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Biomedical Engineering Online Jan 2023Every year, more than 2.5 million critically ill patients in the ICU are dependent on mechanical ventilation. The positive pressure in the lungs generated by the...
BACKGROUND
Every year, more than 2.5 million critically ill patients in the ICU are dependent on mechanical ventilation. The positive pressure in the lungs generated by the ventilator keeps the diaphragm passive, which can lead to a loss of myofibers within a short time. To prevent ventilator-induced diaphragmatic dysfunction (VIDD), phrenic nerve stimulation may be used.
OBJECTIVE
The goal of this study is to show the feasibility of transesophageal phrenic nerve stimulation (TEPNS). We hypothesize that selective phrenic nerve stimulation can efficiently activate the diaphragm with reduced co-stimulations.
METHODS
An in vitro study in saline solution combined with anatomical findings was performed to investigate relevant stimulation parameters such as inter-electrode spacing, range to target site, or omnidirectional vs. sectioned electrodes. Subsequently, dedicated esophageal electrodes were inserted into a pig and single stimulation pulses were delivered simultaneously with mechanical ventilation. Various stimulation sites and response parameters such as transdiaphragmatic pressure or airway flow were analyzed to establish an appropriate stimulation setting.
RESULTS
Phrenic nerve stimulation with esophageal electrodes has been demonstrated. With a current amplitude of 40 mA, similar response figures of the diaphragm activation as compared to conventional stimulation with needle electrodes at 10mA were observed. Directed electrodes best aligned with the phrenic nerve resulted in up to 16.9 % higher amplitude at the target site in vitro and up to 6 cmH20 higher transdiaphragmatic pressure in vivo as compared to omnidirectional electrodes. The activation efficiency was more sensitive to the stimulation level inside the esophagus than to the inter-electrode spacing. Most effective and selective stimulation was achieved at the level of rib 1 using sectioned electrodes 40 mm apart.
CONCLUSION
Directed transesophageal phrenic nerve stimulation with single stimuli enabled diaphragm activation. In the future, this method might keep the diaphragm active during, and even support, artificial ventilation. Meanwhile, dedicated sectioned electrodes could be integrated into gastric feeding tubes.
Topics: Animals; Swine; Phrenic Nerve; Feasibility Studies; Diaphragm; Respiration, Artificial; Electrodes; Electric Stimulation
PubMed: 36717872
DOI: 10.1186/s12938-023-01071-5 -
Life (Basel, Switzerland) Sep 2023To restore elbow flexor muscle function in case of traumatic brachial plexus avulsion, the phrenic nerve transfer to the musculocutaneous nerve has become part of...
BACKGROUND
To restore elbow flexor muscle function in case of traumatic brachial plexus avulsion, the phrenic nerve transfer to the musculocutaneous nerve has become part of clinical practice. The nerve transfer can be done by means of video-assisted thoracic surgery without nerve graft or via supraclavicular approach in combination with an autograft. This study focuses on a detailed microscopic and macroscopic examination of the phrenic nerve. It will allow a better interpretation of existing clinical results and, thus, serve as a basis for future clinical studies.
MATERIAL AND METHODS
An anatomical study was conducted on 28 body donors of Caucasian origin (female n = 14, male n = 14). A sliding caliper and measuring tape were used to measure the diameter and length of the nerves. Sudan black staining was performed on 15 µm thick cryostat sections mounted on glass slides and the number of axons was determined by the ImageJ counting tool. In 23 individuals, the phrenic nerve could be examined on both sides. In 5 individuals, however, only one side was examined. Thus, a total of 51 nerves were examined.
RESULTS
The mean length of the left phrenic nerves (33 cm (29-38 cm)) was significantly longer compared to the mean length of the right phrenic nerves (30 cm (24-33 cm)) ( < 0.001). Accessory phrenic nerves were present in 9 of 51 (18%) phrenic nerves. The mean number of phrenic nerves axons at the level of the first intercostal space in body donors with a right accessory phrenic nerve was significantly greater compared to the mean number of phrenic nerves axons at the same level in body donors without a right accessory phrenic nerve (3145 (range, 2688-3877) vs. 2278 (range, 1558-3276)), = 0.034. A negative correlation was registered between age and the nerve number of axons in left (0.742, < 0.001) and right (-0.273, = 0.197) phrenic nerves. The mean distance from the upper edge of the ventral ramus of the fourth cervical spinal nerve to the point of entrance of the musculocutaneous nerve between the two parts of the coracobrachialis muscle was 19 cm (range, 15-24 cm) for the right and 20 cm (range, 15-25 cm) for the left arm.
CONCLUSIONS
If an accessory phrenic nerve is available, it presumably should be spared. Thus, in that case, a supraclavicular approach in combination with a nerve graft would probably be of advantage.
PubMed: 37763296
DOI: 10.3390/life13091892 -
Respiratory Physiology & Neurobiology Jul 2019Acute intermittent hypoxia (AIH) elicits distinct mechanisms of phrenic motor plasticity initiated by brainstem neural network activation versus local (spinal) tissue... (Review)
Review
Acute intermittent hypoxia (AIH) elicits distinct mechanisms of phrenic motor plasticity initiated by brainstem neural network activation versus local (spinal) tissue hypoxia. With moderate AIH (mAIH), hypoxemia activates the carotid body chemoreceptors and (subsequently) brainstem neural networks associated with the peripheral chemoreflex, including medullary raphe serotonergic neurons. Serotonin release and receptor activation in the phrenic motor nucleus then elicits phrenic long-term facilitation (pLTF). This mechanism is independent of tissue hypoxia, since electrical carotid sinus nerve stimulation elicits similar serotonin-dependent pLTF. In striking contrast, severe AIH (sAIH) evokes a spinal adenosine-dependent, serotonin-independent mechanism of pLTF. Spinal tissue hypoxia per se is the likely cause of sAIH-induced pLTF, since local tissue hypoxia elicits extracellular adenosine accumulation. Thus, any physiological condition exacerbating spinal tissue hypoxia is expected to shift the balance towards adenosinergic pLTF. However, since these mechanisms compete for dominance due to mutual cross-talk inhibition, the transition from serotonin to adenosine dominant pLTF is rather abrupt. Any factor that compromises spinal cord circulation will limit oxygen availability in spinal cord tissue, favoring a shift in the balance towards adenosinergic mechanisms. Such shifts may arise experimentally from treatments such as carotid denervation, or spontaneous hypotension or anemia. Many neurological disorders, such as spinal cord injury or stroke compromise local circulatory control, potentially modulating tissue oxygen, adenosine levels and, thus, phrenic motor plasticity. In this brief review, we discuss the concept that local (spinal) circulatory control and/or oxygen delivery regulates the relative contributions of distinct pathways to phrenic motor plasticity.
Topics: Adenosine; Animals; Cervical Cord; Humans; Hypoxia; Neuronal Plasticity; Oxygen; Phrenic Nerve; Respiratory Physiological Phenomena; Serotonin; Synaptic Potentials
PubMed: 30639504
DOI: 10.1016/j.resp.2019.01.004 -
Multimedia Manual of Cardiothoracic... Aug 2021The authors demonstrate a video-assisted thoracoscopic surgical technique for diaphragmatic plication, which is used to treat acquired diaphragmatic paralysis resulting...
The authors demonstrate a video-assisted thoracoscopic surgical technique for diaphragmatic plication, which is used to treat acquired diaphragmatic paralysis resulting from injury to the phrenic nerve. The objective of the surgical procedure is to return the abdominal contents to their normal position and restore optimal lung expansion by reducing the size of the diaphragmatic surface. Successful diaphragmatic plication improves lung function, reduces dyspnea, and restores quality of life.
Topics: Diaphragm; Humans; Phrenic Nerve; Quality of Life; Respiratory Paralysis; Thoracic Surgery, Video-Assisted
PubMed: 35616985
DOI: 10.1510/mmcts.2021.043 -
Chest May 2022Central sleep apnea (CSA) frequently coexists with heart failure and atrial fibrillation and contributes to cardiovascular disease progression and mortality. A... (Review)
Review
Central sleep apnea (CSA) frequently coexists with heart failure and atrial fibrillation and contributes to cardiovascular disease progression and mortality. A transvenous phrenic nerve stimulation (TPNS) system has been approved for the first time by the Food and Drug Administration for the treatment of CSA. This system, remedē System (Zoll Medical, Inc.), is implanted during a minimally invasive outpatient procedure and has shown a favorable safety and efficacy profile. Currently, patient access to this therapy remains limited by the small number of specialized centers in the United States and the absence of a standard coverage process by insurers. Although a period of evaluation by insurers is expected for new therapies in their early stages, the impact on patients is particularly severe given the already limited treatment options for CSA. Implantation and management of this novel therapy require the establishment of a specialized multidisciplinary program as part of a sleep medicine practice and support from health care systems and hospitals. Several centers in the United States have been successful in building sustainable TPNS programs offering this novel therapy to their patients by navigating the current reimbursement environment. In this article, we review the background and efficacy data of TPNS and briefly address relevant aspects of the clinical activities involved in a TPNS program. The article presents the status of coverage and reimbursement for this novel therapy. We also discuss the current approach to obtaining reimbursement from third-party payors during this transitional period of evaluation by Medicare and other insurers.
Topics: Aged; Electric Stimulation Therapy; Humans; Medicare; Phrenic Nerve; Sleep Apnea, Central; Treatment Outcome; United States
PubMed: 34808108
DOI: 10.1016/j.chest.2021.11.012 -
Thoracic Surgery Clinics Aug 2015Immediate postoperative complications are common after lobectomy. The most effective management of postoperative crises is prevention, which starts with preoperative... (Review)
Review
Immediate postoperative complications are common after lobectomy. The most effective management of postoperative crises is prevention, which starts with preoperative preparation and patient screening. There are many factors that can be controlled and improved by the patient. Equally important is patient selection, which is influenced by pulmonary function tests, cardiopulmonary reserve, and preexisting comorbidities. After the operation, the care team can also greatly improve outcomes with aggressive cardiopulmonary therapies, ambulation, vigilant monitoring, and frequent assessments of the patient. Prevention strategies can minimize risks; however, when they occur, a proactive approach may minimize the long-term sequelae.
Topics: Atrial Fibrillation; Humans; Laryngeal Nerve Injuries; Lung Diseases; Phrenic Nerve; Pneumonectomy; Pneumothorax; Postoperative Hemorrhage; Postoperative Period
PubMed: 26210931
DOI: 10.1016/j.thorsurg.2015.04.003 -
Experimental Physiology Nov 2019What is the topic of this review? Rubral modulation of pontomedullary respiratory rhythm and pattern generating circuitry powerfully contributes to regulation of... (Review)
Review
NEW FINDINGS
What is the topic of this review? Rubral modulation of pontomedullary respiratory rhythm and pattern generating circuitry powerfully contributes to regulation of breathing. What advances does it highlight? Studies have demonstrated extensive rubromedullary and rubrospinal projections to zones generating and organizing the respiratory rhythm and pattern. Rubral modulation of respiratory output effects inspiratory expiratory phase transitions with stimulation generating inhibitory or excitatory responses of medullary inspiratory and expiratory units. The red nucleus mediates hypoxic ventilatory depression, integrates respiratory output with oromotor and locomotor activity, and modulates respiratory output during noxious stimulation.
ABSTRACT
Although normal triphasic eupnoea can be produced by the pontomedullary respiratory network after pontomesencephalic transection, the midbrain provides important modulation of respiration. Specifically, stimulation of the red nucleus elicits inspiratory inhibition, as manifest in the phrenic neurogram, in addition to excitation and inhibition of individual medullary respiratory-related units, with the majority of premotor units that receive rubral modulation being inhibited. Stimulation of the red nucleus also induces respiratory phase transitions, which appear to be pontine independent. These effects might be mediated by rubrobulbar and/or rubrospinal tracts. Although lesioning of the red nucleus does not alter respiration in normoxic conditions, it eliminates hypoxic ventilatory depression, which is the second phase of the biphasic ventilatory response to low oxygen tension. The finding that the red nucleus also plays a role in anti-nociception suggests that it might coordinate respiratory responses during noxious stimulation and, given that the red nucleus regulates upper limb flexors, it might represent one region in a distributed bulbar network contributing to respiratory-locomotor integration. Modulation of jaw opening by the red nucleus would support a model whereby it coordinates oromotor activity with breathing. Thus, the multiplicity of roles played by the red nucleus aptly position it to coordinate respiration in a variety of behavioural states. In this review, we seek to highlight the different features and regional specializations of the rubral contribution to respiratory control and underscore its vital importance to breathing in the freely behaving mammal.
Topics: Animals; Exhalation; Locomotion; Medulla Oblongata; Phrenic Nerve; Respiration; Respiratory Center
PubMed: 31408227
DOI: 10.1113/EP087720 -
American Journal of Respiratory and... May 2022
Topics: Diaphragm; Humans; Phrenic Nerve; Sleep Apnea, Central
PubMed: 35320061
DOI: 10.1164/rccm.202202-0315ED -
Anesthesiology Jul 2017Regional anesthesia has an established role in providing perioperative analgesia for shoulder surgery. However, phrenic nerve palsy is a significant complication that... (Review)
Review
Regional anesthesia has an established role in providing perioperative analgesia for shoulder surgery. However, phrenic nerve palsy is a significant complication that potentially limits the use of regional anesthesia, particularly in high-risk patients. The authors describe the anatomical, physiologic, and clinical principles relevant to phrenic nerve palsy in this context. They also present a comprehensive review of the strategies for reducing phrenic nerve palsy and its clinical impact while ensuring adequate analgesia for shoulder surgery. The most important of these include limiting local anesthetic dose and injection volume and performing the injection further away from the C5-C6 nerve roots. Targeting peripheral nerves supplying the shoulder, such as the suprascapular and axillary nerves, may be an effective alternative to brachial plexus blockade in selected patients. The optimal regional anesthetic approach in shoulder surgery should be tailored to individual patients based on comorbidities, type of surgery, and the principles described in this article.
Topics: Anesthesia, Conduction; Humans; Paralysis; Phrenic Nerve; Shoulder
PubMed: 28514241
DOI: 10.1097/ALN.0000000000001668 -
The Journal of Thoracic and... May 2021
Topics: Cardiac Surgical Procedures; Chest Tubes; Humans; Infant; Infant, Newborn; Paralysis; Phrenic Nerve
PubMed: 32711996
DOI: 10.1016/j.jtcvs.2020.06.048