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on 26-Oct-2020 (Mon)

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#GarjoToux
The receptors are placed throughout the bronchial tree and, although in a lesser extent, also in other areas: ear, paranasal sinuses, pleura, diaphragm, pericardium and esophagus
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Cough, a vital reflex. Mechanisms, determinants and measurements
tions (1). Cough may be a voluntary act or a spontaneous reflex arc and in this case involves receptors, an afferent pathway, a center processing information, an efferent pathway and effectors. <span>The receptors are placed throughout the bronchial tree and, although in a lesser extent, also in other areas: ear, paranasal sinuses, pleura, diaphragm, pericardium and esophagus. From receptors the afferent impulses are channeled through the vagus nerve in the medulla oblongata, where they are processed. Then, efferent impulses are conveyed by motor nerves and




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Schematically, we may distinguish four different phases of cough, as a vital reflex arc, the first of which is a part in the afferent pathway while the last three in the efferent one (2)
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Cough, a vital reflex. Mechanisms, determinants and measurements
he vagus nerve in the medulla oblongata, where they are processed. Then, efferent impulses are conveyed by motor nerves and reach the effectors, which are the respiratory and laryngeal muscles. <span>Schematically, we may distinguish four different phases of cough, as a vital reflex arc, the first of which is a part in the afferent pathway while the last three in the efferent one (2): Receptorial phase: there is the stimulation of cough receptors that are activated and, accordingly, send an impulse to the center through the vagus nerve; Inspiratory phase: that consi




#GarjoToux
Since the result of the cough reflex arc is the production of an airflow, the determinant factor of cough efficacy is the operational volume of the lung (3), which in turn relies on the strength and coordination of respiratory and laryngeal muscles as well as on lung mechanics
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Cough, a vital reflex. Mechanisms, determinants and measurements
e determinants of the cough efficacy and the clinical conditions affecting cough efficacy as well as the cough’s efficacy measurements in clinical setting. Go to: Determinants of cough efficacy <span>Since the result of the cough reflex arc is the production of an airflow, the determinant factor of cough efficacy is the operational volume of the lung (3), which in turn relies on the strength and coordination of respiratory and laryngeal muscles as well as on lung mechanics. The weakness and/or the incoordination of the respiratory and/or laryngeal muscles may significantly decrease the driving pressure applied to the alveoli and to the bronchial airways.




#GarjoToux
The decrease of operational volume of the lung can be the consequence not only of a weakness of respiratory muscles, but also of the expiratory flow limitation and lung hyperinflation
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Cough, a vital reflex. Mechanisms, determinants and measurements
ase Myasthenia Myasthenia gravis Lambert-Eaton syndrome Muscular dystrophies Duchenne dystrophy Myotonic dystrophy Toxic myopathies Alcoholic myopathy Steroid myopathy Open in a separate window <span>The decrease of operational volume of the lung can be the consequence not only of a weakness of respiratory muscles, but also of the expiratory flow limitation and lung hyperinflation. These pathophysiological features may occur in some obstructive airway diseases, such as chronic obstructive pulmonary disease (COPD), cystic fibrosis, bronchiectasis, tracheomalacia a




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CPF evaluation is clinically relevant and it can be considered an overall parameter of cough efficacy (7)
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Cough, a vital reflex. Mechanisms, determinants and measurements
r mechanical insufflation-exsufflation (4). CEV can be measured together with CPF assessment. In healthy individuals, CEV values are usually greater than 1 L with an average value of 2.4 L (6). <span>CPF evaluation is clinically relevant and it can be considered an overall parameter of cough efficacy (7). Neuromuscular patients with values of CPF less than 270 L/minute are at risk of retention of bronchial secretions and respiratory failure in case of bronchial infection (8). Interestin




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The measurement of cough efficacy should be a routine assessment in patients suffering from progressive neurological disorders with lung involvement and in patients who are at high risk of an ineffective cough
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Cough, a vital reflex. Mechanisms, determinants and measurements
with acute stroke, higher values of CPF are associated with a low risk of secondary aspiration pneumonia. Up to now, no data has been published on the clinical relevance of the CEV measurement. <span>The measurement of cough efficacy should be a routine assessment in patients suffering from progressive neurological disorders with lung involvement and in patients who are at high risk of an ineffective cough. In these patients, a non-invasive evaluation of respiratory muscles function is required and usually consists in some volitional tests. These tests include the vital capacity (CV) meas




#GarjoToux
Moreover, in case of a documented impairment of respiratory muscle function, an arterial blood-gas analysis may be requested to ascertain whether a hypoxemic-hypercapnic respiratory failure due to a ventilatory pump impairment may occur
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Cough, a vital reflex. Mechanisms, determinants and measurements
difficulties to perform MEP manoeuvre (13). Non-volitional and invasive tests may be required in non-cooperative patients or in patients providing non-univocal results at volitional tests (4). <span>Moreover, in case of a documented impairment of respiratory muscle function, an arterial blood-gas analysis may be requested to ascertain whether a hypoxemic-hypercapnic respiratory failure due to a ventilatory pump impairment may occur. Patients with a decreased operational volume of the lung due to an obstructive ventilatory defect and lung hyperinflation show a reduced forced expiratory volume at 1st second (FEV1)/C




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Moreover, in patients with COPD the use of bronchodilators, such as beta2-agonists or muscarinic antagonists, can significantly reduce the exacerbation rate and this effect might be linked to an improvement in operational volume of the lung and, accordingly, to a more effective cough
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Cough, a vital reflex. Mechanisms, determinants and measurements
operational volume of the lung are now available. Notably, in bulbar and in non-bulbar ALS patients, mechanical insufflation-exsufflation can significantly increase air flow during cough (14). <span>Moreover, in patients with COPD the use of bronchodilators, such as beta2-agonists or muscarinic antagonists, can significantly reduce the exacerbation rate and this effect might be linked to an improvement in operational volume of the lung and, accordingly, to a more effective cough. Go to: References 1. Bouros D, Siafakas N, Green M. second edition. New York: Marcel Dekker Inc; 1995. Cough. Physiological and Pathophysiological Considerations. In: C. Roussos (Ed).




#GarjoToux
Under normal conditions cough serves an important protective role in the airways and lungs, but in some conditions it may become excessive and nonproductive, and is troublesome and potentially harmful to the airway mucosa
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Anatomy and neuro-pathophysiology of the cough reflex arc
erials occurring as a consequence of aspiration or inhalation of particulate matter, pathogens, accumulated secretions, postnasal drip, inflammation, and mediators associated with inflammation. <span>Under normal conditions cough serves an important protective role in the airways and lungs, but in some conditions it may become excessive and nonproductive, and is troublesome and potentially harmful to the airway mucosa. These contrasting consequences of coughing can be attributed to the parallel afferent pathways regulating this important defensive reflex of the airways. Each cough occurs through the




#GarjoToux
In addition, more airway receptors are in the external auditory canals, eardrums, paranasal sinuses, pharynx, diaphragm, pleura, pericardium, and stomach. These are probably mechanical receptors only, which can be stimulated by triggers such as touch or displacement
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Anatomy and neuro-pathophysiology of the cough reflex arc
anical and chemical stimuli. Chemical receptors sensitive to acid, heat, and capsaicin-like compounds trigger the cough reflex via activation of the type 1 vanilloid (capsaicin) receptor [3-5]. <span>In addition, more airway receptors are in the external auditory canals, eardrums, paranasal sinuses, pharynx, diaphragm, pleura, pericardium, and stomach. These are probably mechanical receptors only, which can be stimulated by triggers such as touch or displacement. Impulses from stimulated cough receptors traverse an afferent pathway via the vagus nerve to a ‘cough center’ in the medulla, which itself may be under some control by higher cortical




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These attributes can be used to identify at least three broad classes of airway afferent nerves:

1. Rapidly Adapting Receptors (RAR)

2. Slowly Adapting Stretch Receptors (SARs)

3. C-Fibers

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Anatomy and neuro-pathophysiology of the cough reflex arc
ensitivity, adaptation to sustained lung inflation, neurochemistry, origin, myelination, conduction velocity (A-fiber, > 3 m/s; C-fiber, < 2 m/s), and sites of termination in the airways. <span>These attributes can be used to identify at least three broad classes of airway afferent nerves: 1. Rapidly Adapting Receptors (RAR) 2. Slowly Adapting Stretch Receptors (SARs) 3. C-Fibers Rapidly adapting receptors (RAR) Functional studies of RARs suggest that they terminate within or beneath the epithelium of both intrapulmonary and extrapulmonary airways, but primarily




#GarjoToux
RARs are activated by stimuli that evoke bronchospasm or obstruction resulting from mucus secretion or edema. Substances such as histamine, capsaicin, substance P, and bradykinin activate RARs in a way that can be markedly inhibited or abolished by preventing the local end-organ effects that these stimuli produce (e.g. bronchospasm and mucus secretion)
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Anatomy and neuro-pathophysiology of the cough reflex arc
ughout the respiratory cycle, are activated by the dynamic mechanical forces accompanying lung inflation and deflation, and become more active as the rate and volume of lung inflation increase. <span>RARs are activated by stimuli that evoke bronchospasm or obstruction resulting from mucus secretion or edema. Substances such as histamine, capsaicin, substance P, and bradykinin activate RARs in a way that can be markedly inhibited or abolished by preventing the local end-organ effects that these stimuli produce (e.g. bronchospasm and mucus secretion). RAR activation initiates reflex bronchospasm and mucus secretion through parasympathetic pathways. RARs can also respond to stimuli that evoke cough and fulfill many criteria for media




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RAR activation initiates reflex bronchospasm and mucus secretion through parasympathetic pathways
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Anatomy and neuro-pathophysiology of the cough reflex arc
, and bradykinin activate RARs in a way that can be markedly inhibited or abolished by preventing the local end-organ effects that these stimuli produce (e.g. bronchospasm and mucus secretion). <span>RAR activation initiates reflex bronchospasm and mucus secretion through parasympathetic pathways. RARs can also respond to stimuli that evoke cough and fulfill many criteria for mediating cough. Further evidence for their role in coughing comes from studies of vagal cooling, which




#GarjoToux
RARs may act synergistically with other afferent nerve subtypes to induce coughing
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Anatomy and neuro-pathophysiology of the cough reflex arc
le in coughing comes from studies of vagal cooling, which blocks cough at temperatures that selectively abolish activity in myelinated fibers (including RARs) while preserving C-fiber activity. <span>RARs may act synergistically with other afferent nerve subtypes to induce coughing. Slowly adapting stretch receptors (SARs) SARs are highly sensitive to the mechanical forces that are put on the lung during breathing. SAR activity increases during inspiration and pea




#GarjoToux
SARs are highly sensitive to the mechanical forces that are put on the lung during breathing. SAR activity increases during inspiration and peaks just prior to the initiation of expiration [13]
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Anatomy and neuro-pathophysiology of the cough reflex arc
yelinated fibers (including RARs) while preserving C-fiber activity. RARs may act synergistically with other afferent nerve subtypes to induce coughing. Slowly adapting stretch receptors (SARs) <span>SARs are highly sensitive to the mechanical forces that are put on the lung during breathing. SAR activity increases during inspiration and peaks just prior to the initiation of expiration [13]. SARs are thus thought to be the afferent fibers involved in the Hering-Breuer reflex, which terminates inspiration and initiates expiration when the lungs are adequately inflated. SARs




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SARs are thus thought to be the afferent fibers involved in the Hering-Breuer reflex, which terminates inspiration and initiates expiration when the lungs are adequately inflated
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Anatomy and neuro-pathophysiology of the cough reflex arc
ARs are highly sensitive to the mechanical forces that are put on the lung during breathing. SAR activity increases during inspiration and peaks just prior to the initiation of expiration [13]. <span>SARs are thus thought to be the afferent fibers involved in the Hering-Breuer reflex, which terminates inspiration and initiates expiration when the lungs are adequately inflated. SARs can be differentiated from RARs in some species based on action potential conduction velocity, and in most species by their lack of adaptation to sustained lung inflations. SARs m




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SAR activation results in the central inhibition of respiration and the inhibition of the cholinergic drive to the airways, leading to decreased phrenic nerve activity and decreased airway smooth muscle tone (due to a withdrawal of cholinergic nerve activity) [ 14]
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Anatomy and neuro-pathophysiology of the cough reflex arc
be differentially distributed throughout the airways: they appear to terminate primarily in the intrapulmonary airways. SARs also differ from RARs with respect to the reflexes they precipitate. <span>SAR activation results in the central inhibition of respiration and the inhibition of the cholinergic drive to the airways, leading to decreased phrenic nerve activity and decreased airway smooth muscle tone (due to a withdrawal of cholinergic nerve activity) [14]. The sensory terminals of SARs assume a complex and varying position within the airway wall: most of these SARs are found in the peripheral airways (associated with alveoli or bronchiol




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SARs may facilitate coughing by a central cough network via activation of brainstem second-order neurons of the SAR reflex pathway.
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Anatomy and neuro-pathophysiology of the cough reflex arc
rway wall: most of these SARs are found in the peripheral airways (associated with alveoli or bronchioles). Occasionally, SAR dendritic arbors are associated with the bronchiolar smooth muscle. <span>SARs may facilitate coughing by a central cough network via activation of brainstem second-order neurons of the SAR reflex pathway. C-fibers The majority of afferent nerves innervating the airways and lungs are unmyelinated C-fibers. They are similar in many ways to the unmyelinated somatic sensory nerves innervatin




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The majority of afferent nerves innervating the airways and lungs are unmyelinated C-fibers
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Anatomy and neuro-pathophysiology of the cough reflex arc
s are associated with the bronchiolar smooth muscle. SARs may facilitate coughing by a central cough network via activation of brainstem second-order neurons of the SAR reflex pathway. C-fibers <span>The majority of afferent nerves innervating the airways and lungs are unmyelinated C-fibers. They are similar in many ways to the unmyelinated somatic sensory nerves innervating the skin, skeletal muscle, joints, and bones that respond to noxious chemical and mechanical stimul




#GarjoToux
In addition to their conduction velocity (< 2 m/s), airway vagal afferent C-fibers are distinguished from RARs and SARs by their relative insensitivity to mechanical stimulation and lung inflation. C-fibers are further distinguished from RARs by the observation that they are directly activated by bradykinin and capsaicin, not indirectly through effects on smooth muscle or the airway vasculature
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Anatomy and neuro-pathophysiology of the cough reflex arc
ar in many ways to the unmyelinated somatic sensory nerves innervating the skin, skeletal muscle, joints, and bones that respond to noxious chemical and mechanical stimuli (called nociceptors). <span>In addition to their conduction velocity (< 2 m/s), airway vagal afferent C-fibers are distinguished from RARs and SARs by their relative insensitivity to mechanical stimulation and lung inflation. C-fibers are further distinguished from RARs by the observation that they are directly activated by bradykinin and capsaicin, not indirectly through effects on smooth muscle or the airway vasculature. Moreover, prostaglandin E2, adrenaline, and adenosine, which by bronchodilating the airways might inhibit RAR activation by bradykinin and capsaicin, actually sensitize C-fibers to cap




Article 6008294739212

Insight Joy

JOY The emotion excited by the acquisition or expectation of good; state of happiness; exultation. The Hebrew and Greek words used in the Bible for joy, exultation, rejoicing, and being glad express various shades of meaning, different stages or degrees of joy. The verbs involved express the inner feeling and the outward manifestation of joy and variously mean “be joyful; exult; shout for joy; leap for joy.” Jehovah God and Jesus Christ. Jehovah is called “the happy God.” (1Ti 1:11) He creates and works with joy for himself and his creatures. What he brings about makes him joyful. (Ps 104:31) He wants his creatures likewise to enjoy his works and to enjoy their own work. (Ec 5:19) Since he is the Source of all good things (Jas 1:17), all intelligent creatures, both mankind and angels, can find their chief enjoyment in coming to know him. (Jer 9:23, 24) King David said: “Let my musing about him be pleasurable. I, for my part, shall rejoice in Jehovah.” (Ps 104:34) He also sang: “The righteous one will