Respiratory physiology & neurobiology
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Respir Physiol Neurobiol · Sep 2020
Activation of μ-opioid receptors differentially affects the preBötzinger Complex and neighbouring regions of the respiratory network in the adult rabbit.
The role of the different components of the respiratory network in the mediation of opioid-induced respiratory depression is still unclear. We investigated the contribution of the preBötzinger Complex (preBötC) and the neighbouring Bötzinger Complex (BötC) and inspiratory portion of the ventral respiratory group (iVRG) in anesthetized, vagotomized, paralyzed and artificially ventilated adult rabbits making use of bilateral microinjections (30-50 nl) of the μ-opioid receptor agonist [D-Ala2, N-Me-Phe4, Gly5-ol]-enkephalin (DAMGO). Dose-dependent effects were observed. ⋯ In the iVRG DAMGO provoked decreases in amplitude and frequency of phrenic bursts at 0.1 mM and apnea at 0.5 mM. Local 5 mM naloxone reversed the apneic effects. The results imply that different components of the respiratory network may contribute to opioid-induced respiratory disorders.
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Respir Physiol Neurobiol · Aug 2020
ReviewDistinct phenotypes require distinct respiratory management strategies in severe COVID-19.
Coronavirus disease 2019 (COVID-19) can cause severe respiratory failure requiring mechanical ventilation. The abnormalities observed on chest computed tomography (CT) and the clinical presentation of COVID-19 patients are not always like those of typical acute respiratory distress syndrome (ARDS) and can change over time. This manuscript aimed to provide brief guidance for respiratory management of COVID-19 patients before, during, and after mechanical ventilation, based on the recent literature and on our direct experience with this population. ⋯ Also, peripheral macro- and microemboli are common, and attention should be paid to the risk of pulmonary embolism. We suggest use of personalized mechanical ventilation strategies based on respiratory mechanics and chest CT patterns. Further research is warranted to confirm our hypothesis.
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Respir Physiol Neurobiol · Jun 2020
Endogenous glutamatergic inputs to the Parabrachial Nucleus/Kölliker-Fuse Complex determine respiratory rate.
The Kölliker-Fuse Nucleus (KF) has been widely investigated for its contribution to "inspiratory off-switch" while more recent studies showed that activation of the Parabrachial Nucleus (PBN) shortened expiratory duration. This study used an adult, in vivo, decerebrate rabbit model to delineate the contribution of each site to inspiratory and expiratory duration through sequential block of glutamatergic excitation with the receptor antagonists 2,3-dihydroxy-6-nitro-7-sulfamoyl-benzo[f]quinoxaline-2,3-dione (NBQX) and d(-)-2-amino-5-phosphonopentanoic acid (AP5). ⋯ The contribution of PBN activity to inspiratory and expiratory duration was equal while block of the KF affected inspiratory duration more than expiratory. We conclude that in the in vivo preparation respiratory rate greatly depends on PBN/KF activity, which contributes to the "inspiratory on- "and "off-switch", but is of minor importance for the magnitude of phrenic motor output.
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Respir Physiol Neurobiol · Jun 2020
Evidence for the emergence of an opioid-resistant respiratory rhythm following fentanyl overdose.
Breathing resumes within one to two minutes following fentanyl overdose induced apnea in spontaneously breathing rats. As this regular rhythm is produced at a time wherein fentanyl concentrations and receptor occupancy are likely to be extremely high, the mechanisms initiating and sustaining such a respiratory activity remain unclear. Forty-four un-anesthetized adult rats were studied in an open-flow plethysmograph. ⋯ When a second injection of the highest dose of fentanyl (300 μg.kg-1) was performed at 10 min, ventilation was not significantly affected and no apnea was produced in major contrast to the first injection. When a similar injection was performed 30 min after the first injection, in a separate group of rats, an apnea and breathing depression was produced in 30 % of the animals, while in the other rats, ventilation was unaffected. We conclude that the depressed regular respiratory activity emerging during and following fentanyl overdose is uniquely resistant to fentanyl.
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Respir Physiol Neurobiol · Jun 2020
Randomized Controlled TrialNasal high flow improves ventilation during propofol sedation: A randomized cross-over study in healthy volunteers.
Hypoventilation and carbon dioxide (CO2) retention are common during sedation. The current study investigated the ventilation responses to nasal high flow (NHF) during sedation with propofol. ⋯ During sedation with propofol, NHF without supplemental oxygen attenuated CO2 retention and reduced the respiratory rate. The findings show that NHF can improve ventilation during sedation, which may reduce the risk of complications related to hypoventilation.