-
Respiratory Medicine Mar 2013Inspiratory muscle fatigue (IMF) may contribute to the development of exercise limitation and respiratory failure. Identifying fatigue of the inspiratory muscles... (Review)
Review
Inspiratory muscle fatigue (IMF) may contribute to the development of exercise limitation and respiratory failure. Identifying fatigue of the inspiratory muscles requires a rigorous and integrative methodological approach. However, there is no consensus about an optimal protocol to induce and assess the fatigability of the inspiratory muscles. A systematic review was performed to identify, evaluate, and summarize the literature related to the assessment of induced IMF in healthy individuals. The aim was to identify factors that are related consistently to IMF, as well as to suggest possible assessment methods. MEDLINE and EMBASE were searched for relevant articles until February 2012. Only studies with a quantitative description of assessment and outcome were included. The search yielded 460 citations and a total of 77 studies were included. Inspiratory muscle fatigue was produced acutely by inspiratory resistive loading (IRL), whole body exercise (WBE), hyperpnea, or WBE combined with IRL, and under normocapnic, hypoxic or hypercapnic conditions. To detect IMF, most studies (64%) used phrenic nerve stimulation, 44% used a maximal voluntary inspiratory maneuver and the remainder used electromyography. The heterogeneity of the published reports precluded a quantitative analysis. Inspiratory resistive loadings at intensities of 60-80% of maximum, and cycling at 85% of maximum were found to produce IMF most consistently. Hypoxic or hypercapnic conditions, and WBE combined with IRL, exacerbated IMF. The specific outcome measures employed to detect IMF, the magnitude of their change, as well as their functional significance, are ultimately dependent upon the research question being addressed.
Topics: Diaphragm; Electric Stimulation; Exercise Test; Humans; Muscle Fatigue; Phrenic Nerve; Respiratory Muscles
PubMed: 23273596
DOI: 10.1016/j.rmed.2012.11.019 -
Singapore Medical Journal Dec 2007During routine dissection in the department of anatomy, the following anatomical variations of the phrenic nerve were observed on the right side of the neck of a... (Review)
Review
During routine dissection in the department of anatomy, the following anatomical variations of the phrenic nerve were observed on the right side of the neck of a 30-year-old male cadaver. The phrenic nerve, in its early course close to its origin, gave a communicating branch to the C5 root of the brachial plexus. At the level of the root of neck just before entering the thorax, the phrenic nerve was located anterior to the subclavian vein. This unique case of phrenic nerve variation gains tremendous importance in the context of subclavian vein cannulation, implanted venous access portals, and supraclavicular nerve block for regional anaesthesia.
Topics: Adult; Brachial Plexus; Cadaver; Dissection; Humans; Male; Phrenic Nerve; Singapore
PubMed: 18043847
DOI: No ID Found -
Journal of Neurophysiology Apr 2015Anatomical evidence indicates that midcervical interneurons can be synaptically coupled with phrenic motoneurons. Accordingly, we hypothesized that interneurons in the... (Comparative Study)
Comparative Study
Anatomical evidence indicates that midcervical interneurons can be synaptically coupled with phrenic motoneurons. Accordingly, we hypothesized that interneurons in the C3-C4 spinal cord can display discharge patterns temporally linked with inspiratory phrenic motor output. Anesthetized adult rats were studied before, during, and after a 4-min bout of moderate hypoxia. Neuronal discharge in C3-C4 lamina I-IX was monitored using a multielectrode array while phrenic nerve activity was extracellularly recorded. For the majority of cells, spike-triggered averaging (STA) of ipsilateral inspiratory phrenic nerve activity based on neuronal discharge provided no evidence of discharge synchrony. However, a distinct STA phrenic peak with a 6.83 ± 1.1 ms lag was present for 5% of neurons, a result that indicates a monosynaptic connection with phrenic motoneurons. The majority (93%) of neurons changed discharge rate during hypoxia, and the diverse responses included both increased and decreased firing. Hypoxia did not change the incidence of STA peaks in the phrenic nerve signal. Following hypoxia, 40% of neurons continued to discharge at rates above prehypoxia values (i.e., short-term potentiation, STP), and cells with initially low discharge rates were more likely to show STP (P < 0.001). We conclude that a population of nonphrenic C3-C4 neurons in the rat spinal cord is synaptically coupled to the phrenic motoneuron pool, and these cells can modulate inspiratory phrenic output. In addition, the C3-C4 propriospinal network shows a robust and complex pattern of activation both during and following an acute bout of hypoxia.
Topics: Action Potentials; Animals; Cervical Vertebrae; Hypoxia; Male; Motor Neurons; Phrenic Nerve; Rats; Rats, Sprague-Dawley; Spinal Cord
PubMed: 25552641
DOI: 10.1152/jn.00834.2014 -
Respiratory Physiology & Neurobiology Jun 2013The mammalian nervous system exhibits fast synchronous oscillations, which are especially prominent in respiratory-related nerve discharges. In the phrenic nerve, they... (Review)
Review
The mammalian nervous system exhibits fast synchronous oscillations, which are especially prominent in respiratory-related nerve discharges. In the phrenic nerve, they include high- (HFO), medium- (MFO), and low-frequency (LFO) oscillations. Because motoneurons firing at HFO-related frequencies had never been recorded, an epiphenomenological mechanism for their existence had been posited. We have recently recorded phrenic motoneurons firing at HFO-related frequencies in unanesthetized decerebrate rats and showed that they exhibit dynamic coherence with the phrenic nerve, validating synchronous motoneuronal discharge as a mechanism underlying the generation of HFO. In so doing, we have helped validate the conclusions of previous studies by us and other investigators who have used changes in fast respiratory oscillations to make inferences about central respiratory pattern generation. Here, we seek to review changes occurring in fast synchronous oscillations during non-eupneic respiratory behaviors, with special emphasis on gasping, and the inferences that can be drawn from these dynamics regarding respiratory pattern formation.
Topics: Animals; Apnea; Biological Clocks; Hand Strength; Humans; Nonlinear Dynamics; Phrenic Nerve; Respiratory Mechanics
PubMed: 23545119
DOI: 10.1016/j.resp.2013.03.010 -
Minerva Anestesiologica Dec 2023
Topics: Humans; Phrenic Nerve; Paralysis; Peripheral Nervous System Diseases
PubMed: 37534885
DOI: 10.23736/S0375-9393.23.17595-X -
The Journal of Thoracic and... Mar 2007The feasibility of a nerve guide tube for regeneration of the phrenic nerve with the aim of restoring diaphragmatic function was evaluated in a canine model.
OBJECTIVE
The feasibility of a nerve guide tube for regeneration of the phrenic nerve with the aim of restoring diaphragmatic function was evaluated in a canine model.
METHODS
The nerve tube, made of woven polyglycolic acid mesh, had a diameter of 3 mm and was filled with collagen sponge. This polyglycolic acid-collagen tube was implanted into a 10-mm gap created by transection of the right phrenic nerve in 9 beagle dogs. The tubes were implanted without a tissue covering in 5 of the 9 dogs (group I), and the tubes were covered with a pedicled pericardial fat pad in 4 dogs (group II). Chest x-ray films, muscle action potentials, and histologic samples were examined 4 to 12 months after implantation.
RESULTS
All of the dogs survived without any complications. x-ray film examination showed that the right diaphragm was paralyzed and elevated in all dogs until 3 months after implantation. At 4 months, movement of the diaphragm in the implanted side was observed during spontaneous breathing in 1 dog of group I and in 3 dogs of group II. In the dogs showing diaphragm movement, muscle action potentials were evoked in the diaphragm muscle, indicating restoration of nerve function. Regeneration of the phrenic nerve structure was also examined on the reconstructed site using electron microscopy.
CONCLUSION
The polyglycolic acid-collagen tube induced functional recovery of the injured phrenic nerve and was aided by coverage with a pedicled pericardial fat pad.
Topics: Animals; Biopsy, Needle; Collagen; Disease Models, Animal; Dogs; Electrophysiology; Immunohistochemistry; Implants, Experimental; Nerve Regeneration; Neurosurgical Procedures; Phrenic Nerve; Polyglycolic Acid; Sensitivity and Specificity
PubMed: 17320572
DOI: 10.1016/j.jtcvs.2006.08.089 -
Journal of Applied Physiology... Jun 2008At the time of birth, respiratory muscles must be activated to sustain ventilation. The perinatal development of respiratory motor units (comprising an individual... (Review)
Review
At the time of birth, respiratory muscles must be activated to sustain ventilation. The perinatal development of respiratory motor units (comprising an individual motoneuron and the muscle fibers it innervates) shows remarkable features that enable mammals to transition from in utero conditions to the air environment in which the remainder of their life will occur. In addition, significant postnatal maturation is necessary to provide for the range of motor behaviors necessary during breathing, swallowing, and speech. As the main inspiratory muscle, the diaphragm muscle (and the phrenic motoneurons that innervate it) plays a key role in accomplishing these behaviors. Considerable diversity exists across diaphragm motor units, but the determinant factors for this diversity are unknown. In recent years, the mechanisms underlying the development of respiratory motor units have received great attention, and this knowledge may provide the opportunity to design appropriate interventions for the treatment of respiratory disease not only in the perinatal period but likely also in the adult.
Topics: Adaptation, Physiological; Aging; Animals; Deglutition; Diaphragm; Humans; Inhalation; Models, Animal; Motor Neurons; Muscle Development; Neuromuscular Junction; Phrenic Nerve; Respiration; Speech
PubMed: 18403452
DOI: 10.1152/japplphysiol.01192.2007 -
BMC Anesthesiology Aug 2020Hyperthermia is relatively rare during general anesthesia; however, a few studies have been conducted on hyperthermia and the neuromuscular blockade (NMB) induced by...
BACKGROUND
Hyperthermia is relatively rare during general anesthesia; however, a few studies have been conducted on hyperthermia and the neuromuscular blockade (NMB) induced by rocuronium, and the reversal of NMB by sugammadex. We investigated the effect of hyperthermia status on the NMB induced by rocuronium, and its reversal by sugammadex, in isolated phrenic nerve hemidiaphragm (PNHD) preparations of the rat.
METHODS
Thirty-three male Sprague-Dawley rat PNHD preparations were randomly assigned to three groups at different temperatures (36 °C, 38 °C, and 40 °C; each group, n = 11, in Krebs solution). The train-of-four (TOF) and twitch height responses were checked mechanomyographically. The PNHD were treated with progressively increasing doses of rocuronium and three effective concentrations (ECs), EC50, EC90, and EC95, of rocuronium were analyzed in each group via nonlinear regression analysis. Then, sugammadex was administered in doses equimolar to rocuronium. Thereafter, the T1 height (%), TOFR (%) and the duration index were measured.
RESULTS
The EC of rocuronium (EC50, EC90, and EC95) decreased significantly in accordance with increasing temperature. The groups at 36 °C and 40 °C showed clear differences in all areas (all P < 0.001). Moreover, the T1 height (%) and the duration index upon sugammadex administration showed faster recovery results in the36 °C than the 38 °C and 40 °C groups.
CONCLUSION
A rise of temperature from 38 °C to 40 °C in rat PNHD preparations proportionally enhanced the NMB induced by rocuronium. In addition, equimolar doses of sugammadex to the administered rocuronium showed a slower recovery time as the temperature rises.
Topics: Animals; Diaphragm; Dose-Response Relationship, Drug; Hyperthermia; Male; Neuromuscular Blockade; Neuromuscular Nondepolarizing Agents; Organ Culture Techniques; Phrenic Nerve; Rats; Rats, Sprague-Dawley; Rocuronium; Sugammadex
PubMed: 32767970
DOI: 10.1186/s12871-020-01114-7 -
Neuropharmacology Feb 2021Sudden unexpected death in epilepsy (SUDEP) is a leading cause of death in patients with refractory epilepsy. Centrally-mediated respiratory dysfunction has been...
Sudden unexpected death in epilepsy (SUDEP) is a leading cause of death in patients with refractory epilepsy. Centrally-mediated respiratory dysfunction has been identified as one of the principal mechanisms responsible for SUDEP. Seizures generate a surge in adenosine release. Elevated adenosine levels suppress breathing. Insufficient metabolic clearance of a seizure-induced adenosine surge might be a precipitating factor in SUDEP. In order to deliver targeted therapies to prevent SUDEP, reliable biomarkers must be identified to enable prompt intervention. Because of the integral role of the phrenic nerve in breathing, we hypothesized that suppression of phrenic nerve activity could be utilized as predictive biomarker for imminent SUDEP. We used a rat model of kainic acid-induced seizures in combination with pharmacological suppression of metabolic adenosine clearance to trigger seizure-induced death in tracheostomized rats. Recordings of EEG, blood pressure, and phrenic nerve activity were made concomitant to the seizure. We found suppression of phrenic nerve burst frequency to 58.9% of baseline (p < 0.001, one-way ANOVA) which preceded seizure-induced death; importantly, irregularities of phrenic nerve activity were partly reversible by the adenosine receptor antagonist caffeine. Suppression of phrenic nerve activity may be a useful biomarker for imminent SUDEP. The ability to reliably detect the onset of SUDEP may be instrumental in the timely administration of potentially lifesaving interventions.
Topics: Adenosine Kinase; Animals; Kainic Acid; Male; Phrenic Nerve; Predictive Value of Tests; Rats; Rats, Wistar; Seizures; Sudden Unexpected Death in Epilepsy; Tubercidin
PubMed: 33212114
DOI: 10.1016/j.neuropharm.2020.108405 -
Biomedical Research (Tokyo, Japan) 2023Seizure-like burst activities are induced by blockade of GABAA and/or glycine receptors in various spinal ventral roots of brainstem-spinal cord preparation from...
Seizure-like burst activities are induced by blockade of GABAA and/or glycine receptors in various spinal ventral roots of brainstem-spinal cord preparation from neonatal rodents. We found that this is not applicable to the phrenic nerve and that a new inhibitory descending pathway may suppress seizure-like activity in the phrenic nerve. Experiments were performed in brainstem-spinal cord preparation from newborn rats (age: 0-1 day). Left phrenic nerve and right C4 activities were recorded simultaneously. When GABAA and glycine receptors were blocked by 10 μM bicuculline and 10 μM strychnine (Bic+Str), seizure-like burst activities appeared in the fourth cervical ventral root (C4) but not the phrenic nerve. After making a transverse section at C1, the inspiratory burst activity disappeared from both C4 and the phrenic nerve, whereas seizure-like activity appeared in both nerves. We hypothesized that inhibitory descending pathways other than those via GABAA and/or glycine receptors (from the medulla to the spinal cord) work to avoid disturbance of regular respiratory-related diaphragm contraction by seizure-like activity. We found that cannabinoid receptor antagonist, AM251 was effective for the induction of seizure-like activity by Bic+Str in the phrenic nerve in brainstem-spinal cord preparation. Cannabinoid receptors may be involved in this descending inhibitory system.
Topics: Animals; Rats; Receptors, Glycine; Animals, Newborn; Receptors, Cannabinoid; Spinal Cord; Bicuculline; Strychnine; Seizures; Phrenic Nerve
PubMed: 37005282
DOI: 10.2220/biomedres.44.41