Ultrasonographic diaphragm thickness correlates with compound muscle action potential amplitude and forced vital capacity

Perioperative Diaphragm Dysfunction

Diaphragm Dysfunction (DD) is a respiratory disorder with multiple causes. Although both unilateral and bilateral DD could ultimately lead to respiratory failure, the former is more common. Increasing research has recently delved into perioperative diaphragm protection. It has been established that DD promotes atelectasis development by affecting lung and chest wall mechanics. Diaphragm function must be specifically assessed for clinicians to optimally select an anesthetic approach, prepare for adequate monitoring, and implement the perioperative plan. Recent technological advancements, including dynamic MRI, ultrasound, and esophageal manometry, have critically aided disease diagnosis and management. In this context, it is noteworthy that therapeutic approaches for DD vary depending on its etiology and include various interventions, either noninvasive or invasive, aimed at promoting diaphragm recruitment. This review aims to unravel alternative anesthetic and operative strategies that minimize postoperative dysfunction by elucidating the identification of patients at a higher risk of DD and procedures that could cause postoperative DD, facilitating the recognition and avoidance of anesthetic and surgical interventions likely to impair diaphragmatic function.

The utility of diaphragm ultrasound thickening indices for assessing respiratory decompensation in amyotrophic lateral sclerosis

INTRODUCTION/AIMS

Amyotrophic lateral sclerosis (ALS) leads to diaphragmatic weakness at some point during its course, which is a major cause of respiratory insufficiency. The aim of this study was to evaluate ultrasound-based measures for assessing the diaphragmatic competency and the need for ventilatory support.

METHODS

Twenty-six subjects with ALS and 12 healthy controls were enrolled. All participants underwent B-mode diaphragm ultrasound (DUS). Diaphragm thickness and thickening indices were recorded. In the subjects with ALS, further assessments included functional scales and spirometry. We investigated the diagnostic accuracy of DUS thickening indices in predicting diaphragmatic dysfunction and the correlation between clinical, spirometric, and DUS data.

RESULTS

Significant relationships were found between forced vital capacity and all diaphragmatic thickening indices. Similarly, all diaphragmatic thickening indices correlated with both Milano Torino staging and disease progression rate. Only thickening fraction (TFdi) correlated with score on the revised ALS Functional Rating Scale (r = 0.459, P = .024). TFdi had better accuracy in predicting diaphragmatic dysfunction (area under the curve [AUC] = 0.839, 95% confidence interval [CI] 0.643 to 0.953) and the need for initiation of noninvasive ventilation (NIV) (AUC = 0.989, 95% CI 0.847 to 1.000) compared with the other indices. A TFdi cut-off point of 0.50 was a sensitive threshold to consider NIV.

DISCUSSION

DUS successfully identifies diaphragmatic dysfunction in ALS, being a valuable accessory modality for investigating respiratory symptoms. TFdi was found to be the most useful DUS index, which encourages further investigation.

COVID-19 Lung Ultrasound Scores and Lessons from the Pandemic: A Narrative Review

The WHO recently declared that COVID-19 no longer constitutes a public health emergency of international concern; however, lessons learned through the pandemic should not be left behind. Lung ultrasound was largely utilized as a diagnostic tool thanks to its feasibility, easy application, and the possibility to reduce the source of infection for health personnel. Lung ultrasound scores consist of grading systems used to guide diagnosis and medical decisions, owning a good prognostic value. In the emergency context of the pandemic, several lung ultrasound scores emerged either as new scores or as modifications of pre-existing ones. Our aim is to clarify the key aspects of lung ultrasound and lung ultrasound scores to standardize their clinical use in a non-pandemic context. The authors searched on PubMed for articles related to "COVID-19", "ultrasound", and "Score" until 5 May 2023; other keywords were "thoracic", "lung", "echography", and "diaphragm". A narrative summary of the results was made. Lung ultrasound scores are demonstrated to be an important tool for triage, prediction of severity, and aid in medical decisions. Ultimately, the existence of numerous scores leads to a lack of clarity, confusion, and an absence of standardization.

Diaphragm thickness by ultrasound in pediatric patients with primary malnutrition

Skeletal muscle atrophy is known to be a marker for nutritional deficiency. The diaphragm is both a skeletal muscle and a respiratory muscle. There is not enough data in the literature about the change in diaphragm thickness (DT) in children with malnutrition. We think that malnutrition may have negative effects on diaphragm thickness. Therefore, in this study, we aimed to compare the diaphragm thicknesses of pediatric patients with primary malnutrition and a healthy control group. The DT of pediatric patients diagnosed with primary malnutrition by a pediatric gastroenterologist was prospectively evaluated by a radiology specialist by ultrasonography (USG). The obtained data were statistically compared with the data of the healthy control group. There was no statistically significant difference between the groups in terms of age and gender (p = 0.244, p = 0.494). We found that right and left diaphragm thicknesses were significantly thinner in the malnourished group than in the healthy control group (p = 0.001, p = 0.009, respectively). We found that right and left diaphragm thicknesses were thinner in those with moderate and severe malnutrition compared to the normal group (p < 0.001, p = 0.003, respectively). We found a significant weak positive correlation between weight and height Z score and right and left diaphragm thickness (respectively, r: 0.297, p < 0.001; r: 0.301, p < 0.001).   Conclusion: Malnutrition is a disease that affects all systems. Our study shows that the DT is thinner in patients with malnutrition. What is Known: •Malnutrition causes skeletal muscle atrophy. What is New: •Diaphragm muscle thickness decreases in malnutrition. •There is a significant positive correlation between diaphragm muscle thickness and height, weight and BMI z scores.

New International Guidelines and Consensus on the Use of Lung Ultrasound

Following the innovations and new discoveries of the last 10 years in the field of lung ultrasound (LUS), a multidisciplinary panel of international LUS experts from six countries and from different fields (clinical and technical) reviewed and updated the original international consensus for point-of-care LUS, dated 2012. As a result, a total of 20 statements have been produced. Each statement is complemented by guidelines and future developments proposals. The statements are furthermore classified based on their nature as technical (5), clinical (11), educational (3), and safety (1) statements.

Ultrasonography in Assessment of Respiratory Muscles Function: A Systematic Review

INTRODUCTION

The purpose of this study was to evaluate the potential utility of respiratory muscles ultrasound (US) imaging for assessing respiratory function and identify US variables that best correlate with pulmonary parameters.

MATERIALS AND METHODS

A search of 5 databases was conducted. Initially, there was no language, study design, or time frame restrictions. All studies assessing the relationship between pulmonary and US parameters were included. Two reviewers independently extracted and documented data regarding to examined population, age, gender, health condition, methodology, US, and pulmonary function measurements. All studies were qualitative synthesis.

RESULTS

A total of 1,272 participants from 31 studies were included. Diaphragm thickness, diaphragm thickening ratio, and diaphragm excursion amplitude were mainly used as US parameters. Forced vital capacity, forced expiratory volume1sec, and maximal inspiratory pressure were mainly used as pulmonary parameters. The relationships between pulmonary and US parameters varied from negligible to strong (depend on examined population and methodology used). Data were not quantitatively synthesis due to high heterogeneity in terms of study design, population examined, and various pulmonary and US parameters.

CONCLUSION

A strong relationship between US measurements and pulmonary parameters was demonstrated in some studies but not others. This review confirmed that US measurements can complement spirometry, but the exact role of the US remains to be confirmed. Further studies using standardized methodology are needed to obtain more conclusive evidence on the usefulness of US for assessing respiratory function.

Diaphragm impairment in patients admitted for severe COVID-19

Among patients affected by the virus COVID-19, physicians have observed ventilation disorders. It is relevant to assess neurological involvement, including the role of diaphragmatic function. Its possible impairment could be related to the systemic inflammatory response and disease progression that both typify COVID-19 infection. We distinguished two groups (severe group (SG) and mild group (MG)) according to the severity of respiratory symptomatology. We performed neurophysiological and sonography studies to evaluate the diaphragmatic function. Regarding the sonography variables, we identified statistically significant differences in the right mean diaphragmatic thickness along with the expiration, showing 1.56 mm (SEM: 0.11) in the SG vs 1.92 mm (SEM: 0.19) in the MG (p = 0.042). The contractibility of both hemidiaphragms was 15% lower in the severe group, though this difference is not statistically significant. In our examination of the neurophysiological variables, in the amplitude responses, we observed a greater difference between responses from both phrenic nerves as follows: the raw differences in amplitude were 0.40 μV (SEM: 0.14) in the SG vs 0.35 μV (SEM: 0.19) in the MG and the percentage difference was 25.92% (SEM: 7.22) in the SG vs 16.28% (SEM: 4.38%) in the MG. Although diaphragmatic dysfunction is difficult to detect, our combined functional and morphological approach with phrenic electroneurograms and chest ultrasounds could improve diagnostic sensitivity. We suggest that diaphragmatic dysfunction could play a relevant role in respiratory disturbance in hospitalised patients with severe COVID-19.

Thoracic Excursion Is a Biomarker for Evaluating Respiratory Function in Amyotrophic Lateral Sclerosis

Objective

To evaluate the usefulness of thoracic excursion as a biomarker in patients with amyotrophic lateral sclerosis (ALS).

Methods

We measured the forced the vital capacity (FVC), thoracic excursion, baseline-to-peak diaphragmatic compound muscle action potential (DCMAP) amplitude, diaphragm thickness at full inspiration (DTfi), Medical Research Council (MRC) sum score for muscle strength, and arterial partial pressures of oxygen and carbon dioxide and administered the Amyotrophic Lateral Sclerosis Functional Rating Scale-Revised (ALSFRS-R) and modified Medical Research Council (mMRC) Dyspnea Scale. The test–retest reliability of thoracic excursion was determined.

Results and Conclusions

Thirty-four patients with ALS and 26 age- and sex-matched healthy participants were enrolled. Thoracic excursion measurement had excellent test–retest reliability (intraclass coefficient: 0.974). Thoracic excursion was more strongly correlated with FVC (r = 0.678, p &lt; 0.001) than DCMAP amplitude (r = 0.501, p = 0.003) and DTfi (r = 0.597, p &lt; 0.001). It was also correlated with ALSFRS-R score (r = 0.610, p &lt; 0.001), MRC sum score (r = 0.470, p = 0.005), and mMRC Dyspnea Scale score (r = −0.446, p = 0.008) and was the most sensitive parameter for assessing dyspnea and FVC. Thoracic excursion decreased as FVC declined in the early and late stages, there were no differences in DCMAP amplitude and DTfi between the early and late stages, and ALSFRS-R score and MRC sum score decreased only in the late stage. Thoracic excursion was well correlated with respiratory function and is useful for predicting respiratory and general dysfunction in patients with ALS regardless of stage.

Influence of gender on diaphragm thickness using a method for determining intima media thickness in healthy young adults

BACKGROUND

To clarify the differences in diaphragm thickness between male and female participants in healthy young adults with ultrasonography using the mean intima media thickness (IMT) method and to investigate the relationship between diaphragm thickness and respiratory pressure.

METHODS

Twenty-nine healthy individuals (16 females and 13 males) participated in the study. Diaphragm thickness was measured at total lung capacity (TLC) and at functional residual capacity (FRC) in each participant. We measured the diaphragm thickness using a method for mean intima media thickness. Moreover, change ratio of diaphragm thickness was calculated with the diaphragm thickness at TLC and FRC.

RESULTS

Mean diaphragm thicknesses at FRC in males were significantly narrower than those in females (p < 0.001). The change ratio of diaphragm thickness was significantly augmented in males compared with that in females (p < 0.001). There was a positive correlation between the change ratio of diaphragm thickness and pulmonary function data and respiratory muscle strength in healthy young adults.

CONCLUSIONS

The change ratio of diaphragm thickness using the IMT method can be accurately performed with a high degree of reproducibility by clinical laboratory technicians and may be a useful indicator for evaluating diaphragm muscle strength.

Spinal cord injury and degenerative cervical myelopathy

Spinal cord injury (SCI) often results in impaired respiratory function. Paresis or paralysis of inspiratory and expiratory muscles can lead to respiratory dysfunction depending on the level and severity of the injury, which can affect the management and care of SCI patients. Respiratory dysfunction after SCI is more severe in high cervical injuries, with vital capacity (VC) being an essential indicator of overall respiratory health. Respiratory complications include hypoventilation, a reduction in surfactant production, mucus plugging, atelectasis, and pneumonia. Respiratory management includes mechanical ventilation and tracheostomy in high cervical SCI, while noninvasive ventilation is more common in patients with lower cervical and thoracic injuries. Mechanical ventilation can negatively impact the function of the diaphragm and weaning should start as soon as possible. Patients can sometimes be weaned from mechanical ventilation with assistance of electrical stimulation of the phrenic nerve or the diaphragm. Respiratory muscle training regimens may also improve patients' inspiratory function following SCI. Despite the critical advances in preventing, diagnosing, and treating respiratory complications, they continue to significantly affect persons living with SCI. Additional studies of interventions to reduce respiratory complications are likely to further decrease the morbidity and mortality associated with these injuries.

Ultrasonographic evaluation of diaphragm thickness and excursion in patients with cervical spinal cord injury

Objective: To evaluate the diaphragm thickness and excursion in patients with cervical spinal cord injury and reliability of diaphragmatic ultrasonography.Design: A Pilot Case-Control Study.Setting: China Rehabilitation Research Center (CRRC) /Beijing BO AI Hospital.Participants: Sixty participants with cervical spinal cord injury and sixty control participants were eligible for inclusion in this study.Interventions: Ultrasonographic evaluation of the diaphragm.Outcome Measures: All demographic data were evaluated. Diaphragm thickness, thickening ratio, and diaphragm excursions were assessed at the end of quiet tidal breathing and maximal inspiration. The reliability of inter- and intra-ultrasonography operators were evaluated.Results: Diaphragm thickness was significantly higher in patients with cervical spinal cord injury than the control group (P < 0.001). Diaphragmatic excursion of the right hemidiaphragm was significantly greater in patients with cervical spinal cord injury than the control group (P < 0.001) at the end of quiet tidal breathing. No difference was found in diaphragmatic excursion between two groups (P = 0.32) at the end of maximal inspiration. No significant difference was shown between two groups in thickening ratio. Intraclass correlation coefficients of inter-and intra-ultrasonography operators for the thickness and excursions of the diaphragm were greater than 0.93.Conclusion: Compared with the control group the diaphragm in patients with cervical spinal cord injury is hypertrophied and the diaphragm excursion is greater. Ultrasound is a highly reliable tool for the evaluation of diaphragm thickness and excursion in patients with cervical spinal cord injury.Trial Registration: This trail was registered in Chinese Clinical Trial Registry (NO. ChiCTR-ROC-17010973).

Phrenic Nerve Reconstruction for Effective Surgical Treatment of Diaphragmatic Paralysis

ABSTRACT

Diaphragmatic paralysis due to phrenic nerve injury may cause orthopnea, exertional dyspnea, and sleep-disordered breathing. Phrenic nerve reconstruction may relieve symptoms and improve respiratory function. A retrospective review of 400 consecutive patients undergoing phrenic nerve reconstruction for diaphragmatic paralysis at 2 tertiary treatment centers was performed between 2007 and 2019. Symptomatic patients were identified, and the diagnosis was confirmed on radiographic evaluations. Assessment parameters included pulmonary spirometry (forced expiratory volume in 1 second and FVC), maximal inspiratory pressure, compound muscle action potentials, diaphragm thickness, chest fluoroscopy, and Short Form 36 Health Survey Questionnaire (SF-36) survey. There were 81 females and 319 males with an average age of 54 years (range, 19-79 years). The mean duration from diagnosis to surgery was 29 months (range, 1-320 months). The most common etiologies were acute or chronic injury (29%), interscalene nerve block (17%), and cardiothoracic surgery (15%). The mean improvements in forced expiratory volume in 1 second and FVC at 1 year were 10% (P < 0.01) and 8% (P < 0.05), respectively. At 2-year follow-up, the corresponding values were 22% (P < 0.05) and 18% (P < 0.05), respectively. Improvement on chest fluoroscopy was demonstrated in 63% and 71% of patients at 1 and 2-year follow-up, respectively. There was a 20% (P < 0.01) improvement in maximal inspiratory pressure, and compound muscle action potentials increased by 82% (P < 0.001). Diaphragm thickness demonstrated a 27% (P < 0.01) increase, and SF-36 revealed a 59% (P < 0.001) improvement in physical functioning. Symptomatic diaphragmatic paralysis should be considered for surgical treatment. Phrenic nerve reconstruction can achieve symptomatic relief and improve respiratory function. Increasing spirometry and improvements on Sniff from 1 to 2 years support incremental recovery with longer follow-up.

Diaphragm dysfunction: A comprehensive review from diagnosis to management

Although the diaphragm represents a critical component of the respiratory pump, the clinical presentations of diaphragm dysfunction are often non-specific and can be mistaken for other more common causes of dyspnoea. While acute bilateral diaphragm dysfunction typically presents dramatically, progressive diaphragm dysfunction associated with neuromuscular disorders and unilateral hemidiaphragm dysfunction may be identified incidentally or by recognising subtle associated symptoms. Diaphragm dysfunction should be considered in individuals with unexplained dyspnoea, restrictive respiratory function tests or abnormal diaphragm position on plain chest imaging. A higher index of suspicion should occur for individuals with profound orthopnoea, those who have undergone procedures in proximity to the phrenic nerve(s) or those with co-morbid conditions that are associated with diaphragm dysfunction, particularly neuromuscular disorders. A systematic approach to the evaluation of diaphragm function using non-invasive diagnostic techniques such as respiratory function testing and diaphragm imaging can often confirm a diagnosis. Neurophysiological assessment may confirm diaphragm dysfunction and assist in identifying an underlying cause. Identifying those with or at risk of respiratory failure can allow institution of respiratory support, while specific cases may also benefit from surgical plication or phrenic nerve pacing techniques. This article is protected by copyright. All rights reserved.

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.

Ultrasound and non-ultrasound imaging techniques in the assessment of diaphragmatic dysfunction

Diaphragm muscle dysfunction is increasingly recognized as an important element of several diseases including neuromuscular disease, chronic obstructive pulmonary disease and diaphragm dysfunction in critically ill patients. Functional evaluation of the diaphragm is challenging. Use of volitional maneuvers to test the diaphragm can be limited by patient effort. Non-volitional tests such as those using neuromuscular stimulation are technically complex, since the muscle itself is relatively inaccessible. As such, there is a growing interest in using imaging techniques to characterize diaphragm muscle dysfunction. Selecting the appropriate imaging technique for a given clinical scenario is a critical step in the evaluation of patients suspected of having diaphragm dysfunction. In this review, we aim to present a detailed analysis of evidence for the use of ultrasound and non-ultrasound imaging techniques in the assessment of diaphragm dysfunction. We highlight the utility of the qualitative information gathered by ultrasound imaging as a means to assess integrity, excursion, thickness, and thickening of the diaphragm. In contrast, quantitative ultrasound analysis of the diaphragm is marred by inherent limitations of this technique, and we provide a detailed examination of these limitations. We evaluate non-ultrasound imaging modalities that apply static techniques (chest radiograph, computerized tomography and magnetic resonance imaging), used to assess muscle position, shape and dimension. We also evaluate non-ultrasound imaging modalities that apply dynamic imaging (fluoroscopy and dynamic magnetic resonance imaging) to assess diaphragm motion. Finally, we critically review the application of each of these techniques in the clinical setting when diaphragm dysfunction is suspected.

Ultrasonographic measurement of diaphragm thickness in patients with severe thoracic scoliosis

PURPOSE

This study aimed to measure diaphragm thickness using ultrasound in adult patients with severe idiopathic scoliosis.

METHODS

This prospective case-control study included patients with severe idiopathic scoliosis and a healthy control group. The control and patient groups' demographic features, pulmonary function tests, diaphragm thickness, and thickening fraction measured using ultrasonography were compared.

RESULTS

End-expirium values were similar between the two groups (p = 0.902). However, end of inspirium, change level, and diaphragm thickening fraction were significantly lower in the scoliosis group (p < 0.001 for all). Cobb degree values were inversely correlated with forced expiratory volume in 1 s (%) (r =  - 0.909, p < 0.001), forced vital capacity (%) (r =  - 0.887, p < 0.001), and end-inspirium thickness (r =  - 0.673 and p < 0.001) values. Furthermore, diaphragm thickness at the end of inspirium was positively correlated with forced expiratory volume in 1 s (%) (r = 0.636, p = 0.001) and forced vital capacity (%) (r = 0.646, p = 0.001) values. No significant correlation was found between diaphragm thickening fraction and forced expiratory volume in 1 s or forced vital capacity.

CONCLUSION

Ultrasound can provide valuable information about diaphragm morphology and quantify diaphragm contraction.

Diaphragm ultrasound in the diagnosis of respiratory dysfunction in patients with amyotrophic lateral sclerosis

OBJECTIVE

In this study, we aimed to select the best diaphragm ultrasonography (DUS) parameter as an alternative index for the diagnosis of lung function impairment in amyotrophic lateral sclerosis (ALS).

METHODS

Twenty-nine patients with ALS and 15 healthy subjects were enrolled in the study. DUS, lung function tests, phrenic nerve conduction study and arterial blood gas analysis were performed.

RESULTS

Patients with respiratory dysfunction had a significantly lower level of ΔTmax than those without (P=0.039). Significant correlations (P<0.05) were found between forced vital capacity (FVC) and Tdi-ins (r=0.665, P<0.0001) and ΔTmax (r=-0.748, P<0.0001) and Δins-exp (r=0.627, P<0.0001) and ΔTdi (r=0.485, P<0.0001). Receiver Operating Curves analysis demonstrated that ΔTmax (AUC=0.76, P=0.044) had a better overall accuracy for detection of respiratory dysfunction compared with Tdi-ins (AUC=0.27, P=0.067), Δins-exp (AUC=0.312, P=0.139), and ΔTdi (AUC=0.38, P=0.359).

CONCLUSION

ΔTmax is the most valuable DUS index in the diagnosis of diaphragmatic dysfunction.

SIGNIFICANCE

DUS can provide functional and structural information of diaphragm and help to diagnose diaphragmatic dysfunction in ALS.

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.

Evaluation of Respiratory Muscle Strength and Diaphragm Ultrasound: Normative Values, Theoretical Considerations, and Practical Recommendations

BACKGROUND

Reference values derived from existing diaphragm ultrasound protocols are inconsistent, and the association between sonographic measures of diaphragm function and volitional tests of respiratory muscle strength is still ambiguous.

OBJECTIVE

To propose a standardized and comprehensive protocol for diaphragm ultrasound in order to determine lower limits of normal (LLN) for both diaphragm excursion and thickness in healthy subjects and to explore the association between volitional tests of respiratory muscle strength and diaphragm ultrasound parameters.

METHODS

Seventy healthy adult subjects (25 men, 45 women; age 34 ± 13 years) underwent spirometric lung function testing, determination of maximal inspiratory and expiratory pressure along with ultrasound evaluation of diaphragm excursion and thickness during tidal breathing, deep breathing, and maximum voluntary sniff. Excursion data were collected for amplitude and velocity of diaphragm displacement. Diaphragm thickness was measured in the zone of apposition at total lung capacity (TLC) and functional residual capacity (FRC). All participants underwent invasive measurement of transdiaphragmatic pressure (Pdi) during different voluntary breathing maneuvers.

RESULTS

Ultrasound data were successfully obtained in all participants (procedure duration 12 ± 3 min). LLNs (defined as the 5th percentile) for diaphragm excursion were as follows: (a) during tidal breathing: 1.2 cm (males; M) and 1.2 cm (females; F) for amplitude, and 0.8 cm/s (M) and 0.8 cm/s (F) for velocity, (b) during maximum voluntary sniff: 2.0 cm (M) and 1.5 cm (F) for amplitude, and 6.7 (M) cm/s and 5.2 cm/s (F) for velocity, and (c) at TLC: 7.9 cm (M) and 6.4 cm (F) for amplitude. LLN for diaphragm thickness was 0.17 cm (M) and 0.15 cm (F) at FRC, and 0.46 cm (M) and 0.35 cm (F) at TLC. Values for males were consistently higher than for females, independent of age. LLN for diaphragmatic thickening ratio was 2.2 with no difference between genders. LLN for invasively measured Pdi during different breathing maneuvers are presented. Voluntary Pdi showed only weak correlation with both diaphragm excursion velocity and amplitude during forced inspiration.

CONCLUSIONS

Diaphragm ultrasound is an easy-to-perform and reproducible diagnostic tool for noninvasive assessment of diaphragm excursion and thickness. It supplements but does not replace respiratory muscle strength testing.

Reliability of phrenic nerve conduction study: In healthy controls and in patients with primary lateral sclerosis

OBJECTIVE

Phrenic nerve conduction study is a marker of hypoventilation in amyotrophic lateral sclerosis. We aimed to evaluate its intra-rater reliability in healthy subjects and in a cohort of Primary Lateral Sclerosis (PLS) patients.

METHODS

Eighteen healthy subjects and 16 PLS patients were included. All subjects underwent three phrenic nerve conduction evaluations (time interval: 1 week for healthy controls; 1 year for PLS patients). We analyzed intra-rater reliability for five parameters of the diaphragmatic motor response: latency; negative-peak duration, area and amplitude; peak-to-peak amplitude.

RESULTS

Healthy subjects showed excellent inter-test reliability for most parameters (coefficients of variation <10%). In PLS patients coefficients of variation resulted <10% for latency and peak-to-peak amplitude, <20% for remaining parameters. Inter-test reliability was excellent for latency and peak-to-peak amplitude [intra-class correlation coefficient (ICC) > 0.9] and good for negative-peak amplitude and area (ICC 0.75 ≥ 0.9); duration was not reliable (ICC = 0.383). Negative peak and peak-to-peak amplitude had the least random error (respectively ±0.136 mV and ± 0.177 mV). All parameters showed homoscedasticity (R2 < 0.1).

CONCLUSIONS

Intra-rater reliability is high for phrenic nerve study, especially for latency, peak-to-peak and negative-peak amplitude.

SIGNIFICANCE

Phrenic nerve conduction study is a reliable method to monitor respiratory function.

Ultrasound assessment of diaphragm function in patients with late-onset Pompe disease

INTRODUCTION

Late-Onset Pompe Disease (LOPD) is characterized by progressive limb-girdle muscle weakness and respiratory dysfunction. Diaphragm is the most impaired muscle in LOPD and its dysfunction cause major respiratory symptoms. The aim of this study was to evaluate the correlation between diaphragm thickness and mobility assessed by ultrasonography and respiratory function and muscle strength tests in patients with LOPD.

METHODS

17 patients with LOPD (9 female, 47 ± 15 years) and 17 age and gender-matched healthy controls underwent spirometry, muscle strength testing, and ultrasound evaluation of diaphragm excursion and thickness.

RESULTS

The following parameters were significantly reduced in LOPD patients versus controls (all p < 0.001): forced vital capacity (FVC) in seated and supine position, maximum inspiratory and expiratory pressure (MIP and MEP), diaphragm excursion, thickness at functional residual capacity (FRC) and total lung capacity (TLC), and thickness fraction (TF). Ultrasound studies of diaphragm thickness at FRC correlated with MIP (r = 0.74; p < 0.0001) and seated FVC(r = 0.73; p < 0.05). Diaphragm thickness at TLC correlated with MIP (r = 0.85; p < 0.0001) and FVC in both seated (r = 0.77; p < 0.0001) and supine position (r = 0.68; p < 0.05). TF correlated significantly with MIP (r = 0.80; p < 0.001), FVC in both seated (r = 0.66; p < 0,005) and supine position (r = 0.61; p < 0.05). Interestingly diaphragm thickness at FRC correlated with disease duration (years) in LOPD patients (r = -0.53; p < 0,05). Ultrasound diaphragm mobility correlated with diaphragm thickness at TLC(r = 0.87; p < 0.0001), FRC (r = 0.84; p < 0.005) and TF (r = 0.73; p < 0.05). Moreover diaphragm mobility correlated with FVC in seated(r = 0.79; p < 0.005) and supine position(r = 0.74; p < 0.05) and MIP (r = 0.81; p < 0.005).

CONCLUSION

Diaphragm ultrasonography is a simple and reproducible technique for manage respiratory dysfunction in LOPD patients.

Cervical spinal stenosis and risk of pulmonary dysfunction

Background:

Cervical spinal stenosis (CSS) is defined as an abnormal narrowing of the cervical spinal canal. The essential clinical challenges with CSS are altered cervical spinal cord function and cervical radiculopathy. Phrenic nerve palsy leading to hemidiaphragmatic paresis may be a temporary or persistent phenomenon after cervical cord injury and CSS.

Objective:

The objective of the study is to elucidate the potential effect of CSS on the pulmonary functions.

Methods:

This is a case–control study which included 40 patients divided into two groups 30 females and 10 males patients with CSS (C5 and above) and 60 healthy volunteers with body mass index (BMI) <30 Kg/m². Pulmonary function tests have been done for all the patients.

Results:

The present study showed that VC in expiration (VC EX%), forced expiratory volume (FEV%), forced vital capacity % (FVC%), PEF%, and mean voluntary ventilation % (MVV%), were low in patients CSS compared with the control groups; P < 0.001, P < 0.001, P < 0.001, P = 0.042, and P = 0.037, respectively. As well, VC EX%, FEV1%, and FVC% were low in male patients in comparison to the controls P < 0.05. Besides, there were no significant differences regarding age, BMI, VC in inspiration (VC IN%), PEF%, FEV1/FVC%, and MVV%. Moreover, VC EX%, FEV1%, and FVC% were low in female patients compared to the controls, P < 0.001. Whereas, there were no significant differences that had been identified between female patients and female controls regarding age, BMI, VC IN%, PEF%, FEV1/FVC%, and MVV%. On the other hand, weight, height, and MVV% were low in female patients compared to male patients, P < 0.001.

Conclusion:

Chronic CSS leads to subclinical pulmonary dysfunction due to the involvement of the phrenic nerve. FEV% is the most sensitive parameter in the detection these disorders.

Incidence and predictive factors of diaphragmatic dysfunction in acute stroke

Background

The most characteristic clinical signs of stroke are motor and/or sensory involvement of one side of the body. Respiratory involvement has also been described, which could be related to diaphragmatic dysfunction contralateral to the brain injury. Our objective is to establish the incidence of diaphragmatic dysfunction in ischaemic stroke and analyse the relationship between this and the main prognostic markers.

Methods

A prospective study of 60 patients with supratentorial ischaemic stroke in the first 48 h. Demographic and clinical factors were recorded. A diaphragmatic ultrasound was performed for the diagnosis of diaphragmatic dysfunction by means of the thickening fraction, during normal breathing and after forced inspiration. Diaphragmatic dysfunction was considered as a thickening fraction lower than 20%. The appearance of respiratory symptoms, clinical outcomes and mortality were recorded for 6 months. A bivariate and multivariate statistical analysis was designed to relate the incidence of respiratory involvement with the diagnosis of diaphragmatic dysfunction and with the main clinical determinants.

Results

An incidence of diaphragmatic dysfunction of 51.7% was observed. 70% (23 cases) of these patients developed symptoms of severe respiratory compromise during follow-up. Independent predictors were diaphragmatic dysfunction in basal respiration (p = 0.026), hemiparesis (p = 0.002) and female sex (p = 0.002). The cut-off point of the thickening fraction with greater sensitivity (75.75%) and specificity (62.9%) was 24% (p = 0.003).

Conclusions

There is a high incidence of diaphragmatic dysfunction in patients with supratentorial ischaemic stroke which can be studied by calculating the thickening fraction on ultrasound. Among these patients we have detected a higher incidence of severe respiratory involvement.

Thickening fraction as a measure of ultrasonographic diaphragm dysfunction in amyotrophic lateral sclerosis

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The leading cause of the death in ALS is respiratory failure secondary to diaphragm dysfunction.

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Three ALS patients with respiratory dysfunction had low phrenic motor nerve action potential.

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The diaphragm thickening fraction when measured, is low (<15%) in all of them.

Objective

Respiratory failure is the most common cause of death in ALS patients secondary to diaphragmatic dysfunction. Herein, we report three ALS patients, and we sought to determine the diaphragm dysfunction by the measurement of ultrasonographic diaphragmatic thickness fraction (DTf).

Methods

High-resolution linear US probe of 10 MHz (Philips Healthcare EPIQ 7 Ultrasound System Inc.) was used to measure the diaphragm thickness (DT) using B mode at the Zone of Apposition. Phrenic nerve compound muscle action potential measured stimulating the nerve, posterior to the sternocleidomastoid muscle, approximately 3 cm above the clavicle and recording the diaphragm with electrode G1 placed fingerbreadth above the xiphoid process and electrode G2 placed over the anterior costal margin 16 cm from G1.

Results

The diaphragmatic thickening fraction (DTf) measured in these three patients recorded was less than 15%. Diaphragm dysfunction was also suggested by low amplitude of the diaphragmatic compound muscle action potential in each patient.

Conclusion

Diaphragm dysfunction, secondary to lower motor neuron loss, was mirrored by the low amplitude of the diaphragm CMAP in the 3 patient case reports. These cases suggest that a thickening fraction ≤15% is associated with severe diaphragm weakness and risk of respiratory failure.

Significance

Before appropriate data obtained in a population of ALS patients are available, we propose DTf (%) <20% as a possible indicator of diaphragm dysfunction in ALS patients.

Effect of local anesthetic volume (20 mL vs 30 mL ropivacaine) on electromyography of the diaphragm and pulmonary function after ultrasound-guided supraclavicular brachial plexus block: a randomized controlled trial

BACKGROUND AND OBJECTIVES

Diaphragmatic paralysis following supraclavicular brachial plexus block (SCBPB) is ascribed to phrenic nerve palsy. This study investigated the effect of 2 volumes of 0.375% ropivacaine on efficacy of block as a surgical anesthetic and as an analgesic and examined diaphragm compound muscle action potentials (CMAPs) and pulmonary function before and after SCBPB.

METHODS

Eighty patients scheduled for removal of hardware for internal fixation after healing of an upper limb fracture distal to the shoulder were randomized to receive ultrasound-guided SCBPC for surgical anesthesia with 20 mL (Group A) or 30 mL (Group B) 0.375% ropivacaine. The latency and amplitude of diaphragm CMAPs and forced vital capacity (FVC), FVC% predicted, and forced expiratory volume in 1 s (FEV1) were measured before and 30 min after SCBPB.

RESULTS

Block success as primary anesthetic in addition to analgesia was 81% in Group A and 91% in Group B. There were no obvious differences in the effectiveness of analgesia between the two groups. The mean time to onset of motor block was significantly longer in Group A (8.1±2.7 min) than in Group B (5.4 ± 2.8 min; p<0.05). The mean amplitude of the diaphragm CMAP was significantly lower in Group B than in Group A (p=0.03). The changes in FVC (Group A, - 8.1% vs Group B, -16.5%), FVC% (Group A, -8.0% vs Group B, -17.1%), and FEV1 (Group A, -9.5% vs Group B, -15.2%) from pre-SCBPB to post-SCBPB were significantly less in Group A than in Group B (all p=0.03).

CONCLUSIONS

The incidence rates of phrenic nerve palsy and diaphragm paralysis were reduced, and lung function was less impaired in patients who received 20 mL vs 30 mL of 0.375% ropivacaine without any differences in block success. Selecting a lower volume of anesthetic for nerve block may be especially beneficial in obese patients or patients with cardiopulmonary disease.

TRIAL REGISTRATION NUMBER

ChiCTR-IND-17012166.

The C9orf72 expansion is associated with accelerated respiratory function decline in a large Amyotrophic Lateral Sclerosis cohort

Introduction: The C9orf72 hexanucleotide repeat expansion is causal in amyotrophic lateral sclerosis (ALS) and has a negative effect on prognosis. The C9orf72 repeat expansion has been associated with an accelerated deterioration of respiratory function and survival in a cohort of 372 Portuguese patients. Methods: Cases presenting to the Irish ALS clinic with both longitudinal occluded sniff nasal inspiratory pressure (SNIP) and C9orf72 testing were including in the study. Clinical variables and survival characteristics of these patients were collected. Joint longitudinal and time to event models were constructed to explore the longitudinal characteristics of the cohort by C9orf72 status. Results: In total, 630 cases were included, of which 58 (9.2%) carried the C9orf72 repeat expansion. Plots of the longitudinal trend after joint modelling revealed that those carrying the expansion had worse respiratory function throughout the course of their disease than those without. The ALS Functional Rating Scale-revised (ALSFRS-R) respiratory sub-score did not distinguish C9orf72 normal from expanded cases. Furthermore, modelling by site of onset and gender sub-groups revealed that this difference was greatest in male spinal onset cases. Joint models further indicated that occluded SNIP values were of prognostic importance. Conclusions: Our results confirm findings from Portugal that the C9orf72 repeat expansion is associated with accelerated respiratory function decline. Analysis via joint models indicate that respiratory function is of prognostic importance and may explain previous observations of poorer prognosis in male spinal onset patients carrying the C9orf72 expansion.

Ultrasonographic measurement of the diaphragm thickness in patients with obstructive sleep apnea syndrome

PURPOSE

The aim of this study was to evaluate the diaphragm thickness in patients with obstructive sleep apnea syndrome (OSAS).

METHODS

This prospective study included patients who underwent polysomnography evaluation for the first time with a clinical suspicion of OSAS. All patients underwent polysomnographic evaluation with a 55-channel Alice 6 computerized system (Respironics; Philips, IL). Diaphragm thickness was measured as the distance between the peritoneum and the pleura using electronic calipers with a 7-12-MHz linear probe (PHILIPS EPIQ 5G).

RESULTS

A total of 108 patients (67 males, 41 females) were enrolled in the current study. The mean age of the patients was 48.92 ± 11.47 years. The diaphragm thicknesses were significantly higher in OSAS patients both at end-inspirium and end-expirium compared with the normal group (p < 0.05). No significant difference was observed regarding the change level and thickening ratio (%) (p > 0.05). When the patients were allocated into OSAS subtypes; diaphragm thicknesses at the end of inspirium and expirium on both sides were significantly higher in the severe OSAS group and OSAS+OHS group compared with the other groups of normal, mild OSAS, and moderate OSAS subgroups (p < 0.05 for all). There was no significant difference between the groups regarding the thickening ratio (p > 0.05 for all). There was a positive correlation between the severity of OSAS and diaphragm thickness.

CONCLUSION

Diaphragm thickness seems to be increased in OSAS patients and the thickness correlates with the severity of OSAS. However, the thickness ratio of OSAS patients does not differ from that of normal subjects.

Ultrasonographic evaluation of the diaphragm thickness in patients with multiple sclerosis

BACKGROUND

Diaphragm weakness or dysfunction have been previously reported in multiple sclerosis (MS) patients. The aim of this study was to evaluate diaphragm thickness and thickenning ratio (TR) using ultrasound in MS patients.

METHODS

This prospective study comprised MS patients and a control group. Ultrasound examination was performed using a linear transducer (6-15 MHz). The diaphragm was seen as a hypoechoic structre between the peritoneum and pleura. End-expirium and end-inspirium measurements were obtained. Change levels and TR (%) were calculated. All participants were assessed using the Expanded Distability Status Scale (EDSS) and Fatigue Severity Scale (FSS).

RESULTS

Evaluation was made of 45 MS patients (11 males, 34 females) with a mean age of 37.36±9.0 years and 36 healthy subjects (3 males, 33 females) with a mean age of 35.19±9.3 years. The diaphragm thicknesses were similar at end-expirium (1.86±0.3 vs. 1.83±0.3 mm) and end-inspirium (3.14±0.6 vs. 3.46±0.6 mm). The change level with inspirium (0.90±0.6 vs. 1.31±0.7 mm) and TR (49.77±37.7 vs. 72.30±40.1%) were significantly higher in the control group compared to the values of MS patients. A weak and negative correlation was determined between EDSS and TR values (r=-0.293, p = 0.008), and no significant correlation was observed between the FSS values and diaphragm thickness (p>0.05 for all).

CONCLUSION

Although the diaphragm thickness of MS patients seems to be similar to those of healthy subjects, the change level and TR of MS patients seem to be lower. Furthermore, the change level and TR were found to be associated with EDSS.

Noninvasive Prediction of Twitch Transdiaphragmatic Pressure: Insights from Spirometry, Diaphragm Ultrasound, and Phrenic Nerve Stimulation Studies

BACKGROUND

Twitch transdiaphragmatic pressure (twPdi) following magnetic stimulation (MS) of the phrenic nerves is the gold standard for non-volitional assessment of diaphragm strength. Expiratory muscle function can be investigated using MS of the abdominal muscles and measurement of twitch gastric pressure (twPgas).

OBJECTIVES

To investigate whether twitch pressures following MS of the phrenic and lower thoracic nerve roots can be predicted noninvasively by diaphragm ultrasound parameters and volitional tests of respiratory muscle strength.

METHODS

Sixty-three healthy subjects underwent standard spirometry, measurement of maximum inspiratory (PImax) and expiratory pressure (PEmax), and diaphragm ultrasound. TwPdi following cervical MS of the phrenic nerve roots and twPgas after lower thoracic MS (twPgas-Thor) were measured using esophageal and gastric balloon catheters inserted transnasally. Using surface electrodes, compound muscle action potentials (CMAP) were simultaneously recorded from the diaphragm or obliquus abdominis muscles, respectively.

RESULTS

Forced expiratory flow (FEF25-75) was significantly correlated with twPdi (r = 0.37; p = 0.003) and its components (twPgas and twitch esophageal pressure, twPes). Diaphragm excursion velocity during tidal breathing was correlated to twPes (r = 0.44; p = 0.02). No prediction of twitch pressures was possible from CMAP amplitude, forced vital capacity (FVC), or PImax. TwPgas-Thor was correlated with FEF25-75 (r = 0.46; p = 0.05) and diaphragm thickness at total lung capacity (r = 0.38; p = 0.04) but could not be predicted from CMAP amplitude, FVC, or PEmax.

CONCLUSIONS

TwPdi and twPgas-Thor cannot be predicted from volitional measures of respiratory muscle strength, diaphragm and abdominal CMAP, or diaphragm ultrasound. Invasive recording of esophageal and gastric pressures following MS remains indispensable for objective assessment of respiratory muscle strength.

Clinical and research applications of neuromuscular ultrasound in amyotrophic lateral sclerosis

Amyotrophic lateral sclerosis (ALS) is a devastating neurodegenerative disorder characterized by dysfunction at multiple levels of the neuraxis. It remains a clinical diagnosis without a definitive diagnostic investigation. Electrodiagnostic testing provides supportive information and, along with imaging and biochemical markers, can help exclude mimicking conditions. Neuromuscular ultrasound has a valuable role in the diagnosis and monitoring of ALS and provides complementary information to clinical assessment and electrodiagnostic testing as well as insights into the underlying pathophysiology of this disease. This review highlights the evidence for ultrasound in the evaluation of bulbar, limb and respiratory musculature and peripheral nerves in ALS. Further research in this evolving area is required.

Diaphragmatic Neurophysiology and Respiratory Markers in ALS

The main reason for short survival in amyotrophic lateral sclerosis (ALS) is involvement of respiratory muscles. Severe compromise of diaphragmatic function due to marked loss of motor units causes poor inspiratory strength leading to symptomatic respiratory fatigue, and hypercapnia and hypoxemia, often firstly detected while sleeping supine. Weakness of expiratory muscles leads to cough weakness and poor bronchial clearance, increasing the risk of respiratory infection. Respiratory tests should therefore encompass inspiratory and expiratory function, and include measurements of blood gases during sleep. Non-volitional tests, such as phrenic nerve stimulation, are particularly convenient for investigating respiratory function in patients unable to perform standard respiratory function tests due to poor cooperation or facial weakness. However, SNIP is a sensitive test when patients with bulbar involvement are able to perform the necessary maneuvers. It is likely that central respiratory regulation is disturbed in some ALS patients, but its evaluation is more complex and not regularly implemented. Practical tests should incorporate tolerability, sensitivity, easy application for regular monitoring, and prognostic value. Impending respiratory failure can cause increased circulating inflammatory markers, but molecular assessment of respiratory distress requires further study. In future, home-monitoring of patients with accessible devices should be developed.

ACR Appropriateness Criteria® Chronic Dyspnea-Noncardiovascular Origin

Chronic dyspnea may result from a variety of disorders of cardiovascular, pulmonary, gastrointestinal, neuromuscular, systemic, and psychogenic etiology. This article discusses guidelines for the initial imaging of six variants for chronic dyspnea of noncardiovascular origin: (1) Chronic dyspnea of unclear etiology; (2) Chronic dyspnea with suspected chronic obstructive pulmonary disease; (3) Chronic dyspnea with suspected central airways disease; (4) Chronic dyspnea with suspected interstitial lung disease; (5) Chronic dyspnea with suspected disease of the pleura or chest wall; and (6) Chronic dyspnea with suspected diaphragm dysfunction. The American College of Radiology Appropriateness Criteria are evidence-based guidelines for specific clinical conditions that are reviewed annually by a multidisciplinary expert panel. The guideline development and revision include an extensive analysis of current medical literature from peer reviewed journals and the application of well-established methodologies (RAND/UCLA Appropriateness Method and Grading of Recommendations Assessment, Development, and Evaluation or GRADE) to rate the appropriateness of imaging and treatment procedures for specific clinical scenarios. In those instances where evidence is lacking or equivocal, expert opinion may supplement the available evidence to recommend imaging or treatment.

Diaphragm: Pathophysiology and Ultrasound Imaging in Neuromuscular Disorders

Respiratory muscles are classically involved in neuromuscular disorders, leading to a restrictive respiratory pattern. The diaphragm is the main respiratory muscle involved during inspiration. Ultrasound imaging is a noninvasive, radiation-free, accurate and safe technique allowing assessment of diaphragm anatomy and function. The authors review the pathophysiology of diaphragm in neuromuscular disorders, the methodology and indications of diaphragm ultrasound imaging as well as possible pitfalls in the interpretation of results.

Respiratory involvement in neuromuscular disorders

PURPOSE OF REVIEW

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

RECENT FINDINGS

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

SUMMARY

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

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

BACKGROUND

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

SURVEILLANCE AND PULMONARY FUNCTION TESTS

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

LOWER AIRWAY OBSTRUCTION

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

PATIENT-CENTERED MANAGEMENT

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

Diaphragmatic thickness ratio (inspiratory/expiratory) as a diagnostic method of diaphragmatic palsy associated with interescalene block

INTRODUCTION

Diaphragmatic paralysis is a side-effect associated with interscalene block. Thickness index of the diaphragm muscle (inspiratory thickness/expiratory thickness) obtained by ultrasound has recently been introduced in clinical practice for diagnosis of diaphragm muscle atrophy. Our objective was to evaluate this index for the diagnosis of acute phrenic paresis associated with interscalene block.

PATIENTS AND METHODS

We designed an observational study in 22 patients scheduled for shoulder arthroscopy. Spirometry was performed (criteria of phrenic paresis was a decrease in FVC and FEV1 ≥20%). Ultrasound apposition zone was assessed in anterior axillary line and diaphragmatic displacement was evaluated on inspiration and expiration (number of intercostal spaces; phrenic paresis considered a reduction ≥25%) and thickness of the diaphragm muscle (a phrenic paresis was considered an index <1.2). These determinations were performed before and at 20min after interscalene block at C5-C6 with 20ml of 0.5% ropivacaine.

RESULTS

Twenty-one patients (95%) presented phrenic nerve block according to one or more of the methods used. One patient did not show any symptoms or signs suggestive of phrenic paralysis and was excluded. All the patients presented phrenic paresis based on the diaphragmatic thickness index, with the pre-block index being 1.8±0.5 and post-block of 1.05±0.06 (P<0.001). Ninety percent of the patients (19) presented phrenic paresis according to spirometry and all the patients had a reduction in diaphragmatic movement after the block (from 1.9±0.5 intercostal spaces to 0.5±0.3; P<0.001).

CONCLUSION

The index of inspiratory / expiratory diaphragmatic thickness at cut-off <1.2 seems to be useful in the diagnosis of phrenic paresis associated with interscalene block. This index does not require a baseline pre-assessment.

Diaphragm Dysfunction in Mechanically Ventilated Patients

Muscle involvement is found in most critical patients admitted to the intensive care unit (ICU). Diaphragmatic muscle alteration, initially included in this category, has been differentiated in recent years, and a specific type of muscular dysfunction has been shown to occur in patients undergoing mechanical ventilation. We found this muscle dysfunction to appear in this subgroup of patients shortly after the start of mechanical ventilation, observing it to be mainly associated with certain control modes, and also with sepsis and/or multi-organ failure. Although the specific etiology of process is unknown, the muscle presents oxidative stress and mitochondrial changes. These cause changes in protein turnover, resulting in atrophy and impaired contractility, and leading to impaired functionality. The term 'ventilator-induced diaphragm dysfunction' was first coined by Vassilakopoulos et al. in 2004, and this phenomenon, along with injury cause by over-distention of the lung and barotrauma, represents a challenge in the daily life of ventilated patients. Diaphragmatic dysfunction affects prognosis by delaying extubation, prolonging hospital stay, and impairing the quality of life of these patients in the years following hospital discharge. Ultrasound, a non-invasive technique that is readily available in most ICUs, could be used to diagnose this condition promptly, thus preventing delays in starting rehabilitation and positively influencing prognosis in these patients.