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Patients with acute respiratory distress syndrome (ARDS) require periods of deep sedation and mechanical ventilation, leading to diaphragm dysfunction. Our study seeks to determine whether the combination of temporary transvenous diaphragm neurostimulation (TTDN) and mechanical ventilation changes the degree of diaphragm injury and cytokines concentration in a preclinical ARDS model. Moderate ARDS was induced in pigs using oleic acid, followed by ventilation for 12 hours post-injury with volume-control at 8 ml/kg, PEEP 5 cmH2O, respiratory rate and FiO2 set to achieve normal arterial blood gases. Two groups received TTDN: every second breath (MV+TTDN50%, n=6) or every breath (MV+TTDN100%, n=6). One group received ventilation only (MV, n=6). Full thickness diaphragm and quadricep muscle biopsies were taken at study end. Samples were fixed and stained with Hematoxylin and Eosin and a point counting technique was applied to calculate abnormal muscle area fraction. Cytokine concentrations were measured in homogenized tissue using porcine-specific ELISA and compared to serum samples. Percentage of abnormal diaphragm tissue was different between MV (8.1% (6.0-8.8)) vs. MV+TTDN50% (3.4% (2.1-4.8)), p=0.010 and MV vs. MV+TTDN100% (3.1% (2.5-4.0)), p=0.005. Percentage of abnormal quadriceps tissue was not different between groups. Cytokine concentration patterns in diaphragm samples were different between all groups (p<0.001) and the interaction between TTDN application and resultant cytokine concentration pattern was significant (p=0.025). TTDN, delivered in synchrony with mechanical ventilation, mitigated diaphragm injury, as evidenced by less abnormal tissue in the diaphragm samples, in pigs with oleic acid-induced ARDS and is an exciting tool for lung and diaphragm-protective ventilation.

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The utilization of a radical robotic thymectomy, with clearance of the mediastinal tissue between the two phrenic nerves for a thymoma, is well established. The complex mediastinal anatomy, limited space and the location of the heart introduce a distinctive challenge, particularly when adopting a right-sided approach to identify and dissect along the left phrenic nerve. We present our technique for performing a robotic radical thymectomy from a right-sided approach, tailored for a localized thymoma. Our goal is to showcase the efficacy and safety of this method, offering insights that can enhance surgical outcomes.

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We present the case of an 18-year-old male with a ventriculoperitoneal (VP) shunt for hydrocephalus who experienced right shoulder pain. The patient was thoroughly investigated for gastrointestinal disease, including abdominal ultrasound and upper endoscopy, which revealed no abnormalities that could explain his symptoms. X-ray imaging subsequently revealed that the shunt's distal peritoneal tubing was positioned in a supra-hepatic subdiaphragmatic location. Surgical shortening and repositioning of the peritoneal tubing successfully alleviated the patient's shoulder pain. A review of the literature uncovered four articles, comprising a total of six patients, who exhibited similar symptoms of shoulder pain linked to their VP shunts. Given the rarity of this complication, it can be easily overlooked or misdiagnosed. It is crucial for physicians to consider this possibility when evaluating patients with VP shunts who present with shoulder pain to ensure prompt and effective treatment.

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BACKGROUND: In the United States in 2017, there were an estimated 903,745 hospitalizations involving mechanical ventilation (MV). Complications from ventilation can result in longer hospital stays, increased risk of disability, and increased healthcare costs. It has been hypothesized that electrically pacing the diaphragm by phrenic nerve stimulation during mechanical ventilation may minimize or reverse diaphragm dysfunction, resulting in faster weaning. METHODS: The ReInvigorate Trial is a prospective, multicenter, randomized, controlled clinical trial evaluating the safety and efficacy of Stimdia's pdSTIM System for facilitating weaning from MV. The pdSTIM system employs percutaneously placed multipolar electrodes to stimulate the cervical phrenic nerves and activate contraction of the diaphragm bilaterally. Patients who were on mechanical ventilation for at least 96 h and who failed at least one weaning attempt were considered for enrollment in the study. The primary efficacy endpoint was the time to successful liberation from mechanical ventilation (treatment vs. control). Secondary endpoints will include the rapid shallow breathing index and other physiological and system characteristics. Safety will be summarized for both primary and additional analyses. All endpoints will be evaluated at 30 days or at the time of removal of mechanical ventilation, whichever is first. DISCUSSION: This pivotal study is being conducted under an investigational device exception with the U.S. Food and Drug Administration. The technology being studied could provide a first-of-kind therapy for difficult-to-wean patients on mechanical ventilation in an intensive care unit setting. TRIAL REGISTRATION: Clinicaltrials.gov, NCT05998018 , registered August 2023.

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INTRODUCTION: Pulsed-field ablation (PFA) is a novel nonthermal energy that shows unique features that can be of use beyond pulmonary vein ablation, like tissue selectivity or proximity rather than contact dependency. METHODS AND RESULTS: We report three cases of right focal atrial tachycardias arising from the superior cavoatrial junction and the crista terminalis, in close relationship with the phrenic nerve, effectively ablated using a commercially available PFA catheter designed for pulmonary vein isolation without collateral damage. CONCLUSION: PFA can be useful for treating right atrial tachycardias involving sites near the phrenic nerve, avoiding the need for complex nerve-sparing strategies.

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INTRODUCTION/AIMS: Phrenic neuropathy (PhN) impairs diaphragm muscle function, causing a spectrum of breathing disability. PhN etiologies and their natural history are ill-defined. This knowledge gap hinders informed prognosis and management decisions. This study aims to help fill this knowledge gap on PhN etiologies, outcomes, and recovery patterns, especially in the context of nonsurgical clinical practice. METHODS: This was a retrospective study from two interdisciplinary clinics, physiatry and neurology based. Patients were included if PhN was identified, and other causes of hemi-diaphragm muscle dysfunction excluded. Patients were followed serially at the discretion of the neuromuscular-trained neurologist or physiatrist. Recovery was assessed using pulmonary function tests (PFTs), diaphragm muscle ultrasound (US) thickening ratio, and patient-reported outcomes in patients presenting within 2 years of PhN onset. RESULTS: We identified 151 patients with PhN. The most common etiologies were idiopathic (27%), associated with cardiothoracic procedure (24%), and intensive care unit (17%). Of these patients, 117 (77%) were evaluated within 2 years of PhN onset. Of patients included in outcome analyses, 64% saw improvement on serial US, 50% on serial PFTs and 79% reported symptomatic improvement at an average of 15, 16, and 17 months, respectively. DISCUSSION: A clear majority of PhN patients show improvement in diaphragm muscle function, but on average, improvements took 15-17 months depending on the assessment type. These insights are vital for developing tailored treatments and can guide physicians in prognosis and decision-making, especially if more invasive interventions are being considered.

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A major portion of spinal cord injury (SCI) cases occur in the cervical region, where essential components of the respiratory neural circuitry are located. Phrenic motor neurons (PhMNs) housed at cervical spinal cord level C3-C5 directly innervate the diaphragm, and SCI-induced damage to these cells severely impairs respiratory function. In this study, we tested a biomaterial-based approach aimed at preserving this critical phrenic motor circuitry after cervical SCI by locally delivering hepatocyte growth factor (HGF). HGF is a potent mitogen that promotes survival, proliferation, migration, repair, and regeneration of a number of different cell and tissue types in response to injury. We developed a hydrogel-based HGF delivery system that can be injected into the intrathecal space for local delivery of high levels of HGF without damaging the spinal cord. Implantation of HGF hydrogel after unilateral C5 contusion-type SCI in rats preserved diaphragm function, as assessed by in vivo recordings of both compound muscle action potentials and inspiratory electromyography amplitudes. HGF hydrogel also preserved PhMN innervation of the diaphragm, as assessed by both retrograde PhMN tracing and detailed neuromuscular junction morphological analysis. Furthermore, HGF hydrogel significantly decreased lesion size and degeneration of cervical motor neuron cell bodies, as well as reduced levels surrounding the injury site of scar-associated chondroitin sulfate proteoglycan molecules that limit axon growth capacity. Our findings demonstrate that local biomaterial-based delivery of HGF hydrogel to injured cervical spinal cord is an effective strategy for preserving respiratory circuitry and diaphragm function.

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Mutual interactions between the diaphragm and lung transplantation (LTx) are known to exist. Before LTx, many factors can exert notable impact on the diaphragmatic function, such as the underlying respiratory disease, the comorbidities, and the chronic treatments of the patient. In the post-LTx setting, even the surgical procedure itself can cause a stressful trauma to the diaphragm, potentially leading to morphological and functional alterations. Conversely, the diaphragm can significantly influence various aspects of the LTx process, ranging from graft-to-chest cavity size matching to the long-term postoperative respiratory performance of the recipient. Despite this, there are still no standard criteria for evaluating, defining, and managing diaphragmatic dysfunction in the context of LTx to date. This deficiency hampers the accurate assessment of those factors which affect the diaphragm and its reciprocal influence on LTx outcomes. The objective of this narrative review is to delve into the complex role the diaphragm plays in the different stages of LTx and into the modifications of this muscle following surgery.

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BACKGROUND: Traumatic high cervical spinal cord injury (SCI) can result in a devastating loss of functional respiration, leaving patients permanently dependent on mechanical ventilation. Nerve transfer is a promising reinnervation strategy that has the potential to restore connectivity in paralyzed distal muscles. The spinal accessory nerve (SAN) remains functional in most cases after high cervical SCI and can serve as a donor to reinnervate the phrenic nerve (PN), thereby improving diaphragmatic function. OBSERVATIONS: Information regarding thorough physical, electrodiagnostic, and pulmonary assessments to establish candidacy for nerve transfer, as well as the surgical procedure, was summarized with an illustrative case. The patient demonstrated improvement in pulmonary function testing but did not achieve independent respiration. A systematic literature review identified 3 studies with 9 additional patients who had undergone SAN-to-PN transfer. The nerve transfer meaningfully restored diaphragmatic function, improving pulmonary function tests and reducing ventilator dependency. LESSONS: Respiratory dependency significantly impacts the quality of life of patients with a high cervical SCI. The use of the lower SAN motor branch for PN transfer is safe and does not result in a meaningful downgrade in trapezius function. Outcomes following this procedure are promising but heterogeneous, indicating a need for significant innovation and improvement for future therapies. https://thejns.org/doi/10.3171/CASE24236.

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Phrenic nerve stimulation is currently being investigated for the prevention of diaphragm atrophy in patients with mechanically supported breathing. Patients receiving breathing support from mechanical ventilation are at risk of mismatches between respiratory demand and ventilator support. Our objectives were to determine if a novel phrenic nerve stimulation device provided stimulation during inspiration as intended and did not exacerbate any potential discordances. A benchtop electromechanical simulation model was developed to validate phrenic nerve stimulation with simulated breathing. The phrenic nerve stimulation device was evaluated with a mechanical ventilator attached to a breathing simulator. The trigger ratio and time lag between phrenic nerve stimulation and mechanical ventilation was measured for multiple disease and ventilator parameters. For the 1:1 breath trigger ratio test, 99.79% of intended stimulation breaths received stimulation at the correct time. For the 1:4 breath trigger ratio test, 99.72% of intended stimulation breaths received stimulation at the correct time. For trigger lag times for the inspiratory and expiratory phases, the mean inspiratory lag was 36.10 ± 10.50 ms and 16.61 ± 3.61 ms, respectively. The following discordance scenarios were evaluated in conjunction with simulated phrenic nerve stimulation: asynchrony-false trigger, dyssynchrony-early trigger, dyssynchrony-late trigger, dyssynchrony-early cycling, dyssynchrony-late cycling. Testing demonstrated none of these discordances were exacerbated by the simulated phrenic nerve stimulation. The novel phrenic nerve stimulation device delivered electrical stimulation therapy as intended and did not exacerbate any simulated discordances.

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PURPOSE: Phrenic nerve stimulation (PNS) was approved by the Food and Drug Administration (FDA) to treat moderate to severe central sleep apnea. We report here, results of a retrospective study regarding our institutional outcomes at one year. In this study we evaluated the change in the apnea hypopnea index, epworth sleepiness score, and functional outcomes of sleep score at one year post implant. METHODS: This is a retrospective analysis of patients ≥ 18 years of age who had PNS implanted for moderate to severe CSA at the Ohio State University Wexner Medical Center apnea between Feb 1, 2018 to July 1, 2021. Sleep disordered breathing parameters and objective sleepiness as measured by the Epworth Sleepiness Scale (ESS) scores, and Functional Outcomes of Sleep Questionnaire (FOSQ) scores were assessed at baseline and one-year post-implant. RESULTS: Twenty-two patients were implanted with PNS at OSU between February 1, 2018 and May, 31, 2022. The AHI showed a statistically significant decrease from a median of 40 events/hour at baseline to 18 at follow-up (p-value = 0.003). The CAI decreased from 16 events/hour to 2 events/hour (p-value of 0.001). The obstructive apnea index, mixed apnea index, and hypopnea index did not significantly change. The ESS scores had a statistically significant improvement from a median score of 12 to 9 (p-value = 0.028). While the FOSQ showed a trend to improvement from 15.0 to 17.8, it was not statistically significant (p-value of 0.086). CONCLUSION: Our study found that PNS therapy for moderate to severe CSA improves overall AHI and CAI. Objective sleepiness as measured by the ESS also improved at one-year post implant.

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AIMS: Right phrenic nerve (RPN) injury is a disabling but uncommon complication of atrial fibrillation (AF) radiofrequency ablation. Pace-mapping is widely used to infer RPN's course, for limiting the risk of palsy by avoiding ablation at capture sites. However, information is lacking regarding the distance between the endocardial sites of capture and the actual anatomic RPN location. We aimed at determining the distance between endocardial sites of capture and anatomic CT location of the RPN, depending on the capture threshold. METHODS AND RESULTS: In consecutive patients undergoing AF radiofrequency ablation, we defined the course of the RPN on the electroanatomical map with high-output pacing at up to 50 mA/2 ms, and assessed RPN capture threshold (RPN-t). The true anatomic course of the RPN was delineated and segmented using CT scan, then merged with the electroanatomical map. The distance between pacing sites and the RPN was assessed. In 45 patients, 1033 pacing sites were analysed. Distances from pacing sites to RPN ranged from 7.5 ± 3.0 mm (min 1) when RPN-t was ≤10 mA to 19.2 ± 6.5 mm (min 9.4) in cases of non-capture at 50 mA. A distance to the phrenic nerve > 10 mm was predicted by RPN-t with a ROC curve area of 0.846 [0.821-0.870] (P < 0.001), with Se = 80.8% and Sp = 77.5% if RPN-t > 20 mA, Se = 68.0% and Sp = 91.6% if RPN-t > 30 mA, and Se = 42.4% and Sp = 97.6% if non-capture at 50 mA. CONCLUSION: These data emphasize the utility of high-output pace-mapping of the RPN. Non-capture at 50 mA/2 ms demonstrated very high specificity for predicting a distance to the RPN > 10 mm, ensuring safe radiofrequency delivery.

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Inferior phrenic artery (IPA) aneurysms are the rarest type of visceral aneurysms. It usually occurs secondary to trauma, surgery, or as a complication of pancreatitis. In addition, it can be a manifestation of underlying systemic pathology such as vasculitis, collagen vascular disorders, sepsis, or segmental arterial mediolysis. It can be associated with hypertension in 43% of cases. The presentation of IPA aneurysm is nonspecific with abdominal pain, melena, hematochezia, and anemia. The ruptured and actively bleeding aneurysm can lead to hemorrhagic shock, and immediate management is required with angiography and endovascular embolization with coil or gel foam or stent etc. Inaccessible locations are reached with surgical intervention, but it is associated with high morbidity and mortality. We here report a rare case of spontaneously ruptured IPA pseudoaneurysm extending from the posterior mediastinum to the subdiaphragmatic area and managed with coil and gel foam embolization.

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OBJECTIVE: Traumatic brachial plexus injury (BPI) is a high-morbidity condition with an escalating incidence. One of the treatment options is neurotization using the ipsilateral phrenic nerve. Therefore, diagnosis of nerve dysfunction is a crucial step in preoperative planning. This study aimed to assess the accuracy and reliability of the fluoroscopic sniff test for preoperative diagnosis of phrenic nerve injury in patients with traumatic BPI. METHODS: The study was conducted from June 2019 to August 2023 at a tertiary care hospital. A preoperative fluoroscopic sniff test was performed. During brachial plexus surgery, direct phrenic nerve stimulation was conducted as a gold standard of phrenic nerve function. Two nonoperating orthopedic surgeons interpreted the accuracy and reliability of the test. RESULTS: Seventy-four patients with traumatic BPI (66 males and 8 females) with a median age of 26 years were enrolled. Sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the fluoroscopic sniff test were 90.9% (95% CI 75.7%-98.1%), 100% (95% CI 91.4%-100%), 100% (95% CI 88.4%-100%), 93.2% (95% CI 82.3%-97.6%), and 95.9% (95% CI 88.6%-99.2%), respectively. Interobserver reliability showed excellent agreement (κ = 1, p < 0.001). CONCLUSIONS: The fluoroscopic sniff test was proven to be an accurate, reliable, and simple tool to evaluate phrenic nerve function in patients with traumatic BPI. Preoperative testing should be performed to reduce operative time to identify the phrenic nerve as a donor for nerve transfer surgery in cases in which no function is detected from the fluoroscopic sniff test.

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Background: Brachial plexus injuries are debilitating injuries resulting in paralyzed shoulder to global paralysis of the upper extremity. Treatment strategies have evolved over the years with nerve transfer forming the mainstay of surgical management. Phrenic nerve provides certain advantages as donor over other options but has been less preferred due to fear of pulmonary complications. In this study, we assess the functional outcomes of phrenic nerve transfer in brachial plexus injuries. Materials and Methods: A retrospective study was performed on 18 patients operated between 2012 and 2017. The mean duration of injury to surgery was 4.56 months and mean follow-up was for 3.66 years. Phrenic nerve was used as donor to neurotize either biceps and brachialis branch of musculocutaneous nerve or suprascapular nerve. Assessment was done through Waikakul score for elbow flexion and Medical Research Council grading for shoulder abduction. Respiratory function assessment was done through questionnaire. Results: Twelve (80%) patients recovered grade 3 and above elbow flexion with 6 patients having a positive endurance test according to Waikakul and a "very good" result. In phrenic to suprascapular transfer group (3 patients), all patients had more than grade 3 recovery of shoulder abduction. No patient complained of respiratory problems. Conclusion: Phrenic nerve can be used as a reliable donor with suitable patient selection with good results in regaining muscle power without any anticipated effects on respiratory function.