and prognosis.

SUMMARY

First, it is outlined in which subtypes of NMD respiratory muscle dysfunction is particularly relevant. Second, new developments regarding diagnostic procedures, including respiratory muscle strength testing, spirometry, and sleep studies, are covered. Third, this article gives an overview on current concepts of ventilatory support and management of secretions in patients with NMD.

Pulmonary functions and sleep-related breathing disorders in lipid storage disease

PURPOSE

Pulmonary function abnormalities and sleep-related breathing disorders (SRBD) are frequent in subjects with several neuromuscular diseases but there is no data about lipid storage diseases (LSD). Therefore, we aimed to evaluate pulmonary functions and SRBD in adults with LSD.

METHODS

Pulmonary functions (forced expiratory volume (FEV₁), forced vital capacity (FVC), supine FVC, upright-supine FVC% change, maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), peak cough flow (PCF)), arterial blood gases, and polysomnographic data of all subjects were evaluated.

RESULTS

Twenty-five subjects with LSD were evaluated [17 males, 8 females; age 34.9 ± 15 years; BMI 26.5 ± 3.4 kg/m²]. MIP was - 72.2 ± 32.7 cmH₂O (< - 80 cmH₂O in 13 subjects), MEP was 80.9 ± 39.1 cmH₂O (< 80 cmH₂O in 9 subjects, < 40 cmH₂O in 6 subjects), and PCF was 441.3 ± 190.9 L/min (< 360 L/min in 11 subjects). FVC was 87.8% ± 25.7 and 6 subjects had FVC < 80%. Seven subjects had diaphragm dysfunction (four upright-supine FVC% ≥ 15, three dyspnea in supine position with paradoxical abdominal respiration). Five subjects had hypoxemia (PaO₂ < 80 mmHg) and 8 subjects had hypercapnia (PaCO₂ > 45 mmHg). REM sleep had decreased in all subjects (10.2% ± 6.1). Obstructive sleep apnea (OSA) was found in 80% of the subjects (n = 20; 9 mild, 9 moderate, 2 severe). For subjects with OSA, apnea-hypopnea index (AHI) was 20.8 ± 15.9/h, oxygen desaturation index (ODI) was 11.9 ± 15.4/h, AHI_REM was 30.6 ± 19.7/h, AHI_NREM was 19.7 ± 16.6/h, ODI_REM was 27.2 ± 26.1/h, and ODI_NREM was 11.4 ± 15/h. Five subjects (20%) diagnosed as REM-related OSA. Nocturnal mean SpO₂ was 94.9% ± 1.7, lowest SpO₂ was 73.3% ± 13.9, and time spent with SpO₂ < 90% was 2.4% ± 7.2.

CONCLUSION

In subjects with LSD, pulmonary function impairment, daytime hypercapnia and hypoxemia, and OSA, especially REM-related OSA, are frequent. Therefore, pulmonary functions and polysomnography should be performed routinely.

The impact of Pompe disease on smooth muscle: a review

Pompe disease (OMIM 232300) is an autosomal recessive disorder caused by mutations in the gene encoding acid α-glucosidase (GAA) (EC 3.2.1.20), the enzyme responsible for hydrolyzing lysosomal glycogen. The primary cellular pathology is lysosomal glycogen accumulation in cardiac muscle, skeletal muscle, and motor neurons, which ultimately results in cardiorespiratory failure. However, the severity of pathology and its impact on clinical outcomes are poorly described in smooth muscle. The advent of enzyme replacement therapy (ERT) in 2006 has improved clinical outcomes in infantile-onset Pompe disease patients. Although ERT increases patient life expectancy and ventilator free survival, it is not entirely curative. Persistent motor neuron pathology and weakness of respiratory muscles, including airway smooth muscles, contribute to the need for mechanical ventilation by some patients on ERT. Some patients on ERT continue to experience life-threatening pathology to vascular smooth muscle, such as aneurysms or dissections within the aorta and cerebral arteries. Better characterization of the disease impact on smooth muscle will inform treatment development and help anticipate later complications. This review summarizes the published knowledge of smooth muscle pathology associated with Pompe disease in animal models and in patients.

The humanistic burden of Pompe disease: are there still unmet needs? A systematic review

BACKGROUND

Humanistic burden considers the impact of an illness on a patient's health-related quality of life (HRQoL), activities of daily living (ADL), caregiver health, and caregiver QoL. Humanistic burden also considers treatment satisfaction and adherence to treatment regimens. Pompe disease is an autosomal recessive, progressive, multisystemic neuromuscular disease. Approval of enzyme-replacement therapy (ERT) markedly improved prognosis for patients, but considerable morbidity and a substantial humanistic burden remain. This article characterizes the humanistic burden of Pompe disease through a systematic literature review.

METHODS

A systematic search of MEDLINE® and Embase® with back-referencing and supplementary literature searches was performed to retrieve data from interventional and non-interventional studies on the humanistic burden of Pompe disease. Publications were screened according to predefined criteria, extracted, and assessed for quality. Extracted data were narratively synthesized.

RESULTS

No publications on the humanistic burden of infantile-onset Pompe disease (IOPD) were identified. As such, of 17 publications included here, all are in patients with late-onset Pompe disease (LOPD). Thirteen publications were initiated after approval of ERT, two were initiated before, and two overlapped the approval of ERT. The review shows that LOPD patients have a significantly lower HRQoL than the general population, even if treated with ERT. On transitioning to ERT, treatment was associated with improvement in the physical component score of the SF-36 and fatigue, although the SF-36 mental component score remained stable. Physical HRQoL remained below population norms after 4 years of ERT. Significantly more ERT-treated patients reported pain than controls, and bodily pain worsened in later years following ERT initiation. Treatment-naïve LOPD patients had significantly poorer ADL functioning compared with the general population, although ERT stabilized deteriorating functioning impairment. ERT studies showed caregivers provide 17.7 h/week informal care on average. Fifty percent, 40% and <20% of caregivers reported mental health, physical health, and financial/relational problems, respectively. In ERT-naïve patients, wheelchair use and home ventilatory support was associated with lower physical HRQoL and ADL functioning. In ERT-treated patients, key factors predicting worse HRQoL and ADL functioning were higher respiratory distress, poorer sleep quality, greater pain, and more fatigue.

CONCLUSIONS

Pompe disease has a substantial humanistic burden, with strong inter-relationships among and between humanistic burden parameters and clinical progression.

Maximum inspiratory pressure as a clinically meaningful trial endpoint for neuromuscular diseases: a comprehensive review of the literature

Respiratory muscle strength is a proven predictor of long-term outcome of neuromuscular disease (NMD), including amyotrophic lateral sclerosis, Duchenne muscular dystrophy, and spinal muscular atrophy. Maximal inspiratory pressure (MIP), a sensitive measure of respiratory muscle strength, one of several useful tests of respiratory muscle strength, is gaining interest as a therapeutic clinical trial endpoint for NMD. In this comprehensive review we investigate the use of MIP as a measure of respiratory muscle strength in clinical trials of therapeutics targeting respiratory muscle, examine the correlation of MIP with survival, quality of life, and other measures of pulmonary function, and outline the role of MIP as a clinically significantly meaningful outcome measure. Our analysis supports the utility of MIP for the early evaluation of respiratory muscle strength, especially of the diaphragm, in patients with NMD and as a surrogate endpoint in clinical trials of therapies for NMD.

The emerging phenotype of late-onset Pompe disease: A systematic literature review

BACKGROUND

Pompe disease is an autosomal recessive disorder caused by deficiency of the lysosomal glycogen-hydrolyzing enzyme acid α-glucosidase (GAA). The adult-onset form, late-onset Pompe disease (LOPD), has been characterized by glycogen accumulation primarily in skeletal, cardiac, and smooth muscles, causing weakness of the proximal limb girdle and respiratory muscles. However, increased scientific study of LOPD continues to enhance understanding of an evolving phenotype.

PURPOSE

To expand our understanding of the evolving phenotype of LOPD since the approval of enzyme replacement therapy (ERT) with alglucosidase alfa (Myozyme™/Lumizyme™) in 2006.

METHODS

All articles were included in the review that provided data on the charactertistics of LOPD identified via the PubMed database published since the approval of ERT in 2006. All signs and symptoms of the disease that were reported in the literature were identified and included in the review.

RESULTS

We provide a comprehensive review of the evolving phenotype of LOPD. Our findings support and extend the knowledge of the multisystemic nature of the disease.

CONCLUSIONS

With the advent of ERT and the concurrent increase in the scientific study of LOPD, the condition once primarily conceptualized as a limb-girdle muscle disease with prominent respiratory involvement is increasingly recognized to be a condition that results in signs and symptoms across body systems and structures.

Sleep-Disordered Breathing and Effects of Noninvasive Ventilation in Patients with Late-Onset Pompe Disease

STUDY OBJECTIVES

In neuromuscular disease, non-invasive ventilation (NIV) is indicated if sleep-disordered breathing (SDB) or significant respiratory muscle weakness (RMW) is present. We investigated immediate and long-term effects of NIV on sleep and nocturnal ventilation in patients with late-onset Pompe disease (LOPD).

METHODS

Polysomnography and transcutaneous capnometry were performed in 22 adult patients. If indicated, NIV was initiated the subsequent night and follow-up sleep studies were scheduled. Sleep quality and health-related quality of life (HRQoL) were self-assessed using standard questionnaires.

RESULTS

Fourteen patients received enzyme replacement therapy (ERT), five patients were treatment-naÏve, and three individuals had previously stopped ERT. Fifteen patients reported symptoms of SDB, all showing abnormal sleep studies. Two patients had obstructive sleep apnea (OSA), three patients showed both OSA and nocturnal hypercapnia, four individuals had nocturnal hypercapnia, and two patients had both OSA and daytime hypercapnia. Four patients showed normal apnea-hypopnea index and CO₂ measures but nocturnal tachypnea, orthopnea, and significant RMW were present. Supine forced vital capacity (FVC) and positional drop of FVC were independent predictors of SDB. In patients with SDB, HRQoL was significantly reduced. NIV was initiated in 15 individuals and led to significant improvement of ventilation and oxygenation in the first night of treatment. Follow-up sleep studies revealed stable normoxia and normocapnia without deterioration of sleep outcomes for up to 40 months.

CONCLUSIONS

In LOPD, SDB is common and comprises both hypoventilation and OSA. NIV significantly improves respiration already in the first night of treatment. NIV warrants nocturnal long-term normoventilation without deterioration of sleep quality.

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.

Practical Recommendations for Diagnosis and Management of Respiratory Muscle Weakness in Late-Onset Pompe Disease

Pompe disease is an autosomal-recessive lysosomal storage disorder characterized by progressive myopathy with proximal muscle weakness, respiratory muscle dysfunction, and cardiomyopathy (in infants only). In patients with juvenile or adult disease onset, respiratory muscle weakness may decline more rapidly than overall neurological disability. Sleep-disordered breathing, daytime hypercapnia, and the need for nocturnal ventilation eventually evolve in most patients. Additionally, respiratory muscle weakness leads to decreased cough and impaired airway clearance, increasing the risk of acute respiratory illness. Progressive respiratory muscle weakness is a major cause of morbidity and mortality in late-onset Pompe disease even if enzyme replacement therapy has been established. Practical knowledge of how to detect, monitor and manage respiratory muscle involvement is crucial for optimal patient care. A multidisciplinary approach combining the expertise of neurologists, pulmonologists, and intensive care specialists is needed. Based on the authors' own experience in over 200 patients, this article conveys expert recommendations for the diagnosis and management of respiratory muscle weakness and its sequelae in late-onset Pompe disease.

Progression from respiratory dysfunction to failure in late-onset Pompe disease

To identify determinants of respiratory disease progression in late-onset Pompe disease (LOPD), we studied relationships between pulmonary function, respiratory muscle strength, gas exchange, and respiratory control. Longitudinal evaluation of 22 LOPD patients (mean age 38 years) was performed at 6-month intervals for 6-24 months. Measurements included vital capacity (VC), maximum inspiratory pressure (MIP), maximum expiratory pressure (MEP), tidal volume (VT), dead space (VD), and ventilatory response to CO2. Although reduction in VC correlated with MIP and MEP (p < 0.0001), some patients had normal VC despite reduced MIP and MEP (5 [23%] and 9 [41%] patients, respectively). Daytime hypercapnia was associated with reduced VC (<60% predicted) and MIP (<40% predicted). Moreover, chronic hypercapnia was associated with elevated VD/VT (≥0.44) due to falling VT (≈300 ml), compatible with reduced efficiency of CO2 clearance. The presence of hypercapnia and/or ventilatory support was associated with reduced ventilatory responsiveness to CO2 (≤0.7 l/min/mmHg). We conclude that daytime hypercapnia, an indicator of chronic respiratory failure, is tightly linked to the degree of respiratory muscle weakness and severity of pulmonary dysfunction in LOPD patients. Reductions in CO2 clearance efficiency and ventilatory responsiveness may contribute to the development of chronic daytime hypercapnia.

Inspiratory Muscle Training in Late-Onset Pompe Disease: The Effects on Pulmonary Function Tests, Quality of Life, and Sleep Quality

INTRODUCTION

Late-onset Pompe disease (LOPD) is characterized by progressive skeletal and respiratory muscle weakness. Little is known about the effect of inspiratory muscle training (IMT) on pulmonary function in subjects with LOPD. The aim of the present study was to investigate the effect of an 8-week IMT program on pulmonary function tests, quality of life, and sleep quality in eight patients with LOPD who were receiving enzyme replacement therapy (ERT).

METHODS

Before and after the IMT program, spirometric measurements in sitting and supine positions, and measurements of maximum inspiratory and expiratory pressures, peak cough flow, quality of life (assessed using the Nottingham Health Profile), and sleep quality (assessed using the Pittsburgh sleep quality index) were performed.

RESULTS

A significant increase in maximum inspiratory pressure (cmH2O and % predicted) (median [interquartile range]: 30.0 cmH2O [21.5-48] versus 39 cmH2O [31.2-56.5] and 38.3 % [28.1-48.4] versus 50.5 % [37.7-54.9]) was observed after training (p = 0.01). There were no significant changes in the other pulmonary function measurements. With the exception of the social isolation subscore (p = 0.02), quality of life subscores did not change after IMT (p > 0.05). Sleep quality subscores and total scores were similar before and after IMT.

CONCLUSION

These results suggest that IMT has a positive effect on maximum inspiratory pressure in subjects with LOPD who are under ERT.

Respiratory muscle training (RMT) in late-onset Pompe disease (LOPD): Effects of training and detraining

BACKGROUND

Determine the effects of a 12-week respiratory muscle training (RMT) program in late-onset Pompe disease (LOPD).

METHODS

We investigated the effects of 12-weeks of RMT followed by 3-months detraining using a single-subject A-B-A experimental design replicated across 8 adults with LOPD. To assess maximal volitional respiratory strength, our primary outcomes were maximum inspiratory pressure (MIP) and maximum expiratory pressure (MEP). Effect sizes for changes in MIP and MEP were determined using Cohen's d statistic. Exploratory outcomes targeted motor function, and peak cough flow (PCF) was measured in the last 5 subjects.

RESULTS

From pretest to posttest, all 8 subjects exhibited increases in MIP, and 7 of 8 showed increases in MEP. Effect size data reveal the magnitude of increases in MIP to be large in 4 (d≥1.0) and very large in 4 (d≥2.0), and effect sizes for increases in MEP were large in 1 (d≥1.0) and very large in 6 (d≥2.0). Across participants, pretest to posttest MIP and MEP increased by a mean of 19.6% (sd=9.9) and 16.1% (sd=17.3), respectively. Respiratory strength increases, particularly for the inspiratory muscles, were generally durable to 3-months detraining.

CONCLUSIONS

These data suggest our 12-week RMT program results in large to very large increases in inspiratory and expiratory muscle strength in adults with LOPD. Additionally, increases in respiratory strength appeared to be relatively durable following 3-months detraining. Although additional research is needed, RMT appears to offer promise as an adjunctive treatment for respiratory weakness in LOPD.