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1
De Troyer, A., and G. A. Farkas. "Linkage between parasternals and external intercostals during resting breathing." Journal of Applied Physiology 69, no. 2 (August 1, 1990): 509–16. http://dx.doi.org/10.1152/jappl.1990.69.2.509.
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To assess the mechanical coupling between the parasternal and external intercostals in the cranial portion of the rib cage, we measured the respiratory changes in length and the electromyograms of the two muscles in the same third or fourth intercostal space in 24 spontaneously breathing dogs. We found that 1) the amount of inspiratory shortening of the external intercostal was considerably smaller than the amount of shortening of the parasternal; 2) after selective denervation of the parasternal, the inspiratory shortening of both the parasternal and the external intercostal was almost abolished; 3) on the other hand, after selective denervation of the external intercostal, the inspiratory shortening of the parasternal was unchanged, and the inspiratory shortening of the external intercostal was reduced but not suppressed; and 4) this persistent shortening of the external intercostal was reversed into a clear-cut inspiratory lengthening when the parasternal was subsequently denervated. We conclude that in the dog 1) the inspiratory contraction of the external intercostals in the cranial portion of the rib cage is agonistic in nature as is the contraction of the parasternals; 2) during resting breathing, however, the changes in length of these external intercostals are largely determined by the action of the parasternals. These observations are consistent with the idea that in the dog, the parasternals play a larger role than the external intercostals in elevating the ribs during resting inspiratio
2
De Troyer, A. "Inspiratory elevation of the ribs in the dog: primary role of the parasternals [published errata appear in J Appl Physiol 1991 Aug;71(2):following Table of Contents and 1991 Dec;71(6):following Author Index]." Journal of Applied Physiology 70, no. 4 (April 1, 1991): 1447–55. http://dx.doi.org/10.1152/jappl.1991.70.4.1447.
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To assess the relative contributions of the different groups of inspiratory intercostal muscles to the cranial motion of the ribs in the dog, we have measured the axial displacement of the fourth rib and recorded the electromyograms of the parasternal intercostal, external intercostal, and levator costae in the third interspace in 15 anesthetized animals breathing at rest. In eight animals, the parasternal intercostals were denervated in interspaces 1-5. This procedure caused a marked increase in the amount of external intercostal and levator costae inspiratory activity, and yet the inspiratory cranial motion of the rib was reduced by 55%. On the other hand, the external intercostals in interspaces 1-5 were sectioned in seven animals, and the reduction in the cranial rib motion was only 22%; the amount of parasternal and levator costae activity, however, was unchanged. When the parasternals in these animals were subsequently denervated, the levator costae inspiratory activity increased markedly, but the inspiratory cranial motion of the rib was abolished or reversed into an inspiratory caudal motion. These studies thus confirm that, in the dog breathing at rest, the parasternal intercostals have a larger role than the external intercostals and levator costae in causing the cranial motion of the ribs during inspiration. A quantitative analysis suggests that the parasternal contribution is approximately 80%.
3
De Troyer, A., and G. A. Farkas. "Mechanical arrangement of the parasternal intercostals in the different interspaces." Journal of Applied Physiology 66, no. 3 (March 1, 1989): 1421–29. http://dx.doi.org/10.1152/jappl.1989.66.3.1421.
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When the parasternal intercostal in a single interspace is selectively denervated in dogs with diaphragmatic paralysis, it continues to shorten during both quiet and occluded inspiration. In the present studies, we have tested the hypothesis that this passive parasternal inspiratory shortening is due to the action of the other parasternal intercostals. Changes in length of the denervated third right parasternal were measured in eight supine phrenicotomized animals. We found that 1) the inspiratory muscle shortening increased after denervation of the third left parasternal but gradually decreased with denervation of the parasternals situated in the second, fourth, and fifth interspaces; 2) the muscle, however, always continued to shorten during inspiration, even after denervation of all the parasternals; 3) stimulating selectively the third left parasternal caused a muscle lengthening; and 4) bilateral stimulation of the parasternals in the second or the fourth interspace produced a muscle shortening. We conclude that 1) the two parasternals situated in the same interspace on both sides of the sternum are mechanically arranged in series, whereas the parasternals located in adjacent interspaces are mechanically arranged in parallel; and 2) if a denervated parasternal continues to shorten during inspiration, this is in part because of the action of the parasternals in the adjacent interspaces and in part because of other inspiratory muscles of the rib cage, possibly the external intercostals and the levator costae.
4
Kelsen, S. G., S. Bao, A. J. Thomas, I. A. Mardini, and G. J. Criner. "Structure of parasternal intercostal muscles in the adult hamster: topographic effects." Journal of Applied Physiology 75, no. 3 (September 1, 1993): 1150–54. http://dx.doi.org/10.1152/jappl.1993.75.3.1150.
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The parasternal intercostals are primary inspiratory muscles like the costal and crural diaphragm. However, the structure of the rib cage and its impedance to inspiration and expiration varies regionally. We questioned whether topographic differences in rib cage structure and impedance were associated with regional differences in parasternal intercostal muscle structure. Therefore, we examined the size and percentage of histochemically stained fibers in the parasternal intercostal muscles in the first, second, third, fourth, and sixth interspaces in the hamster. We observed a rostrocaudal gradient in the percentage and size of slow oxidative (SO), fast oxidative-glycolytic, and fast glycolytic (FG) fibers in the parasternal intercostal muscles. In particular, the percentage of SO decreased while the percentage of FG increased in a rostrocaudal direction in the first through sixth interspaces. In addition, the size of SO and FG fibers increased from the first to sixth interspace. Furthermore, changes in the size and percent of the three fiber types produced, in a rostrocaudal direction, significant reductions in the relative mass of the parasternal intercostal muscle made up of SO fibers and increases in the mass of fast fibers. We speculate that topographical differences in the size and percentage of fast and slow twitch fibers in the parasternal intercostal are likely to alter force-generating capacity of the parasternal muscles in a rostrocaudal direction and likely reflect regional differences in muscle load and/or activity.
5
Leenaerts, P., and M. Decramer. "Respiratory changes in parasternal intercostal intramuscular pressure." Journal of Applied Physiology 68, no. 3 (March 1, 1990): 868–75. http://dx.doi.org/10.1152/jappl.1990.68.3.868.
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In an attempt to obtain insight in the forces developed by the parasternal intercostal muscles during breathing, changes in parasternal intramuscular pressure (PIP) were measured in 14 supine anesthetized dogs using a microtransducer method. In six animals, during bilateral parasternal stimulation a linear relationship between contractile force exerted on the rib and PIP was demonstrated (r greater than 0.95). In eight animals, during quiet active inspiration, substantial (55 +/- 11.5 cmH2O) PIP was developed. During inspiratory resistive loading and airway occlusion the inspiratory rise in PIP increased in proportion to the inspiratory fall in pleural pressure (r = 0.82). Phrenicotomy and vagotomy resulted in an increase in the inspiratory rise in PIP of 21% and 99%, respectively. During passive deflation, when the parasternal intercostals were passively lengthened, large rises (320 +/- 221 cmH2O) in intramuscular pressure were observed. During passive inflation intramuscular pressure remained constant or even decreased slightly (-8 +/- 25 cmH2O) as expected on the basis of the passive shortening of the muscles. PIP thus invariably increased when tension increased either actively or passively. From PIP it is clear that the parasternals exert significant forces on the ribs during respiratory maneuvers.
6
Wilson, T. A., and A. De Troyer. "Respiratory effect of the intercostal muscles in the dog." Journal of Applied Physiology 75, no. 6 (December 1, 1993): 2636–45. http://dx.doi.org/10.1152/jappl.1993.75.6.2636.
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In a previous paper (J. Appl. Physiol. 73: 2283–2288, 1992), respiratory effect was defined as the change in airway pressure produced by active tension in a muscle with the airway closed, mechanical advantage was defined as the respiratory effect per unit mass per unit active stress, and it was shown that mechanical advantage is proportional to muscle shortening during the relaxation maneuver. Here, we report values of mechanical advantage and maximum respiratory effect of the intercostal muscles of the dog. Orientations of the intercostal muscles in the third and sixth interspaces were measured. Mechanical advantages of the muscles in these interspaces were computed by computing their shortening from these data and data in the literature on rib displacement. We found that parasternal internal intercostals and dorsal external intercostals of the upper interspace have large inspiratory mechanical advantages and that dorsal internal intercostals of the lower interspace and triangularis sterni have large expiratory mechanical advantages. Mass distributions in the two interspaces were also measured, and maximum respiratory effects of the muscles were calculated from their mass, mechanical advantage, and the value for maximum stress in skeletal muscle. Estimated maximum respiratory effects of the inspiratory and expiratory muscle groups of the entire rib cage were tested by measuring the maximum inspiratory pressures that were generated by the parasternal and external intercostals acting alone. Measured pressures, -13 cmH2O for the parasternals and -11 cmH2O for the external intercostals, agreed well with the computed values.
7
De Troyer, André, and Dimitri Leduc. "Effect of diaphragmatic contraction on the action of the canine parasternal intercostals." Journal of Applied Physiology 101, no. 1 (July 2006): 169–75. http://dx.doi.org/10.1152/japplphysiol.01465.2005.
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The inspiratory intercostal muscles enhance the force generated by the diaphragm during lung expansion. However, whether the diaphragm also alters the force developed by the inspiratory intercostals is unknown. Two experiments were performed in dogs to answer the question. In the first experiment, external, cranially oriented forces were applied to the different rib pairs to assess the effect of diaphragmatic contraction on the coupling between the ribs and the lung. The fall in airway opening pressure (ΔPao) produced by a given force on the ribs was invariably greater during phrenic nerve stimulation than with the diaphragm relaxed. The cranial rib displacement (Xr), however, was 40–50% smaller, thus indicating that the increase in ΔPao was exclusively the result of the increase in diaphragmatic elastance. In the second experiment, the parasternal intercostal muscle in the fourth interspace was selectively activated, and the effects of diaphragmatic contraction on the ΔPao and Xr caused by parasternal activation were compared with those observed during the application of external loads on the ribs. Stimulating the phrenic nerves increased the ΔPao and reduced the Xr produced by the parasternal intercostal, and the magnitudes of the changes were identical to those observed during external rib loading. It is concluded, therefore, that the diaphragm has no significant synergistic or antagonistic effect on the force developed by the parasternal intercostals during breathing. This lack of effect is probably related to the constraint imposed on intercostal muscle length by the ribs and sternum.
8
Shibata, Yasuyuki. "Parasternal Intercostal Nerve Block." Ultrasound in Medicine & Biology 43 (2017): S183. http://dx.doi.org/10.1016/j.ultrasmedbio.2017.08.1618.
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Levine, Sanford, Taitan Nguyen, Michael Friscia, Jianliang Zhu, Wilson Szeto, John C. Kucharczuk, Boris A. Tikunov, Neal A. Rubinstein, Larry R. Kaiser, and Joseph B. Shrager. "Parasternal intercostal muscle remodeling in severe chronic obstructive pulmonary disease." Journal of Applied Physiology 101, no. 5 (November 2006): 1297–302. http://dx.doi.org/10.1152/japplphysiol.01607.2005.
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Studies in experimental animals indicate that chronic increases in neural drive to limb muscles elicit a fast-to-slow transformation of fiber-type proportions and myofibrillar proteins. Since neural drive to the parasternal intercostal muscles (parasternals) is chronically increased in patients with severe chronic obstructive pulmonary diseases (COPDs), we carried out the present study to test the hypothesis that the parasternals of COPD patients exhibit an increase in the proportions of both slow fibers and slow myosin heavy chains (MHCs). Accordingly, we obtained full thickness parasternal muscle biopsies from the third interspace of seven COPD patients (mean ± SE age: 59 ± 4 yr) and seven age-matched controls (AMCs). Fiber typing was done by immunohistochemistry, and MHC proportions were determined by SDS-PAGE followed by densitometry. COPD patients exhibited higher proportions of slow fibers than AMCs (73 ± 4 vs. 51 ± 3%; P < 0.01). Additionally, COPD patients exhibited higher proportions of slow MHC than AMCs (56 ± 4 vs. 46 ± 4%, P < 0.04). We conclude that the parasternal muscles of patients with severe COPD exhibit a fast-to-slow transformation in both fiber-type and MHC proportions. Previous workers have demonstrated that remodeling of the external intercostals, another rib cage inspiratory muscle, elicited by severe COPD is characterized by a slow-to-fast transformation in both fiber types and MHC isoform proportions. The physiological significance of this difference in remodeling between these two inspiratory rib cage muscles remains to be elucidated.
10
De Troyer, A., and G. Farkas. "Mechanics of the parasternal intercostals in prone dogs: statics and dynamics." Journal of Applied Physiology 74, no. 6 (June 1, 1993): 2757–62. http://dx.doi.org/10.1152/jappl.1993.74.6.2757.
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It is well established that the parasternal intercostal muscles in supine dogs play a major role in causing the inspiratory elevation of the ribs. This posture, however, is not physiological in the dog. In the present study, we measured the electromyographic (EMG) activity and the respiratory changes in length of these muscles in the prone (standing) and supine postures in seven anesthetized spontaneously breathing dogs. With a change from the supine to the prone posture, the parasternal intercostals showed a 3.2% reduction in their relaxation length (Lr), but their mechanical behavior was essentially unchanged. Thus, the muscles continued to shorten below Lr during inspiration and to lengthen beyond Lr during expiration. With the adoption of the prone posture, the amount of parasternal inspiratory EMG activity and the amount of inspiratory muscle shortening each increased by 30–35%. Furthermore, when the parasternal intercostal in a single interspace was selectively denervated, the shortening of the muscle during inspiration in both postures was virtually eliminated. These observations indicate that in the dog the parasternal intercostals still play a major role in causing the inspiratory elevation of the ribs in the prone posture. These observations also suggest that these muscles in prone animals continue to operate on the descending limb of their length-tension curve.
11
Easton, Paul A., Harvey G. Hawes, Bruce Rothwell, and Andre de Troyer. "Postinspiratory activity of the parasternal and external intercostal muscles in awake canines." Journal of Applied Physiology 87, no. 3 (September 1, 1999): 1097–101. http://dx.doi.org/10.1152/jappl.1999.87.3.1097.
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Previous studies have shown in awake dogs that activity in the crural diaphragm, but not in the costal diaphragm, usually persists after the end of inspiratory airflow. It has been suggested that this difference in postinspiratory activity results from greater muscle spindle content in the crural diaphragm. To evaluate the relationship between muscle spindles and postinspiratory activity, we have studied the pattern of activation of the parasternal and external intercostal muscles in the second to fourth interspaces in eight chronically implanted animals. Recordings were made on 2 or 3 successive days with the animals breathing quietly in the lateral decubitus position. The two muscles discharged in phase with inspiration, but parasternal intercostal activity usually terminated with the cessation of inspiratory flow, whereas external intercostal activity persisted for 24.7 ± 12.3% of inspiratory time ( P < 0.05). Forelimb elevation in six animals did not affect postinspiratory activity in the parasternal but prolonged postinspiratory activity in the external intercostal to 45.4 ± 16.3% of inspiratory time ( P < 0.05); in two animals, activity was still present at the onset of the next inspiratory burst. These observations support the concept that muscle spindles are an important determinant of postinspiratory activity. The absence of such activity in the parasternal intercostals and costal diaphragm also suggests that the mechanical impact of postinspiratory activity on the respiratory system is smaller than conventionally thought.
12
Greer, J. J., and T. P. Martin. "Distribution of muscle fiber types and EMG activity in cat intercostal muscles." Journal of Applied Physiology 69, no. 4 (October 1, 1990): 1208–11. http://dx.doi.org/10.1152/jappl.1990.69.4.1208.
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The electromyogram (EMG) activity and histochemical properties of intercostal muscles in the anesthetized cat were studied. The parasternal muscles were consistently active during inspiration. The external intercostals in the rostral spaces and the ventral portions of the midthoracic spaces were also recruited during inspiration. The remaining external intercostals were typically silent, regardless of the level of respiratory drive. The internal intercostal muscles located in the caudal spaces were occasionally recruited during expiration. There was a clear correlation between recruitment patterns of the intercostals and the histochemically defined fiber type properties of the muscles. Intercostal muscles that were routinely recruited during inspiration had a significantly higher proportion of slow-oxidative muscle fibers.
13
Oliven, A., E. C. Deal, S. G. Kelsen, and N. S. Cherniack. "Effects of bronchoconstriction on respiratory muscle activity during expiration." Journal of Applied Physiology 62, no. 1 (January 1, 1987): 308–14. http://dx.doi.org/10.1152/jappl.1987.62.1.308.
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The effect of methacholine-induced bronchoconstriction on the electrical activity of respiratory muscles during expiration was studied in 12 anesthetized spontaneously breathing dogs. Before and after aerosols of methacholine, diaphragm, parasternal intercostal, internal intercostal, and external oblique electromyograms were recorded during 100% O2 breathing and CO2 rebreathing. While breathing 100% O2, five dogs showed prolonged electrical activity of the diaphragm and parasternal intercostals in early expiration, postinspiratory inspiratory activity (PIIA). Aerosols of methacholine increased pulmonary resistance, decreased tidal volume, and elevated arterial PCO2. During bronchoconstriction, when PCO2 was varied by CO2 rebreathing, PIIA was shorter at low levels of PCO2, and external oblique and internal intercostal were higher at all levels of PCO2. Vagotomy shortened PIIA in dogs with prolonged PIIA. After vagotomy, methacholine had no effects on PIIA but continued to increase external oblique and internal intercostal activity at all levels of PCO2. These findings indicate that bronchoconstriction influences PIIA through a vagal reflex but augments expiratory activity, at least in part, by extravagal mechanisms.
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Tagliabue, Giovanni, Michael Sukjoon Ji, Jenny V. Suneby Jagers, Danny J. Zuege, John B. Kortbeek, and Paul A. Easton. "Parasternal intercostal, costal, and crural diaphragm neural activation during hypercapnia." Journal of Applied Physiology 131, no. 2 (August 1, 2021): 672–80. http://dx.doi.org/10.1152/japplphysiol.00261.2020.
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This investigation directly compares neural activation of the parasternal intercostal muscle with the two distinct segments of the diaphragm, costal and crural, during room air and hypercapnic ventilation. During eupnea and hypercapnia, the parasternal intercostal muscle and costal diaphragm share a similar neural activation, whereas they both differ significantly from the crural diaphragm. The parasternal intercostal muscle maintains and increases active inspiratory mechanical action with shortening during ventilation, even with high levels of diaphragm recruitment.
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Cappello, Matteo, and André De Troyer. "On the respiratory function of the ribs." Journal of Applied Physiology 92, no. 4 (April 1, 2002): 1642–46. http://dx.doi.org/10.1152/japplphysiol.01053.2001.
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To assess the respiratory function of the ribs, we measured the changes in airway opening pressure (Pao) induced by stimulation of the parasternal and external intercostal muscles in anesthetized dogs, first before and then after the bony ribs were removed from both sides of the chest. Stimulating either set of muscles with the rib cage intact elicited a fall in Pao in all animals. After removal of the ribs, however, the fall in Pao produced by the parasternal intercostals was reduced by 60% and the fall produced by the external intercostals was eliminated. The normal outward curvature of the rib cage was also abolished in this condition, and when the curvature was restored by a small inflation, external intercostal stimulation consistently elicited a rise rather than a fall in Pao. These findings thus confirm that the ribs play a critical role in the act of breathing by converting intercostal muscle shortening into lung volume expansion. In addition, they carry the compression that is required to balance the pressure difference across the chest wall.
16
Road, J. D., S. Osborne, and A. Cairns. "Stability of evoked parasternal intercostal muscle electromyogram at increased end-expiratory lung volume." Journal of Applied Physiology 78, no. 4 (April 1, 1995): 1485–88. http://dx.doi.org/10.1152/jappl.1995.78.4.1485.
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The diaphragmatic electromyogram has been measured as an index of the level of diaphragmatic activation. The diaphragmatic electromyogram, however, even when measured by intramuscular electrodes, can be artifactually altered by a change in lung volume (A. Brancatisano, S. M. Kelly, A. Tully, S. H. Loring, and L. A. Engel. J. Appl. Physiol. 66: 1699–1705, 1989) or by a change in body position. The parasternal intercostal muscle may be less subject to the mechanisms that are believed to produce this artifactual change. We asked whether the parasternal intercostal electromyographic activity could be reliable when lung volume changes. Six supine rabbits were anesthetized with ketamine and xylazine. Fine bipolar copper wires, with their tips exposed, were inserted into the left parasternal intercostal muscle in the third interspace. A stimulus that was three times maximal was applied to the corresponding intercostal nerve, and the resulting action potential (AP) was photographed. Parasternal intercostal muscle length was measured by sonomicrometry over the vital capacity range. There were small nonsignificant changes in the AP from functional residual capacity (FRC) to total lung capacity. From FRC to residual volume there was variation in the AP. The AP was also quite stable when regional conductivity was altered but showed variation when the parasternal intercostal muscle length change was accentuated by traction on the rib cage. We conclude that the parasternal intercostal electromyographic activity can be reliably used to measure inspiratory motoneuron output to it over the range of lung volumes from FRC to total lung capacity.
17
Hudson, Anna L., Jane E. Butler, Simon C. Gandevia, and Andre De Troyer. "Interplay Between the Inspiratory and Postural Functions of the Human Parasternal Intercostal Muscles." Journal of Neurophysiology 103, no. 3 (March 2010): 1622–29. http://dx.doi.org/10.1152/jn.00887.2009.
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The parasternal intercostal muscles are obligatory inspiratory muscles. To test the hypothesis that they are also involved in trunk rotation and to assess the effect of any postural role on inspiratory drive to the muscles, intramuscular electromyographic (EMG) recordings were made from the parasternal intercostals on the right side in six healthy subjects during resting breathing in a neutral posture (“neutral breaths”), during an isometric axial rotation effort of the trunk to the right (“ipsilateral rotation”) or left (“contralateral rotation”), and during resting breathing with the trunk rotated. The parasternal intercostals were commonly active during ipsilateral rotation but were consistently silent during contralateral rotation. In addition, with ipsilateral rotation, peak parasternal inspiratory activity was 201 ± 19% (mean ± SE) of the peak inspiratory activity in neutral breaths ( P < 0.001), and activity commenced earlier relative to the onset of inspiratory flow. These changes resulted from an increase in the discharge frequency of motor units (14.3 ± 0.3 vs. 11.0 ± 0.3 Hz; P < 0.001) and the recruitment of new motor units. The majority of units that discharged during ipsilateral rotation were also active in inspiration. However, with contralateral rotation, parasternal inspiratory activity was delayed relative to the onset of inspiratory flow, and peak activity was reduced to 72 ± 4% of that in neutral breaths ( P < 0.001). This decrease resulted from a decrease in the inspiratory discharge frequency of units (10.5 ± 0.2 vs. 12.0 ± 0.2 Hz; P < 0.001) and the derecruitment of units. These observations confirm that in addition to an inspiratory function, the parasternal intercostal muscles have a postural function. Furthermore the postural and inspiratory drives depolarize the same motoneurons, and the postural contraction of the muscles alters their output during inspiration in a direction-dependent manner.
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De Troyer, A., G. A. Farkas, and V. Ninane. "Mechanics of the parasternal intercostals during occluded breaths in dogs." Journal of Applied Physiology 64, no. 4 (April 1, 1988): 1546–53. http://dx.doi.org/10.1152/jappl.1988.64.4.1546.
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The electrical activity and the respiratory changes in length of the third parasternal intercostal muscle were measured during single-breath airway occlusion in 12 anesthetized, spontaneously breathing dogs in the supine posture. During occluded breaths in the intact animal, the parasternal intercostal was electrically active and shortened while pleural pressure fell. In contrast, after section of the third intercostal nerve at the chondrocostal junction and abolition of parasternal electrical activity, the muscle always lengthened. This inspiratory muscle lengthening must be related to the fall in pleural pressure; it was, however, approximately 50% less than the amount of muscle lengthening produced, for the same fall in pleural pressure, by isolated stimulation of the phrenic nerves. These results indicate that 1) the parasternal inspiratory shortening that occurs during occluded breaths in the dog results primarily from the muscle inspiratory contraction per se, and 2) other muscles of the rib cage, however, contribute to this parasternal shortening by acting on the ribs or the sternum. The present studies also demonstrate the important fact that the parasternal inspiratory contraction in the dog is really agonistic in nature.
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Darian, G. B., A. F. DiMarco, S. G. Kelsen, G. S. Supinski, and S. B. Gottfried. "Effects of progressive hypoxia on parasternal, costal, and crural diaphragm activation." Journal of Applied Physiology 66, no. 6 (June 1, 1989): 2579–84. http://dx.doi.org/10.1152/jappl.1989.66.6.2579.
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The distribution of motor drive to the costal and crural diaphragm and parasternal intercostal muscles was evaluated during progressive isocapnic hypoxia in anesthetized dogs. Bipolar stainless steel wire electrodes were placed unilaterally into the costal and crural portions of the diaphragm and into the parasternal intercostal muscle in the second or third intercostal space. Both peak and rate of rise of electromyographic activity of each chest wall muscle increased in curvilinear fashion in response to progressive hypoxia. Both crural and parasternal intercostal responses, however, were greater than those of the costal diaphragm. The onset of crural activation preceded that of the costal portion of the diaphragm and parasternal intercostal muscle activation. Despite differences in the degree of activation among the various chest wall muscles, the rate of increase in activation for any given muscle was linearly related to the rate of increases for the other two. This suggests that respiratory drive during progressive hypoxia increases in fixed proportion to the different chest wall inspiratory muscles. Our findings lend further support to the concept that the costal and crural diaphragm are governed by separate neural control mechanisms and, therefore, may be considered separate muscles.
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Lozano-García, Manuel, Luis Estrada-Petrocelli, Abel Torres, Gerrard F. Rafferty, John Moxham, Caroline J. Jolley, and Raimon Jané. "Noninvasive Assessment of Neuromechanical Coupling and Mechanical Efficiency of Parasternal Intercostal Muscle during Inspiratory Threshold Loading." Sensors 21, no. 5 (March 4, 2021): 1781. http://dx.doi.org/10.3390/s21051781.
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This study aims to investigate noninvasive indices of neuromechanical coupling (NMC) and mechanical efficiency (MEff) of parasternal intercostal muscles. Gold standard assessment of diaphragm NMC requires using invasive techniques, limiting the utility of this procedure. Noninvasive NMC indices of parasternal intercostal muscles can be calculated using surface mechanomyography (sMMGpara) and electromyography (sEMGpara). However, the use of sMMGpara as an inspiratory muscle mechanical output measure, and the relationships between sMMGpara, sEMGpara, and simultaneous invasive and noninvasive pressure measurements have not previously been evaluated. sEMGpara, sMMGpara, and both invasive and noninvasive measurements of pressures were recorded in twelve healthy subjects during an inspiratory loading protocol. The ratios of sMMGpara to sEMGpara, which provided muscle-specific noninvasive NMC indices of parasternal intercostal muscles, showed nonsignificant changes with increasing load, since the relationships between sMMGpara and sEMGpara were linear (R2 = 0.85 (0.75–0.9)). The ratios of mouth pressure (Pmo) to sEMGpara and sMMGpara were also proposed as noninvasive indices of parasternal intercostal muscle NMC and MEff, respectively. These indices, similar to the analogous indices calculated using invasive transdiaphragmatic and esophageal pressures, showed nonsignificant changes during threshold loading, since the relationships between Pmo and both sEMGpara (R2 = 0.84 (0.77–0.93)) and sMMGpara (R2 = 0.89 (0.85–0.91)) were linear. The proposed noninvasive NMC and MEff indices of parasternal intercostal muscles may be of potential clinical value, particularly for the regular assessment of patients with disordered respiratory mechanics using noninvasive wearable and wireless devices.
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Leduc, Dimitri, and André De Troyer. "The effect of lung inflation on the inspiratory action of the canine parasternal intercostals." Journal of Applied Physiology 100, no. 3 (March 2006): 858–63. http://dx.doi.org/10.1152/japplphysiol.00739.2005.
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Inflation induces a marked decrease in the lung-expanding ability of the diaphragm, but its effect on the parasternal intercostal muscles is uncertain. To assess this effect, the phrenic nerves and the external intercostals were severed in anesthetized, vagotomized dogs, such that the parasternal intercostals were the only muscles active during inspiration, and the endotracheal tube was occluded at different lung volumes. Although the inspiratory electromyographic activity recorded from the muscles was constant, the change in airway opening pressure decreased with inflation from −7.2 ± 0.6 cmH2O at functional residual capacity to −2.2 ± 0.2 cmH2O at 20-cmH2O transrespiratory pressure ( P < 0.001). The inspiratory cranial displacement of the ribs remained virtually unchanged, and the inspiratory caudal displacement of the sternum decreased moderately. However, the inspiratory outward rib displacement decreased markedly and continuously; at 20 cmH2O, this displacement was only 23 ± 2% of the value at functional residual capacity. Calculations based on this alteration yielded substantial decreases in the change in airway opening pressure. It is concluded that, in the dog, 1) inflation affects adversely the lung-expanding actions of both the parasternal intercostals and the diaphragm; and 2) the adverse effect of inflation on the parasternal intercostals is primarily related to the alteration in the kinematics of the ribs. As a corollary, it is likely that hyperinflation also has a negative impact on the parasternal intercostals in patients with chronic obstructive pulmonary disease.
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Ohgoshi, Yuichi, Kentaro Ino, and Masakazu Matsukawa. "Ultrasound-guided parasternal intercostal nerve block." Journal of Anesthesia 30, no. 5 (June 20, 2016): 916. http://dx.doi.org/10.1007/s00540-016-2202-5.
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Decramer, M., T. X. Jiang, and M. Demedts. "Effects of acute hyperinflation on chest wall mechanics in dogs." Journal of Applied Physiology 63, no. 4 (October 1, 1987): 1493–98. http://dx.doi.org/10.1152/jappl.1987.63.4.1493.
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We studied chest wall mechanics at functional residual capacity (FRC) and near total lung capacity (TLC) in 14 supine anesthetized and vagotomized dogs. During breathing near TLC compared with FRC, tidal volume decreased (674 +/- 542 vs. 68 +/- 83 ml; P less than 0.025). Both inspiratory changes in gastric pressure (4.5 +/- 2.5 vs. -0.2 +/- 2.0 cmH2O; P less than 0.005) and changes in abdominal cross-sectional area (25 +/- 17 vs. -1.0 +/- 4.2%; P less than 0.001) markedly decreased; they were both often negative during inspiration near TLC. Parasternal intercostal shortening decreased (-3.0 +/- 3.7 vs. -2.0 +/- 2.7%), whereas diaphragmatic shortening decreased slightly more in both costal and crural parts (costal -8.4 +/- 2.9 vs. -4.3 +/- 4.1%, crural -22.8 +/- 13.2 vs. -10.0 +/- 7.5%; P less than 0.05). As a result, the ratio of parasternal to diaphragm shortening increased near TLC (0.176 +/- 0.135 vs. 0.396 +/- 0.340; P less than 0.05). Electromyographic (EMG) activity in the parasternals slightly decreased near TLC, whereas the EMG activity in the costal and crural parts of the diaphragm slightly increased. We conclude that 1) the mechanical outcome of diaphragmatic contraction near TLC is markedly reduced, and 2) the mechanical outcome of parasternal intercostal contraction near TLC is clearly less affected.
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Leduc, Dimitri, and André De Troyer. "Mechanism of increased inspiratory rib elevation in ascites." Journal of Applied Physiology 107, no. 3 (September 2009): 734–40. http://dx.doi.org/10.1152/japplphysiol.00470.2009.
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The detrimental effect of ascites on the lung-expanding action of the diaphragm is partly compensated for by an increase in the inspiratory elevation of the ribs, but the mechanism of this increase is uncertain. To identify this mechanism, the effect of ascites on the response of rib 4 to isolated phrenic nerve stimulation was first assessed in four dogs with bilateral pneumothoraces. Stimulation did not produce any axial displacement of the rib ( Xr) in the control condition and caused a cranial rib displacement in the presence of ascites. This displacement, however, was small. In a second experiment, the effects of ascites on the pleural pressure swing (ΔPpl), intercostal activity, and Xr during spontaneous inspiration were measured in eight animals. As the volume of ascites increased from 0 to 200 ml/kg body wt, Xr increased from 3.5 ± 0.5 to 7.5 ± 0.9 mm ( P < 0.001), ΔPpl decreased from −6.4 ± 0.4 to −3.6 ± 0.3 cmH20 ( P < 0.001), and parasternal intercostal activity increased 61 ± 19% ( P < 0.001). The role of the decrease in ΔPpl in causing the increase in Xr was then separated from that of the increase in intercostal muscle force using the relation between Xr and ΔPpl during passive lung inflation. The loss in ΔPpl accounted for two-thirds of the increase in Xr. These observations indicate that 1) the increased inspiratory elevation of the ribs in ascites is not the result of the increase in the rib cage-expanding action of the diaphragm and 2) it is due mostly to the decrease in ΔPpl and partly to the increase in the force exerted by the parasternal intercostals on the ribs. These observations also suggest, however, that the rib cage expansion caused by ascites makes the parasternal intercostals less effective in pulling the ribs cranially.
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Legrand, Alexandre, Serge Goldman, Philippe Damhaut, and André De Troyer. "Heterogeneity of metabolic activity in the canine parasternal intercostals during breathing." Journal of Applied Physiology 90, no. 3 (March 1, 2001): 811–15. http://dx.doi.org/10.1152/jappl.2001.90.3.811.
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In the dog, the inspiratory mechanical advantage of the parasternal intercostals shows a marked spatial heterogeneity, whereas the expiratory mechanical advantage of the triangularis sterni is relatively uniform. The contribution of a particular respiratory muscle to lung volume expansion during breathing, however, depends both on the mechanical advantage of the muscle and on its neural input. To evaluate the distribution of neural input across the canine parasternal intercostals and triangularis sterni, we have examined the distribution of metabolic activity among these muscles in seven spontaneously breathing animals by measuring the uptake of the glucose tracer analog [18F]fluorodeoxyglucose (FDG). FDG uptake in any given parasternal intercostal was greatest in the medial bundles and decreased rapidly toward the costochondral junctions. In addition, FDG uptake in the medial parasternal bundles increased from the first to the second interspace, plateaued in the second through fifth interspaces, and then decreased progressively toward the eighth interspace. In contrast, uptake in the triangularis sterni showed no significant rostrocaudal gradient. These results overall strengthen the idea that the spatial distribution of neural input within a particular set of respiratory muscles is closely matched with the spatial distribution of mechanical advantage.
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Decramer, M., M. B. Reid, and A. De Troyer. "Relationship between parasternal intercostal length and rib cage displacement in dogs." Journal of Applied Physiology 58, no. 5 (May 1, 1985): 1517–20. http://dx.doi.org/10.1152/jappl.1985.58.5.1517.
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The relationship between parasternal intercostal length and rib cage cross-sectional area was examined in nine supine dogs during passive inflation and during quiet breathing before and after phrenicotomy. Parasternal intercostal length (PSL) was measured with a sonomicrometry technique, and rib cage cross-sectional area (Arc) was measured with a Respitrace coil placed around the middle rib cage. During active inspiration as well as during passive inflation, PSL decreased as Arc increased. However, the relationship between PSL and Arc during active inspiration, whether in the intact or phrenicotomized animal, was almost invariably different from that during passive inflation, so that the same increase in Arc was associated with a greater decrease in PSL in the former than in the latter instance. This difference between passive inflation and active inspiration is probably due to the active contraction of the parasternals during inspiration and the consequent caudal displacement of the sternum. In upright humans, the sternum moves cephalad and not caudad during inspiration, so the relationship between PSL and Arc during active breathing might be similar to that during passive inflation.
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De Troyer, A., and G. A. Farkas. "Passive shortening of canine parasternal intercostals during breathing." Journal of Applied Physiology 66, no. 3 (March 1, 1989): 1414–20. http://dx.doi.org/10.1152/jappl.1989.66.3.1414.
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We have previously demonstrated that the shortening of the canine parasternal intercostals during inspiration results primarily from the muscles' own activation (J. Appl. Physiol. 64: 1546–1553, 1988). In the present studies, we have tested the hypothesis that other inspiratory rib cage muscles may contribute to the parasternal inspiratory shortening. Eight supine, spontaneously breathing dogs were studied. Changes in length of the third or fourth right parasternal intercostal were measured during quiet breathing and during single-breath airway occlusion first with the animal intact, then after selective denervation of the muscle, and finally after bilateral phrenicotomy. Denervating the parasternal virtually eliminated the muscle shortening during quiet inspiration and caused the muscle to lengthen during occluded breaths. After phrenicotomy, however, the parasternal, while being denervated, shortened again a significant amount during both quiet inspiration and occluded breaths. These data thus confirm that a component of the parasternal inspiratory shortening is not active and results from the action of other inspiratory rib cage muscles. Additional studies in four animals demonstrated that the scalene and serratus muscles do not play any role in this phenomenon; it must therefore result from the action of intrinsic rib cage muscles.
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Dres, Martin, Bruno-Pierre Dubé, Ewan Goligher, Stefannie Vorona, Suela Demiri, Elise Morawiec, Julien Mayaux, Laurent Brochard, Thomas Similowski, and Alexandre Demoule. "Usefulness of Parasternal Intercostal Muscle Ultrasound during Weaning from Mechanical Ventilation." Anesthesiology 132, no. 5 (May 1, 2020): 1114–25. http://dx.doi.org/10.1097/aln.0000000000003191.
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Abstract Background The assessment of diaphragm function with diaphragm ultrasound seems to bring important clinical information to describe diaphragm work and weakness. When the diaphragm is weak, extradiaphragmatic muscles may play an important role, but whether ultrasound can also assess their activity and function is unknown. This study aimed to (1) evaluate the feasibility of measuring the thickening of the parasternal intercostal and investigate the responsiveness of this muscle to assisted ventilation; and (2) evaluate whether a combined evaluation of the parasternal and the diaphragm could predict failure of a spontaneous breathing trial. Methods First, an exploratory evaluation of the parasternal in 23 healthy subjects. Second, the responsiveness of parasternal to several pressure support levels were studied in 16 patients. Last, parasternal activity was compared in presence or absence of diaphragm dysfunction (assessed by magnetic stimulation of the phrenic nerves and ultrasound) and in case of success/failure of a spontaneous breathing trial in 54 patients. Results The parasternal was easily accessible in all patients. The interobserver reproducibility was good (intraclass correlation coefficient, 0.77 (95% CI, 0.53 to 0.89). There was a progressive decrease in parasternal muscle thickening fraction with increasing levels of pressure support (Spearman ρ = −0.61 [95% CI, −0.74 to −0.44]; P &lt; 0.0001) and an inverse correlation between parasternal muscle thickening fraction and the pressure generating capacity of the diaphragm (Spearman ρ = −0.79 [95% CI, −0.87 to −0.66]; P &lt; 0.0001). The parasternal muscle thickening fraction was higher in patients with diaphragm dysfunction: 17% (10 to 25) versus 5% (3 to 8), P &lt; 0.0001. The pressure generating capacity of the diaphragm, the diaphragm thickening fraction and the parasternal thickening fraction similarly predicted failure or the spontaneous breathing trial. Conclusions Ultrasound assessment of the parasternal intercostal muscle is feasible in the intensive care unit and provides novel information regarding the respiratory capacity load balance. Editor’s Perspective What We Already Know about This Topic What This Article Tells Us That Is New
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Carrier, D. R. "Function of the intercostal muscles in trotting dogs: ventilation or locomotion?" Journal of Experimental Biology 199, no. 7 (July 1, 1996): 1455–65. http://dx.doi.org/10.1242/jeb.199.7.1455.
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Although the intercostal muscles play an important role in lung ventilation, observations from fishes and ectothermic tetrapods suggest that their primary function may be locomotion. To provide a broader understanding of the role these muscles play in locomotion, I measured ventilatory airflow at the mouth and activity of the fourth and ninth intercostal muscles in four dogs trotting on a treadmill. During rest and thermoregulatory panting, activity of the intercostal muscles was associated with inspiratory and expiratory airflow. However, during trotting, activity of the interosseous portions of the intercostal muscles was correlated with locomotion. When ventilation and stride cycles were not synchronized, activity of the interosseous intercostal muscles stayed locked to the locomotor events and drifted in time relative to ventilation. In contrast, activity of the parasternal portion of the internal intercostal muscles was always associated with inspiratory airflow. These observations suggest that, in dogs, locomotion is the dominant function of the interosseous portions of the intercostal muscles. However, the parasternal intercostal muscles are primarily inspiratory in function.
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De Troyer, A., and A. Legrand. "Inhomogeneous activation of the parasternal intercostals during breathing." Journal of Applied Physiology 79, no. 1 (July 1, 1995): 55–62. http://dx.doi.org/10.1152/jappl.1995.79.1.55.
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Recent computations of the mechanical advantage of the canine intercostal muscles have suggested that the inspiratory advantage of the parasternal intercostals is not uniform. In the present studies, we have initially tested this hypothesis. Using a caliper and markers implanted in the costal cartilages, we have thus measured, in four supine paralyzed dogs, the length of the medial, middle, and lateral parasternal fibers at functional residual capacity and after a 1-liter mechanical inflation. With inflation, the medial fibers always shortened more than did the middle fibers (-9.8 +/- 0.8 vs. -6.0 +/- 0.8%; P < 0.001), whereas the lateral fibers remained virtually constant in length (-0.2 +/- 0.8%). This gradient of mechanical advantage agreed well with the gradient of orientation of the muscle fibers. Therefore, we have also recorded the electromyograms of the medial, middle, and lateral parasternal bundles during spontaneous breathing in nine anesthetized animals (20 interspaces); each activity was expressed as a percentage of the activity recorded during tetanic, supramaximal stimulation of the internal intercostal nerve (maximal activity). The medial bundle was invariably more active than was the middle bundle during resting breathing (57.3 +/- 3.3 vs. 25.5 +/- 3.4% of maximum; P < 0.001), and in 10 interspaces, medial activity consistently preceded middle activity at the onset of inspiration. These differences persisted during hypercapnia, during inspiratory resistive loading, as well as after phrenicotomy. Activity was never recorded from the lateral bundle.
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Yokoba, Masanori, Harvey G. Hawes, Teresa M. Kieser, Masato Katagiri, and Paul A. Easton. "Parasternal intercostal and diaphragm function during sleep." Journal of Applied Physiology 121, no. 1 (April 28, 2016): 59–65. http://dx.doi.org/10.1152/japplphysiol.00508.2015.
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DiMarco, A. F., J. R. Romaniuk, and G. S. Supinski. "Parasternal and external intercostal responses to various respiratory maneuvers." Journal of Applied Physiology 73, no. 3 (September 1, 1992): 979–86. http://dx.doi.org/10.1152/jappl.1992.73.3.979.
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Recent studies suggest that the external intercostal (EI) muscles of the upper rib cage, like the parasternals (PA), play an important ventilatory role, even during eupneic breathing. The purpose of the present study was to further assess the ventilatory role of the EI muscles by determining their response to various static and dynamic respiratory maneuvers and comparing them with the better-studied PA muscles. Applied interventions included 1) passive inflation and deflation, 2) abdominal compression, 3) progressive hypercapnia, and 4) response to bilateral cervical phrenicotomy. Studies were performed in 11 mongrel dogs. Electromyographic (EMG) activities were monitored via bipolar stainless steel electrodes. Muscle length (percentage of resting length) was monitored with piezoelectric crystals. With passive rib cage inflation produced either with a volume syringe or abdominal compression, each muscle shortened; with passive deflation, each muscle lengthened. During eupneic breathing, each muscle was electrically active and shortened to a similar degree. In response to progressive hypercapnia, peak EMG of each intercostal muscle increased linearly and to a similar extent. Inspiratory shortening also increased progressively with increasing PCO2, but in a curvilinear fashion with no significant differences in response among intercostal muscles. In response to phrenicotomy, the EMG and degree of inspiratory shortening of each intercostal muscle increased significantly. Again, the response among intercostal muscles was not significantly different.(ABSTRACT TRUNCATED AT 250 WORDS)
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Hudson, Anna L., Jane E. Butler, Simon C. Gandevia, and Andre De Troyer. "Role of the diaphragm in trunk rotation in humans." Journal of Neurophysiology 106, no. 4 (October 2011): 1622–28. http://dx.doi.org/10.1152/jn.00155.2011.
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The objectives of the present study were to test the hypothesis that the costal diaphragm contracts during ipsilateral rotation of the trunk and that such trunk rotation increases the motor output of the muscle during inspiration. Monopolar electrodes were inserted in the right costal hemidiaphragm in six subjects, and electromyographic (EMG) recordings were made during isometric rotation efforts of the trunk to the right (“ipsilateral rotation”) and to the left (“contralateral rotation”). EMG activity was simultaneously recorded from the parasternal intercostal muscles on the right side. The parasternal intercostals were consistently active during ipsilateral rotation but silent during contralateral rotation. In contrast, the diaphragm was silent in the majority of rotations in either direction, and whenever diaphragm activity was recorded, it involved very few motor units. In addition, whereas parasternal inspiratory activity substantially increased during ipsilateral rotation and decreased during contralateral rotation, inspiratory activity in the diaphragm was essentially unaltered and the discharge frequency of single motor units in the muscle remained at 13–14 Hz in the different postures. It is concluded that 1) the diaphragm makes no significant contribution to trunk rotation and 2) even though the diaphragm and parasternal intercostals contract in a coordinated manner during resting breathing, the inspiratory output of the two muscles is affected differently by voluntary drive during trunk rotation.
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De Troyer, A., A. Legrand, G. Gayan-Ramirez, M. Cappello, and M. Decramer. "On the mechanism of the mediolateral gradient of parasternal activation." Journal of Applied Physiology 80, no. 5 (May 1, 1996): 1490–94. http://dx.doi.org/10.1152/jappl.1996.80.5.1490.
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Recent studies have shown that in spontaneously breathing dogs the parasternal intercostals are activated according to a mediolateral gradient. To assess the mechanism of this regionalization of activity, we assessed the pattern of activation of these muscles after section of the dorsal roots and examined the topographic distribution of the muscle fiber types from the sternum to the chondrocostal junctions. The pattern of parasternal activity after dorsal rhizotomy was similar in all respects to that previously observed in intact animals. Thus activity in the medial parasternal bundles at the onset of inspiration frequently preceded activity in the middle bundles, and no activity was recorded from the lateral bundles. The amount of medial activity, when expressed as a percentage of the activity recorded during supramaximal tetanic stimulation of the internal intercostal nerve (maximal activity), was also consistently greater than the amount of middle activity (52.6 +/- 4.6 vs. 23.1 +/- 2.6% maximal activity; P < 0.001). Furthermore, the medial, middle, and lateral parasternal bundles had a higher proportion of slow-twitch oxidative fibers than of fast-twitch oxidative-glycolytic fibers; no topographic difference in fiber type distribution was observed. We conclude, therefore, that the mediolateral gradient of parasternal activity is probably due to the unequal distribution of central inputs throughout the pool of alpha-motoneurons.
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Legrand, Alexandre, Theodore A. Wilson, and André De Troyer. "Rib cage muscle interaction in airway pressure generation." Journal of Applied Physiology 85, no. 1 (July 1, 1998): 198–203. http://dx.doi.org/10.1152/jappl.1998.85.1.198.
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We have previously demonstrated in dogs that the change in airway opening pressure (ΔPao) produced by isolated maximum activation of the parasternal intercostal or triangularis sterni muscle in a single interspace, the sternomastoids, and the scalenes is proportional to the product of muscle mass and the fractional change in muscle length per unit volume increase of the relaxed chest wall. In the present study, we have assessed the interactions between these muscles by comparing the ΔPao obtained during simultaneous activation of a pair of muscles (measured ΔPao) to the sum of the ΔPao values obtained during their separate activation (predicted ΔPao). Measured and predicted ΔPao values were compared for the following pairs of muscles: the parasternal intercostals in two interspaces, the parasternal intercostals in one interspace and either the sternomastoids or the scalenes, two segments of the triangularis sterni, and the interosseous intercostals in two contiguous interspaces. For all these pairs, the measured ΔPao was within ∼10% of the predicted value. We therefore conclude that 1) the pressure changes generated by the rib cage muscles are essentially additive; and 2) measurements of the mass of a particular muscle and of its fractional change in length during passive inflation can be used to estimate the potential pressure-generating ability of the muscle during coordinated activity as well as during isolated activation.
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van Lunteren, E., M. A. Haxhiu, E. C. Deal, J. S. Arnold, and N. S. Cherniack. "Respiratory changes in thoracic muscle length during bronchoconstriction." Journal of Applied Physiology 63, no. 1 (July 1, 1987): 221–28. http://dx.doi.org/10.1152/jappl.1987.63.1.221.
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The purpose of the present study was to assess the effects of bronchoconstriction on respiratory changes in length of the costal diaphragm and the parasternal intercostal muscles. Ten dogs were anesthetized with pentobarbital sodium and tracheostomized. Respiratory changes in muscle length were measured using sonomicrometry, and electromyograms were recorded with bipolar fine-wire electrodes. Administration of histamine aerosols increased pulmonary resistance from 6.4 to 14.5 cmH2O X l–1 X s, caused reductions in inspiratory and expiratory times, and decreased tidal volume. The peak and rate of rise of respiratory muscle electromyogram (EMG) activity increased significantly after histamine administration. Despite these increases, bronchoconstriction reduced diaphragm inspiratory shortening in 9 of 10 dogs and reduced intercostal muscle inspiratory shortening in 7 of 10 animals. The decreases in respiratory muscle tidal shortening were less than the reductions in tidal volume. The mean velocity of diaphragm and intercostal muscle inspiratory shortening increased after histamine administration but to a smaller extent than the rate of rise of EMG activity. This resulted in significant reductions in the ratio of respiratory muscle velocity of shortening to the rate of rise of EMG activity after bronchoconstriction for both the costal diaphragm and the parasternal intercostal muscles. Bronchoconstriction changed muscle end-expiratory length in most animals, but for the group of animals this was statistically significant only for the diaphragm. These results suggest that impairments of diaphragm and parasternal intercostal inspiratory shortening occur after bronchoconstriction; the mechanisms involved include an increased load, a shortening of inspiratory time, and for the diaphragm possibly a reduction in resting length.
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MacBean, Victoria, Claire L. Pringle, Alan C. Lunt, Keith D. Sharp, Ashraf Ali, Anne Greenough, John Moxham, and Gerrard F. Rafferty. "Parasternal intercostal muscle activity during methacholine-induced bronchoconstriction." Experimental Physiology 102, no. 4 (March 14, 2017): 475–84. http://dx.doi.org/10.1113/ep086120.
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De Troyer, André, and Theodore A. Wilson. "Effect of acute inflation on the mechanics of the inspiratory muscles." Journal of Applied Physiology 107, no. 1 (July 2009): 315–23. http://dx.doi.org/10.1152/japplphysiol.91472.2008.
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When the lung is inflated acutely, the capacity of the diaphragm to generate pressure, in particular pleural pressure (Ppl), is impaired because the muscle during contraction is shorter and generates less force. At very high lung volumes, the pressure-generating capacity of the diaphragm may be further reduced by an increase in the muscle radius of curvature. Lung inflation similarly impairs the pressure-generating capacity of the inspiratory intercostal muscles, both the parasternal intercostals and the external intercostals. In contrast to the diaphragm, however, this adverse effect is largely related to the orientation and motion of the ribs, rather than the ability of the muscles to generate force. During combined activation of the two sets of muscles, the change in Ppl is larger than during isolated diaphragm activation, and this added load on the diaphragm reduces the shortening of the muscle and increases muscle force. In addition, activation of the diaphragm suppresses the cranial displacement of the passive diaphragm that occurs during isolated intercostal contraction and increases the respiratory effect of the intercostals. As a result, the change in Ppl generated during combined diaphragm-intercostal activation is greater than the sum of the pressures generated during separate muscle activation. Although this synergistic interaction becomes particularly prominent at high lung volumes, lung inflation, either bilateral or unilateral, places a substantial stress on the inspiratory muscle pump.
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Cala, Stephen J., Christopher M. Kenyon, Allan Lee, Kenneth Watkin, Peter T. Macklem, and Dudley F. Rochester. "Respiratory Ultrasonography of Human Parasternal Intercostal Muscle In Vivo." Ultrasound in Medicine & Biology 24, no. 3 (March 1998): 313–26. http://dx.doi.org/10.1016/s0301-5629(97)00271-8.
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DiMarco, A. F., J. R. Romaniuk, and G. S. Supinski. "Parasternal and external intercostal muscle shortening during eupneic breathing." Journal of Applied Physiology 69, no. 6 (December 1, 1990): 2222–26. http://dx.doi.org/10.1152/jappl.1990.69.6.2222.
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The interosseous external intercostal (EI) muscles of the upper rib cage are electrically active during inspiration, but the mechanical consequence of their activation is unclear. In 16 anesthetized dogs, we simultaneously measured EI (3rd and 4th interspaces) and parasternal intercostal (PA) (3rd interspace) electromyogram and length. Muscle length was measured by sonomicrometry and expressed as a percentage of resting length (%LR). During resting breathing, each muscle was electrically active and shortened to a similar extent. Sequential EI muscle denervation (3rd and 4th interspaces) followed by PA denervation (3rd interspace) demonstrated significant reductions in the degree of inspiratory shortening for each muscle. Mean EI muscle shortening of the third and fourth interspaces decreased from -3.4 +/- 0.5 and -3.0 +/- 0.4% LR (SE) under control conditions to -0.2 +/- 0.2 and -0.8 +/- 0.3% LR, respectively, after selective denervation of each of these muscles (P less than 0.001 for each). After selective denervation of the PA muscle, its shortening decreased from -3.5 +/- 0.3 to +0.6% LR (SE) (P less than 0.001). PA muscle denervation also caused the EI muscle in the third interspace to change from inspiratory shortening of -0.2% to inspiratory lengthening of +0.2% +/- 0.2 (P less than 0.05). We conclude that during eupneic breathing 1) the EI muscles of the upper rib cage, like the PA muscles, are inspiratory agonists and actively contribute to rib cage expansion and 2) PA muscle contraction contributes to EI muscle shortening.
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Legrand, A., T. A. Wilson, and A. D. Troyer. "Mediolateral gradient of mechanical advantage in the canine parasternal intercostals." Journal of Applied Physiology 80, no. 6 (June 1, 1996): 2097–101. http://dx.doi.org/10.1152/jappl.1996.80.6.2097.
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Previous theoretical studies have postulated that the potential effect of a given respiratory muscle on lung volume or pleural pressure (i.e., its respiratory effect) is proportional to the change in length of the muscle during inflation of the passive chest wall (T. A. Wilson and A. De Troyer J. Appl. Physiol. 73: 2283-2288, 1992). To test this prediction, we have studied the parasternal intercostals in 18 interspaces in 8 supine anesthetized dogs. In each interspace, we have measured the changes in length of the medial and lateral portions of the parasternal during passive inflation and we have also assessed the changes in airway opening pressure (delta Pao) generated by these portions during isolated bilateral stimulation of the internal intercostal nerve. The results showed that 1) the medial fibers shorten more than the lateral fibers during passive inflation (P < 0.001); 2) when stimulated, the medial portion generated a larger fall in Pao than the lateral portion (P < 0.001); and 3) delta Pao was closely related to change in length (r = 0.81; P < 0.001). These observations thus imply that the medial portion of the parasternal intercostals contributes much more to lung expansion during breathing than the lateral portion. These observations also suggest, in agreement with the theoretical prediction, that measurements of the changes in length of the different respiratory muscles during passive inflation can be used to predict the potential respiratory effect of these muscles and to compare their mechanical advantages.
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van Lunteren, E., and N. S. Cherniack. "Electrical and mechanical activity of respiratory muscles during hypercapnia." Journal of Applied Physiology 61, no. 2 (August 1, 1986): 719–27. http://dx.doi.org/10.1152/jappl.1986.61.2.719.
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In nine anesthetized supine spontaneously breathing dogs, we compared moving average electromyograms (EMGs) of the costal diaphragm and the third parasternal intercostal muscles with their respective respiratory changes in length (measured by sonomicrometry). During resting O2 breathing the pattern of diaphragm and intercostal muscle inspiratory shortening paralleled the gradually incrementing pattern of their moving average EMGs. Progressive hypercapnia caused progressive increases in the amount and velocity of respiratory muscle inspiratory shortening. For both muscles there were linear relationships during the course of CO2 rebreathing between their peak moving average EMGs and total inspiratory shortening and between tidal volume and total inspiratory shortening. During single-breath airway occlusions, the electrical activity of both the diaphragm and intercostal muscles increased, but there were decreases in their tidal shortening. The extent of muscle shortening during occluded breaths was increased by hypercapnia, so that both muscles shortened more during occluded breaths under hypercapnic conditions (PCO2 up to 90 Torr) than during unoccluded breaths under normocapnic conditions. These results suggest that for the costal diaphragm and parasternal intercostal muscles there is a close relationship between their electrical and mechanical behavior during CO2 rebreathing, this relationship is substantially altered by occluding the airway for a single breath, and thoracic respiratory muscles do not contract quasi-isometrically during occluded breaths.
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Watson, T. W., and W. A. Whitelaw. "Voluntary hyperventilation changes recruitment order of parasternal intercostal motor units." Journal of Applied Physiology 62, no. 1 (January 1, 1987): 187–93. http://dx.doi.org/10.1152/jappl.1987.62.1.187.
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The order of recruitment of single-motor units in parasternal intercostal muscles during inspiration was studied in normal human subjects during quiet breathing and voluntary hyperventilation. Electromyograms were recorded from the second and third intercostal spaces by means of bipolar fine wire electrodes. Flow at the mouth, volume, end-expired CO2, and rib cage and abdominal anterior-posterior diameters were monitored. Single-motor units were identified using criteria of amplitude and shape, and the time of first appearance of each unit in each inspiration was noted. Hyperventilation was performed with visual feedback of the display of rib cage and abdomen excursions, keeping the ratio of rib cage to abdominal expansion. Subjects were normocapnic in quiet breathing and developed hypocapnia during hyperventilation. Recruitment order was stable in quiet breathing, but in some cases was altered during voluntary hyperventilation. Some low threshold units that fired early in the breath in quiet breathing fired earlier at the beginning of a period of voluntary hyperventilation but progressively later in the breath as hyperventilation went on, whereas later firing units moved progressively toward the early part of inspiration. This suggests that different groups of motoneurons in the pool supplying parasternal intercostal muscles receive different patterns of synaptic input.
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Estenne, M., M. Gorini, A. Van Muylem, V. Ninane, and M. Paiva. "Rib cage shape and motion in microgravity." Journal of Applied Physiology 73, no. 3 (September 1, 1992): 946–54. http://dx.doi.org/10.1152/jappl.1992.73.3.946.
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We studied the effect of microgravity (0 Gz) on the anteroposterior diameters of the upper (URC-AP) and lower (LRC-AP) rib cage, the transverse diameter of the lower rib cage (LRC-TR), and the xiphipubic distance and on the electromyographic (EMG) activity of the scalene and parasternal intercostal muscles in five normal subjects breathing quietly in the seated posture. Gastric pressure was also recorded in four subjects. At 0 Gz, end-expiratory LRC-AP and xiphipubic distance increased but LRC-TR invariably decreased, as did end-expiratory gastric pressure. No consistent effect was observed on tidal LRC-TR and xiphipubic displacements, but tidal changes in URC-AP and LRC-AP were reduced. Although scalene and parasternal phasic inspiratory EMG activity tended to decrease at 0 Gz, both muscle groups demonstrated an increase in tonic activity. We conclude that during brief periods of weightlessness 1) the rib cage at end expiration is displaced in the cranial direction and adopts a more circular shape, 2) the tidal expansion of the ventral rib cage is reduced, particularly in its upper portion, and 3) the scalenes and parasternal intercostals generally show a decrease in phasic inspiratory EMG activity and an increase in tonic activity.
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De Troyer, André, Peter A. Kirkwood, and Theodore A. Wilson. "Respiratory Action of the Intercostal Muscles." Physiological Reviews 85, no. 2 (April 2005): 717–56. http://dx.doi.org/10.1152/physrev.00007.2004.
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The mechanical advantages of the external and internal intercostals depend partly on the orientation of the muscle but mostly on interspace number and the position of the muscle within each interspace. Thus the external intercostals in the dorsal portion of the rostral interspaces have a large inspiratory mechanical advantage, but this advantage decreases ventrally and caudally such that in the ventral portion of the caudal interspaces, it is reversed into an expiratory mechanical advantage. The internal interosseous intercostals in the caudal interspaces also have a large expiratory mechanical advantage, but this advantage decreases cranially and, for the upper interspaces, ventrally as well. The intercartilaginous portion of the internal intercostals (the so-called parasternal intercostals), therefore, has an inspiratory mechanical advantage, whereas the triangularis sterni has a large expiratory mechanical advantage. These rostrocaudal gradients result from the nonuniform coupling between rib displacement and lung expansion, and the dorsoventral gradients result from the three-dimensional configuration of the rib cage. Such topographic differences in mechanical advantage imply that the functions of the muscles during breathing are largely determined by the topographic distributions of neural drive. The distributions of inspiratory and expiratory activity among the muscles are strikingly similar to the distributions of inspiratory and expiratory mechanical advantages, respectively. As a result, the external intercostals and the parasternal intercostals have an inspiratory function during breathing, whereas the internal interosseous intercostals and the triangularis sterni have an expiratory function.
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Budzinska, K., G. Supinski, and A. F. DiMarco. "Inspiratory action of separate external and parasternal intercostal muscle contraction." Journal of Applied Physiology 67, no. 4 (October 1, 1989): 1395–400. http://dx.doi.org/10.1152/jappl.1989.67.4.1395.
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We have previously shown that electrical stimulation of the thoracic spinal cord produces near maximal activation of the inspiratory intercostal muscles. In the present investigation, we used this technique to evaluate the relative capacity of separate external (EI) and parasternal intercostal (PA) muscle contraction to produce changes in airway pressure and inspired volume. Studies were performed in 23 anesthetized phrenicotomized dogs. Electrical stimuli were applied to the spinal cord after hyperventilation-induced apnea, before and after sequentially severing either the PA or EI muscles from the first through sixth intercostal spaces. During spinal cord stimulation (SCS), measurements were made of inspired volume (delta V) with the airway open and negative airway pressure (delta P) during tracheal occlusion. Compared with control values, sectioning of the PA muscles resulted in a 40.9% reduction in delta P and 35.7% reduction in delta V during SCS. In other animals, initial sectioning of the EI muscles produced reductions in delta P and delta V of 67.4 and 63.0, respectively, during SCS. After subsequent section of the PA muscles, SCS produced only negligible inspired volumes and changes in airway pressure. We conclude that 1) the EI and PA muscles are each capable of generating substantial changes in airway pressure and large inspired volumes and 2) the ventilatory capacity of the EI muscles exceeds that of the PA muscles.
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Troyer, André De, and Dimitri Leduc. "Role of pleural pressure in the coupling between the intercostal muscles and the ribs." Journal of Applied Physiology 102, no. 6 (June 2007): 2332–37. http://dx.doi.org/10.1152/japplphysiol.01403.2006.
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The inspiratory intercostal muscles elevate the ribs and thereby elicit a fall in pleural pressure (ΔPpl) when they contract. In the present study, we initially tested the hypothesis that this ΔPpl does, in turn, oppose the rib elevation. The cranial rib displacement (Xr) produced by selective activation of the parasternal intercostal muscle in the fourth interspace was measured in dogs, first with the rib cage intact and then after ΔPpl was eliminated by bilateral pneumothorax. For a given parasternal contraction, Xr was greater after pneumothorax; the increase in Xr per unit decrease in ΔPpl was 0.98 ± 0.11 mm/cmH2O. Because this relation was similar to that obtained during isolated diaphragmatic contraction, we subsequently tested the hypothesis that the increase in Xr observed during breathing after diaphragmatic paralysis was, in part, the result of the decrease in ΔPpl, and the contribution of the difference in ΔPpl to the difference in Xr was determined by using the relation between Xr and ΔPpl during passive inflation. With diaphragmatic paralysis, Xr during inspiration increased approximately threefold, and 47 ± 8% of this increase was accounted for by the decrease in ΔPpl. These observations indicate that 1) ΔPpl is a primary determinant of rib motion during intercostal muscle contraction and 2) the decrease in ΔPpl and the increase in intercostal muscle activity contribute equally to the increase in inspiratory cranial displacement of the ribs after diaphragm paralysis.
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Cappello, Matteo, and André de Troyer. "Interaction between left and right intercostal muscles in airway pressure generation." Journal of Applied Physiology 88, no. 3 (March 1, 2000): 817–20. http://dx.doi.org/10.1152/jappl.2000.88.3.817.
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The interactions between the different rib cage inspiratory muscles in the generation of pleural pressure remain largely unknown. In the present study, we have assessed in dogs the interactions between the parasternal intercostals and the interosseous intercostals situated on the right and left sides of the sternum. For each set of muscles, the changes in airway opening pressure (ΔPao) obtained during separate right and left activation were added, and the calculated values (predicted ΔPao) were then compared with the ΔPao values obtained during symmetric, bilateral activation (measured ΔPao). When the parasternal intercostals in one or two interspaces were activated, the measured ΔPao was commonly greater than the predicted value. The difference, however, was only 10%. When the interosseous intercostals were activated, the measured ΔPao was nearly equal to the predicted value. These observations strengthen our previous conclusion that the pressure changes produced by the rib cage inspiratory muscles are essentially additive. As a corollary, the rib cage can be considered as a linear elastic structure over a wide range of distortion.
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Nishii, Y., Y. Okada, M. Yokoba, M. Katagiri, T. Yanaihara, N. Masuda, P. A. Easton, and T. Abe. "Aminophylline increases parasternal intercostal muscle activity during hypoxia in humans." Respiratory Physiology & Neurobiology 161, no. 1 (March 2008): 69–75. http://dx.doi.org/10.1016/j.resp.2007.12.004.
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Hudson, Anna L., and Jane E. Butler. "Assessment of ‘neural respiratory drive’ from the parasternal intercostal muscles." Respiratory Physiology & Neurobiology 252-253 (June 2018): 16–17. http://dx.doi.org/10.1016/j.resp.2017.11.003.
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