Ultrasound assessment of diaphragmatic function in type 1 spinal muscular atrophy

Reliability and reference values for diaphragmatic excursion, thickness, and thickening fraction and quadriceps femoris muscle thickness in full-term newborns evaluated by ultrasound

To determine the diaphragm thickness, thickening fraction, and excursion and thickness of the quadriceps femoris muscle in full-term newborns and to evaluate the intra- and interrater reliability of these measurements. This was a prospective, observational clinical study including full-term newborns born within the first 48 h after birth. Serial measurements of the thickness, thickening fraction, and mobility of the diaphragm muscles and the thickness of the quadriceps muscle were obtained using ultrasound images. A total of 69 newborns with a mean gestational age of 39 weeks were included. The following measurements were obtained and are expressed as the mean (standard deviation): inspiratory diaphragm thickness, 0.19 cm (0.04); expiratory diaphragm thickness, 0.16 cm (0.04); diaphragm thickness fraction, 16.70 cm (10.27); diaphragmatic excursion, 0.68 cm (0.22); and quadriceps thickness, 0.99 cm (0.14). Intrarater reliability was assessed using intraclass correlation coefficients (ICCs). Excellent intrarater agreement was observed for the two groups of operators (ICC > 0.86, p < 0.001) for all measurements except for the diaphragm thickening fraction, which showed good agreement for both operator groups (ICC = 0.70, p < 0.001). Regarding interrater reliability, moderate agreement between the raters was observed in the means of all measures (ICC > 0.49, p < 0.001), except for the diaphragm thickening fraction, which showed poor agreement.    Conclusion: Good intrarater and moderate interrater reliability were achieved in ultrasound evaluations of the thickness and mobility of the diaphragm and quadriceps femoris muscles in full-term newborns, demonstrating the feasibility of this technique for clinical use. This pioneering study offers reference values for these muscles in a single study, allowing comparisons between different clinical conditions. What is Known: • Ultrasound is a highly reliable tool for muscle assessment that can be used to assess muscular atrophy in critically ill patients. • Muscle atrophy worsens the patient's condition and has been associated with worse outcomes. What is New: • To our knowledge, this is the first study to jointly evaluate the diaphragm and quadriceps muscle thickness and evaluate the reliability of all measurements. • Our study presents reference values for both muscles, enabling comparisons between different clinical conditions.

Non-invasive diagnosis of diaphragmatic paralysis in botulism using ultrasound

This case study explores foodborne botulism, a severe illness caused by botulinum neurotoxin-contaminated food. It leads to bilateral descending paralysis, involving the diaphragm. We highlight diaphragmatic ultrasound as a non-invasive diagnostic tool. A 50-year-old obese male developed diplopia and weakness after consuming contaminated food, rapidly progressing to severe symptoms. Mechanical ventilation became necessary due to respiratory failure. Diaphragmatic ultrasound confirmed bilateral diaphragm paralysis despite early antitoxin treatment. The patient experienced complications, requiring tracheostomy and rehabilitation. After five months, he fully recovered diaphragmatic function. This study underscores botulism's life-threatening nature and the vital role of supportive care. Diaphragmatic ultrasound is a safe and effective method for assessing diaphragmatic function in such cases, obviating ionizing radiation exposure. We recommend its routine use for evaluating botulism-induced paralysis.

Biomarkers in 5q-associated spinal muscular atrophy-a narrative review

5q-associated spinal muscular atrophy (SMA) is a rare genetic disease caused by mutations in the SMN1 gene, resulting in a loss of functional SMN protein and consecutive degeneration of motor neurons in the ventral horn. The disease is clinically characterized by proximal paralysis and secondary skeletal muscle atrophy. New disease-modifying drugs driving SMN gene expression have been developed in the past decade and have revolutionized SMA treatment. The rise of treatment options led to a concomitant need of biomarkers for therapeutic guidance and an improved disease monitoring. Intensive efforts have been undertaken to develop suitable markers, and numerous candidate biomarkers for diagnostic, prognostic, and predictive values have been identified. The most promising markers include appliance-based measures such as electrophysiological and imaging-based indices as well as molecular markers including SMN-related proteins and markers of neurodegeneration and skeletal muscle integrity. However, none of the proposed biomarkers have been validated for the clinical routine yet. In this narrative review, we discuss the most promising candidate biomarkers for SMA and expand the discussion by addressing the largely unfolded potential of muscle integrity markers, especially in the context of upcoming muscle-targeting therapies. While the discussed candidate biomarkers hold potential as either diagnostic (e.g., SMN-related biomarkers), prognostic (e.g., markers of neurodegeneration, imaging-based markers), predictive (e.g., electrophysiological markers) or response markers (e.g., muscle integrity markers), no single measure seems to be suitable to cover all biomarker categories. Hence, a combination of different biomarkers and clinical assessments appears to be the most expedient solution at the time.

Impaired diaphragmatic motility in treatment-naive adult patients with spinal muscular atrophy improved during nusinersen treatment

INTRODUCTION/AIMS

The leading clinical feature of 5q-associated spinal muscular atrophy (SMA) is symmetric, proximal muscle weakness. Muscles involved in ventilation exhibit a specific pattern of denervation: intercostal muscles are severely atrophic, whereas the diaphragm muscle is less affected. The aim of this study was to investigate the involvement of diaphragmatic function by ultrasound imaging in adult patients with SMA and to quantify dynamics of diaphragmatic function during nusinersen treatment.

METHODS

Diaphragmatic thickness, thickening, and excursion during quiet breathing were assessed in 24 adult patients with SMA type 2 and 3 by diaphragm ultrasound imaging before and during nusinersen treatment and were correlated with spirometric parameters.

RESULTS

Diaphragm thickness was not reduced, but increased in a remarkable proportion of patients, whereas diaphragm thickening and excursion were reduced in about 20% to 30% of nusinersen-naive, adult patients with SMA types 2 and 3. During 26 months of nusinersen treatment, diaphragm thickening fraction and excursion improved.

DISCUSSION

Diaphragm ultrasound imaging can provide disease- and treatment-relevant information that is not identified during routine clinical assessments and may therefore be a valuable complementary outcome measure.

Muscle Ultrasound Changes Correlate With Functional Impairment in Spinal Muscular Atrophy

OBJECTIVE

We investigated ultrasound patterns of muscle involvement in different types of spinal muscular atrophy (SMA) and their correlation with functional status to determine the pattern of muscle compromise in patients with SMA and the potential role of ultrasound to evaluate disease progression.

METHODS

We examined muscles (biceps brachii, rectus femoris, diaphragm, intercostals and thoracic multifidus) of 41 patients with SMA (types 1 to 4) and 46 healthy age- and sex-matched control individuals using B-mode ultrasound for gray-scale analysis (GSA), area (biceps brachii and rectus femoris) and diaphragm thickening ratio. Functional scales were applied to patients only. We analyzed ultrasound abnormalities in specific clinical subtypes and correlated findings with functional status.

RESULTS

Compared with controls, patients had reduced muscle area and increased mean GSA for all muscles (p < 0.001), with an established correlation between the increase in GSA and the severity of SMA for biceps brachii, rectus femoris and intercostals (p = 0.03, 0.01 and 0.004 respectively) when using the Hammersmith Functional Motor Scale Expanded. Diaphragm thickening ratio was normal in the majority of patients, and intercostal muscles had higher GSA than diaphragm in relation to the controls.

CONCLUSION

Ultrasound is useful for quantifying muscular changes in SMA and correlates with functional status. Diaphragm thickening ratio can be normal even with severe compromise of respiratory muscles in quantitative analysis, and intercostal muscles were more affected than diaphragm.

Ultrasound Imaging for Diaphragm Function in a Population of Healthy Infants: A Short Observational Report

Introduction: Diaphragm ultrasound is increasingly used in adults, and more recently in pediatric practice. However, normal diaphragm parameters in healthy infants are unknown. This was a prospective observational pilot study aiming to define the normal diaphragm ultrasound characteristics in healthy infants during the first 6 months of life. Methods: We recruited healthy neonates at 7 to 15 days of life, who were followed until the sixth month of life, undergoing five assessments in different time points. The measurements included diaphragm thickness at end expiration (TEE) and at end inspiration (TEI). The thickening fraction (TF) was calculated as (TEI-TEE)/TEE and expressed as a percentage, and as (TEI-TEE)/TEI. Results: A total of 37 toddlers, 16 of which were females (43.2%), were enrolled. Thirty-four children (91.9%) were of Caucasian ethnicity and the median gestational age was 38.4 (35.7–40) weeks. Normal TEE, TEI, and TF have been provided for each time point. Conclusion: We provided new insight regarding data about thickness and thickening function in healthy children to be used for future physiologic and pathologic pediatric studies.

Intra-Rater Reliability of Shear Wave Elastography for the Quantification of Respiratory Muscles in Adolescent Athletes

The aim of this study was to assess the intra-rater reliability and agreement of diaphragm and intercostal muscle elasticity and thickness during tidal breathing. The diaphragm and intercostal muscle parameters were measured using shear wave elastography in adolescent athletes. To calculate intra-rater reliability, intraclass correlation coefficient (ICC) and Bland-Altman statistics were used. The reliability/agreement for one-day both muscle measurements (regardless of probe orientation) were at least moderate. During the seven-day interval between measurements, the reliability of a single measurement depended on the measured parameter, transducer orientation, respiratory phase, and muscle. Excellent reliability was found for diaphragm shear modulus at the peak of tidal expiration in transverse probe position (ICC_3.1 = 0.91-0.96; ICC₃.₂ = 0.95), and from poor to excellent reliability for the intercostal muscle thickness at the peak of tidal inspiration with the longitudinal probe position (ICC_3.1 = 0.26-0.95; ICC₃.₂ = 0.15). The overall reliability/agreement of the analysed data was higher for the diaphragm measurements (than the intercostal muscles) regardless of the respiratory phase and probe position. It is difficult to identify a more appropriate probe position to examine these muscles. The shear modulus/thickness of the diaphragm and intercostal muscles demonstrated good reliability/agreement so this appears to be a promising technique for their examination in athletes.

Point of care diaphragm ultrasound in mechanically ventilated children: A predictive tool to detect extubation failure

BACKGROUND

Children should be weaned from the ventilator once their clinical condition improves. Extubation failure is associated with poorer clinical outcomes in children. Predictive indicators of successful extubation are needed. This study aims to evaluate the predictive value of ultrasonographic diaphragm imaging could help predict weaning success.

METHODS

In this prospective, observational study conducted between March and December 2021, children between 1 month and 10 years of age who were mechanically ventilated for more than 48 h were included. Diaphragm ultrasound (DUS) examinations were performed at the end of 2-h extubation readiness test (ERT). The end-inspiratory thickness (DTi), end-expiratory thickness (DTe), diaphragmatic thickening fraction (DTF), diaphragmatic excursion (DE), inspiratory slope (IS), and expiratory slope (ES) were evaluated.

RESULTS

Twenty-four (60%) patients were successfully extubated, while 16 (40%) required invasive or noninvasive mechanical ventilation support which were classified as failed extubation group. Three of the sixteen patients in the failed extubation group required reintubation. DTF was significantly greater in the successful weaning group (55.05 ± 23.75% vs. 30.9 ± 10.38%) (p < 0.001). DE was significantly greater in the successful weaning group (14 ± 4.4 mm vs. 11.05 ± 3.25 mm) (p < 0.001). DTF and DE were found to have a sensitivity and specificity of 91.67%, 87.50%, 83.33%, and 81.25%, respectively.

CONCLUSION

Diaphragm ultrasound is a feasible and promising tool to guide physicians during weaning from invasive mechanical ventilation. Among all DUS measurements, the DE and DTF indexes showed better performance in extubation failure than other diaphragmatic parameters.

Affection of Respiratory Muscles in ALS and SMA

Respiratory dysfunction is a common cause of morbidity and mortality in motor neuron disease (MND). However, classical volitional measures of respiratory function in these patients are impeded by, e.g., bulbar paralysis or progressive disability. Diaphragm ultrasound imaging might be a valuable tool for assessing respiratory impairment, albeit different ultrasound measures have not been systematically investigated in adult MND patients and, in particular, have not yet been comparatively applied in adult patients with amyotrophic lateral sclerosis (ALS) and spinal muscular atrophy (SMA). We hypothesized that in contrast to ALS patients, adult SMA patients show a relative sparing of diaphragm function. We retrospectively analyzed diaphragm ultrasound imaging data of 40 patients with ALS and 23 patients with SMA in comparison to a multitude of established parameters of respiratory function. Indeed, ALS patients showed more severe diaphragm dysfunction than adult SMA patients, however, diaphragm dysfunction was also common in adult SMA patients. Notably, dynamic measures of diaphragm function rather than thickness measures were impaired in ALS compared to SMA. Thus, diaphragm ultrasound imaging might be a useful tool to evaluate respiratory dysfunction in adult MND patients. Future larger and prospective studies are needed to validate our initial findings.

Diaphragmatic Point-of-Care Ultrasound in COVID-19 Patients in the Emergency Department-A Proof-of-Concept Study

Background: Lung Ultrasound Evaluation (LUS) is usefully applied in the Emergency Department (ED) to patients with suspected or confirmed COVID-19. Diaphragmatic Ultrasound (DUS) may provide additional insight into ventilatory function. This proof-of-concept study aimed to evaluate the feasibility of LUS and DUS in a third level ED during the COVID-19 pandemic. Methods: Adult patients presenting with COVID-19 symptoms were eligible. After the physical examination, both LUS and DUS (i.e., diaphragmatic motion and thickness) were performed. All patients were followed after 30 days to determine their need for ventilation, admission, and/or a new ED evaluation after discharge. The diagnostic accuracies of diaphragm measurements in assessing the risk of the 30-day outcome were calculated as well as the measurements’ usefulness. Bland–Altman plots were used for comparing bedside and off-line diaphragm measurements. Results: 118 patients were enrolled. Median thickness and motion were 1.7 mm (iqr 0.4) and 1.8 cm (iqr 0.7), respectively, with a mean difference of 0.009 mm (95% CI −0.037–0.056 mm) and −0.051 cm (95% CI −0.108–0.006 cm), respectively. The 30-day outcome was associated with an increase in thickness (OR 5.84, 95% CI 0.96–35.4), and a lower motion (OR 0.49, 95% CI 0.2–1.21). Conclusion: DUS seemed to be feasible and reliable in the ED in a population of patients presenting with symptoms related to COVID-19 infection.

A narrative review of diaphragmatic ultrasound in pediatric critical care

The use of point of care ultrasound (POCUS) at the bedside has increased dramatically within emergency medicine and in critical care. Applications of POCUS have spread to include diaphragmatic assessments in both adults and children. Diaphragm POCUS can be used to assess for diaphragm dysfunction (DD) and atrophy or to guide ventilator titration and weaning. Quantitative, semi-quantitative and qualitative measurements of diaphragm thickness, diaphragm excursion, and diaphragm thickening fraction provide objective data related to DD and atrophy. The potential for quick, noninvasive, and repeatable bedside diaphragm assessments has led to a growing amount of literature on diaphragm POCUS. To date, there are no reviews of the current state of diaphragm POCUS in pediatric critical care. The aims of this narrative review are to summarize the current literature regarding techniques, reference values, applications, and future innovations of diaphragm POCUS in critically ill children. A summary of current practice and future directions will be discussed.

Respiratory muscle imaging by ultrasound and MRI in neuromuscular disorders

Respiratory muscle weakness is common in neuromuscular disorders and leads to significant respiratory difficulties. Therefore, reliable and easy assessment of respiratory muscle structure and function in neuromuscular disorders is crucial. In the last decade, ultrasound and MRI emerged as promising imaging techniques to assess respiratory muscle structure and function. Respiratory muscle imaging directly measures the respiratory muscles and, in contrast to pulmonary function testing, is independent of patient effort. This makes respiratory muscle imaging suitable to use as tool in clinical respiratory management and as outcome parameter in upcoming drug trials for neuromuscular disorders, particularly in children. In this narrative review, we discuss the latest studies and technological developments in imaging of the respiratory muscles by US and MR, and its clinical application and limitations. We aim to increase understanding of respiratory muscle imaging and facilitate its use as outcome measure in daily practice and clinical trials.

Point-of-care lung and diaphragm ultrasound in a patient with spinal muscular atrophy with respiratory distress type 1

Spinal muscular atrophy with respiratory distress type 1 (SMARD1, OMIM #604,320), is a rare autosomal recessive disease resulting from degeneration of motor neurons in the anterior horns, which leads irreversible diaphragmatic palsy and progressive distal symmetrical muscular weakness. Respiratory distress is the main symptom and is severe, rapidly progressive, and frequently requiring invasive ventilation. Despite diaphragm being one of the target organ of the disease, no specific study has been done using ultrasound.We report diaphragm and lung ultrasound findings of a 13-month-old girl affected by SMARD1 (homozygosis c.1540G > A mutation in IGHMPB2 gene) with respiratory failure requiring permanent mechanical ventilation since birth and we discuss the role of diaphragmatic and lung ultrasound in this category of patients and its clinical implications.

Reproducibility and reference values of diaphragmatic shortening fraction for term and premature infants

BACKGROUND

New ultrasound measurements to diagnose diaphragmatic dysfunction, including diaphragmatic shortening fraction (DSF), have been studied in adults and children, but there are no data on reference values for neonates.

OBJECTIVE

To describe DSF reference values for term neonate (TN) and preterm neonate (PTN), and to calculate its reproducibility.

METHODS

We included asymptomatic TN and PTN during their first 24 hours of life. We measured DSF at the zone of apposition in both hemithoraces. Reproducibility of image acquisition, including inter- and intra-rater agreement of the measurements were calculated among an experienced and a novel operator (after completion of a 1-day course on lung ultrasound [LU] and performance of 10 diaphragm ultrasounds [DUs] under supervision), and a more-trained examiner (completion of a 1-day course on LU and performance of 60 DUs under supervision).

RESULTS

Two groups of 33 TN and 33 PTN were studied. Median DSF values did not differ between the groups, although diaphragm thickness was higher in the TN group. Intra-observer reproducibility: the intraclass correlation coefficient (ICC) was 0.95 (95% confidence interval [95% CI] 0.86-0.98). Interobserver reproducibility with novel operator had an ICC of 0.42 (95% CI -0.74 to 0.81), and with a more experienced operator improved to 0.76 (95% CI 0.27-0.92). Both intra- and interobserver agreement were high.

CONCLUSIONS

Asymptomatic TN and PTN have similar DSF values in the first 24 hours of life. The intra- and interobserver agreement is high. Reproducibility is acceptable, but intensive training is necessary to perform adequate DU.