Changes in the neural drive to abdominal expiratory muscles in hemorrhagic hypotension

1994 ◽  
Vol 266 (6) ◽  
pp. H2423-H2429 ◽  
Author(s):  
R. F. Fregosi
Keyword(s):  
Pulmonary Ventilation ◽  
Respiratory Rhythm ◽  
Abdominal Muscle ◽  
Rectus Abdominis ◽  
Abdominal Muscles ◽  
Neural Drive ◽  
Hemorrhagic Hypotension ◽  
Severe Hypotension ◽  
Expiratory Muscles ◽  
External Oblique

The purpose of this study was to test the hypothesis that hemorrhage-induced hypotension increases the neural drive to the abdominal expiratory muscles in chloralose-urethan-anesthetized cats that are studied under conditions of constant arterial PCO2 (PaCO2) and hyperoxia. A secondary aim was to describe in detail the concomitant changes in inspired pulmonary ventilation (VI) and the pattern of breathing under these conditions. The rectified and integrated electromyogram (EMG) of the external oblique and rectus abdominis muscles and VI were recorded in moderate and severe hemorrhagic hypotension, leading to reductions in mean blood pressure of approximately 30 and 60%, respectively. The PaCO2 was prevented from falling, and the arterial PO2 was maintained at a hyperoxic level (> 200 mmHg) by adding CO2 and O2 to the inspired gas mixture. VI increased by 2.5- and 5-fold in moderate and severe hypotension (P < 0.05). The changes in VI were mediated exclusively by changes in tidal volume, indicating that the reflex did not alter the activity of respiratory rhythm-generating structures. The EMG of external oblique muscles averaged 2, 44, and 100% in control conditions and in moderate and severe hypotension, respectively; corresponding values in rectus abdominis muscles were 10, 28, and 100% (P < 0.05 for both muscles). Bilateral cervical vagotomy caused a one- to three-fold decrease in the ventilatory response to hemorrhage and abolished the increase in abdominal muscle EMG activities. In conclusion, hemorrhagic hypotension reflexly increases pulmonary ventilation and the neural drive to the abdominal muscles. The reflex is vagally mediated, but the location of the receptors was not identified.

Abdominal muscle activity during hypercapnia in awake dogs

1994 ◽  
Vol 77 (3) ◽  
pp. 1393-1398 ◽  
Author(s):  
A. M. Leevers ◽  
J. D. Road
Keyword(s):  
Tidal Volume ◽  
Muscle Layer ◽  
Abdominal Muscle ◽  
Rectus Abdominis ◽  
Transversus Abdominis ◽  
Emg Activity ◽  
Abdominal Muscles ◽  
Co2 Rebreathing ◽  
External Oblique ◽  
Internal Oblique

We previously found the internal abdominal muscle layer to be preferentially recruited during expiratory threshold loading in anesthetized and awake dogs. Expiratory threshold loading increases end-expiratory lung volume and hence can activate reflex pathways such as tonic vagal reflexes, which could influence abdominal muscle recruitment. Our objectives in the present study were to determine the effects of hypercapnia on abdominal muscle activation and the pattern of recruitment in awake dogs. Five tracheotomized dogs were chronically implanted with sonomicrometer transducers and fine-wire electromyogram (EMG) electrodes in each of the four abdominal muscles: transversus abdominis, internal oblique, external oblique, and rectus abdominis. Muscle length changes and EMG activity were studied in the awake dog at rest and during CO2 rebreathing. CO2 rebreathing produced a tripling of tidal volume and activation of the abdominal muscles. Despite the increase in tidal volume, there was no significant change in abdominal muscle end-inspiratory length. Both tonic and phasic expiratory shortening were greater in the internal muscle layer (transversus abdominis and internal oblique) than in the external muscle layer (external oblique and rectus abdominis). We conclude that the internal abdominal muscles are preferentially recruited by hypercapnia and vagal reflexes probably do not contribute to this differential recruitment but that segmental reflexes may be involved. The mechanical consequences of this recruitment are discussed.

Abdominal muscle use during breathing in unanesthetized dogs

1989 ◽  
Vol 66 (1) ◽  
pp. 20-27 ◽  
Author(s):  
A. De Troyer ◽  
J. J. Gilmartin ◽  
V. Ninane
Keyword(s):  
Respiratory Muscle ◽  
Abdominal Muscle ◽  
Rectus Abdominis ◽  
Transversus Abdominis ◽  
Abdominal Muscles ◽  
Quiet Breathing ◽  
Sitting Posture ◽  
Cervical Vagotomy ◽  
External Oblique ◽  
Conscious Animals

The pattern of abdominal muscle use during breathing in unanesthetized dogs is unknown. Therefore, we have recorded the electromyograms of the rectus abdominis, external oblique, and transversus abdominis in eight conscious animals breathing quietly in the sitting, standing, and prone postures. During quiet breathing in the sitting posture, all animals invariably had a large amount of phasic expiratory activity in the transversus abdominis. In contrast, only four animals showed some expiratory activity in the external oblique, and only one animal had expiratory activity in the rectus abdominis. A similar pattern was observed when the animals were standing or lying prone, although the amount of expiratory activity was less in this posture. Bilateral cervical vagotomy in four animals did not affect the degree of transversus abdominis expiratory activation or the influence of posture. We conclude that in conscious dogs 1) the abdominal muscles play an important role during breathing and make spontaneous quiet expiration a very active process, 2) the transversus abdominis is the primary respiratory muscle of the abdomen, and 3) unlike in anesthetized animals, extrapulmonary receptors play a major role in promoting abdominal expiratory contraction.

Responses of the anterolateral abdominal muscles during cough and expiratory threshold loading in the cat

2000 ◽  
Vol 88 (4) ◽  
pp. 1207-1214 ◽  
Author(s):  
Donald C. Bolser ◽  
Paul J. Reier ◽  
Paul W. Davenport
Keyword(s):  
Abdominal Muscle ◽  
Rectus Abdominis ◽  
Transversus Abdominis ◽  
Emg Activity ◽  
Abdominal Muscles ◽  
Cough Reflex ◽  
Gastric Pressure ◽  
Simultaneous Activation ◽  
External Oblique ◽  
Internal Oblique

The present study was conducted to determine the pattern of activation of the anterolateral abdominal muscles during the cough reflex. Electromyograms (EMGs) of the rectus abdominis, external oblique, internal oblique, transversus abdominis, and parasternal muscles were recorded along with gastric pressure in anesthetized cats. Cough was produced by mechanical stimulation of the lumen of the intrathoracic trachea or larynx. The pattern of EMG activation of these muscles during cough was compared with that during graded expiratory threshold loading (ETL; 1–30 cmH2O). ETL elicited differential recruitment of abdominal muscle EMG activity (transversus abdominis > internal oblique > rectus abdominis ≅ external oblique). In contrast, both laryngeal and tracheobronchial cough resulted in simultaneous activation of all four anterolateral abdominal muscles with peak EMG amplitudes 3- to 10-fold greater than those observed during the largest ETL. Gastric pressures during laryngeal and tracheobronchial cough were at least eightfold greater than those produced by the largest ETL. These results suggest that, unlike their behavior during expiratory loading, the anterolateral abdominal muscles act as a unit during cough.

Effect of hypercapnia and PEEP on expiratory muscle EMG and shortening

1989 ◽  
Vol 66 (3) ◽  
pp. 1408-1413 ◽  
Author(s):  
A. Oliven ◽  
S. G. Kelsen
Keyword(s):  
Electrical Activity ◽  
Abdominal Muscle ◽  
Rectus Abdominis ◽  
Emg Activity ◽  
Expiratory Muscle ◽  
Integrated Emg ◽  
Length Changes ◽  
Expiratory Muscles ◽  
External Oblique ◽  
Spontaneously Breathing

The present study examined the effects of hypercapnia and positive end-expiratory pressure (PEEP) on the electromyographic (EMG) activity and tidal length changes of the expiratory muscles in 12 anesthetized, spontaneously breathing dogs. The integrated EMG activity of both abdominal (external oblique, internal oblique, rectus abdominis, and transverse abdominis) and thoracic (triangularis sterni, internal intercostal) expiratory muscles increased linearly with increasing PCO2 and PEEP. However, with both hypercapnia and PEEP, the percent increase in abdominal muscle electrical activity exceeded that of thoracic expiratory muscle activity. Both hypercapnia and PEEP increased the tidal shortening of the external oblique and rectus abdominis muscles. Changes in tidal length correlated closely with simultaneous increases in muscle electrical activity. However, during both hypercapnia and PEEP, length changes of the external oblique were significantly greater than those of the rectus abdominis. We conclude that both progressive hypercapnia and PEEP increase the electrical activity of all expiratory muscles and augment their tidal shortening but produce quantitatively different responses in the several expiratory muscles.

Effects of posture on abdominal muscle shortening in awake dogs

1993 ◽  
Vol 75 (4) ◽  
pp. 1452-1459 ◽  
Author(s):  
A. M. Leevers ◽  
J. D. Road
Keyword(s):  
Respiratory Activity ◽  
Abdominal Muscle ◽  
Rectus Abdominis ◽  
Transversus Abdominis ◽  
Abdominal Muscles ◽  
Muscle Shortening ◽  
Lateral Decubitus ◽  
Length Changes ◽  
External Oblique ◽  
Internal Oblique

The objective of this study was to examine the effects of posture on tonic and phasic expiratory activity of the abdominal muscles in awake dogs. Six tracheostomized dogs were chronically instrumented with sonomicrometer transducers and bipolar electromyographic electrodes placed in each of the four abdominal muscles. To determine the effects of posture on tonic and phasic activity of individual abdominal muscles, muscle resting length (Lr) and tidal length changes (%Lr), respectively, were measured in awake dogs in the left lateral decubitus (LLD), sitting, and standing (STAND) positions. The transversus abdominis Lr consistently shortened when the dog was moved from LLD to STAND and lengthened when the dog was moved from LLD to the sitting position, and the external oblique Lr consistently lengthened when the dog went from LLD to STAND. The internal oblique and rectus abdominis had no consistent changes in Lr with a change in position. All four abdominal muscles actively shortened (%Lr) more in the upright positions. In addition, the internal layer (transversus abdominis and internal oblique) actively shortened more than the external layer (rectus abdominis and external oblique). In conclusion, both tonic and phasic respiratory activity of the abdominal muscles, reflected by changes in Lr and %Lr, respectively, were affected by changes in posture.

Triangularis sterni muscle use in supine humans

1987 ◽  
Vol 62 (3) ◽  
pp. 919-925 ◽  
Author(s):  
A. De Troyer ◽  
V. Ninane ◽  
J. J. Gilmartin ◽  
C. Lemerre ◽  
M. Estenne
Keyword(s):  
Normal Subjects ◽  
Abdominal Muscle ◽  
Abdominal Muscles ◽  
Neural Activation ◽  
Trained Subjects ◽  
Rib Cage ◽  
Residual Capacity ◽  
External Oblique ◽  
Head Flexion ◽  
Static Head

The electrical activity of the triangularis sterni (transversus thoracis) muscle was studied in supine humans during resting breathing and a variety of respiratory and nonrespiratory maneuvers known to bring the abdominal muscles into action. Twelve normal subjects, of whom seven were uninformed and untrained, were investigated. The electromyogram of the triangularis sterni was recorded using a concentric needle electrode, and it was compared with the electromyograms of the abdominal (external oblique and rectus abdominis) muscles. The triangularis sterni was usually silent during resting breathing. In contrast, the muscle was invariably activated during expiration from functional residual capacity, expulsive maneuvers, “belly-in” isovolume maneuvers, static head flexion and trunk rotation, and spontaneous events such as speech, coughing, and laughter. When three trained subjects expired voluntarily with considerable recruitment of the triangularis sterni and no abdominal muscle activity, rib cage volume decreased and abdominal volume increased. These results indicate that unlike in the dog, spontaneous quiet expiration in supine humans is essentially a passive process; the human triangularis sterni, however, is a primary muscle of expiration; and its neural activation is largely coupled with that of the abdominals. The triangularis sterni probably contributes to the deflation of the rib cage during active expiration.

Effects of postural changes and vestibular lesions on diaphragm and rectus abdominis activity in awake cats

2001 ◽  
Vol 91 (1) ◽  
pp. 137-144 ◽  
Author(s):  
L. A. Cotter ◽  
H. E. Arendt ◽  
J. G. Jasko ◽  
C. Sprando ◽  
S. P. Cass ◽  
...  
Keyword(s):  
Vestibular System ◽  
Muscle Activity ◽  
Abdominal Muscle ◽  
Rectus Abdominis ◽  
Abdominal Muscles ◽  
Body Rotation ◽  
Postural Changes ◽  
Before And After ◽  
Awake Cats

Changes in posture can affect the resting length of the diaphragm, requiring alterations in the activity of both the abdominal muscles and the diaphragm to maintain stable ventilation. To determine the role of the vestibular system in regulating respiratory muscle discharges during postural changes, spontaneous diaphragm and rectus abdominis activity and modulation of the firing of these muscles during nose-up and ear-down tilt were compared before and after removal of labyrinthine inputs in awake cats. In vestibular-intact animals, nose-up and ear-down tilts from the prone position altered rectus abdominis firing, whereas the effects of body rotation on diaphragm activity were not statistically significant. After peripheral vestibular lesions, spontaneous diaphragm and rectus abdominis discharges increased significantly (by ∼170%), and augmentation of rectus abdominis activity during nose-up body rotation was diminished. However, spontaneous muscle activity and responses to tilt began to recover after a few days after the lesions, presumably because of plasticity in the central vestibular system. These data suggest that the vestibular system provides tonic inhibitory influences on rectus abdominis and the diaphragm and in addition contributes to eliciting increases in abdominal muscle activity during some changes in body orientation.

Abdominal Muscles Dominate Contributions to Vertebral Joint Stiffness during the Push-up

2008 ◽  
Vol 24 (2) ◽  
pp. 130-139 ◽  
Author(s):  
Samuel J. Howarth ◽  
Tyson A.C. Beach ◽  
Jack P. Callaghan
Keyword(s):  
Lumbar Spine ◽  
Rectus Abdominis ◽  
Erector Spinae ◽  
Abdominal Muscles ◽  
Rotational Stiffness ◽  
Flexion Extension ◽  
External Oblique ◽  
Axial Twist ◽  
Internal Oblique ◽  
Push Up

The goal of this study was to quantify the relative contributions of each muscle group surrounding the spine to vertebral joint rotational stiffness (VJRS) during the push-up exercise. Upper-body kinematics, three-dimensional hand forces and lumbar spine postures, and 14 channels (bilaterally from rectus abdominis, external oblique, internal oblique, latissimus dorsi, thoracic erector spinae, lumbar erector spinae, and multifidus) of trunk electromyographic (EMG) activity were collected from 11 males and used as inputs to a biomechanical model that determined the individual contributions of 10 muscle groups surrounding the lumbar spine to VJRS at five lumbar vertebral joints (L1-L2 to L5-S1). On average, the abdominal muscles contributed 64.32 ± 8.50%, 86.55 ± 1.13%, and 83.84 ± 1.95% to VJRS about the flexion/extension, lateral bend, and axial twist axes, respectively. Rectus abdominis contributed 43.16 ± 3.44% to VJRS about the flexion/extension axis at each lumbar joint, and external oblique and internal oblique, respectively contributed 52.61 ± 7.73% and 62.13 ± 8.71% to VJRS about the lateral bend and axial twist axes, respectively, at all lumbar joints with the exception of L5-S1. Owing to changes in moment arm length, the external oblique and internal oblique, respectively contributed 55.89% and 50.01% to VJRS about the axial twist and lateral bend axes at L5-S1. Transversus abdominis, multifidus, and the spine extensors contributed minimally to VJRS during the push-up exercise. The push-up challenges the abdominal musculature to maintain VJRS. The orientation of the abdominal muscles suggests that each muscle primarily controls the rotational stiffness about a single axis.

scholarly journals Quantification of the Differences in Electromyographic Activity Magnitude Between the Upper and Lower Portions of the Rectus Abdominis Muscle During Selected Trunk Exercises

2001 ◽  
Vol 81 (5) ◽  
pp. 1096-1101 ◽  
Author(s):  
Gregory J Lehman ◽  
Stuart M McGill
Keyword(s):  
Muscle Activity ◽  
Abdominal Muscle ◽  
Rectus Abdominis ◽  
Oblique Muscle ◽  
Emg Activity ◽  
Electromyographic Activity ◽  
Rectus Abdominis Muscle ◽  
Emg Signal ◽  
External Oblique Muscle ◽  
External Oblique

Abstract Background and Purpose. Controversy exists around exercises and clinical tests that attempt to differentially activate the upper or lower portions of the rectus abdominis muscle. The purpose of this study was to assess the activation of the upper and lower portions of the rectus abdominis muscle during a variety of abdominal muscle contractions. Subjects. Subjects (N=11) were selected from a university population for athletic ability and low subcutaneous fat to optimize electromyographic (EMG) signal collection. Methods. Controlling for spine curvature, range of motion, and posture (and, therefore, muscle length), EMG activity of the external oblique muscle and upper and lower portions of rectus abdominis muscle was measured during the isometric portion of curl-ups, abdominal muscle lifts, leg raises, and restricted or attempted leg raises and curl-ups. A one-way repeated-measures analysis of variance was used to test for differences in activity between exercises in the external oblique and rectus abdominis muscles as well as between the portions of the rectus abdominis muscle. Results. No differences in muscle activity were found between the upper and lower portions of the rectus abdominis muscle within and between exercises. External oblique muscle activity, however, showed differences between exercises. Discussion and Conclusion. Normalizing the EMG signal led the authors to believe that the differences between the portions of the rectus abdominis muscle are small and may lack clinical or therapeutic relevance.

Inhomogeneous response of expiratory muscle activity to cold block of the ventral medullary surface

1991 ◽  
Vol 71 (5) ◽  
pp. 1723-1728 ◽  
Author(s):  
T. Chonan ◽  
S. Okabe ◽  
W. Hida ◽  
T. Izumiyama ◽  
Y. Kikuchi ◽  
...  
Keyword(s):  
Transversus Abdominis ◽  
Abdominal Muscles ◽  
Temperature Dependent ◽  
Rib Cage ◽  
Inspiratory Activity ◽  
Ventral Medullary Surface ◽  
Expiratory Muscles ◽  
External Oblique ◽  
Intermediate Part ◽  
Internal Oblique

We assessed the effects of cooling the ventral medullary surface (VMS) on the activity of chest wall and abdominal expiratory muscles in eight anesthetized artificially ventilated dogs after vagotomy and denervation of the carotid sinus nerves. Electromyograms (EMGs) of the triangularis sterni, internal intercostal, abdominal external oblique, abdominal internal oblique, and transversus abdominis muscles were measured with EMG of the diaphragm as an index of inspiratory activity. Bilateral localized cooling (2 x 2 mm) in the thermosensitive intermediate part of the VMS produced temperature-dependent reduction in the EMG of diaphragm and abdominal muscles. The rib cage expiratory EMGs were little affected at 25 degrees C; their amplitudes decreased at lower VMS temperatures (less than 20 degrees C) but by significantly fewer degrees than the diaphragmatic and abdominal expiratory EMGs at a constant VMS temperature. With moderate to severe cooling (less than 20 degrees C) diaphragmatic EMG disappeared, but rib cage expiratory EMGs became tonic and resumed a phasic pattern shortly before the recovery of diaphragmatic EMG during rewarming of the VMS. These results indicate that the effects of cooling the VMS differ between the activity of rib cage and abdominal expiratory muscles. This variability may be due to inhomogeneous inputs from the VMS to expiratory motoneurons or to a different responsiveness of various expiratory motoneurons to the same input either from the VMS or the inspiratory neurons.

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