Diaphragm and Phrenic Nerve Ultrasound in COVID-19 Patients and Beyond: Imaging Technique, Findings, and Clinical Applications

Predictive Value of Diaphragm Muscle Ultrasound for Ventilator Weaning Outcomes After Cervical Spinal Cord Injury: A Retrospective Case Series

OBJECTIVES

Neuromuscular respiratory failure after cervical spinal cord injury (cSCI) can lead to dependence on an invasive mechanical ventilator. Ventilator-free breathing after cSCI is associated with improved morbidity, mortality, and quality of life. We investigated the use of diaphragm muscle ultrasound to predict ventilator weaning outcomes after cSCI.

METHODS

This is a retrospective case series conducted at a university-affiliated freestanding inpatient rehabilitation facility. We identified patients with cSCI who had a tracheostomy and were dependent on an invasive mechanical ventilator at the time of admission to inpatient rehabilitation. A diaphragm muscle ultrasound was performed, which included measurements of the thickness of the diaphragm and a calculation of the thickening ratio (TR), which reflects diaphragm muscle contraction. The primary outcome measure was the need for mechanical ventilation at time of discharge from the inpatient rehabilitation facility. Successful ventilator weaning was defined as either daytime or full 24-hour ventilator-free breathing.

RESULTS

Of the 21 patients enrolled, 11 (52%) were able to wean successfully (partially or fully) from the ventilator. Of the ultrasound measurements that were taken, the TR was the optimal predictor for ventilator weaning outcomes. A threshold of TR ≥ 1.2 as the maximum hemidiaphragm measurement had a sensitivity of 1.0 and specificity of 0.90 for predicting ventilator weaning.

CONCLUSION

Normal diaphragm contractility (TR ≥ 1.2) as determined by diaphragm muscle ultrasound is a strong positive predictor for successful ventilator weaning in patients with cSCI. Utilizing diaphragm ultrasound, rehabilitation physicians can set precision rehabilitation goals regarding ventilator weaning for inpatients with respiratory failure after cSCI, potentially improving both outcomes and quality of life.

Poor Correlation between Diaphragm Ultrasound and Invasive Gold Standard Technique Derived Respiratory Muscle Strength Assessment in Patients after Hospitalisation for COVID-19

INTRODUCTION

Individuals who survive acute coronavirus disease 2019 (COVID-19) might experience diaphragm muscle weakness. Diaphragm ultrasound may be an easy-to-obtain bedside tool for determining diaphragm function. However, twitch transdiaphragmatic pressure (twPdi) following magnetic stimulation (MS) of the phrenic nerves is the gold standard for non-volitional assessment of diaphragm strength. This study investigated whether diaphragm thickening ratio (DTR) measured on diaphragm ultrasound reflects diaphragm strength as measured by twPdi following MS of the phrenic nerves or other (volitional) invasively obtained pressure values and could therefore be used to accurately diagnose diaphragm weakness.

METHODS

One year after discharge, 50 individuals (14 female, age 58 ± 12 years) who had been hospitalised and treated for moderate-severe COVID-19 underwent standard spirometry and diaphragm ultrasound. TwPdi following cervical MS of the phrenic nerve and volitional inspiratory manoeuvres (Sniff and Mueller manoeuvre) were measured using oesophageal and gastric balloon catheters after transnasal placement.

RESULTS

At follow-up, no clinically meaningful restrictive lung function impairment was evident on spirometry. On diaphragm ultrasound, diaphragm dysfunction, i.e., an impaired DTR was detected in 24% (12/50) of participants. An objective diagnosis of diaphragm dysfunction, defined as twPdi <16 cm H2O, was made in 60% (30/50) of participants. The measurement results of the two methods did not agree, given that there were many false-negative but also false-positive results, so diaphragm ultrasound diagnosed in parts other patients with diaphragm dysfunction than twPdi. Diaphragm ultrasound had a sensitivity of 26.67% and a specificity of 80.0% in the detection of diaphragm dysfunction (positive predictive value 66.67%, negative predictive value 42.10%).

CONCLUSION

Diagnosis of diaphragm weakness in individuals who have recovered from COVID-19 cannot be made accurately on diaphragm ultrasound (via DTR) but requires twPdi as the gold standard for assessment of diaphragm strength.

Impact of COVID-19 on Diaphragmatic Function: Understanding Multiorgan Involvement and Long-Term Consequences

The COVID-19 pandemic has brought significant attention to the respiratory system, with much focus on lung-related disorders. However, the diaphragm, a crucial component of respiratory physiology, has not been adequately studied, especially in the context of long COVID. This review explores the multipotential role of the diaphragm in both respiratory health and disease, emphasizing its involvement in long-term complications following SARS-CoV-2 infection. The diaphragm's fundamental role in respiratory physiology and its impact on balance and posture control, breathing patterns, and autonomic nervous system regulation are discussed. This review examines complications arising from COVID-19, highlighting the diaphragm's involvement in neurological, musculoskeletal, and inflammatory responses. Particular attention is given to the neuroinvasive impact of SARS-CoV-2, the inflammatory response, and the direct viral effects on the diaphragm. The diaphragm's role in long COVID is explored, with a focus on specific symptoms such as voice disorders, pelvic floor dysfunction, and sleep disturbances. Diagnostic challenges, current methods for assessing diaphragmatic dysfunction, and the complexities of differentiating it from other conditions are also explored. This article is the first to comprehensively address diaphragmatic dysfunction resulting from COVID-19 and long COVID across various physiological and pathological aspects, offering a new perspective on its diagnosis and treatment within a multisystem context.

Obesity-related reduced spirometry and altered breathing pattern are associated with mechanical disadvantage of the diaphragm

The aim of this study was to characterize the breathing patterns of individuals with obesity during routine activities such as sitting and standing, and to identify potential contributors to alterations in these patterns. Measurements performed in 20 male subjects with obesity (BMI, 31.8±1.5 kg/m2) and 20 controls (BMI, 23.5±1.4 kg/m2) included anthropometric parameters, breathing-patterns in sitting and standing positions, spirometry, maximal respiratory pressures, and diaphragm B-mode ultrasonography. Individuals with obesity exhibited lower tidal volume and increased respiratory rate to maintain a similar minute-ventilation (p<0.05). Subjects with obesity demonstrated impaired spirometry and respiratory muscle strength, with inspiratory functions being notably compromised (p<0.05). Individuals with obesity had a greater diaphragm thickness at end inspiration but lower thickening-fraction at end quiet and forced breathings and reduced diaphragmatic displacement and excursion during maximal breaths (p<0.05). BMI was negatively associated with all respiratory function markers (p<0.05). Individuals with obesity exhibit a higher respiratory rate but lower tidal volume, likely to accommodate decreased compliance and excess thoracic and abdominal fat, further hindering inspiratory function. Moreover, increased adiposity is associated with a thicker but weaker diaphragm, primarily due to the diaphragm's mechanical disadvantage rather than its intrinsic inability to generate force.

Sonographic Phrenic Nerve Changes in Amyotrophic Lateral Sclerosis

Amyotrophic lateral sclerosis (ALS) is a progressive neurodegenerative disease that affects both the upper and lower motor neurons in the nervous system, causing muscle weakness and severe disability. The progressive course of the disease reduces the functional capacity of the affected patients, limits daily activities, and leads to complete dependence on caregivers, ultimately resulting in a fatal outcome. Respiratory dysfunction mostly occurs later in the disease and is associated with a worse prognosis. Forty-six participants were included in our study, with 23 patients in the ALS group and 23 individuals in the control group. The ultrasound examination of the phrenic nerve (PN) was performed by two authors using a high-resolution "Philips EPIQ 7" ultrasound machine with a linear 4-18 MHz transducer. Our study revealed that the phrenic nerve is significantly smaller on both sides in ALS patients compared to the control group (p < 0.001). Only one significant study on PN ultrasound in ALS, conducted in Japan, also showed significant results (p < 0.00001). These small studies are particularly promising, as they suggest that ultrasound findings could serve as an additional diagnostic tool for ALS.

Exercise Position to Improve Synergy Between the Diaphragm and Pelvic Floor Muscles in Women With Pelvic Floor Dysfunction: A Cross Sectional Study

OBJECTIVE

This study aimed to investigate the synergy between the diaphragm and pelvic floor muscles (PFM) according to different exercise positions in women with pelvic floor dysfunction. Our secondary aim was to determine the short-term effects of single-week pelvic floor muscle training (PFMT) program on diaphragmatic function.

METHODS

The cross-sectional study included 64 women with pelvic floor dysfunction. The participants' diaphragm and abdominal muscle functions during voluntary PFM contraction and relaxation were assessed by surface electromyography and ultrasonography. The surface electromyography assessments were performed in supine (P1), crawling (P2) and sitting (P3) positions. A single week-PFMT was conducted on women who agreed to determine the short-term responses of the diaphragm function. The muscle functions according to exercise positions were compared with Friedman Analysis of Variance, and the short-term effects of single-week PFMT on diaphragm function was analyzed with Wilcoxon Signed-Ranks Test.

RESULTS

The diaphragm activity during voluntary PFM contraction was highest in P2 before and after single-week PFMT (P < .001). Positive significant correlations were found between the activities diaphragm and abdominal muscles in different exercise positions (P < .05). After single-week PFMT, diaphragm thickness increased (P = .030) in P1, but diaphragm activity did not change in all 3 exercise positions (P > .05).

CONCLUSION

The synergy between the diaphragm and PFM was greater in the crawling position in women with pelvic floor dysfunction. The abdominal muscles seemed to contribute to maintaining this synergy. Therefore, PFMT combined with diaphragmatic breathing exercises in the crawling position should be considered. In addition, single-week PFMT may positively affect diaphragm function in the short-term.

Research on clinical-paraclinical and evolutive aspects in pati-ents with post spinal cord injury (SCI) statuses and Covid-19 – a systematic literature review

The COVID-19 pandemic has generated a lot of interest among doctors as well as scientists around the world. Studies on the impact of the Covid-19 pandemic, including in people with post SCI sufferance, are ongoing, aiming to understand the pathophysiological mechanisms of SARS-CoV2 in target tissues, to optimize related methods of diagnosis and treatment in both, in-itial and later phases of the disease – e.g.: ”long Covid” status – and thus, to make a substantial contribution to the quality of life improvement of the affected patients. After using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (acronym PRISMA) method to quest for afferent knowledge, it resulted a quite small number (12) of arti-cles, most of them indirectly approaching this topic. Therefore, is important to deepen this niche – which is scarcely approached – in order to find new therapeutic approaches able to combat COVID-19-associated to SCI manifestations – like, for instance, to check whether the principle of intermittent hypoxia treatment is effective and worth to be included in the rehabilitation treat-ment protocols – as neither an indubitable effective drug or vaccine, or respectively, cure for SCI, has been provided so far.

Lung Transplantation for Coronavirus Disease-2019 Patients and Coronavirus Disease-2019 in Lung Transplant Recipients

Lung transplant is a life-saving treatment for carefully selected patients with respiratory failure related to the infection with coronavirus disease-2019. Despite a complex pretransplant medical course, the posttransplant outcomes are excellent when performed by experienced centers.

Echocardiography and Lung Ultrasound in Long COVID and Post-COVID Syndrome, a Review Document of the Austrian Society of Pneumology and the Austrian Society of Ultrasound in Medicine

Lung ultrasound has the potential to enable standardized follow-up without radiation exposure and with lower associated costs in comparison to CT scans. It is a valuable tool to follow up on patients after a COVID-19 infection and evaluate if there is pulmonary fibrosis developing. Echocardiography, including strain imaging, is a proven tool to assess various causes of dyspnea and adds valuable information in the context of long COVID care. Including two-dimensional (2D) strain imaging, a better comprehension of myocardial damage in post-COVID syndrome can be made. Especially 2D strain imaging (left and the right ventricular strain) can provide information about prognosis.

Lung transplantation in patients with lung disease secondary to coronavirus disease 2019 infection

PURPOSE OF REVIEW

In this article, we describe preoperative patient selection and outcomes of patients with lung disease secondary to infection from COVID-19 who receive lung transplantation.

RECENT FINDINGS

Lung transplants for patients with lung disease secondary to infection from COVID-19 have been performed successfully in over 200 patients in the United States. The preoperative course of these patients is somewhat atypical in comparison with patients who have had lung transplants related to chronic lung diseases, where there are more traditional indications for lung transplants. COVID-19 patients have more severe pulmonary disease often requiring mechanical ventilation and extracorporeal mechanical ventilation (ECMO), frequent nosocomial infections, and renal and cardiac dysfunction. The intraoperative course of these COVID-19 patients is often longer and requires increased transfusions of blood products in comparison with non-COVID-19 patients. Additionally, in the postoperative period, COVID-19 patients more frequently require mechanical ventilation and ECMO support. However, the survival rate of such patients at 6 months is greater than 90%.

SUMMARY

Patients with respiratory failure secondary to COVID-19 infection that require a lung transplant generally have a complicated preoperative course and the operations are more complex, but the long-term outcomes are excellent.

Persistent unilateral diaphragmatic paralysis in the course of Coronavirus Disease 2019 pneumonia: a case report

Coronavirus Disease 2019 infections can cause a wide range of symptoms, particularly in the respiratory system. Diaphragmatic paralysis is a rare condition that is poorly documented in the literature. We present the case of a 38-year-old Caucasian male adult who developed unilateral diaphragmatic paralysis during the course of the disease. The patient presented to the Emergency Department with fever, cough, and dyspnea, was admitted, and was immediately fitted with a high flow nasal cannula. When his condition worsened eight days later, he was admitted to the Intensive Care Unit and a tracheostomy was performed. A CT scan of the chest revealed significant left diaphragm elevation. On the 48th day, the patient gradually improved and was discharged. The paralysis of the diaphragm persisted three months later in the follow-up examination. This case illustrates a possible neuromuscular virus invasion that may have an impact on the patient's health after discharge.

The effects of COVID-19 on respiratory muscle performance: making the case for respiratory muscle testing and training

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection results in multiorgan damage primarily mediated by viral infiltration via angiotensin-converting enzyme-2 receptors on the surface of cells. A primary symptom for many patients is exertional dyspnoea which may persist even beyond recovery from the viral infection. Respiratory muscle (RM) performance was hypothesised as a contributing factor to the severity of coronavirus disease 2019 (COVID-19) symptoms, such as dyspnoea, and outcomes. This was attributed to similarities between patient populations at elevated risk for severe COVID-19 symptoms and those with a greater likelihood of baseline RM weakness and the effects of prolonged mechanical ventilation. More recent evidence suggests that SARS-CoV-2 infection itself may cause damage to the RM, and many patients who have recovered report persistent dyspnoea despite having mild cases, normal lung function or undamaged lung parenchyma. These more recent findings suggest that the role of RM in the persistent dyspnoea due to COVID-19 may be more substantial than originally hypothesised. Therefore, screening for RM weakness and providing interventions to improve RM performance appears to be important for patients with COVID-19. This article will review the impact of SARS-CoV-2 infection on RM performance and provide clinical recommendations for screening RM performance and treatment interventions.

Advances in diagnostic tools for respiratory tract infections: from tuberculosis to COVID-19 - changing paradigms?

Respiratory tract infections (RTIs) are one of the most common reasons for seeking healthcare, but are amongst the most challenging diseases in terms of clinical decision-making. Proper and timely diagnosis is critical in order to optimise management and prevent further emergence of antimicrobial resistance by misuse or overuse of antibiotics. Diagnostic tools for RTIs include those involving syndromic and aetiological diagnosis: from clinical and radiological features to laboratory methods targeting both pathogen detection and host biomarkers, as well as their combinations in terms of clinical algorithms. They also include tools for predicting severity and monitoring treatment response. Unprecedented milestones have been achieved in the context of the COVID-19 pandemic, involving the most recent applications of diagnostic technologies both at genotypic and phenotypic level, which have changed paradigms in infectious respiratory diseases in terms of why, how and where diagnostics are performed. The aim of this review is to discuss advances in diagnostic tools that impact clinical decision-making, surveillance and follow-up of RTIs and tuberculosis. If properly harnessed, recent advances in diagnostic technologies, including omics and digital transformation, emerge as an unprecedented opportunity to tackle ongoing and future epidemics while handling antimicrobial resistance from a One Health perspective.

The Possible Impact of COVID-19 on Respiratory Muscles Structure and Functions: A Literature Review

The impact of SARS-CoV-2 infection on respiratory muscle functions is an important area of recent enquiry. COVID-19 has effects on the respiratory muscles. The diaphragm muscle is perturbed indirectly due to the mechanical-ventilation-induced-disuse, but also by direct mechanisms linked with SARS-CoV-2 viral infection. In this sense, a deeper understanding of the possible links between COVID-19 and alterations in structure and functions of the respiratory muscles may increase the success rate of preventive and supportive strategies. Ultrasound imaging alongside respiratory muscle strength tests and pulmonary function assessment are valid approaches to the screening and monitoring of disease, for mild to severe patients. The aim of the present review is to highlight the current literature regarding the links between COVID-19 and respiratory muscle functions. We examine from the pathophysiological aspects of disease, up to approaches taken to monitor and rehabilitate diseased muscle. We hope this work will add to a greater understanding of the pathophysiology and disease management of respiratory muscle pathology subsequent to SARS-CoV-2 infection.

COVID-19 associated phrenic nerve mononeuritis: a case series

This study characterised the hemidiaphragm elevation on 3-month interval chest X-rays (CXRs) of patients post COVID-19 pneumonia. 467 CXRs were screened; 19 (4.1%) had an elevated hemidiaphragm. There were 15 (3.2%) patients of interest with new hemidiaphragm elevation, persisting on average 7 months post COVID-19 diagnosis. Symptomatic patients underwent diaphragm ultrasound (n=12), pulmonary function test (n=10), muscle function test (n=6) and neurophysiology (n=5), investigating phrenic nerve function. Ultrasound demonstrated reduced/paradoxical diaphragmatic movements in eight; four of eight had reduced thickening fraction. Neurophysiology peripheral limb studies did not support the differential diagnoses of critical illness neuropathy/myopathy. We propose that, in selected patients, COVID-19 may cause phrenic nerve mononeuritis.

Frailty and senile apathy in the everyday clinical practice in the conditions of COVID-19

The article covers the pathogenesis, clinical manifestations, and diagnostic criteria of frailty and senile apathy in the elderly. Special attention is paid to sarcopenia: the phenotypic classification and modern approaches to the treatment are discussed. The knowledge and understanding of the main pathogenetic links of sarcopenia, frailty and senile apathy, as well as the development of a single therapeutic line for these pathological conditions can significantly improve the life quality and expectancy of the elderly.

Bilateral diaphragmatic dysfunction: A cause of persistent dyspnea in patients with post-acute sequelae of SARS-CoV-2

Persistent shortness of breath is one of the most common concerns reported by patients with post-acute sequelae of SARS-CoV-2. Here, we present a case of bilateral diaphragmatic paralysis as a cause shortness of breath that developed after SARS-CoV-2 infection. A middle-aged gentleman with history of sleep apnea and body mass index 27.9 kg/m2 presented to our post-COVID clinic with 3 months of dyspnea and orthopnea after contracting SARS-CoV-2 in November 2020. During acute infection, he was hospitalized for hypoxemia, which improved with steroids and supplemental oxygen. At 3 months, he continued to report dyspnea and orthopnea. On examination, he had tachycardia and increased respiratory rate with paradoxical respiratory abdominal movement. Chest imaging showed elevated bilateral hemidiaphragms without any parenchymal lung disease. Pulmonary function test revealed severe ventilatory defect with restrictive lung disease. He was diagnosed with bilateral diaphragmatic dysfunction which was confirmed by absence of evoked potentials in diaphragm after phrenic nerve stimulation bilaterally. He was advised to use continuous positive airway pressure machine to assist with breathing at night. At his last follow-up (1-year post-infection), he was symptomatically improving without specific interventions.

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.

Implantation and Control of Wireless, Battery-free Systems for Peripheral Nerve Interfacing

Peripheral nerve interfaces are frequently used in experimental neuroscience and regenerative medicine for a wide variety of applications. Such interfaces can be sensors, actuators, or both. Traditional methods of peripheral nerve interfacing must either tether to an external system or rely on battery power that limits the time frame for operation. With recent developments of wireless, battery-free, and fully implantable peripheral nerve interfaces, a new class of devices can offer capabilities that match or exceed those of their wired or battery-powered precursors. This paper describes methods to (i) surgically implant and (ii) wirelessly power and control this system in adult rats. The sciatic and phrenic nerve models were selected as examples to highlight the versatility of this approach. The paper shows how the peripheral nerve interface can evoke compound muscle action potentials (CMAPs), deliver a therapeutic electrical stimulation protocol, and incorporate a conduit for the repair of peripheral nerve injury. Such devices offer expanded treatment options for single-dose or repeated dose therapeutic stimulation and can be adapted to a variety of nerve locations.