Respiratory muscle fibres: specialisation and plasticity

Mucopolysaccharidosis (MPS IIIA) mice have increased lung compliance and airway resistance, decreased diaphragm strength, and no change in alveolar structure

Mucopolysaccharidosis type IIIA (MPS IIIA) is characterized by neurological and skeletal pathologies caused by reduced activity of the lysosomal hydrolase, sulfamidase, and the subsequent primary accumulation of undegraded heparan sulfate (HS). Respiratory pathology is considered secondary in MPS IIIA and the mechanisms are not well understood. Changes in the amount, metabolism, and function of pulmonary surfactant, the substance that regulates alveolar interfacial surface tension and modulates lung compliance and elastance, have been reported in MPS IIIA mice. Here we investigated changes in lung function in 20-wk-old control and MPS IIIA mice with a closed and open thoracic cage, diaphragm contractile properties, and potential parenchymal remodeling. MPS IIIA mice had increased compliance and airway resistance and reduced tissue damping and elastance compared with control mice. The chest wall impacted lung function as observed by an increase in airway resistance and a decrease in peripheral energy dissipation in the open compared with the closed thoracic cage state in MPS IIIA mice. Diaphragm contractile forces showed a decrease in peak twitch force, maximum specific force, and the force-frequency relationship but no change in muscle fiber cross-sectional area in MPS IIIA mice compared with control mice. Design-based stereology did not reveal any parenchymal remodeling or destruction of alveolar septa in the MPS IIIA mouse lung. In conclusion, the increased storage of HS which leads to biochemical and biophysical changes in pulmonary surfactant also affects lung and diaphragm function, but has no impact on lung or diaphragm structure at this stage of the disease.NEW & NOTEWORTHY Heparan sulfate storage in the lungs of mucopolysaccharidosis type IIIA (MPS IIIA) mice leads to changes in lung function consistent with those of an obstructive lung disease and includes an increase in lung compliance and airway resistance and a decrease in tissue elastance. In addition, diaphragm muscle contractile strength is reduced, potentially further contributing to lung function impairment. However, no changes in parenchymal lung structure were observed in mice at 20 wk of age.

Evaluation of the therapeutic effects of rehabilitation therapy on patients with amyotrophic lateral sclerosis-a meta-analysis

Objective

To investigate the effect of rehabilitation therapy on the global function, respiratory function, and quality of life in patients with amyotrophic lateral sclerosis (ALS).

Methods

PubMed, Web of Science, and The National Library of Medicine (NLM) were systematically searched and the search period was between the date of database establishment and December 31, 2023. The outcome measures finally analyzed included the ALS functional rating scale/revised (ALSFRS/ALSFRS-R), forced vital capacity percentage predicted (FVC%), fatigue severity scale (FSS), and maximal expiratory pressure (MEP).

Results

A total of 13 randomized controlled trials (RCTs) were included, and 5 outcome measures were pooled and analyzed. A total of 657 patients with ALS were enrolled, with 299 in the experimental group (rehabilitation therapy, such as resistance training, endurance training, aerobic training, respiratory muscle training, and standard rehabilitation therapy) and 358 in the control group (conventional interventions, such as simple joint movements or daily stretching). The ALSFRS scores were better in the experimental group than in the control group at 0-4 months (MD = 3.36, 95% CI: 0.82, 5.91, Z = 2.59, p = 0.009) and at 5-8 months (MD = 5.00, 95% CI: -2.42, 7.58, Z = 3.80, p < 0.001). Moreover, the ALSFRS-R scores of the experimental group was better than that of the control group at 5-8 months (MD = 2.83, 95% CI: 1.21, 4.45, Z = 3.42, p < 0.001) and 9-12 months (MD = 1.87, 95% CI: -0.37, 4.11, Z = 1.63, p = 0.10). It was also found that the MEP value of the experimental group was significantly better than that of the control group after intervention (MD = 18.49, 95% CI: 1.47, 35.50, Z = 2.13, p = 0.03). However, there were no significant differences in FVC% value and FSS scores at 0-5 months and 6-12 months between the two groups.

Conclusion

Rehabilitation therapy is helpful in improving the short-, medium-, and long-term global function score of patients with ALS, with positive effects on respiratory function.

A comprehensive physical functional assessment of survivors of critical care unit stay due to COVID-19

OBJECTIVE

To examine the physical function and respiratory muscle strength of patients - who recovered from critical COVID-19 - after intensive care unit discharge to the ward on Days one (D1) and seven (D7), and to investigate variables associated with functional impairment.

METHODS

This was a prospective cohort study of adult patients with COVID-19 who needed invasive mechanical ventilation, non-invasive ventilation or high-flow nasal cannula and were discharged from the intensive care unit to the ward. Participants were submitted to Medical Research Council sum-score, handgrip strength, maximal inspiratory pressure, maximal expiratory pressure, and short physical performance battery tests. Participants were grouped into two groups according to their need for invasive ventilation: the Invasive Mechanical Ventilation Group (IMV Group) and the Non-Invasive Mechanical Ventilation Group (Non-IMV Group).

RESULTS

Patients in the IMV Group (n = 31) were younger and had higher Sequential Organ Failure Assessment scores than those in the Non-IMV Group (n = 33). The short physical performance battery scores (range 0 - 12) on D1 and D7 were 6.1 ± 4.3 and 7.3 ± 3.8, respectively for the Non-Invasive Mechanical Ventilation Group, and 1.3 ± 2.5 and 2.6 ± 3.7, respectively for the IMV Group. The prevalence of intensive care unit-acquired weakness on D7 was 13% for the Non-IMV Group and 72% for the IMV Group. The maximal inspiratory pressure, maximal expiratory pressure, and handgrip strength increased on D7 in both groups, but the maximal expiratory pressure and handgrip strength were still weak. Only maximal inspiratory pressure was recovered (i.e., > 80% of the predicted value) in the Non-IMV Group. Female sex, and the need and duration of invasive mechanical were independently and negatively associated with the short physical performance battery score and handgrip strength.

CONCLUSION

Patients who recovered from critical COVID-19 and who received invasive mechanical ventilation presented greater disability than those who were not invasively ventilated. However, they both showed marginal functional improvement during early recovery, regardless of the need for invasive mechanical ventilation. This might highlight the severity of disability caused by SARS-CoV-2.

Glucocorticoid-Induced Myopathy: Typology, Pathogenesis, Diagnosis, and Treatment

Glucocorticoid-induced myopathy is a non-inflammatory toxic myopathy typified by proximal muscle weakness, muscle atrophy, fatigue, and easy fatigability. These vague symptoms coupled with underlying disorders may mask the signs of glucocorticoid-induced myopathy, leading to an underestimation of the disease's impact. This review briefly summarizes the classification, pathogenesis, and treatment options for glucocorticoid-induced muscle wasting. Additionally, we discuss current diagnostic measures in clinical research and routine care used for diagnosing and monitoring glucocorticoid-induced myopathy, which includes gait speed tests, muscle strength tests, hematologic tests, bioelectrical impedance analysis (BIA), dual-energy X-ray absorptiometry (DXA), computed tomography (CT), magnetic resonance imaging (MRI), electromyography, quantitative muscle ultrasound, histological examination, and genetic analysis. Continuous monitoring of patients receiving glucocorticoid therapy plays an important role in enabling early detection of glucocorticoid-induced myopathy, allowing physicians to modify treatment plans before significant clinical weakness arises.

Impact of preterm birth on muscle mass and function: a systematic review and meta-analysis

Individuals born preterm present lower exercise capacity. Along with the cardiopulmonary responses and activity level, muscle strength is a key determinant of exercise capacity. This systematic review aimed to summarize the current knowledge on the impact of preterm birth on skeletal muscle mass and function across the lifespan. The databases PubMed, MEDLINE, EBM, Embase, CINAHL Plus, Global Index Medicus, and Google Scholar were searched using keywords and MeSH terms related to skeletal muscle, preterm birth, and low birth weight. Two independent reviewers undertook study selection, data extraction, and quality appraisal using Covidence review management. Data were pooled to estimate the prematurity effect on muscle mass and function using the R software. From 4378 studies retrieved, 132 were full-text reviewed and 25 met the inclusion/exclusion criteria. Five studies presented a low risk of bias, and 5 had a higher risk of bias due to a lack of adjustment for confounding factors and presenting incomplete outcomes. Meta-analyses of pooled data from homogenous studies indicated a significant reduction in muscle thickness and jump test (muscle power) in individuals born preterm versus full-term with standardized mean difference and confidence interval of - 0.58 (0.27, 0.89) and - 0.45 (0.21, 0.69), respectively.    Conclusion: Overall, this systematic review summarizing the existing literature on the impact of preterm birth on skeletal muscle indicates emerging evidence that individuals born preterm, display alteration in the development of their skeletal muscle mass and function. This work also highlights a clear knowledge gap in understanding the effect of preterm birth on skeletal muscle development. What is Known: • Preterm birth, which occurs at a critical time of skeletal muscle development and maturation, impairs the development of different organs and tissues leading to a higher risk of comorbidities such as cardiovascular diseases. • Preterm birth is associated with reduced exercise capacity. What is New: • Individuals born preterm display alterations in muscle mass and function compared to individuals born at term from infancy to adulthood. • There is a need to develop preventive or curative interventions to improve skeletal muscle health in preterm-born individuals.

Diaphragmatic morphological post-mortem findings in critically ill COVID-19 patients: an observational study

Our study investigates the post-mortem findings of the diaphragm's muscular structural changes in mechanically ventilated COVID-19 patients. Diaphragm samples of the right side from 42 COVID-19 critically ill patients were analyzed and correlated with the type and length of mechanical ventilation (MV), ventilatory parameters, prone positioning, and use of sedative drugs. The mean number of fibers was 550±626. The cross-sectional area was 4120±3280 μm2, while the muscular fraction was 0.607±0.126. The overall population was clustered into two distinct populations (clusters 1 and 2). Cluster 1 showed a lower percentage of slow myosin fiber and higher fast fiber content than cluster 2, 68% versus 82%, p<0.00001, and 29.8% versus 18.8%, p=0.00045 respectively. The median duration of MV was 180 (41-346) hours. In cluster 1, a relationship between assisted ventilation and fast myosin fiber percentage (R2=-0.355, p=0.014) was found. In cluster 2, fast fiber content increased with increasing the length of the controlled MV (R2=0.446, p=0.006). A high grade of fibrosis was reported. Cluster 1 was characterized by fibers' atrophy and cluster 2 by hypertrophy, supposing different effects of ventilation on the diaphragm but without excluding a possible direct viral effect on diaphragmatic fibers.

Distinct transcriptomic profile of satellite cells contributes to preservation of neuromuscular junctions in extraocular muscles of ALS mice

Amyotrophic lateral sclerosis (ALS) is a fatal neuromuscular disorder characterized by progressive weakness of almost all skeletal muscles, whereas extraocular muscles (EOMs) are comparatively spared. While hindlimb and diaphragm muscles of end-stage SOD1G93A (G93A) mice (a familial ALS mouse model) exhibit severe denervation and depletion of Pax7 + satellite cells (SCs), we found that the pool of SCs and the integrity of neuromuscular junctions (NMJs) are maintained in EOMs. In cell sorting profiles, SCs derived from hindlimb and diaphragm muscles of G93A mice exhibit denervation-related activation, whereas SCs from EOMs of G93A mice display spontaneous (non-denervation-related) activation, similar to SCs from wild-type mice. Specifically, cultured EOM SCs contain more abundant transcripts of axon guidance molecules, including Cxcl12 , along with more sustainable renewability than the diaphragm and hindlimb counterparts under differentiation pressure. In neuromuscular co-culture assays, AAV-delivery of Cxcl12 to G93A-hindlimb SC-derived myotubes enhances motor neuron axon extension and innervation, recapitulating the innervation capacity of EOM SC-derived myotubes. G93A mice fed with sodium butyrate (NaBu) supplementation exhibited less NMJ loss in hindlimb and diaphragm muscles. Additionally, SCs derived from G93A hindlimb and diaphragm muscles displayed elevated expression of Cxcl12 and improved renewability following NaBu treatment in vitro . Thus, the NaBu-induced transcriptomic changes resembling the patterns of EOM SCs may contribute to the beneficial effects observed in G93A mice. More broadly, the distinct transcriptomic profile of EOM SCs may offer novel therapeutic targets to slow progressive neuromuscular functional decay in ALS and provide possible "response biomarkers" in pre-clinical and clinical studies.

A Tutorial on Skeletal Muscle Metabolism and the Role of Blood Lactate: Implications for Speech Production

PURPOSE

The purpose of this tutorial is threefold: (a) present relevant exercise science literature on skeletal muscle metabolism and synthesize the limited available research on metabolism of the adult human speech musculature in an effort to elucidate the role of metabolism in speech production; (b) introduce a well-studied metabolic serum biomarker in exercise science, lactate, and the potential usefulness of investigating this metabolite, through a well-established exercise science methodology, to better understand metabolism of the musculature involved in voice production; and (c) discuss exercise physiology considerations for future voice science research that seeks to investigate blood lactate and metabolism in voice physiology in an ecologically valid manner.

METHOD

This tutorial begins with relevant exercise science literature on the basic cellular processes of muscle contraction that require energy and the metabolic mechanisms that regenerate the energy required for task execution. The tutorial next synthesizes the available research investigating metabolism of the adult human speech musculature. This is followed by the authors proposing a hypothesis of speech metabolism based on the voice science literature and the application of well-studied exercise science principles of muscle physiology. The tutorial concludes with a discussion and the potential usefulness of lactate in investigations to better understand the metabolism of the musculature involved in vocal demand tasks.

CONCLUSION

The role of metabolism during speech (respiratory, laryngeal, and articulatory) is an understudied yet critical aspect of speech physiology that warrants further study to better understand the metabolic systems that are used to meet vocal demands.

Trans-spinal magnetic stimulation induces co-activation of the diaphragm and biceps in healthy subjects

The present study was designed to examine the effect of trans-spinal magnetic stimulation on bilateral respiratory and forelimb muscles in healthy subjects. Two wings of a figure-of-eight magnetic coil were placed on the dorsal vertebrae, from the fifth cervical to the second thoracic dorsal vertebra with a center at the seventh cervical vertebra. The surface electromyograms of bilateral diaphragm and biceps were recorded in response to trans-spinal magnetic stimulation with 20%-100% maximum output of the stimulatory device in male (n = 12) and female participants (n = 8). Trans-spinal magnetic stimulation can induce a co-activation of bilateral diaphragm and biceps when the stimulation intensity is above 60%. The onset latency was comparable between the left and right sides of the muscles, suggesting bilateral muscles could be simultaneously activated by trans-spinal magnetic stimulation. In addition, the intensity-response curve of the biceps was shifted upward compared with that of the diaphragm in males, indicating that the responsiveness of the biceps was greater than that of the diaphragm. This study demonstrated the feasibility of utilizing trans-spinal magnetic stimulation to co-activate the bilateral diaphragm and biceps. We proposed that this stimulatory configuration can be an efficient approach to activate both respiratory and forelimb muscles.

Prognostic Value of Diaphragmatic Ultrasound in Patients Admitted for COVID-19 Pneumonia

Introduction

COVID-19 pneumonia results in an impairment of the diaphragmatic musculature that influences the development of respiratory failure during the patient's hospitalization. Diaphragmatic ultrasound is a useful, non-invasive, and accessible tool for measuring the function of this muscle.

Objective

Assessing the morphological and functional ultrasound status of the diaphragm in patients admitted within the first 24 h for COVID-related pneumonia and its association with hospital morbidity and mortality (NCT05805579).

Material and methods

Observational, prospective cohort study that included 68 patients admitted for COVID-19 pneumonia with respiratory failure. Diaphragmatic ultrasound was performed within the first 24 h of admission to the pulmonology ward. Clinical, analytical, and ultrasound variables were collected: excursion, thickness, and diaphragmatic shortening fraction (DSF). DSF < 20% was used to define diaphragmatic dysfunction (DD). Patients who showed favorable progression and were managed on the ward (HCONV) were compared to those who required admission to the respiratory monitoring unit (RMU).

Results

A total of 68 patients were included, of which 22 (32.35%) were admitted to the RMU. Diaphragmatic excursion at maximum volume was higher in the HCONV group compared to the RMU group (58.41 ± 17.83 vs. 50.03 ± 16.23; p = 0.123). Diaphragmatic dysfunction (DD) was observed in 21 (30.88%) patients, with a higher prevalence in the RMU group than in the HCONV group (15 (68.18%) vs. 6 (13.04%); p = 0.0001). In the multivariate analysis, age and DSF at admission were the best predictors of failure to discharge.

Conclusions

Performing diaphragmatic ultrasound to assess mobility and DSF within the first 24 h of admission for COVID-19 pneumonia proves valuable in determining short-term progression and the need for admission to a respiratory monitoring unit.

Exploration of macromolecular phenotype of human skeletal muscle in diabetes using infrared spectroscopy

Introduction

The global burden of diabetes mellitus is escalating, and more efficient investigative strategies are needed for a deeper understanding of underlying pathophysiological mechanisms. The crucial role of skeletal muscle in carbohydrate and lipid metabolism makes it one of the most susceptible tissues to diabetes-related metabolic disorders. In tissue studies, conventional histochemical methods have several technical limitations and have been shown to inadequately characterise the biomolecular phenotype of skeletal muscle to provide a holistic view of the pathologically altered proportions of macromolecular constituents.

Materials and methods

In this pilot study, we examined the composition of five different human skeletal muscles from male donors diagnosed with type 2 diabetes and non-diabetic controls. We analysed the lipid, glycogen, and collagen content in the muscles in a traditional manner with histochemical assays using different staining techniques. This served as a reference for comparison with the unconventional analysis of tissue composition using Fourier-transform infrared spectroscopy as an alternative methodological approach.

Results

A thorough chemometric post-processing of the infrared spectra using a multi-stage spectral decomposition allowed the simultaneous identification of various compositional details from a vibrational spectrum measured in a single experiment. We obtained multifaceted information about the proportions of the different macromolecular constituents of skeletal muscle, which even allowed us to distinguish protein constituents with different structural properties. The most important methodological steps for a comprehensive insight into muscle composition have thus been set and parameters identified that can be used for the comparison between healthy and diabetic muscles.

Conclusion

We have established a methodological framework based on vibrational spectroscopy for the detailed macromolecular analysis of human skeletal muscle that can effectively complement or may even serve as an alternative to histochemical assays. As this is a pilot study with relatively small sample sets, we remain cautious at this stage in drawing definitive conclusions about diabetes-related changes in skeletal muscle composition. However, the main focus and contribution of our work has been to provide an alternative, simple and efficient approach for this purpose. We are confident that we have achieved this goal and have brought our methodology to a level from which it can be successfully transferred to a large-scale study that allows the effects of diabetes on skeletal muscle composition and the interrelationships between the macromolecular tissue alterations due to diabetes to be investigated.

Phrenic Nerve Stimulation for Acute Respiratory Failure

Diaphragm inactivity during invasive mechanical ventilation leads to diaphragm atrophy and weakness, hemodynamic instability, and ventilatory heterogeneity. Absent respiratory drive and effort can, therefore, worsen injury to both lung and diaphragm and is a major cause of failure to wean. Phrenic nerve stimulation (PNS) can maintain controlled levels of diaphragm activity independent of intrinsic drive and as such may offer a promising approach to achieving lung and diaphragm protective ventilatory targets. Whereas PNS has an established role in the management of chronic respiratory failure, there is emerging interest in how its multisystem putative benefits may be temporarily harnessed in the management of invasively ventilated patients with acute respiratory failure.

Dynapenia and Sarcopenia in Post-COVID-19 Syndrome Hospitalized Patients Are Associated with Severe Reduction in Pulmonary Function

BACKGROUND

After hospital discharge, post-COVID-19 syndrome has been observed to be associated with impaired diffusing capacity, respiratory muscle strength, and lung imaging abnormalities, in addition to loss of muscle mass/strength, sarcopenia, and obesity impact exercise tolerance, pulmonary functions, and overall prognosis. However, the relationship between lung function and the coexistence of obesity with low muscle strength and sarcopenia in post-COVID-19 patients remains poorly investigated. Therefore, our aim was to evaluate the association between lung function and the coexistence of obesity with dynapenia and sarcopenia in post-COVID-19 syndrome patients.

METHODS

This cross-sectional study included subjects who were hospitalized due to moderate to severe COVID-19, as confirmed by PCR testing. Subjects who could not be contacted, declined to participate, or died before the follow-up visit were excluded.

RESULTS

A total of 711 subjects were evaluated; the mean age was 53.64 ± 13.57 years, 12.4% had normal weight, 12.6% were dynapenic without obesity, 8.3% had sarcopenia, 41.6% had obesity, 21.2% had dynapenic obesity, and 3.8% had sarcopenic obesity. In terms of pulmonary function, the dynapenic subjects showed decreases of -3.45% in FEV1, -12.61 cmH2O in MIP, and -12.85 cmH2O in MEP. On the other hand, the sarcopenic subjects showed decreases of -6.14 cmH2O in MIP and -11.64 cmH2O in MEP. The dynapenic obesity group displayed a reduction of -12.13% in PEF.

CONCLUSIONS

In post-COVID-19 syndrome, dynapenia and sarcopenia-both with and without obesity-have been associated with lower lung function.

Prehabilitation: a narrative review focused on exercise therapy for the prevention of postoperative pulmonary complications following lung resection

Extensive preventive strategies in the perioperative period are popular worldwide. Novel "prehabilitation" approaches are being defined for every individual surgical discipline. With intention to reduce perioperative morbidity, "prehabilitation" was developed to increase "physical wellness" considering exercise capacity, nutritional status, and psychological support. Thus, prehabilitation could be well-suited for patients undergoing lung cancer surgery. Theoretically, improving physical condition may increase the chances of having a better post-operative course, especially among frail patients. In this review, we describe the concept of prehabilitation with possible benefits, its role in the Enhanced Recovery After Surgery protocols, and its potential for the future.

Neuromuscular recovery from botulism involves multiple forms of compensatory plasticity

Introduction

Botulinum neurotoxin (BoNT) causes neuroparalytic disease and death by blocking neuromuscular transmission. There are no specific therapies for clinical botulism and the only treatment option is supportive care until neuromuscular function spontaneously recovers, which can take weeks or months after exposure. The highly specialized neuromuscular junction (NMJ) between phrenic motor neurons and diaphragm muscle fibers is the main clinical target of BoNT. Due to the difficulty in eliciting respiratory paralysis without a high mortality rate, few studies have characterized the neurophysiological mechanisms involved in diaphragm recovery from intoxication. Here, we develop a mouse model of botulism that involves partial paralysis of respiratory muscles with low mortality rates, allowing for longitudinal analysis of recovery.

Methods and results

Mice challenged by systemic administration of 0.7 LD50 BoNT/A developed physiological signs of botulism, such as respiratory depression and reduced voluntary running activity, that persisted for an average of 8-12 d. Studies in isolated hemidiaphragm preparations from intoxicated mice revealed profound reductions in nerve-elicited, tetanic and twitch muscle contraction strengths that recovered to baseline 21 d after intoxication. Despite apparent functional recovery, neurophysiological parameters remained depressed for 28 d, including end plate potential (EPP) amplitude, EPP success rate, quantal content (QC), and miniature EPP (mEPP) frequency. However, QC recovered more quickly than mEPP frequency, which could explain the discrepancy between muscle function studies and neurophysiological recordings. Hypothesizing that differential modulation of voltage-gated calcium channels (VGCC) contributed to the uncoupling of QC from mEPP frequency, pharmacological inhibition studies were used to study the contributions of different VGCCs to neurophysiological function. We found that N-type VGCC and P/Q-type VGCC partially restored QC but not mEPP frequency during recovery from paralysis, potentially explaining the accelerated recovery of evoked release versus spontaneous release. We identified additional changes that presumably compensate for reduced acetylcholine release during recovery, including increased depolarization of muscle fiber resting membrane potential and increased quantal size.

Discussion

In addition to identifying multiple forms of compensatory plasticity that occur in response to reduced NMJ function, it is expected that insights into the molecular mechanisms involved in recovery from neuromuscular paralysis will support new host-targeted treatments for multiple neuromuscular diseases.

Emergency ultrasound of respiratory muscles: a promising tool for determining the outcomes of COPD exacerbations

BACKGROUND

The respiratory muscles of patients with chronic obstructive pulmonary disease (COPD) exhibit structural and functional changes that can be evaluated and monitored by ultrasonography.

METHODS

This single-center, prospective study was conducted in the emergency department (ED) of a tertiary care hospital over an eight-month period (September 2020-May 2021). Diaphragmatic excursions, end-expiratory thickness, and thickening fractions, as well as right and left intercostal muscle thicknesses, of all adult subjects manifesting COPD exacerbation, were assessed. The data were analyzed regarding ward/intensive care unit (ICU) hospitalization or discharge from the ED, mortality, and readmission within 15 days.

RESULTS

Sixty-three subjects were recruited for the study. Diaphragmatic excursion, end-expiratory diaphragmatic thickness, and intercostal muscle thickness measurements were significantly different between the ward, ICU, and discharge groups (p < 0.001) but lower in the deceased subjects (all p < 0.05). The diaphragmatic excursion value of 3.25 cm was the threshold value measured for distinguishing discharge from ED, and 1.82 cm was measured for admission to the ICU, both with 100% sensitivity and selectivity (AUC = 1).

DISCUSSION

Diaphragmatic excursion, diaphragmatic end-expiratory thickness, and right and left intercostal muscle thicknesses vary in the prognosis of subjects presenting with COPD exacerbation.

Association of Diaphragm Thickness and Respiratory Muscle Strength With Indices of Sarcopenia

OBJECTIVE

To evaluate the relationship between respiratory muscle strength, diaphragm thickness (DT), and indices of sarcopenia.

METHODS

This study included 45 healthy elderly volunteers (21 male and 24 female) aged 65 years or older. Sarcopenia indices, including hand grip strength (HGS) and body mass index-adjusted appendicular skeletal muscle (ASM/BMI), were measured using a hand grip dynamometer and bioimpedance analysis, respectively. Calf circumference (CC) and gait speed were also measured. Maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) were obtained using a spirometer, as a measure of respiratory muscle strength. DT was evaluated through ultrasonography. The association between indices of sarcopenia, respiratory muscle strength, and DT was evaluated using Spearman's rank correlation test, and univariate and multiple regression analysis.

RESULTS

ASM/BMI (r=0.609, p<0.01), CC (r=0.499, p<0.01), HGS (r=0.759, p<0.01), and gait speed (r=0.319, p<0.05) were significantly correlated with DT. In the univariate linear regression analysis, MIP was significantly associated with age (p=0.003), DT (p<0.001), HGS (p=0.002), CC (p=0.013), and gait speed (p=0.026). MEP was significantly associated with sex (p=0.001), BMI (p=0.033), ASM/BMI (p=0.003), DT (p<0.001), HGS (p<0.001), CC (p=0.001) and gait speed (p=0.004). In the multiple linear regression analysis, age (p=0.001), DT (p<0.001), and ASM/BMI (p=0.008) showed significant association with MIP. DT (p<0.001) and gait speed (p=0.050) were associated with MEP.

CONCLUSION

Our findings suggest that respiratory muscle strength is associated with DT and indices of sarcopenia. Further prospective studies with larger sample sizes are needed to confirm these findings.

Reference values of diaphragmatic dimensions in healthy children aged 0-8 years

Diaphragmatic thickness (Tdi) and diaphragm thickening fraction (dTF) are widely used parameters in ultrasound studies of the diaphragm in mechanically ventilated children, but normal values for healthy children are scarce. We determined reference values of Tdi and dTF using ultrasound in healthy children aged 0-8 years old and assessed their reproducibility. In a prospective, observational cohort, Tdi and dTF were measured on ultrasound images across four age groups comprising at least 30 children per group: group 1 (0-6 months), group 2 (7 months-1 year), group 3 (2-4 years) and group 4 (5-8 years). Ultrasound images of 137 healthy children were included. Mean Tdi at inspiration was 2.07 (SD 0.40), 2.09 (SD 0.40), 1.69 (SD 0.30) and 1.72 (SD 0.30) mm for groups 1, 2, 3 and 4, respectively. Mean Tdi at expiration was 1.64 (SD 0.30), 1.67 (SD 0.30), 1.38 (SD 0.20) and 1.42 (SD 0.20) mm for groups 1, 2, 3 and 4, respectively. Mean Tdi at inspiration and mean Tdi at expiration for groups 1 and 2 were significantly greater than those for groups 3 and 4 (both p < 0.001). Mean dTF was 25.4% (SD 10.4), 25.2% (SD 8.3), 22.8% (SD 10.9) and 21.3% (SD 7.1) for group 1, 2, 3 and 4, respectively. The intraclass correlation coefficients (ICC) representing the level of inter-rater reliability between two examiners performing the ultrasounds was 0.996 (95% CI 0.982-0.999). ICC of the inter-rater reliability between the raters in 11 paired assessments was 0.989 (95% CI 0.973-0.995).   Conclusion: Ultrasound measurements of Tdi and dTF were highly reproducible in healthy children aged 0-8 years.    Trial registration: ClinicalTrials.gov identifier (NCT number): NCT04589910. What is Known: • Diaphragmatic thickness and diaphragm thickening fraction are widely used parameters in ultrasound studies of the diaphragm in mechanically ventilated children, but normal values for healthy children to compare these with are scarce. What is New: • We determined normal values of diaphragmatic thickness and diaphragm thickening fraction using ultrasound in 137 healthy children aged 0-8 years old. The diaphragmatic thickness of infants up to 1 year old was significantly greater than that of children from 2 to 8 years old. Diaphragmatic thickness decreased with an increase in body surface area. These normal values in healthy children can be used to assess changes in respiratory muscle thickness in mechanically ventilated children.

Inspiratory-Expiratory Muscle Training Improved Respiratory Muscle Strength in Dialysis Patients: A Pilot Randomised Trial

End-stage kidney disease (ESKD) exposes patients to progressive physical deconditioning involving the respiratory muscles. The aim of this pilot randomized controlled trial was to determine the feasibility and effectiveness of low-intensity respiratory muscle training (RMT) learned at the hospital and performed at home. A group of ESKD patients (n = 22) were randomized into RMT or usual care (control group, CON) in a 1:1 ratio. The respiratory training was performed at home with an inspiratory-expiratory system for a total of 5 min of breathing exercises in a precise rhythm (8 breaths per minute) interspersed with 1 min of rest, two times per day on nondialysis days for a total of 4 weeks, with the air resistance progressively increasing. Outcome measures were carried out every 4 weeks for 3 consecutive months, with the training executed from the 5th to the 8th week. Primary outcomes were maximal inspiratory and expiratory pressure (MIP, MEP), while secondary outcomes were lung capacity (FEV1, FVC, MVV). Nineteen patients without baseline between-group differences completed the trial (T: n = 10; Age: 63 ± 10; Males: n = 12). Both MIP and MEP significantly improved at the end of training in the T group only, with a significant difference of MEP of 23 cmH₂O in favor of the RMT group (p = 0.008). No significant variations were obtained for FVC, FEV1 or MVV in either group, but there was a greater decreasing trend over time for the CON group, particularly for FVC (t = -2.00; p = 0.046). Low-fatiguing home-based RMT, with a simple device involving both inspiratory and expiratory muscles, may significantly increase respiratory muscle strength.

Manual therapies in cystic fibrosis care: a scoping review

OBJECTIVES

To review the use of manual therapies (MT) for pain, respiratory muscle strength and pulmonary function in cystic fibrosis (CF) care.

METHODS

A search with a systematic approach was conducted by two independent reviewers, using the databases Medline, PubMed, Scopus and Cinahl from their respective inception dates to March 2021.

RESULTS

A total of 199 publications were initially screened by title and abstract, after which 190 were excluded. Following a full-text review of the remaining articles, six studies with a total of 234 participants were included. Decreased pain levels following MT were observed in two studies and, in three studies, patient reports on improvement in ease of breathing and peak airflow were presented. No significant effects on spirometry measures were observed and none of the included studies investigated respiratory muscle strength.

CONCLUSION

Current research on MT in CF care indicates positive trends based on subjective measures. However, research in this context is sparse and disparate in terms of both interventions and methodology. Further investigations including MT as part of multimodal interventions are therefore suggested before any specific recommendations for clinical implementation of MT in CF can be provided.

Distinctive chaperonopathy in skeletal muscle associated with the dominant variant in DNAJB4

DnaJ homolog, subfamily B, member 4, a member of the heat shock protein 40 chaperones encoded by DNAJB4, is highly expressed in myofibers. We identified a heterozygous c.270 T > A (p.F90L) variant in DNAJB4 in a family with a dominantly inherited distal myopathy, in which affected members have specific features on muscle pathology represented by the presence of cytoplasmic inclusions and the accumulation of desmin, p62, HSP70, and DNAJB4 predominantly in type 1 fibers. Both Dnajb4F90L knockin and knockout mice developed muscle weakness and recapitulated the patient muscle pathology in the soleus muscle, where DNAJB4 has the highest expression. These data indicate that the identified variant is causative, resulting in defective chaperone function and selective muscle degeneration in specific muscle fibers. This study demonstrates the importance of DNAJB4 in skeletal muscle proteostasis by identifying the associated chaperonopathy.

Different observation period of exercise training in amyotrophic lateral sclerosis patients: A meta-analysis

Objective

The purpose of this meta-analysis was to evaluate the effect of more intensive exercise training on the functional ability of patients with amyotrophic lateral sclerosis.

Methods

Randomized controlled trials on exercise training in amyotrophic lateral sclerosis patients were retrieved from PubMed, Embase, Web of Science, Cochrane Library and other databases, and meta-analysis was conducted using a fixed effect model or random effect model. Sensitivity analysis was used as a means to study heterogeneity.

Results

A total of 8 randomized controlled trials involving 330 patients with amyotrophic lateral sclerosis were included in this study. The results showed that there was statistical significance in the influence of more intensive exercise training on amyotrophic lateral sclerosis Functional Rating Scale in the short term (0–4 months) and the medium term (5–8 months) (P &lt; 0.05). There was no significant difference in the effect of the amyotrophic lateral sclerosis Functional Rating Scale-Revised in the short term (0–4 months) or long term (9–12 months) (P ≥ 0.05). In the medium term (5–8 months), there was statistical significance (P &lt; 0.05). There was no significant difference in Forced vital capacity (FVC%) in the short term (0–4 months) (P &gt; 0.05).

Conclusion

More intensive exercise training may slow the decline in functional score of amyotrophic lateral sclerosis patients, and more studies should be carried out in the future to verify the effect of more intensive exercise training in patients with amyotrophic lateral sclerosis.

Early clinical and pre-clinical therapy development in Nemaline myopathy

INTRODUCTION

Nemaline myopathies (NM) represent a group of clinically and genetically heterogeneous congenital muscle disorders with the common denominator of nemaline rods on muscle biopsy. NEB and ACTA1 are the most common causative genes. Currently, available treatments are supportive.

AREAS COVERED

We explored experimental treatments for NM, identifying at least eleven mainly pre-clinical approaches utilizing murine and/or human muscle cells. These approaches target either i) the causative gene or associated genes implicated in the same pathway; ii) pathophysiologically relevant biochemical mechanisms such as calcium/myosin regulation of muscle contraction; iii) myogenesis; iv) other therapies that improve or optimize muscle function more generally; v) and/or combinations of the above. The scope and efficiency of these attempts is diverse, ranging from gene-specific effects to those widely applicable to all NM-associated genes.

EXPERT OPINION

The wide range of experimental therapies currently under consideration for NM is promising. Potential translation into clinical use requires consideration of additional factors such as the potential muscle type specificity as well as the possibility of gene expression remodeling. Challenges in clinical translation include the rarity and heterogeneity of genotypes, phenotypes, and disease trajectories, as well as the lack of longitudinal natural history data and validated outcomes and biomarkers.

Breathing, (S)Training and the Pelvic Floor—A Basic Concept

Background: The current scientific literature is inconsistent regarding the potential beneficial or deleterious effects of high-intensity physical activities on the pelvic floor (PF) in women. So far, it has not been established with certainty whether disparate breathing mechanisms may exert short- or long-term influence on the PF function in this context, although based on the established physiological interrelationship of breathing with PF activation, this seems plausible. Objective: To propose a basic concept of the influence of different breathing patterns on the PF during strenuous physical efforts. Methodical approaches: Review of the recent literature, basic knowledge of classical western medicine regarding the principles of muscle physiology and the biomechanics of breathing, additional schematic illustrations, and magnetic resonance imaging (MRI) data corroborate the proposed concept and exemplify the consequences of strenuous efforts on the PF in relation to respective breathing phases. Conclusion: The pelvic floor muscles (PFMs) physiologically act as expiratory muscles in synergy with the anterolateral abdominal muscles, contracting during expiration and relaxing during inspiration. Obviously, a strenuous physical effort requires an expiratory motor synergy with the PFM and abdominal muscles in a co-contracted status to train the PFM and protect the PF against high intra-abdominal pressure (IAP). Holding breath in an inspiratory pattern during exertion stresses the PF because the high IAP impinges on the relaxed, hence insufficiently protected, PFMs. It seems conceivable that such disadvantageous breathing, if performed regularly and repeatedly, may ultimately cause PF dysfunction. At any rate, future research needs to take into account the respective breathing cycles during measurements and interventions addressing PFM function.

The myokine Fibcd1 is an endogenous determinant of myofiber size and mitigates cancer-induced myofiber atrophy

Decline in skeletal muscle cell size (myofiber atrophy) is a key feature of cancer-induced wasting (cachexia). In particular, atrophy of the diaphragm, the major muscle responsible for breathing, is an important determinant of cancer-associated mortality. However, therapeutic options are limited. Here, we have used Drosophila transgenic screening to identify muscle-secreted factors (myokines) that act as paracrine regulators of myofiber growth. Subsequent testing in mouse myotubes revealed that mouse Fibcd1 is an evolutionary-conserved myokine that preserves myofiber size via ERK signaling. Local administration of recombinant Fibcd1 (rFibcd1) ameliorates cachexia-induced myofiber atrophy in the diaphragm of mice bearing patient-derived melanoma xenografts and LLC carcinomas. Moreover, rFibcd1 impedes cachexia-associated transcriptional changes in the diaphragm. Fibcd1-induced signaling appears to be muscle selective because rFibcd1 increases ERK activity in myotubes but not in several cancer cell lines tested. We propose that rFibcd1 may help reinstate myofiber size in the diaphragm of patients with cancer cachexia.

CD38-NADase is a new major contributor to Duchenne muscular dystrophic phenotype

Duchenne muscular dystrophy (DMD) is characterized by progressive muscle degeneration. Two important deleterious features are a Ca²⁺ dysregulation linked to Ca²⁺ influxes associated with ryanodine receptor hyperactivation, and a muscular nicotinamide adenine dinucleotide (NAD⁺) deficit. Here, we identified that deletion in mdx mice of CD38, a NAD⁺ glycohydrolase‐producing modulators of Ca²⁺ signaling, led to a fully restored heart function and structure, with skeletal muscle performance improvements, associated with a reduction in inflammation and senescence markers. Muscle NAD⁺ levels were also fully restored, while the levels of the two main products of CD38, nicotinamide and ADP‐ribose, were reduced, in heart, diaphragm, and limb. In cardiomyocytes from mdx/CD38^−/− mice, the pathological spontaneous Ca²⁺ activity was reduced, as well as in myotubes from DMD patients treated with isatuximab (SARCLISA^®) a monoclonal anti‐CD38 antibody. Finally, treatment of mdx and utrophin–dystrophin‐deficient (mdx/utr^−/−) mice with CD38 inhibitors resulted in improved skeletal muscle performances. Thus, we demonstrate that CD38 actively contributes to DMD physiopathology. We propose that a selective anti‐CD38 therapeutic intervention could be highly relevant to develop for DMD patients.

The phrenic neuromuscular system

The phrenic neuromuscular system consists of the phrenic motor nucleus in the mid-cervical spinal cord, the phrenic nerve, and the diaphragm muscle. This motor system helps sustain breathing throughout life, while also contributing to posture, coughing, swallowing, and speaking. The phrenic nerve contains primarily efferent phrenic axons and afferent axons from diaphragm sensory receptors but is also a conduit for autonomic fibers. On a breath-by-breath basis, rhythmic (inspiratory) depolarization of phrenic motoneurons occurs due to excitatory bulbospinal synaptic pathways. Further, a complex propriospinal network innervates phrenic motoneurons and may serve to coordinate postural, locomotor, and respiratory movements. The phrenic neuromuscular system is impacted in a wide range of neuromuscular diseases and injuries. Contemporary research is focused on understanding how neuromuscular plasticity occurs in the phrenic neuromuscular system and using this information to optimize treatments and rehabilitation strategies to improve breathing and related behaviors.

Type 2 Diabetes Mellitus Related to Decreased Peripheral and Respiratory Muscle Strength in Sarcopenic Thai Elderly

BACKGROUND

Age is related to a decline in muscle mass and physical function in both respiratory and peripheral muscle strength, which could lead to mobility and mortality. In addition, older people have suffered from one or multiple chronic conditions in particular in type 2 Diabetes Mellitus (type 2 DM). However, a few studies have reported the relationship between sarcopenic elderly and respiratory and peripheral muscle strengths in type 2DM.

OBJECTIVE

To explore the prevalence of sarcopenia in type 2 DM elderly people among community- dwelling patients and the relationships with peripheral and respiratory muscle loss in sarcopenic type 2 DM older patients.

METHODS

A total of 330 older individuals were recruited from community-dwelling centers. Respiratory muscle and quadriceps muscle were assessed. According to the defined criteria for sarcopenia (defined by Asian Working Group for Sarcopenia), muscle mass, gait speed (six-meter walk test), and handgrip strength were examined.

RESULTS

Of 330 elderly people, 82 volunteers had a history of type 2 DM. Participants with type 2DM had a risk for sarcopenia (odds ratio= 2.324, 95% CI=1.251-4.317). The prevalence of sarcopenia was 25.61% among older participants with type 2 DM. In addition, decreased respiratory muscle strength and quadriceps muscle strength were observed in type 2 DM with sarcopenia compared to type 2 DM with non-sarcopenia. These relationships also remained after controlling for age and sex.

CONCLUSION

Sarcopenia in type 2 DM leads to a decrease in respiratory muscle and peripheral muscle strength.

Ultrasound assessment of ventilator-induced diaphragmatic dysfunction in mechanically ventilated pediatric patients

INTRODUCTION

Ultrasonography has recently emerged as a promising technique that can rapidly estimate diaphragm function, especially during the weaning period. The aims of this study were to describe the evolution of diaphragmatic morphology and functional measurements by ultrasound in ventilated children.

MATERIAL AND METHODS

This was a prospective, observational, single-center study. All the children admitted to our Pediatric Intensive Care Unit requiring mechanical ventilation for more than 48 h were included. Diaphragmatic thickness and the thickening fraction were assessed by ultrasound.

RESULTS

From June to December 2018, 47 patients (median age 3 months; interquartile range, 1-17) underwent 164 ultrasonographic evaluations. The median duration of mechanical ventilation was 168 h (interquartile range, 96-196). At the initial measurement, the thickness at end-inspiration was 2.2 mm (interquartile range, 1.8-2.5) and the thickness at end-expiration was 1.8 mm (interquartile range, 1.5-2.0) with a median decrease in thickness of -14% (interquartile range, -33% to -3%) and a -2% daily atrophy rate (interquartile range, -4.2% to 0%). Diaphragmatic atrophy was observed in 30/47 cases. Children who had been exposed to neuromuscular blockade infusion (n = 31) had a significantly lower mean thickness [-22% (interquartile range, -34% to -13%) vs. -6% (interquartile range, -12% to 0%); p = 0.009] and increased daily atrophy rate [-2.2% (interquartile range, -4.6 to 0%) vs. -1.4% (interquartile range, -2.6 to 0%); p = 0.049] compared to unexposed children. The decrease in thickness was significantly less in children ventilated for at least 12 hours with pressure support before extubation compared with those with shorter periods of spontaneous respiratory effort [-9.5% (interquartile range, -21 to 0%) vs. -26% (interquartile range, -37 to -12%); p = 0.011].

CONCLUSIONS

Point-of-care diaphragmatic ultrasound can detect diaphragmatic atrophy in mechanically ventilated children. Diaphragmatic atrophy was strongly associated with the use of mechanical ventilation and neuromuscular blockade. Diaphragmatic thickness also tended to decrease less in the pre-extubation stage with pressure support. We found no correlation between progressive diaphragm thinning, extubation failure, or an increased need for non-invasive ventilation post extubation.

Sepsis Disrupts Mitochondrial Function and Diaphragm Morphology

Background

The diaphragm is the primary muscle of inspiration, and its dysfunction is frequent during sepsis. However, the mechanisms associated with sepsis and diaphragm dysfunction are not well understood. In this study, we evaluated the morphophysiological changes of the mitochondrial diaphragm 5 days after sepsis induction.

Methods

Male C57Bl/6 mice were divided into two groups, namely, cecal ligation and puncture (CLP, n = 26) and sham-operated (n = 19). Mice received antibiotic treatment 8 h after surgery and then every 24 h until 5 days after surgery when mice were euthanized and the diaphragms were collected. Also, diaphragm function was evaluated in vivo by ultrasound 120 h after CLP. The tissue fiber profile was evaluated by the expression of myosin heavy chain and SERCA gene by qPCR and myosin protein by using Western blot. The Myod1 and Myog expressions were evaluated by using qPCR. Diaphragm ultrastructure was assessed by electron microscopy, and mitochondrial physiology was investigated by high-resolution respirometry, Western blot, and qPCR.

Results

Cecal ligation and puncture mice developed moderated sepsis, with a 74% survivor rate at 120 h. The diaphragm mass did not change in CLP mice compared with control, but we observed sarcomeric disorganization and increased muscle thickness (38%) during inspiration and expiration (21%). Septic diaphragm showed a reduction in fiber myosin type I and IIb mRNA expression by 50% but an increase in MyHC I and IIb protein levels compared with the sham mice. Total and healthy mitochondria were reduced by 30% in septic mice, which may be associated with a 50% decrease in Ppargc1a (encoding PGC1a) and Opa1 (mitochondria fusion marker) expressions in the septic diaphragm. The small and non-functional OPA1 isoform also increased 70% in the septic diaphragm. These data suggest an imbalance in mitochondrial function. In fact, we observed downregulation of all respiratory chain complexes mRNA expression, decreased complex III and IV protein levels, and reduced oxygen consumption associated with ADP phosphorylation (36%) in CLP mice. Additionally, the septic diaphragm increased proton leak and downregulated Sod2 by 70%.

Conclusion

The current model of sepsis induced diaphragm morphological changes, increased mitochondrial damage, and induced functional impairment. Thus, diaphragm damage during sepsis seems to be associated with mitochondrial dysfunction.

Inspiratory muscle training in interstitial lung disease: a systematic scoping review

Inspiratory muscle training (IMT) has been described as one of the components of the treatment of chronic lung conditions such as obstructive and restrictive lung diseases. Although the number of studies showing results of IMT in patients with interstitial lung disease (ILD) is scarce when compared with studies in patients with COPD, evidence points to benefits of IMT in this population. This scoping review aimed to explore the role and the rationale of IMT in patients with ILD and to gather recent evidence on the effects of IMT in this population. The studies included in this review showed improvements in respiratory muscle function, quality of life, exercise capacity and dyspnea after ILD patients participated in programs that included stand-alone IMT or combined with pulmonary rehabilitation. There is still a gap in the literature to allow a clear conclusion on the indications of IMT as part of ILD treatment because of poor research design and small numbers of participants. Therefore, although IMT seems to have a positive effect in patients with ILD, current evidence prevents us from drawing a definite conclusion. Further studies need to be conducted using better research methodology to demonstrate and confirm the positive effects of IMT.

Pulmonary function decline in amyotrophic lateral sclerosis

Background: There has been no comprehensive longitudinal study of pulmonary functions (PFTS) in ALS determining which measure is most sensitive to declines in respiratory muscle strength. Objective: To determine the longitudinal decline of PFTS in ALS and which measure supports Medicare criteria for NIV initiation first. Methods: Serial PFTs (maximum voluntary ventilation (MVV), maximum inspiratory pressure measured by mouth (MIP) or nasal sniff pressure (SNIP), maximum expiratory pressure (MEP), and Forced Vital Capacity (FVC)) were performed over 12 months on 73 ALS subjects to determine which measure showed the sentinel decline in pulmonary function. The rate of decline for each measure was determined as the median slope of the decrease over time. Medicare-based NIV initiation criteria were met if %FVC was ≤ 50% predicted or MIP was ≤ 60 cMH₂O. Results: 65 subjects with at least 3 visits were included for analyses. All median slopes were significantly different than zero. MEP and sitting FVC demonstrated the largest rate of decline. Seventy subjects were analyzed for NIV initiation criteria, 69 met MIP criteria first; 11 FVC and MIP criteria simultaneously and none FVC criteria first. Conclusions: MEP demonstrated a steeper decline compared to other measures suggesting expiratory muscle strength declines earliest and faster and the use of airway clearance interventions should be initiated early. When Medicare criteria for NIV initiation are considered, MIP criteria are met earliest. These results suggest that pressure-based measurements are important in assessing the timing of NIV and the use of pulmonary clearance interventions.

The Importance of the Posterolateral Area of the Diaphragm Muscle for Palpation and for the Treatment of Manual Osteopathic Medicine

The eupneic act in healthy subjects involves a coordinated combination of functional anatomy and neurological activation. Neurologically, a central pattern generator, the components of which are distributed between the brainstem and the spinal cord, are hypothesized to drive the process and are modeled mathematically. A functionally anatomical approach is easier to understand although just as complex. Osteopathic manipulative treatment (OMT) is part of osteopathic medicine, which has many manual techniques to approach the human body, trying to improve the patient's homeostatic response. The principle on which OMT is based is the stimulation of self-healing processes, researching the intrinsic physiological mechanisms of the person, taking into consideration not only the physical aspect, but also the emotional one and the context in which the patient lives. This article reviews how the diaphragm muscle moves, with a brief discussion on anatomy and the respiratory neural network. The goal is to highlight the critical issues of OMT on the correct positioning of the hands on the posterolateral area of the diaphragm around the diaphragm, trying to respect the existing scientific anatomical-physiological data, and laying a solid foundation for improving the data obtainable from future research. The correctness of the position of the operator's hands in this area allows a more effective palpatory perception and, consequently, a probably more incisive result on the respiratory function.

Changes in electromyographic activity, mechanical power, and relaxation rates following inspiratory ribcage muscle fatigue

Muscle fatigue is a complex phenomenon enclosing various mechanisms. Despite technological advances, these mechanisms are still not fully understood in vivo. Here, simultaneous measurements of pressure, volume, and ribcage inspiratory muscle activity were performed non-invasively during fatigue (inspiratory threshold valve set at 70% of maximal inspiratory pressure) and recovery to verify if inspiratory ribcage muscle fatigue (1) leads to slowing of contraction and relaxation properties of ribcage muscles and (2) alters median frequency and high-to-low frequency ratio (H/L). During the fatigue protocol, sternocleidomastoid showed the fastest decrease in median frequency and slowest decrease in H/L. Fatigue was also characterized by a reduction in the relative power of the high-frequency and increase of the low-frequency. During recovery, changes in mechanical power were due to changes in shortening velocity with long-lasting reduction in pressure generation, and slowing of relaxation [i.e., tau (τ), half-relaxation time (½RT), and maximum relaxation rate (MRR)] was observed with no significant changes in contractile properties. Recovery of median frequency was faster than H/L, and relaxation rates correlated with shortening velocity and mechanical power of inspiratory ribcage muscles; however, with different time courses. Time constant of the inspiratory ribcage muscles during fatigue and recovery is not uniform (i.e., different inspiratory muscles may have different underlying mechanisms of fatigue), and MRR, ½RT, and τ are not only useful predictors of inspiratory ribcage muscle recovery but may also share common underlying mechanisms with shortening velocity.

Antimyostatin Treatment in Health and Disease: The Story of Great Expectations and Limited Success

In the past 20 years, myostatin, a negative regulator of muscle mass, has attracted attention as a potential therapeutic target in muscular dystrophies and other conditions. Preclinical studies have shown potential for increasing muscular mass and ameliorating the pathological features of dystrophic muscle by the inhibition of myostatin in various ways. However, hardly any clinical trials have proven to translate the promising results from the animal models into patient populations. We present the background for myostatin regulation, clinical and preclinical results and discuss why translation from animal models to patients is difficult. Based on this, we put the clinical relevance of future antimyostatin treatment into perspective.

Skeletal muscle (dys)function in heart failure with preserved ejection fraction

PURPOSE OF REVIEW

Skeletal muscle dysfunction contributes to exercise intolerance, which manifests as dyspnea and fatiguability in patients with heart failure with preserved ejection fraction (HFpEF). This review aims to summarize the current understanding of skeletal muscle dysfunction in HFpEF.

RECENT FINDINGS

Animal and human studies in HFpEF provide insights into the pathophysiological alterations in skeletal muscle structure and function with the identification of several molecular mechanisms. Exercise training and novel pharmacological therapies that target skeletal muscle are proposed as therapeutic interventions to treat HFpEF.

SUMMARY

There is evidence that skeletal muscle dysfunction plays a pathophysiological role in HFpEF. However, precise mechanistic insights are needed to understand the contribution of skeletal muscle dysfunction in HFpEF.

Physiological changes and compensatory mechanisms by the action of respiratory muscles in a porcine model of phrenic nerve injury

Phrenic nerve damage may occur as a complication of specific surgical procedures, prolonged mechanical ventilation, or physical trauma. The consequent diaphragmatic paralysis or dysfunction can lead to major complications. The purpose of this study was to elucidate the role of the nondiaphragmatic respiratory muscles during partial or complete diaphragm paralysis induced by unilateral and bilateral phrenic nerve damage at different levels of ventilatory pressure support in an animal model. Ten pigs were instrumented, the phrenic nerve was exposed from the neck, and spontaneous respiration was preserved at three levels of pressure support, namely, high, low, and null, at baseline condition, after left phrenic nerve damage, and after bilateral phrenic nerve damage. Breathing pattern, thoracoabdominal volumes and asynchrony, and pressures were measured at each condition. Physiological breathing was predominantly diaphragmatic and homogeneously distributed between right and left sides. After unilateral damage, the paralyzed hemidiaphragm was passively dragged by the ipsilateral rib cage muscles and the contralateral hemidiaphragm. After bilateral damage, the drive to and the work of breathing of rib cage and abdominal muscles increased, to compensate for diaphragmatic paralysis, ensuing paradoxical thoracoabdominal breathing. Increasing level of pressure support ventilation replaces this muscle group compensation. When the diaphragm is paralyzed (unilaterally and/or bilaterally), there is a coordinated reorganization of nondiaphragmatic respiratory muscles as compensation that might be obscured by high level of pressure support ventilation. Noninvasive thoracoabdominal volume and asynchrony assessment could be useful in phrenic nerve-injured patients to estimate the extent and type of inspiratory muscle dysfunction.NEW & NOTEWORTHY This was the first (to our knowledge) implanted porcine model of phrenic nerve injury with a detailed multidimensional analysis of different degrees of diaphragmatic paralysis (unilateral and bilateral). Noninvasive thoracoabdominal volume and asynchrony assessment was shown to be useful in estimating the extent of diaphragmatic dysfunction and the consequent coordinated reorganization of nondiaphragmatic respiratory muscles. High level of pressure support ventilation was proved to obscure the interaction and compensation of respiratory muscles to deal with phrenic nerve injury.

Update on the Role of High-Flow Nasal Cannula in Infants with Bronchiolitis

Bronchiolitis (BR), a lower respiratory tract infection mainly caused by respiratory syncytial virus (RSV), can be very severe. Presently, adequate nutritional support and oxygen therapy remain the only interventions recommended to treat patients with BR. For years, mild BR cases were treated with noninvasive standard oxygen therapy (SOT), i.e., with cold and poorly or totally non-humidified oxygen delivered by an ambient headbox or low-flow nasal cannula. Children with severe disease were intubated and treated with invasive mechanical ventilation (IMV). To improve SOT and overcome the disadvantages of IMV, new measures of noninvasive and more efficient oxygen administration have been studied. Bi-level positive air way pressure (BiPAP), continuous positive airway pressure (CPAP), and high-flow nasal cannula (HFNC) are among them. For its simplicity, good tolerability and safety, and the good results reported in clinical studies, HFNC has become increasingly popular and is now widely used. However, consistent guidelines for initiation and discontinuation of HFNC are lacking. In this narrative review, the role of HFNC to treat infants with BR is discussed. An analysis of the literature showed that, despite its widespread use, the role of HFNC in preventing respiratory failure in children with BR is not precisely defined. It is not established whether it can offer greater benefits compared to SOT and when and in which infants it can replace CPAP or BiPAP. The analysis of the results clearly indicates the need for multicenter studies and official guidelines. In the meantime, HFNC can be considered a safe and effective method to treat children with mild to moderate BR who do not respond to SOT.

Chest MRI to diagnose early diaphragmatic weakness in Pompe disease

Background

In Pompe disease, an inherited metabolic muscle disorder, severe diaphragmatic weakness often occurs. Enzyme replacement treatment is relatively ineffective for respiratory function, possibly because of irreversible damage to the diaphragm early in the disease course. Mildly impaired diaphragmatic function may not be recognized by spirometry, which is commonly used to study respiratory function. In this cross-sectional study, we aimed to identify early signs of diaphragmatic weakness in Pompe patients using chest MRI.

Methods

Pompe patients covering the spectrum of disease severity, and sex and age matched healthy controls were prospectively included and studied using spirometry-controlled sagittal MR images of both mid-hemidiaphragms during forced inspiration. The motions of the diaphragm and thoracic wall were evaluated by measuring thoracic cranial-caudal and anterior–posterior distance ratios between inspiration and expiration. The diaphragm shape was evaluated by measuring the height of the diaphragm curvature. We used multiple linear regression analysis to compare different groups.

Results

We included 22 Pompe patients with decreased spirometry results (forced vital capacity in supine position < 80% predicted); 13 Pompe patients with normal spirometry results (forced vital capacity in supine position ≥ 80% predicted) and 18 healthy controls. The mean cranial-caudal ratio was only 1.32 in patients with decreased spirometry results, 1.60 in patients with normal spirometry results and 1.72 in healthy controls (p < 0.001). Anterior–posterior ratios showed no significant differences. The mean height ratios of the diaphragm curvature were 1.41 in patients with decreased spirometry results, 1.08 in patients with normal spirometry results and 0.82 in healthy controls (p = 0.001), indicating an increased curvature of the diaphragm during inspiration in Pompe patients.

Conclusions

Even in early-stage Pompe disease, when spirometry results are still within normal range, the motion of the diaphragm is already reduced and the shape is more curved during inspiration. MRI can be used to detect early signs of diaphragmatic weakness in patients with Pompe disease, which might help to select patients for early intervention to prevent possible irreversible damage to the diaphragm.

Nonpharmacological interventions for respiratory health in Parkinson's disease: A systematic review and meta-analysis

BACKGROUND AND PURPOSE

Respiratory dysfunction in Parkinson's disease (PD) is often an underdiagnosed and untreated impairment associated with the disease. Clinically, a reactive approach to respiratory morbidity is taken, rather than preventative approaches that address underlying impairment/s. This systematic review identifies the current evidence to support nonpharmacological interventions to improve respiratory impairments in individuals with PD.

METHODS

The relevant literature was searched using a customised and systematic strategy. Randomised and nonrandomised control trials of nonpharmacological interventions targeting respiratory outcome measures in PD were included. Outcomes of interest were respiratory morbidity and mortality, respiratory muscle strength, spirometry measures, lung volumes, peak cough flow, and perception of dyspnoea.

RESULTS

Nonpharmacological interventions included: functional training, generalised strength training, respiratory muscle strength training, aerobic exercise, qigong, yoga, breath stacking, incentive spirometry and singing. Methodological quality of included studies varied. Meta-analyses of nonpharmacological interventions demonstrated significant effects for inspiratory muscle strength (mean difference [MD] 19.68; confidence interval [CI] 8.49, 30.87; z = 3.45; p = 0.0006; I²  = 2%), expiratory muscle strength (MD 18.97; CI 7.79, 30.14; z = 3.33; p = 0.0009; I²  = 23%) and peak expiratory flow (MD 72.21; CI 31.19, 113.24; z = 3.45; p = 0.0006; I²  = 0%). Best-evidence synthesis identified level 1 evidence supporting nonpharmacological interventions for improving peak cough flow and perceived dyspnoea. No studies were identified reporting outcomes of respiratory rate, inspiration:expiration ratio or respiratory morbidity or mortality in PD.

CONCLUSIONS

Nonpharmacological interventions improved respiratory muscle strength and peak expiratory flow in PD. Additional trials targeting respiratory dysfunction and longitudinal studies examining the relationship between respiratory dysfunction and morbidity and mortality rates in PD are required.

Degenerative and regenerative pathways underlying Duchenne muscular dystrophy revealed by single-nucleus RNA sequencing

Duchenne muscular dystrophy (DMD) is a fatal muscle disorder characterized by cycles of degeneration and regeneration of multinucleated myofibers and pathological activation of a variety of other muscle-associated cell types. The extent to which different nuclei within the shared cytoplasm of a myofiber may display transcriptional diversity and whether individual nuclei within a multinucleated myofiber might respond differentially to DMD pathogenesis is unknown. Similarly, the potential transcriptional diversity among nonmuscle cell types within dystrophic muscle has not been explored. Here, we describe the creation of a mouse model of DMD caused by deletion of exon 51 of the dystrophin gene, which represents a prevalent disease-causing mutation in humans. To understand the transcriptional abnormalities and heterogeneity associated with myofiber nuclei, as well as other mononucleated cell types that contribute to the muscle pathology associated with DMD, we performed single-nucleus transcriptomics of skeletal muscle of mice with dystrophin exon 51 deletion. Our results reveal distinctive and previously unrecognized myonuclear subtypes within dystrophic myofibers and uncover degenerative and regenerative transcriptional pathways underlying DMD pathogenesis. Our findings provide insights into the molecular underpinnings of DMD, controlled by the transcriptional activity of different types of muscle and nonmuscle nuclei.

Diaphragm ultrasonography in adults with sickle cell anemia: evaluation of morphological and functional aspects

OBJECTIVES

To assess morphological and functional aspects of the diaphragm by ultrasonography (US) in adults with sickle cell anemia (SCA) and evaluate if the diaphragmatic musculature can play a role in changes found in pulmonary function tests (PFTs) of these patients.

METHODS

This is a cross-sectional observational and single-center study involving 40 adults with SCA who underwent diaphragm US and PFTs with a maximum of 1 month between the two tests. Diaphragm US was performed in B and M modes, and echogenicity, thickness and movement of the muscle was assessed in different respiratory maneuvers.

RESULTS

Diaphragms had preserved echogenicity and the thickness was not significantly different between the groups. The SCA group exhibited significantly higher movement of the right hemidiaphragm during deep breathing (p = 0.004) and the sniff test (p = 0.0008) and lower movement of the left hemidiaphragm during quiet breathing (p = 0.009). There was a predominance of restrictive pattern (65%) and a global reduction in respiratory muscle strength (RMS) (70%).

CONCLUSIONS

This study shows that adults with SCA had normal morphostructural aspects and absence of diaphragm dysfunction. Otherwise, they presented greater movement of the right hemidiaphragm during deep breathing and sniff test maneuvers. Despite the restrictive pattern and the reduction in RMS found in PFTs, the diaphragm of young adults with SCA did not have weakness or paralysis.

Pattern of respiratory muscle activity during exercise tests in children born prematurely

INTRODUCTION

Preterm children display only slightly lower exercise capacity than term children do during their development, despite their previous cardiopulmonary impairments. This raises doubts about the role of the respiratory muscles' influence on exercise capacity. This study aimed to compare respiratory muscle activity in preterm and term children using an exercise test.

METHODS

This cross-sectional study involved comparison of 35 term children and 39 matched preterm children aged 6-9 years, who were born prematurely with a birth weight <1500 g. An adapted treadmill incremental test was utilized and surface electromyography of the sternocleidomastoid (SCM), upper trapezius (UT), and rectus abdominis (RA) muscles was performed. The root mean square was calculated every minute and compared between and within groups. A Monte Carlo simulation was also applied, and the area under the curve was calculated to evaluate the differences between groups.

RESULTS

During the entire exercise, the SCM muscle activity was higher in preterm children with a larger area under the curve than in the term children. There was no difference in the RA and UT muscle activity between groups throughout the test.

CONCLUSION

The results suggest a greater contribution of the SCM muscle sin preterm children's performance than in term children's performance during high-intensity exercises.

TRIAL REGISTRATION

Brazilian Clinical Trial Registry (ReBec) - RBR-89hr2h.

Is the healthy respiratory system built just right, overbuilt, or underbuilt to meet the demands imposed by exercise?

In the healthy, untrained young adult, a case is made for a respiratory system (airways, pulmonary vasculature, lung parenchyma, respiratory muscles, and neural ventilatory control system) that is near ideally designed to ensure a highly efficient, homeostatic response to exercise of varying intensities and durations. Our aim was then to consider circumstances in which the intra/extrathoracic airways, pulmonary vasculature, respiratory muscles, and/or blood-gas distribution are underbuilt or inadequately regulated relative to the demands imposed by the cardiovascular system. In these instances, the respiratory system presents a significant limitation to O₂ transport and contributes to the occurrence of locomotor muscle fatigue, inhibition of central locomotor output, and exercise performance. Most prominent in these examples of an "underbuilt" respiratory system are highly trained endurance athletes, with additional influences of sex, aging, hypoxic environments, and the highly inbred equine. We summarize by evaluating the relative influences of these respiratory system limitations on exercise performance and their impact on pathophysiology and provide recommendations for future investigation.

Muscle Fiber Properties in Cattle and Their Relationships with Meat Qualities: An Overview

The control of meat quality traits constitutes an important target for any farm animal production, including cattle. Therefore, better understanding of the biochemical properties that drive muscle development and final outcomes constitutes one of the main challenging topics of animal production and meat science. Accordingly, this review has focused on skeletal muscle fibers in cattle and their relationships with beef qualities. It aimed to describe the chemical and structural properties of muscle fibers as well as a comprehensive review of their contractile and metabolic characteristics during the life of the animal. The existing methods for the classification of muscle fibers were reviewed, compared, and discussed. Then, the different stages of myogenesis in cattle were defined. The main factors regulating fetal and postnatal growth and the plasticity of muscle fibers were evidenced, especially the role of myostatin growth factor and the impact of nutritional factors. This review highlights that the knowledge about muscle fibers is paramount for a better understanding of how to control the muscle properties throughout the life of the animal for better management of the final eating qualities of beef. Accordingly, the associations between bovine muscle fibers and different meat eating qualities such as tenderness, pH decline, and color traits were further presented.

‘Mind the gap’: the importance of managing malnutrition in chronic obstructive pulmonary disease

Malnutrition is linked to poor outcomes in patients with chronic obstructive pulmonary disease (COPD), and reduced fat free mass and low BMI are independent risk factors for increased mortality. However, weight loss is not inevitable and can be prevented or reversed so screening for malnutrition is essential. The latest guidelines for managing malnutrition in COPD recommend first-line nutritional support. In particular, patients with a BMI <20 kg/m2 should be prescribed oral nutritional supplements (ONS), which have been shown to significantly improve outcomes. However, this guidance is often not implemented locally, increasing the likelihood of malnutrition, hospital admission and increased healthcare costs. Ready-prepared, low-volume, high-protein, high-energy drinks can improve compliance with ONS, particularly in people who are unable to tolerate high volumes. ONS therefore play an important role in managing malnutrition in COPD, helping to reduce its physiological and economic effects.