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André De Troyer - One of the best experts on this subject based on the ideXlab platform.
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Respiratory effects of the scalene and sternomastoid Muscles in humans
Journal of applied physiology (Bethesda Md. : 1985), 2003Co-Authors: Alexandre Legrand, Elisabeth Marion Schneider, Pierre-alain Gevenois, André De TroyerAbstract:Previous studies have shown that in normal humans the change in airway opening pressure (ΔPao) produced by all the parasternal and External Intercostal Muscles during a maximal contraction is appro...
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Mechanical effect of muscle spindles in the canine External Intercostal Muscles.
The Journal of Physiology, 2003Co-Authors: Dimitri Leduc, André De TroyerAbstract:High-frequency mechanical vibration of the ribcage increases afferent activity from External Intercostal muscle spindles, but the effect of this procedure on the mechanical behaviour of the respiratory system is unknown. In the present study, we have measured the changes in External Intercostal muscle length and the craniocaudal displacement of the ribs during ribcage vibration (40 Hz) in anaesthetized dogs. With vibration, External Intercostal inspiratory activity increased by ∼50 %, but the respiratory changes in muscle length and rib displacement were unaltered. A similar response was obtained after the Muscles in the caudal segments of the ribcage were sectioned and the caudally oriented force exerted by these Muscles on the rib was removed, thus suggesting that activation of External Intercostal muscle spindles by vibration generates little tension. Prompted by this observation, we also examined the role played by the External Intercostal muscle spindles in determining the respiratory displacement of the ribs during breathing against high inspiratory airflow resistances. Although resistances consistently elicited prominent reflex increases in External Intercostal inspiratory activity, the normal inspiratory cranial displacement of the ribs was reversed into an inspiratory caudal displacement. Also, this caudal rib displacement was essentially unchanged after section of the External Intercostal Muscles, whereas it was clearly enhanced after denervation of the parasternal Intercostals. These findings indicate that stretch reflexes in External Intercostal Muscles confer insufficient tension on the Muscles to significantly modify the mechanical behaviour of the respiratory system.
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Mechanical effect of muscle spindles in the canine External Intercostal Muscles.
The Journal of physiology, 2003Co-Authors: Dimitri Leduc, André De TroyerAbstract:High-frequency mechanical vibration of the ribcage increases afferent activity from External Intercostal muscle spindles, but the effect of this procedure on the mechanical behaviour of the respiratory system is unknown. In the present study, we have measured the changes in External Intercostal muscle length and the craniocaudal displacement of the ribs during ribcage vibration (40 Hz) in anaesthetized dogs. With vibration, External Intercostal inspiratory activity increased by approximately 50 %, but the respiratory changes in muscle length and rib displacement were unaltered. A similar response was obtained after the Muscles in the caudal segments of the ribcage were sectioned and the caudally oriented force exerted by these Muscles on the rib was removed, thus suggesting that activation of External Intercostal muscle spindles by vibration generates little tension. Prompted by this observation, we also examined the role played by the External Intercostal muscle spindles in determining the respiratory displacement of the ribs during breathing against high inspiratory airflow resistances. Although resistances consistently elicited prominent reflex increases in External Intercostal inspiratory activity, the normal inspiratory cranial displacement of the ribs was reversed into an inspiratory caudal displacement. Also, this caudal rib displacement was essentially unchanged after section of the External Intercostal Muscles, whereas it was clearly enhanced after denervation of the parasternal Intercostals. These findings indicate that stretch reflexes in External Intercostal Muscles confer insufficient tension on the Muscles to significantly modify the mechanical behaviour of the respiratory system.
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Distribution of inspiratory drive to the External Intercostal Muscles in humans
The Journal of Physiology, 2003Co-Authors: André De Troyer, Robert B. Gorman, Simon C. GandeviaAbstract:The External Intercostal Muscles in humans show marked regional differences in respiratory effect, and this implies that their action on the lung during breathing is primarily determined by the spatial distribution of neural drive among them. To assess this distribution, monopolar electrodes were implanted under ultrasound guidance in different muscle areas in six healthy individuals and electromyographic recordings were made during resting breathing. The Muscles in the dorsal portion of the third and fifth interspace showed phasic inspiratory activity with each breath in every subject. However, the muscle in the ventral portion of the third interspace showed inspiratory activity in only three subjects, and the muscle in the dorsal portion of the seventh interspace was almost invariably silent. Also, activity in the ventral portion of the third interspace, when present, and activity in the dorsal portion of the fifth interspace were delayed relative to the onset of activity in the dorsal portion of the third interspace. In addition, the discharge frequency of the motor units identified in the dorsal portion of the third interspace averaged (mean ±s.e.m.) 11.9 ± 0.3 Hz and was significantly greater than the discharge frequency of the motor units in both the ventral portion of the third interspace (6.0 ± 0.5 Hz) and the dorsal portion of the fifth interspace (6.7 ± 0.4 Hz). The muscle in the dorsal portion of the third interspace started firing simultaneously with the parasternal Intercostal in the same interspace, and the discharge frequency of its motor units was even significantly greater (11.4 ± 0.3 vs. 8.9 ± 0.2 Hz). These observations indicate that the distribution of neural inspiratory drive to the External Intercostals in humans takes place along dorsoventral and rostrocaudal gradients and mirrors the spatial distribution of inspiratory mechanical advantage.
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Contribution of spindle reflexes to post-inspiratory activity in the canine External Intercostal Muscles.
The Journal of Physiology, 2001Co-Authors: Stéphane V. Berdah, André De TroyerAbstract:1The External Intercostal Muscles have greater post-inspiratory activity than the parasternal Intercostal Muscles and are more abundantly supplied with muscle spindles. In the present study, the hypothesis was tested that spindle afferent inputs play a major role in determining this activity. 2The electrical activity of the External and parasternal Intercostal Muscles in the rostral interspaces was recorded in anaesthetized spontaneously breathing dogs, and the ribs were manipulated so as to alter their normal caudal displacement and the normal lengthening of the Muscles in early expiration. 3Post-inspiratory activity in the External Intercostal Muscles showed a reflex decrease when the caudal motion of the ribs and the lengthening of the Muscles was impeded, and it showed a reflex increase when the rate of caudal rib motion and muscle lengthening was increased. In contrast, the small post-inspiratory activity in the parasternal Intercostal Muscles remained unchanged. 4When the two ribs making up the interspace investigated were locked to keep muscle length constant, post-inspiratory activity in the External Intercostal Muscles was reduced and no longer responded to cranial rib manipulation. 5These observations confirm that afferent inputs from muscle receptors, presumably muscle spindles, are a primary determinant of post-inspiratory activity in the canine External Intercostal Muscles. In anaesthetized animals, the contribution of central control mechanisms to this activity is small.
A De Troyer - One of the best experts on this subject based on the ideXlab platform.
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Response of the Canine Internal Intercostal Muscles to Chest Wall Vibration
American Journal of Respiratory and Critical Care Medicine, 2001Co-Authors: Dimitri Leduc, E. Brunko, A De TroyerAbstract:Although high-frequency mechanical vibration of the rib cage reduces dyspnea, its effects on the respiratory Muscles are largely unknown. We have previously shown that in anesthetized dogs, vibrating the rib cage during inspiration elicits a marked increase in the inspiratory electromyographic (EMG) activity recorded from the External Intercostal Muscles but does not affect tidal volume (Vt). In the present studies, we have tested the hypothesis that the maintenance of Vt results from the concomitant contraction of the internal interosseous (expiratory) Intercostals. When the rib cage was vibrated (40 Hz) during hyperventilation-induced apnea, a prominent activity was recorded from the External Intercostals but no activity was recorded from the internal Intercostals, including when the Muscles were lengthened by passive inflation. The internal Intercostals remained also silent when vibration was applied during spontaneous inspiration, and the phasic expiratory EMG activity recorded from them was unaltered...
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The canine parasternal and External Intercostal Muscles drive the ribs differently.
The Journal of physiology, 2000Co-Authors: A De Troyer, T A WilsonAbstract:1. In the dog, the elevation of the ribs during inspiration results from the combined actions of the parasternal and External Intercostal Muscles. In the present studies, the hypothesis was tested that co-ordinated activity among these two sets of Muscles reduces the distortion of the rib cage. 2. During spontaneous inspiration before or after section of the phrenic nerves, the ribs moved cranially and outward in the same way as they did during passive inflation. However, whereas the sternum moved cranially during passive inflation, it was displaced caudally during spontaneous inspiration. 3. When the parasternal Intercostal Muscles were selectively denervated, both the sternum and the ribs moved cranially, but the rib outward displacement was markedly reduced. In contrast, when the External Intercostals were excised and the parasternal Intercostals were left intact, the sternum continued to move caudally and the outward displacement of the ribs was augmented relative to their cranial displacement. 4. These observations establish that the External Intercostal Muscles drive the ribs primarily in the cranial direction, whereas the parasternal Intercostals drive the ribs both cranially and outward. They also indicate, in agreement with the hypothesis, that co-ordinated activity among these two sets of Muscles displaces the ribs on their relaxation curve. 5. However, this co-ordinated activity also displaces the sternum caudally. Although this distortion requires an additional energy expenditure, it enhances the outward component of rib displacement which is more effective with respect to lung expansion.
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Spatial distribution of External and internal Intercostal activity in dogs.
The Journal of physiology, 1999Co-Authors: A Legrand, A De TroyerAbstract:1. The observation that the External and internal interosseous Intercostal Muscles in the dog show marked regional differences in mechanical advantage has prompted us to re-examine the topographic distribution of electrical activity among these Muscles during spontaneous breathing. 2. Inspiratory activity was recorded only from the areas of the External Intercostals with an inspiratory mechanical advantage, and expiratory activity was recorded only from the areas of the internal Intercostals with an expiratory mechanical advantage. The expiratory discharges previously recorded from the caudal External Intercostals and the inspiratory discharges recorded from the rostral internal Intercostals were probably due to cross-contamination. 3. Activity in each muscle area was also quantified relative to the activity measured during tetanic, supramaximal nerve stimulation (maximal activity). External Intercostal inspiratory activity was consistently greater in the areas with a greater inspiratory advantage (i.e. the dorsal aspect of the rostral segments) than in the areas with a smaller inspiratory advantage, and internal Intercostal expiratory activity was invariably greatest in the areas with the greatest expiratory advantage (i.e. the dorsal aspect of the caudal segments). 4. This topographic distribution of neural drive confers to the External Intercostal Muscles an inspiratory action on the lung during breathing and to the internal interosseous Intercostals an expiratory action.
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Spatial distribution of External and internal Intercostal activity in dogs
The Journal of Physiology, 1999Co-Authors: A Legrand, A De TroyerAbstract:The observation that the External and internal interosseous Intercostal Muscles in the dog show marked regional differences in mechanical advantage has prompted us to re-examine the topographic distribution of electrical activity among these Muscles during spontaneous breathing. Inspiratory activity was recorded only from the areas of the External Intercostals with an inspiratory mechanical advantage, and expiratory activity was recorded only from the areas of the internal Intercostals with an expiratory mechanical advantage. The expiratory discharges previously recorded from the caudal External Intercostals and the inspiratory discharges recorded from the rostral internal Intercostals were probably due to cross-contamination. Activity in each muscle area was also quantified relative to the activity measured during tetanic, supramaximal nerve stimulation (maximal activity). External Intercostal inspiratory activity was consistently greater in the areas with a greater inspiratory advantage (i.e. the dorsal aspect of the rostral segments) than in the areas with a smaller inspiratory advantage, and internal Intercostal expiratory activity was invariably greatest in the areas with the greatest expiratory advantage (i.e. the dorsal aspect of the caudal segments). This topographic distribution of neural drive confers to the External Intercostal Muscles an inspiratory action on the lung during breathing and to the internal interosseous Intercostals an expiratory action. The current conventional view of Intercostal muscle actions is based on the theory of Hamberger (1749) and maintains that as a result of the orientation of the muscle fibres, the External Intercostals have an inspiratory action on the lung whereas the internal interosseous Intercostals have an expiratory action. In the preceding paper, however, we have shown that in supine dogs, these Muscles show marked topographic differences in mechanical advantage (De Troyer et al. 1999). Specifically, the External Intercostals in the dorsal third of the rostral interspaces were found to have a large inspiratory mechanical advantage (i.e. a great ability to cause lung inflation), but this inspiratory mechanical advantage decreases rapidly toward the costochondral junctions and toward the base of the rib cage. Consequently, the Muscles in the ventral portion of the caudal segments have an expiratory, rather than inspiratory mechanical advantage. The internal Intercostal Muscles in the dorsal portion of the caudal interspaces have a large expiratory mechanical advantage, but this advantage decreases ventrally and cranially such that in the most rostral interspaces, it is reversed into an inspiratory mechanical advantage (De Troyer et al. 1999). These results imply that the actions of these Muscles on the lung during breathing are largely determined by the topographic distribution of activity among them, rather than the orientation of the muscle fibres. A number of electrical recordings from Intercostal Muscles and nerves in anaesthetized cats (Sears, 1964; Bainton et al. 1978; Kirkwood et al. 1982, 1984; Greer & Martin, 1990) and dogs (De Troyer & Ninane, 1986) have shown that the External Intercostals are active during inspiration. The Muscles also appeared to display greater inspiratory activity in the rostral than in the caudal segments and greater inspiratory activity in the dorsal than in the ventral portion of the rib cage. In contrast, the internal Intercostals were electrically active during expiration and displayed greater activity in the caudal than the rostral segments (Bainton et al. 1978; De Troyer & Ninane, 1986; Greer & Martin, 1990). In view of the distributions of mechanical advantage, such distributions of activity would suggest that the External Intercostals have an inspiratory action on the lung during breathing and that the internal Intercostals have an expiratory action. However, these descriptions of electrical activity are qualitative, and the sites where the recordings were made were not standardized. Consequently, the correspondence between the distributions of activity and the distributions of mechanical advantage can only be approximate, and no estimates can be made of the pressures contributed by the different muscle areas during breathing. More importantly, efferent discharges to the External Intercostals in the caudal segments during expiration and to the internal Intercostal in the second interspace during inspiration have also been recorded in decerebrate cats (Le Bars & Duron, 1984). As these discharges were recorded in animals performing forceful respiratory efforts against an occluded trachea, the possibility exists that they were the result of cross-contamination between the two muscle layers (De Troyer & Ninane, 1986). Yet such discharges would match, respectively, the expiratory mechanical advantage of the External Intercostal Muscles in the caudal segments and the inspiratory mechanical advantage of the internal Intercostals in the most rostral segments, and this raises the possibility that these Muscles may not have distinct effects on the lung during breathing. These issues prompted us to re-examine in detail the spatial distribution of activity among the canine External and internal Intercostal Muscles. The pattern of activation of the External Intercostals in the caudal segments and of the internal Intercostals in the most rostral segments was studied first. Selective muscle denervations were performed so that any cross-contamination could be identified. The distributions of External and internal Intercostal activity along the rostrocaudal and dorsoventral axes of the rib cage were next assessed quantitatively by comparing for each muscle area the amount of activity recorded during breathing with that recorded during supramaximal, tetanic stimulation of the motor nerve. As the recordings were made in muscle areas with well-defined mechanical advantages (De Troyer et al. 1999), the respiratory function of each muscle could therefore be definitely established and the pressures contributed by the various areas could be estimated.
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Respiratory Muscle Response to Flail Chest
American Journal of Respiratory and Critical Care Medicine, 1996Co-Authors: Matteo Cappello, C Yuehua, A De TroyerAbstract:We have previously shown that flail chest in the dog causes an inspiratory inward displacement of the ribs and an increased inspiratory activity in the External Intercostal Muscles, and we have speculated that this increased activity is due to an increased spindle afferent activity. The present studies were designed to test this hypothesis. Twenty-nine supine anesthetized dogs were studied, and flail was produced surgically by fracturing ventrally and dorsally two to four contiguous ribs on the right side of the chest. Although flail elicited an increased inspiratory activity in the External Intercostal and levator costae Muscles in the disconnected segment of the rib cage, it did not alter the inspiratory activity in the diaphragm and parasternal Intercostals. Expiratory activity in the triangularis sterni, internal Intercostals, and transversus abdominis remained unchanged also, as did the inspiratory activity in the External Intercostals on the left side of the chest. After flail, the normal inspiratory shortening of the External Intercostal Muscles in the disconnected segment was also reversed into an inspiratory muscle lengthening. However, when the fractured ribs were connected to the adjacent ribs so that the External Intercostals were prevented from lengthening during inspiration, External Intercostal and levator costae inspiratory activity was unaltered. These observations support the hypothesis that the increased External Intercostal muscle activity seen in flail chest results primarily from an increased activation of the muscle spindles.
Krzysztof E Kowalski - One of the best experts on this subject based on the ideXlab platform.
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Distribution of electrical activation to the External Intercostal Muscles during high frequency spinal cord stimulation in dogs
The Journal of Physiology, 2011Co-Authors: Anthony F Dimarco, Krzysztof E KowalskiAbstract:Non-technical summary Normal breathing is controlled by specialized neurons in the central nervous system including the brainstem and spinal cord. Signals generated in the brainstem and transmitted to the major inspiratory Muscles, including the diaphragm and Intercostal Muscles, are necessary to sustain life. However, we show that the specific pattern of Intercostal muscle activation during breathing does not require input from the brainstem. In other words, the neural circuitry controlling this pattern of activation exists within the spinal cord. This knowledge furthers our understanding of the mechanisms that control breathing and has implications for patients with certain disease states such as cervical spinal cord injury.
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Distribution of electrical activation to the External Intercostal Muscles during high frequency spinal cord stimulation in dogs.
The Journal of physiology, 2011Co-Authors: Anthony F Dimarco, Krzysztof E KowalskiAbstract:In contrast to previous methods of electrical stimulation of the inspiratory Muscles, high frequency spinal cord stimulation (HF-SCS) results in more physiological activation of these Muscles. The spatial distribution of activation to the External Intercostal Muscles by this method is unknown. In anaesthetized dogs, multiunit and single motor unit (SMU) EMG activity was monitored in the dorsal portion of the 3rd, 5th and 7th interspaces and ventral portion of the 3rd interspace during spontaneous breathing and HF-SCS following C2 spinal section. Stimulus amplitude during HF-SCS was adjusted such that inspired volumes matched spontaneous breathing (Protocol 1). During HF-SCS, mean peak SMU firing frequency was highest in the 3rd interspace (dorsal) (18.8 ± 0.3 Hz) and significantly lower in the 3rd interspace (ventral) (12.2 ± 0.2 Hz) and 5th interspace (dorsal) (15.3 ± 0.3 Hz) (P
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Effects of lung volume on parasternal pressure-generating capacity in dogs.
Experimental physiology, 2000Co-Authors: Anthony F Dimarco, J.r. Romaniuk, Gerald S. Supinski, Krzysztof E KowalskiAbstract:Previous studies have suggested that the optimum length for force generation of the parasternal Intercostal (PS) Muscles is well above functional residual capacity (FRC). We further explored this issue by examining the pressure-generating capacity of the PS Muscles as a function of lung volume in anaesthetized dogs. Upper thoracic spinal cord stimulation (SCS) was used to electrically activate the PS Muscles. Changes in airway pressure and parasternal resting length (LR) during airway occlusion were monitored over a wide range of lung volumes during SCS. To assess the effects of parasternal contraction alone, SCS was performed following phrenicotomy and section of the External Intercostal, levator costae and triangularis sterni Muscles. With increasing lung volume, there were progressive decrements in the capacity of the PS Muscles to produce changes in airway pressure. The relationship between PS pressure generation and lung volume was similar to a previous comparable assessment of the External Intercostal Muscles. The PS Muscles shortened during passive inflation and also shortened further (by > 20 % of LR) during SCS. Total shortening (passive plus active) increased progressively with increasing lung volume. Our results indicate that the capacity of the PS Muscles to produce changes in airway pressure (a) falls progressively with increasing lung volume and (b) is similar to that of the External Intercostal Muscles. We speculate that the fall in PS pressure-generating capacity is related, in part, to progressive reductions in end-inspiratory length.
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Load compensatory response of External Intercostal Muscles during assisted ventilation in rabbits.
Acta neurobiologiae experimentalis, 1993Co-Authors: J.r. Romaniuk, J. Celichowski, Krzysztof E KowalskiAbstract:Phrenic and External Intercostal motor responses to inspiratory load were studied in anaesthetized rabbits and after bilateral vagotomy. Animals were ventilated with a phrenic nerve driven respirator set at different gains, i.e. volume to phrenic-signal ratio. Load was imposed by occluding the trachea at the end of expiration for the period of one breath. It was found that vagally mediated low threshold facilitation may be observed in rabbits on late-inspiratory External Intercostal motor units. After vagotomy, External Intercostal EMG response to load depended on the given of the servorespirator set during the period of assisted ventilation.
Anthony F Dimarco - One of the best experts on this subject based on the ideXlab platform.
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Distribution of electrical activation to the External Intercostal Muscles during high frequency spinal cord stimulation in dogs
The Journal of Physiology, 2011Co-Authors: Anthony F Dimarco, Krzysztof E KowalskiAbstract:Non-technical summary Normal breathing is controlled by specialized neurons in the central nervous system including the brainstem and spinal cord. Signals generated in the brainstem and transmitted to the major inspiratory Muscles, including the diaphragm and Intercostal Muscles, are necessary to sustain life. However, we show that the specific pattern of Intercostal muscle activation during breathing does not require input from the brainstem. In other words, the neural circuitry controlling this pattern of activation exists within the spinal cord. This knowledge furthers our understanding of the mechanisms that control breathing and has implications for patients with certain disease states such as cervical spinal cord injury.
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Distribution of electrical activation to the External Intercostal Muscles during high frequency spinal cord stimulation in dogs.
The Journal of physiology, 2011Co-Authors: Anthony F Dimarco, Krzysztof E KowalskiAbstract:In contrast to previous methods of electrical stimulation of the inspiratory Muscles, high frequency spinal cord stimulation (HF-SCS) results in more physiological activation of these Muscles. The spatial distribution of activation to the External Intercostal Muscles by this method is unknown. In anaesthetized dogs, multiunit and single motor unit (SMU) EMG activity was monitored in the dorsal portion of the 3rd, 5th and 7th interspaces and ventral portion of the 3rd interspace during spontaneous breathing and HF-SCS following C2 spinal section. Stimulus amplitude during HF-SCS was adjusted such that inspired volumes matched spontaneous breathing (Protocol 1). During HF-SCS, mean peak SMU firing frequency was highest in the 3rd interspace (dorsal) (18.8 ± 0.3 Hz) and significantly lower in the 3rd interspace (ventral) (12.2 ± 0.2 Hz) and 5th interspace (dorsal) (15.3 ± 0.3 Hz) (P
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Effects of lung volume on parasternal pressure-generating capacity in dogs.
Experimental physiology, 2000Co-Authors: Anthony F Dimarco, J.r. Romaniuk, Gerald S. Supinski, Krzysztof E KowalskiAbstract:Previous studies have suggested that the optimum length for force generation of the parasternal Intercostal (PS) Muscles is well above functional residual capacity (FRC). We further explored this issue by examining the pressure-generating capacity of the PS Muscles as a function of lung volume in anaesthetized dogs. Upper thoracic spinal cord stimulation (SCS) was used to electrically activate the PS Muscles. Changes in airway pressure and parasternal resting length (LR) during airway occlusion were monitored over a wide range of lung volumes during SCS. To assess the effects of parasternal contraction alone, SCS was performed following phrenicotomy and section of the External Intercostal, levator costae and triangularis sterni Muscles. With increasing lung volume, there were progressive decrements in the capacity of the PS Muscles to produce changes in airway pressure. The relationship between PS pressure generation and lung volume was similar to a previous comparable assessment of the External Intercostal Muscles. The PS Muscles shortened during passive inflation and also shortened further (by > 20 % of LR) during SCS. Total shortening (passive plus active) increased progressively with increasing lung volume. Our results indicate that the capacity of the PS Muscles to produce changes in airway pressure (a) falls progressively with increasing lung volume and (b) is similar to that of the External Intercostal Muscles. We speculate that the fall in PS pressure-generating capacity is related, in part, to progressive reductions in end-inspiratory length.
Dimitri Leduc - One of the best experts on this subject based on the ideXlab platform.
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Mechanical effect of muscle spindles in the canine External Intercostal Muscles.
The Journal of physiology, 2003Co-Authors: Dimitri Leduc, André De TroyerAbstract:High-frequency mechanical vibration of the ribcage increases afferent activity from External Intercostal muscle spindles, but the effect of this procedure on the mechanical behaviour of the respiratory system is unknown. In the present study, we have measured the changes in External Intercostal muscle length and the craniocaudal displacement of the ribs during ribcage vibration (40 Hz) in anaesthetized dogs. With vibration, External Intercostal inspiratory activity increased by approximately 50 %, but the respiratory changes in muscle length and rib displacement were unaltered. A similar response was obtained after the Muscles in the caudal segments of the ribcage were sectioned and the caudally oriented force exerted by these Muscles on the rib was removed, thus suggesting that activation of External Intercostal muscle spindles by vibration generates little tension. Prompted by this observation, we also examined the role played by the External Intercostal muscle spindles in determining the respiratory displacement of the ribs during breathing against high inspiratory airflow resistances. Although resistances consistently elicited prominent reflex increases in External Intercostal inspiratory activity, the normal inspiratory cranial displacement of the ribs was reversed into an inspiratory caudal displacement. Also, this caudal rib displacement was essentially unchanged after section of the External Intercostal Muscles, whereas it was clearly enhanced after denervation of the parasternal Intercostals. These findings indicate that stretch reflexes in External Intercostal Muscles confer insufficient tension on the Muscles to significantly modify the mechanical behaviour of the respiratory system.
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Mechanical effect of muscle spindles in the canine External Intercostal Muscles.
The Journal of Physiology, 2003Co-Authors: Dimitri Leduc, André De TroyerAbstract:High-frequency mechanical vibration of the ribcage increases afferent activity from External Intercostal muscle spindles, but the effect of this procedure on the mechanical behaviour of the respiratory system is unknown. In the present study, we have measured the changes in External Intercostal muscle length and the craniocaudal displacement of the ribs during ribcage vibration (40 Hz) in anaesthetized dogs. With vibration, External Intercostal inspiratory activity increased by ∼50 %, but the respiratory changes in muscle length and rib displacement were unaltered. A similar response was obtained after the Muscles in the caudal segments of the ribcage were sectioned and the caudally oriented force exerted by these Muscles on the rib was removed, thus suggesting that activation of External Intercostal muscle spindles by vibration generates little tension. Prompted by this observation, we also examined the role played by the External Intercostal muscle spindles in determining the respiratory displacement of the ribs during breathing against high inspiratory airflow resistances. Although resistances consistently elicited prominent reflex increases in External Intercostal inspiratory activity, the normal inspiratory cranial displacement of the ribs was reversed into an inspiratory caudal displacement. Also, this caudal rib displacement was essentially unchanged after section of the External Intercostal Muscles, whereas it was clearly enhanced after denervation of the parasternal Intercostals. These findings indicate that stretch reflexes in External Intercostal Muscles confer insufficient tension on the Muscles to significantly modify the mechanical behaviour of the respiratory system.
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Response of the Canine Internal Intercostal Muscles to Chest Wall Vibration
American Journal of Respiratory and Critical Care Medicine, 2001Co-Authors: Dimitri Leduc, E. Brunko, A De TroyerAbstract:Although high-frequency mechanical vibration of the rib cage reduces dyspnea, its effects on the respiratory Muscles are largely unknown. We have previously shown that in anesthetized dogs, vibrating the rib cage during inspiration elicits a marked increase in the inspiratory electromyographic (EMG) activity recorded from the External Intercostal Muscles but does not affect tidal volume (Vt). In the present studies, we have tested the hypothesis that the maintenance of Vt results from the concomitant contraction of the internal interosseous (expiratory) Intercostals. When the rib cage was vibrated (40 Hz) during hyperventilation-induced apnea, a prominent activity was recorded from the External Intercostals but no activity was recorded from the internal Intercostals, including when the Muscles were lengthened by passive inflation. The internal Intercostals remained also silent when vibration was applied during spontaneous inspiration, and the phasic expiratory EMG activity recorded from them was unaltered...
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Response of the canine inspiratory Intercostal Muscles to chest wall vibration.
American Journal of Respiratory and Critical Care Medicine, 2000Co-Authors: Dimitri Leduc, E. Brunko, André De TroyerAbstract:High-frequency mechanical vibration of the rib cage reduces dyspnea, but the effect of this procedure on the respiratory Muscles is largely unknown. In the present studies, we have initially assessed the electrical and mechanical response to vibration (40 Hz) of the canine parasternal and External Intercostal Muscles (third interspace) during hyperventilation-induced apnea. When the vibrator was applied to the segment investigated, prominent External Intercostal activity was recorded in the seven animals studied, whereas low-amplitude parasternal Intercostal activity was recorded in only four animals. Similarly, when the vibrator was applied to more rostral and more caudal interspaces, activity was recorded commonly from the External Intercostal but only occasionally from the parasternal. The two Muscles, however, showed similar changes in length. We next examined the response to vibration of the Muscles in seven spontaneously breathing animals. Vibrating the rib cage during inspiration (in-phase) had no ...
