[Pulmonary and nonpulmonary alterations in Duchenne muscular dystrophy]

Translating Dysphagia Evidence into Practice While Avoiding Pitfalls: Assessing Bias Risk in Tracheostomy Literature

Critically ill patients who require a tracheostomy often have dysphagia. Widespread practice guidelines have yet to be developed regarding the acute assessment and management of dysphagia in patients with tracheostomy. In order for clinicians to base their practice on the best available evidence, they must first assess the applicable literature and determine its quality. To inform guideline development, our objective was to assess literature quality concerning swallowing following tracheostomy in acute stages of critical illness in adults. Our systematic literature search (published previously) included eight databases, nine gray literature repositories and citation chasing. Using inclusion criteria determined a priori, two reviewers, blinded to each other, conducted an eligibility review of identified citations. Patients with chronic tracheostomy and etiologies including head and/or neck cancer diagnoses were excluded. Four teams of two reviewers each, blinded to each other, assessed quality of included studies using a modified Cochrane Risk of Bias tool (RoB). Disagreements were resolved by consensus. Data were summarized descriptively according to study design and RoB domain. Of 6,396 identified citations, 74 studies met our inclusion criteria. Of those, 71 were observational and three were randomized controlled trials. Across all studies, the majority (> 75%) had low bias risk with: participant blinding, outcome reporting, and operationally defined outcomes. Areas requiring improvement included assessor and study personnel blinding. Prior to translating the literature into practice guidelines, we recommend attention to study quality limitations and its potential impact on study outcomes. For future work, we suggest an iterative approach to knowledge translation.

Investigating Swallowing and Tracheostomy Following Critical Illness: A Scoping Review

OBJECTIVES

Tracheostomy and dysphagia often coexist during critical illness; however, given the patient's medical complexity, understanding the evidence to optimize swallowing assessment and intervention is challenging. The objective of this scoping review is to describe and explore the literature surrounding swallowing and tracheostomy in the acute care setting.

DATA SOURCES

Eight electronic databases were searched from inception to May 2017 inclusive, using a search strategy designed by an information scientist. We conducted manual searching of 10 journals, nine gray literature repositories, and forward and backward citation chasing.

STUDY SELECTION

Two blinded reviewers determined eligibility according to inclusion criteria: English-language studies reporting on swallowing or dysphagia in adults (≥ 17 yr old) who had undergone tracheostomy placement while in acute care. Patients with head and/or neck cancer diagnoses were excluded.

DATA EXTRACTION

We extracted data using a form designed a priori and conducted descriptive analyses.

DATA SYNTHESIS

We identified 6,396 citations, of which 725 articles were reviewed and 85 (N) met inclusion criteria. We stratified studies according to content domains with some featuring in multiple categories: dysphagia frequency (n = 38), swallowing physiology (n = 27), risk factors (n = 31), interventions (n = 21), and assessment comparisons (n = 12) and by patient etiology. Sample sizes (with tracheostomy) ranged from 10 to 3,320, and dysphagia frequency ranged from 11% to 93% in studies with consecutive sampling. Study design, sampling method, assessment methods, and interpretation approach varied significantly across studies.

CONCLUSIONS

The evidence base surrounding this subject is diverse, complicated by heterogeneous patient selection methods, design, and reporting. We suggest ways the evidence base may be developed.

The Performance of the Upper Limb scores correlate with pulmonary function test measures and Egen Klassifikation scores in Duchenne muscular dystrophy

The Performance of the Upper Limb scale was developed as an outcome measure specifically for ambulant and non-ambulant patients with Duchenne muscular dystrophy and is implemented in clinical trials needing longitudinal data. The aim of this study is to determine whether this novel tool correlates with functional ability using pulmonary function test, cardiac function test and Egen Klassifikation scale scores as clinical measures. In this cross-sectional study, 43 non-ambulatory Duchenne males from ages 10 to 30 years and on long-term glucocorticoid treatment were enrolled. Cardiac and pulmonary function test results were analyzed to assess cardiopulmonary function, and Egen Klassifikation scores were analyzed to assess functional ability. The Performance of the Upper Limb scores correlated with pulmonary function measures and had inverse correlation with Egen Klassifikation scores. There was no correlation with left ventricular ejection fraction and left ventricular dysfunction. Body mass index and decreased joint range of motion affected total Performance of the Upper Limb scores and should be considered in clinical trial designs.

Ventilatory chemosensory drive is blunted in the mdx mouse model of Duchenne Muscular Dystrophy (DMD)

Duchenne Muscular Dystrophy (DMD) is caused by mutations in the DMD gene resulting in an absence of dystrophin in neurons and muscle. Respiratory failure is the most common cause of mortality and previous studies have largely concentrated on diaphragmatic muscle necrosis and respiratory failure component. Here, we investigated the integrity of respiratory control mechanisms in the mdx mouse model of DMD. Whole body plethysmograph in parallel with phrenic nerve activity recordings revealed a lower respiratory rate and minute ventilation during normoxia and a blunting of the hypoxic ventilatory reflex in response to mild levels of hypoxia together with a poor performance on a hypoxic stress test in mdx mice. Arterial blood gas analysis revealed low PaO2 and pH and high PaCO2 in mdx mice. To investigate chemosensory respiratory drive, we analyzed the carotid body by molecular and functional means. Dystrophin mRNA and protein was expressed in normal mice carotid bodies however, they are absent in mdx mice. Functional analysis revealed abnormalities in Dejours test and the early component of the hypercapnic ventilatory reflex in mdx mice. Together, these results demonstrate a malfunction in the peripheral chemosensory drive that would be predicted to contribute to the respiratory failure in mdx mice. These data suggest that investigating and monitoring peripheral chemosensory drive function may be useful for improving the management of DMD patients with respiratory failure.

Cardiac and respiratory dysfunction in Duchenne muscular dystrophy and the role of second messengers

Duchenne muscular dystrophy (DMD) affects young boys and is characterized by the absence of dystrophin, a large cytoskeletal protein present in skeletal and cardiac muscle cells and neurons. The heart and diaphragm become necrotic in DMD patients and animal models of DMD, resulting in cardiorespiratory failure as the leading cause of death. The major consequences of the absence of dystrophin are high levels of intracellular Ca(2+) and the unbalanced production of NO that can finally trigger protein degradation and cell death. Cytoplasmic increase in Ca(2+) concentration directly and indirectly triggers different processes such as necrosis, fibrosis, and activation of macrophages. The absence of the neuronal isoform of nitric oxide synthase (nNOS) and the overproduction of NO by the inducible isoform (iNOS) further increase the intracellular Ca(2+) via a hypernitrosylation of the ryanodine receptor. NO overproduction, which further induces the expression of iNOS but decreases the expression of the endothelial isoform (eNOS), deregulates the muscle tissue blood flow creating an ischemic situation. The high levels of Ca(2+) in dystrophic muscles and the ischemic state of the muscle tissue would culminate in a positive feedback loop. While efforts continue toward optimizing cardiac and respiratory care of DMD patients, both Ca(2+) and NO in cardiac and respiratory muscle pathways have been shown to be important to the etiology of the disease. Understanding the mechanisms behind the fine regulation of Ca(2+) -NO may be important for a noninterventional and noninvasive supportive approach to treat DMD patients, improving the quality of life and natural history of DMD patients.

Muscular dystrophies at different ages: metabolic and endocrine alterations

Common metabolic and endocrine alterations exist across a wide range of muscular dystrophies. Skeletal muscle plays an important role in glucose metabolism and is a major participant in different signaling pathways. Therefore, its damage may lead to different metabolic disruptions. Two of the most important metabolic alterations in muscular dystrophies may be insulin resistance and obesity. However, only insulin resistance has been demonstrated in myotonic dystrophy. In addition, endocrine disturbances such as hypogonadism, low levels of testosterone, and growth hormone have been reported. This eventually will result in consequences such as growth failure and delayed puberty in the case of childhood dystrophies. Other consequences may be reduced male fertility, reduced spermatogenesis, and oligospermia, both in childhood as well as in adult muscular dystrophies. These facts all suggest that there is a need for better comprehension of metabolic and endocrine implications for muscular dystrophies with the purpose of developing improved clinical treatments and/or improvements in the quality of life of patients with dystrophy. Therefore, the aim of this paper is to describe the current knowledge about of metabolic and endocrine alterations in diverse types of dystrophinopathies, which will be divided into two groups: childhood and adult dystrophies which have different age of onset.