Abdominal Electromyogram Research Articles

Antitussive action of nociceptin in the cat

Experiments were conducted to determine the influence of the specific ORL1 receptor agonist, nociceptin, on the cough reflex in the cat. Cats were anesthetized and allowed to breathe spontaneously. Cough was elicited by mechanical stimulation of the intrathoracic airway. Intravenous administration of nociceptin (0.001–3.0 mg kg −1) inhibited cough number and the magnitude of abdominal muscle electromyogram (EMG) discharge during cough in a dose-dependent manner. Nociceptin had no effect on the magnitude of the inspiratory muscle EMG during cough. These effects of nociceptin were antagonized by pretreatment with the ORL1 receptor antagonist, 1-[(3 R,4 R)-1-cyclooctylmethyl-3-hydroxymethyl-4-piperidyl]-3-ethyl-1, 3-dihydro-2 H-benzimidazol-2-one (J-113397, 0.1 mg kg −1, i.v.). We conclude that intravenous nociceptin inhibits cough in the cat.

Effects of aerobatics flight on oxygen consumption and heart rate control: influence on autonomic cardiovascular regulation during recovery.

Oxygen consumption (VO2) and blood pressure regulation were measured on five pilots during and after normal training aerobatics flights of a mean duration of 35 min. The acceleration vector along the longitudinal axis of the body (Gz) ranged from + 6.5 Gz to -3.5 Gz. VO2 was continuously monitored by a miniature telemetric system (K2). Heart rate (fc), the abdominal muscle electromyogram (EMG) and Gz levels were recorded synchronously on a magnetic tape recorder. A tilt test was performed pre- and post-flight to evaluate fc and blood-pressure variability. The left forearm blood flow was measured by strain-gauge plethysmography. The mean VO2 during flight was 1.2 l x min(-1), with a peak VO2 of 2.1 l x min x fc ranged between 55 and 165 beats x min(-1) and showed a progressive increase under the effect of + Gz, with a sudden fall during -Gz. The abdominal muscle EMG indicated the occurrence of muscle contraction under Gz load. Maximal responses were observed during the Gz phase. Comparison between pre- and post-flight data showed lower post-flight systolic blood pressure with higher fc. Before flight, upright tilt induced a significant increase in low/ high frequency fc, as assessed using spectral analysis. This change was suppressed after flight. In summary, these data show that aerobatics flight leads to enhanced energy expenditure, mainly because of increased skeletal muscle work. The post-flight tilt test showed that aerobatic flight favors parasympathetic drive and, consequently, modifies blood pressure regulation during recovery. This action may decrease + Gz tolerance to a second aerobatics flight performed shortly after the first.

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

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 cmH(2)O). ETL elicited differential recruitment of abdominal muscle EMG activity (transversus abdominis > internal oblique > rectus abdominis congruent with 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.

Analyzing uterine EMG: tracking instantaneous burst frequency

The uterine electromyogram (EMG) has been proven to be an efficient tool for pregnancy and parturition monitoring. Temporal and spectral characteristics of this signal, recorded by means of external electrodes, make it possible to discriminate between efficient and inefficient contractions in terms of electrical command capability. As it is possible to record the uterine electrical activity as early as 19 weeks gestational age, abdominal EMG can be of value for pregnancy monitoring especially if this noninvasive recording can be associated with ambulatory instrumentation. Much work has been achieved related to the characteristics of this signal as well as to its ability to explain, to a certain extent, uterine contractility. In previous studies on monkeys, the authors demonstrated the relationship between internal and external recordings, by simultaneously using internal wire electrodes on the uterine muscle itself and external abdominal bipolar Ag/AgCl electrodes. In the same preliminary studies, the authors defined the most relevant frequency bands in terms of significant modifications between pregnancy and parturition. Furthermore, they have proposed a criterion which is representative of contraction efficiency. However, the most important point has been to relate the observations made on the external recordings to internal cellular activity. In fact, uterine smooth muscle cells continuously exhibit resting potentials with small and slow spontaneous fluctuations. When these fluctuations reach a threshold, bursts of action potentials are induced. The frequency of the spikes within a burst appear to control the mechanical contraction. If it could be possible to extract such an information of within-burst frequency by means of external recordings, this should lead to a relevant characterization in terms of contraction efficiency. In addition, the EMG undergoes important modifications from pregnancy to parturition, primarily due to the appearance of gap junctions that facilitate electrical coupling between cells, and increase in the within-burst spike frequency. >

Control of breathing patterns and abdominal muscles during graded loads and tilt.

Tilting from supine to upright purportedly enhances both segmental and pulmonary proprioceptive feedback, whereas an expiratory threshold load (ETL) preferentially enhances pulmonary feedback. To test this we studied 13 adults when supine and 60 degrees and 90 degrees head up. We measured tidal volume, inspiratory duration (TI), and expiratory duration (TE) from flow; estimated end-expiratory lung volume from inspiratory capacity; and determined burst amplitudes and durations from abdominal electromyograms (EMGs). ETLs were incremented from 0 (control) to 25 cmH2O in 5-cmH2O steps. Tidal volume was significantly increased by ETL but was unaffected by body position. Every load prolonged TE, whereas TI remained unchanged. When subjects were supine, abdominal EMGs were silent but became tonically active when subjects were upright. During ETL, abdominal activity became rhythmical and phase locked to expiration. Bursts amplitudes were enhanced with each increment in ETL, but burst durations did not change even though TE was prolonged. The altered breathing pattern and active expiration augmented inspiratory flow and decreased end-tidal PCO2. Responses were greatest when subjects were 90 degrees head up. The load-related increments in abdominal recruitment, with no change in burst durations, fit the concept of two central pattern generators: one controlling pattern and the other controlling rhythm of the central respiratory drive.

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

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.

Respiratory and abdominal muscle responses to expiratory threshold loading in cystic fibrosis.

We hypothesized that the hyperinflation and pulmonary dysfunction of cystic fibrosis (CF) would distort feedback and therefore alter the abdominal muscle response to graded expiratory threshold loads (ETLs). We compared the respiratory and abdominal muscle responses with graded ETLs of seven CF patients with severe lung dysfunction with those of matched healthy control subjects in the supine and 60 degrees head-up positions. Breathing frequency, tidal volume, and ventilatory timing were determined from inspiratory flow recordings. Abdominal electromyograms (EMGs) were detected with surface electrodes placed unilaterally over the external and internal oblique and the rectus abdominis muscles. Thresholds, times of onset, and durations of phasic abdominal activity were determined from raw EMGs; peak amplitudes were determined from integrated EMGs. Graded ETLs were imposed by submerging a tube from the expiratory port of the breathing valve into a column of water at depths of 0-25 cmH2O. We found that breathing frequency, tidal volume, and expired minute ventilation were higher in CF patients than in control subjects during low ETLs; a change in body position did not alter these ventilatory responses in the CF patients but did in the control subjects. All CF patients, but none of the control subjects, had tonic abdominal activity while supine. CF patients recruited abdominal muscles at lower loads, earlier in the respiratory cycle, and to a higher recruitment level in both positions than the control subjects, but burst duration of phasic activity was not different between groups.(ABSTRACT TRUNCATED AT 250 WORDS)

Relationship of Respiratory Effort Sensation to Expiratory Muscle Fatigue during Expiratory Threshold Loading

We investigated whether fatigue of the expiratory muscle, that is, the abdominal muscle, may account for a change in the respiratory effort sensation in normal subjects during expiratory threshold loading. The respiratory effort sensation was scored using a modified Borg scale. Expiratory muscle fatigue was assessed both from changes in the maximal static expiratory pressure and in the centroid frequency (fc) of the abdominal muscle electromyogram (EMG). Expiratory threshold loading (magnitude of threshold; 40 to 60% of the maximal expiratory pressure at FRC, breathing frequency = 15/min, and duty cycle = 0.5) was continued until exhaustion or for 30 min. Loading was repeated following a 15-min recovery period after the end of the first expiratory loading. The maximal static expiratory pressure during loading (Pmmax) decreased initially and then remained decreased. Decreases were smaller with the 40% load (22 +/- 6%, SEM) than with the 60% load (37 +/- 3%) (p less than 0.05). The decrease during the second run of the 60% load was greater than during the first (p less than 0.01 by ANOVA). The maximal expiratory pressure at TLC before the second run of the 60% load was decreased by 9 +/- 3% compared with the control (p less than 0.02) but that with the 40% load was not. The fc with the 60% load decreased initially by 8 +/- 1% and then remained constant, although no change was observed with the 40% load.(ABSTRACT TRUNCATED AT 250 WORDS)

Effects of upper airway pressure on abdominal muscle activity in conscious dogs

We have examined arousal and abdominal muscle electromyogram (EMGabd) responses to upper airway pressure stimuli during physiological sleep in four dogs with permanent side-hole tracheal stomata. The dogs were trained to sleep with a tightly fitting snout mask, hermetically sealed in place, while breathing through a cuffed endotracheal tube inserted through the tracheostomy. Sleep stage was determined by behavioral and electroencephalographic criteria. EMGabd activity was measured using bipolar fine-wire electrodes inserted into the abdominal muscle layers. Static increases or decreases in upper airway pressure (+/- 6 cmH2O), when applied at the snout mask or larynx (upper trachea), caused an immediate decrease in EMGabd on the first two to three breaths; EMGabd usually returned to control levels within the 1-min test interval. In contrast, oscillatory pressure waves at 30 Hz and +/- 3 cmH2O amplitude (or -2 to -8 cmH2O amplitude) produced an immediate and sustained reduction in IMGabd in all sleep states. Inhibition of EMGabd could be maintained over many minutes when the oscillatory pressure stimulus was pulsed by using a cycle of 0.5 s on and 0.5 s off. Oscillatory upper airway pressures were also found to be powerful arousal-promoting stimuli, producing arousal in 94% of tests in drowsiness and 66% of tests in slowwave sleep. The results demonstrate the presence of breath-by-breath upper airway control of abdominal muscle activity.

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

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.

Sleep-Related Abdominal Muscle Behavior during Partial or Complete Obstructed Breathing in Prepubertal Children1

We have evaluated the influence of nonrapid eye movement (NREM), REM sleep, and arousal on abdominal muscle contractions during snoring and/or obstructive apnea in 10 prepubertal children. All children were known habitual snorers and eight had a sleep apnea index above 10. During stage 3-4 non-REM sleep, non-apneic breathing with snoring was always associated with the presence of expiratory abdominal muscle electromyogram (EMG) discharges. During non-REM sleep apneas, abdominal muscle EMG discharges increased from the beginning to the end of each apnea. Termination of non-REM sleep apnea was marked by an "EEG arousal" in 12% of the apneic events and by a "movement arousal" in the other 88%. The highest abdominal muscle EMG discharge was always observed during the arousal response. During "phasic" REM sleep, abdominal muscle EMG discharges were absent during both nonapneic breathing (with or without snoring) and obstructive apneas. All REM sleep apneas ended with a "movement arousal," during which abdominal muscle EMG discharges were observed. Thus, abdominal muscle EMG discharges associated with "arousal" were seen independent of the immediately preceding sleep state.

Relationship between respiratory muscle electromyogram and rib cage motion in tetraplegia.

In an attempt to understand the intersubject variation in rib cage motion in tetraplegia, and to assess the isolated action of the diaphragm on the human rib cage, we studied the pattern of rib cage motion in relation to the pattern of nondiaphragmatic respiratory muscle electromyogram (EMG) in 20 tetraplegic patients breathing at rest in the seated posture. The general pattern included a greater expansion of the lower than of the upper rib cage, and a greater and earlier expansion of the lower rib cage in its transverse than in its anteroposterior (AP) diameter. However, whereas the upper rib cage moved paradoxically inward with inspiration in 11 patients, it did not move or slightly expanded in 9 patients; in 1 of these, all rib cage diameters increased in the same proportion during inspiration as during relaxation. This intersubject variation was not related to the duration of tetraplegia, the pattern of the abdominal muscle EMG, or the presence of continuous spastic EMG activity in the parasternal intercostals. By contrast, it was related in part to the pattern of scalene EMG activity: upper rib cage AP paradox was present in 7 of 8 patients with spastic or silent scalenes but only in 4 of 12 patients with phasic inspiratory scalene EMG activity. When studied during quiet breathing in the supine posture, the 8 subjects with denervated scalene, intercostal, and abdominal muscles still showed inspiratory increase in the rib cage transverse diameter, but in 7 patients the lower rib cage AP diameter decreased in concert with the upper rib cage AP diameter.(ABSTRACT TRUNCATED AT 250 WORDS)

Motor responses to positive-pressure breathing in the developing opossum.

The suckling opossum exhibits an expiration-phased discharge in abdominal muscles during positive-pressure breathing (PPB); the response becomes apparent, however, only after the 3rd-5th wk of postnatal life. The purpose of this study was to determine whether the early lack of activation represented a deficiency of segmental outflow to abdominal muscles or whether comparable effects were observed in cranial outflows to muscles of the upper airways due to immaturity of afferent and/or supraspinal pathways. Anesthetized suckling opossums between 15 and 50 days of age were exposed to PPB; electromyogram (EMG) responses in diaphragm and abdominal muscles were measured, along with EMG of larynx dilator muscles and/or upper airway resistance. In animals older than approximately 30 days of age, the onset of PPB was associated with a prolonged expiration-phased EMG activation of larynx dilator muscles and/or decreased upper airway resistance, along with expiratory recruitment of the abdominal muscle EMG. These effects persisted as long as the load was maintained. Younger animals showed only those responses related to the upper airway; in fact, activation of upper airway muscles during PPB could be associated with suppression of the abdominal motor outflow. After unilateral vagotomy, abdominal and upper airway motor responses to PPB were reduced. The balance between PPB-induced excitatory and inhibitory or disfacilitory influences from the supraspinal level on abdominal motoneurons and/or spinal processing of information from higher centers may shift toward net excitation as the opossum matures.

An electromyographic method of objectively assessing cough intensity and use of the method to assess effects of codeine on the dose-response curve to citric acid.

The integrated surface abdominal electromyogram (EMG) has been used as a simple measurement of cough intensity which correlates well with the volume, air flow and noise produced in different coughs. Using the integrated abdominal EMG as a measure of cough intensity, dose response curves to inhaled citric acid can be drawn which are highly reproducible. We have studied the effects of codeine (60 mg) on these curves, and have demonstrated a reduction in cough intensity. It is suggested that this method of testing the effects of an antitussive on such a dose-response curve may be a useful one.

COMPARISON OF ELECTRICAL AND MECHANICAL RECORDING OF SPONTANEOUS AND EVOKED MUSCLE ACTIVITY. THE CLINICAL VALUE OF CONTINUOUS RECORDING AS AN AID TO THE RATIONAL USE OF MUSCLE RELAXANTS DURING ANESTHESIA.

The electrical and mechanical responses of peripheral skeletal muscle to nerve stimulation, and the integrated abdominal electromyogram were studied during anesthesia and operation to determine the feasibility of their routine use as a guide to the administration of neuromuscular blocking agents. The integrated electromyogram provided a good guide to the degree of relaxation produced by anesthetic agents, as well as the neuromuscular blockers. The electrical and mechanical responses of the muscle to nerve stimulation were not significantly modified by the anesthetics but were affected by the neuromuscular blockers. The mechanical response of the muscle to nerve stimulation was found to be the most accurate, convenient and useful guide to the administration of the neuromuscular blockers. Extensive experience with the routine use of a nerve stimulator during anesthesia and operation led to the conclusion that any time a neuromuscular blocking agent is given, the use of a nerve stimulator to monitor the effects should seriously be considered.

EXPIRATORY ACTIVITY OF THE ABDOMINAL MUSCLES IN MAN DURING GENERAL ANESTHESIA.

The integrated electromyogram was recorded from the lateral abdominal muscles in 24 young normal male volunteers in the supine position, both during consciousness and during light general anesthesia, produced by 50 or 80% N2O in O2, or by 0.5–2% halothane in air after thiopental. No activity was observed during quiet breathing in the conscious state, but throughout anesthesia all subjects exhibited expiratory muscle activity. Activity gradually subsided as consciousness was regained, but suddenly disappeared on vocal arousal. Expiratory intragastric pressure increased up to 7.6 cm H2O above control. End-expiratory Pco2, minute volume, and airway resistance (interrupter technique) did not change significantly. Forced inflation during inspiration, maintained for five to six respiratory cycles, depressed activity during the first three to four cycles; subsequent deflation restored activity. Inflation during expiration immediately reduced activity. Mechanisms that might lead to recruitment of the expiratory muscles are considered. Expiratory activity frequently observed in experimental animals might, at least in part, be due to anesthesia, and thus not represent the breathing pattern during consciousness. abdominal electromyogram; respiratory reflexes Submitted on November 4, 1963

A method of monitoring muscular relaxation by the integrated abdominal electromyogram.

Presented at the Annual Meeting of the American Society of Anesthesiologists. Inc., Miami Beach, Florida, October 8, 1959. and accepted for publication November 19, 1959. Dr. Fink is in the Department of Anesthesiology. College of Physicians and Surgeons, Cohumbia University, New York, N. Y.