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At least 1,099 records · Page 61Linked to original sources
PubMed2006

External anal sphincter contraction during cough: not a simple spinal reflex.

AIMS: To assess whether the anal contraction during voluntary coughing is a simple spinal reflex-mediated activity or not. To address this question we studied the external intercostal (EIC) muscle activity and external anal sphincter (EAS) response to cough. MATERIALS AND METHODS: Electromyographic recordings were made from pre-gelled disposable surface electrodes. EAS electromyographic recordings were made from the EAS of the pelvic floor in 15 continent women all suffering from urgency and/or frequency without urge or stress urinary incontinence, and referred for urodynamic investigation. Electromyographic signal was immediately integrated (EMGi). The abdominal pressure was recorded with bladder and rectal pressure. EAS EMGi was recorded during successive voluntary cough. In three women, we have also recorded EIC EMGi activity since it is synchronous with diaphragmatic EMG activity during cough initiation. RESULTS: In all subjects, EAS EMGi activity precedes the onset of the abdominal pressure increase. The mean latency of EAS EMGi was 615 msec (+/-278). In the three subjects whose EMGi activity was recorded both on EAS and EIC, the onset of EAS EMGi activity occurred before the EIC EMGi activity (latency ranging from 40 to 780 msec) and before the increase in the abdominal pressure. CONCLUSIONS: The present study suggests that during coughing, EAS EMG activity increases before external intercostal muscle EMGi activity. The contraction of the EAS preceding the activation of muscles involved in coughing indicates that this response is not a result of a simple spinal reflex, but more likely the result of a more intricate reflex involving complex integrative centers.

Abdomen↗
PubMed1991

Electromyography of some respiratory muscles in the horse.

To investigate activity in respiratory muscles, insulated wire electrodes were used to record electromyographic activity in the costal diaphragm and in the intercostal, serratus ventralis, internal abdominal oblique, transversalis and rectus abdominis muscles in conscious horses and in the same animals when anaesthetised. Electromyographic activity was related to respiratory phases as recorded by a stethograph around the chest wall. The costal diaphragm showed tonic and inspiratory activity in both conscious and anaesthetised animals. The principal muscle actively involved in expiration was the transversalis muscle. Intercostal muscle activity, and any increased activity in the second part of either inspiration or expiration recorded in the conscious animal, was absent under anaesthesia. The very marked tonic activity found in the serratus ventralis muscle in standing horses disappeared during anaesthesia. It was concluded that any stabilisation of the chest wall contributed by activity in the serratus ventralis and intercostal muscles in conscious, standing horses is greatly reduced during anaesthesia.

Abdominal Muscles↗
PubMed2005

Different breathing patterns in healthy and asthmatic children: responses to an arithmetic task.

UNLABELLED: Asthma patients have been reported to be sensitive to breathlessness, independent of the degree of airway obstruction. Paying attention and task performance may induce changes in breathing pattern and these in turn may mediate such a feeling. The present experiment investigates whether strained breathing induced by an arithmetic task was different in children with asthma compared to healthy children. METHODS: Seven healthy and eight asthmatic but symptom-free school children were equipped with electrodes for surface electromyographic (EMG) measurements of diaphragm, abdominal and intercostal (IC) muscles and with a strain gauge to monitor the pattern of breathing at rest and during an arithmetic task. The relative duration of exhalation and the relative speed of exhalation are used as measures of straining. The phase angle of maximal respiratory muscle activities relative to the maximal chest extension (MCE) are additional discriminating parameters. RESULTS: Asthmatic children breathed more slowly and already at rest the phase of their respiratory muscle activity appears to be different. While in healthy children the maximal activity of the (left)abdominal muscles occurred 5+/-29% later than the MCE, in children with asthma the maximal activity occurred 26+/-30% of the cycle earlier than MCE. In children with asthma the activity of the IC muscles starts weaning already at 10+/-30% before MCE, in contrast to the healthy children in which intercostal muscle weaning starts only at 1+/-24% after MCE. During arithmetic, the significant difference between the groups in this respect disappeared. CONCLUSION: Children with asthma show, even at rest, signs of respiratory muscle straining, probably in order to keep close control over the airflow in a similar way as healthy children during mental tasks. Such a 'careful' breathing pattern may work to prevent airway irritation also when they are free of symptoms.

Adolescent↗
PubMed1985

Influence of central chemoreceptor afferent inputs on respiratory muscle activity.

Respiratory activity can be substantially affected by perturbations confined to the superficial areas of the ventrolateral surface of the medulla, the putative site of central chemoreceptors. In this study we compared the effect of thermal and pharmacological interventions that are known to alter respiration on the electrical activity of the rib cage muscles, diaphragm, and abdominal muscles. With cooling of the intermediate areas to 20 degrees C, tidal volume decreased 50%. The electrical activity of the diaphragm decreased less than the other muscles (diaphragm less than inspiratory intercostal less than expiratory intercostal). Abdominal muscle activity was depressed as much as expiratory intercostal activity but reappeared with further cooling to 10 degrees C if cooling was prolonged and the vagi were intact. gamma-Aminobutyric acid (GABA) and its agonist muscimol, like cooling, reduced expiratory and inspiratory intercostal activity more than diaphragm activity. Nicotine, a respiratory stimulant, applied to the intermediate areas increased inspiratory intercostal activity more than the diaphragm. The results suggest that under the conditions of the experiments the rib cage musculature, and probably the abdominal muscles as well, are more responsive than the diaphragm to depression or excitation of chemosensitive elements in the superficial regions of the medulla.

Animals↗
PubMed2006

Diaphragm and intercostal surface EMG and muscle performance after acute inspiratory muscle loading.

We examined the effect of an acute bout of submaximal non-fatiguing inspiratory loading (IL) on maximal inspiratory pressure (MIP), and on the activation of the diaphragm (DI) and intercostals (IC) using surface electromyography (sEMG). After baseline measurements, 12 healthy subjects performed two sets of 30 inspiratory efforts at a load equivalent to 40% of their initial MIP. MIP and maximal DI and IC sEMG activity were recorded after the first and second set of IL, and 15 min after task cessation. After IL, MIP reached (+/-S.E.M.) 111+/-4% (P=0.032) of baseline values, and during MIP, DI and IC root mean square (RMS) sEMG amplitude increased significantly above baseline (143+/-21%, P=0.039 and 137+/-33%, P=0.016, respectively). The significant increase in MIP and RMS amplitude after IL suggests that MIP efforts were initially submaximal, and that prior loading enabled full activation. The changes in DI and IC RMS amplitude may also reflect an improvement in the synergy between them during these maximal efforts.

Adult↗
PubMed1990

Respiratory muscle control during vomiting.

The changes in thoracic and abdominal pressure that generate vomiting are produced by coordinated action of the major respiratory muscles. During vomiting, the diaphragm and external intercostal (inspiratory) muscles co-contract with abdominal (expiratory) muscles in a series of bursts of activity that culminates in expulsion. Internal intercostal (expiratory) muscles contract out of phase with these muscles during retching and are inactive during expulsion. The periesophageal portion of the diaphragm relaxes during expulsion, presumably facilitating rostral movement of gastric contents. Recent studies have begun to examine to what extent medullary respiratory neurons are involved in the control of these muscles during vomiting. Bulbospinal expiratory neurons in the ventral respiratory group caudal to the obex discharge at the appropriate time during (fictive) vomiting to activate either abdominal or internal intercostal motoneurons. The pathways that drive phrenic and external intercostal motoneurons during vomiting have yet to be identified. Most bulbospinal inspiratory neurons in the dorsal and ventral respiratory groups do not have the appropriate response pattern to initiate activation of these motoneurons during (fictive) vomiting. Relaxation of the periesophageal diaphragm during vomiting could be brought about, at least in part, by reduced firing of bulbospinal inspiratory neurons.

Animals↗
PubMed1998

Mechanical advantage of the human parasternal intercostal and triangularis sterni muscles.

1. Previous studies in dogs have demonstrated that the maximum change in airway pressure (DeltaPao) produced by a particular respiratory muscle is the product of three factors, namely the mass of the muscle, the maximal active muscle tension per unit cross-sectional area ( approximately 3.0 kg cm-2), and the fractional change in muscle length per unit volume increase of the relaxed chest wall (i.e. the muscle's mechanical advantage). In the present studies, we have used this principle to infer the DeltaPao values generated by the parasternal intercostal and triangularis sterni muscles in man. 2. The mass of the muscles and the direction of the muscle fibres relative to the sternum were first assessed in six cadavers. Seven healthy individuals were then placed in a computed tomographic scanner to determine the orientation of the costal cartilages relative to the sternum and their rotation during passive inflation to total lung capacity. The fractional changes in length of the muscles during inflation, their mechanical advantages, and their DeltaPao values were then calculated. 3. Passive inflation induced shortening of the parasternal intercostals in all interspaces and lengthening of the triangularis sterni. The fractional shortening of the parasternal intercostals decreased gradually from 7.7 % in the second interspace to 2.0 % in the fifth, whereas the fractional lengthening of the triangularis sterni increased progressively from 5.9 to 13.8 %. These rostrocaudal gradients were well accounted for by the more caudal orientation of the cartilages of the lower ribs. 4. Since these fractional changes in length corresponded to a maximal inflation, the inspiratory mechanical advantage of the parasternal intercostals was only 2.2-0. 6 % l-1, and the expiratory mechanical advantage of the triangularis sterni was only 1.6-3.8 % l-1. In addition, whatever the interspace, parasternal and triangularis muscle mass was 3-5 and 1-3 g, respectively. As a result, the magnitude of the DeltaPao values generated by a maximal contraction of the parasternal intercostals or triangularis sterni in all interspaces would be only 1-3 cmH2O. 5. These studies therefore confirm that the parasternal intercostals in man have an inspiratory action on the lung whereas the triangularis sterni has an expiratory action. However, these studies also establish the important fact that the pressure-generating ability of both muscles is substantially smaller than in the dog.

Adult↗
PubMed2000

Effects of lung volume on parasternal pressure-generating capacity in dogs.

Previous studies have suggested that the optimum length for force generation of the parasternal intercostal (PS) muscles is well above functional residual capacity (FRC). We further explored this issue by examining the pressure-generating capacity of the PS muscles as a function of lung volume in anaesthetized dogs. Upper thoracic spinal cord stimulation (SCS) was used to electrically activate the PS muscles. Changes in airway pressure and parasternal resting length (LR) during airway occlusion were monitored over a wide range of lung volumes during SCS. To assess the effects of parasternal contraction alone, SCS was performed following phrenicotomy and section of the external intercostal, levator costae and triangularis sterni muscles. With increasing lung volume, there were progressive decrements in the capacity of the PS muscles to produce changes in airway pressure. The relationship between PS pressure generation and lung volume was similar to a previous comparable assessment of the external intercostal muscles. The PS muscles shortened during passive inflation and also shortened further (by > 20 % of LR) during SCS. Total shortening (passive plus active) increased progressively with increasing lung volume. Our results indicate that the capacity of the PS muscles to produce changes in airway pressure (a) falls progressively with increasing lung volume and (b) is similar to that of the external intercostal muscles. We speculate that the fall in PS pressure-generating capacity is related, in part, to progressive reductions in end-inspiratory length.

Animals↗
PubMed1990

Fusimotor control of muscle spindle sensitivity during respiration in the cat.

1. The two types of fusimotor neurones, dynamic and static, can be differentiated by their effects on muscle spindle afferents. We have recorded the activity of muscle spindle primary afferents from the intercostal nerves of anaesthetized or decerebrate cats. A 4 Hz sinusoidal stretch was applied to the muscle containing the spindles of interest before and after crushing the nerve proximal to the recording site to eliminate fusimotor effects. The relative activity of the dynamic and static fusimotor neurones was inferred from the change in the spindle afferents' response. 2. Some areas of intercostal muscle normally showed phasic activity linked to respiration, where as other areas of intercostal muscle showed no EMG activity under our experimental conditions. In areas of intercostal muscle lacking EMG activity, the afferents' mean rate was higher and the modulation around the mean was lower at all phases of the breathing cycle when the efferent supply was intact. This result suggests the muscle spindles were receiving a steady level of static fusimotor activity. 3. Spindle primary afferents from regions of intercostal muscle that were typically recruited during respiration had an additional increase in mean rate and modulation around the mean rate in phase with the EMG activity. This is suggestive of phasic activation of dynamic fusimotor neurones in addition to static fusimotor discharge. 4. Thus, the two types of fusimotor neurones can be activated separately by the CNS to control the sensitivity of muscle spindles. The regional differences in the recruitment patterns of fusimotor neurones parallels the functional specializations of different areas of the intercostal muscles. The temporal modifications of fusimotor activity during each respiratory cycle means that the segmental reflex gain will vary in those intercostal muscles that are active during respiration. 5. These findings regarding the CNS recruitment of the two types of fusimotor neurones during respiration are similar to those reported for the hindlimb extensors during locomotion, but differ from those reported for jaw muscles during chewing. This may reflect differing control strategies being used by the CNS to meet the unique demands of the various rhythmical movements.

Action Potentials↗
PubMed1991

Influences of lung mechanoreceptors and carotid chemoreceptors on the response of respiratory muscle activity to tracheal occlusion.

We examined the responses of respiratory muscle electromyograms (EMGs) from internal (IIC) and external intercostal (EIC) muscles and diaphragm (DIAP) to three successive occluded breaths in anesthetized spontaneously breathing rabbits. Both inspiratory and expiratory muscle EMGs progressively increased in the course of tracheal occlusion. An increase in these muscle EMGs was still observed after release of tracheal occlusion, but those effects were short-lasting. In a separate series of experiments, for assessment of possible reflex effects involved, the responses of slowly adapting pulmonary stretch receptor (SAR), rapidly adapting pulmonary stretch receptor (RAR), and carotid chemoreceptor activities to tracheal occlusion lasting for three respiratory efforts were also examined. The inspiratory discharge of SARs decreased but the expiratory discharge of SARs increased during tracheal occlusion. Although carotid chemoreceptors increased their activity in the latency of 3-6s after the onset of tracheal occlusion, the activity of RARs was greatly reduced throughout the period of tracheal occlusion. A transient increase in both carotid chemoreceptors and RARs was still observed after release of tracheal occlusion. These results suggest that alterations of inspiratory and expiratory muscle EMGs produced by tracheal occlusion would appear to be mediated by the afferent inputs from lung mechanoreceptors and carotid chemoreceptors.

Animals↗
PubMed1996

Muscle fibers, ubiquinone and exercise capacity in effort angina.

Seventeen male patients with ischaemic heart disease (IHD) and effort angina performed OBLA exercise stress tests (set to 2.0 mmol x l-1). They had muscle biopsies from the vastus lateralis muscle the day before coronary by-pass grafting, and from the internal and external intercostal, diaphragm and gastrocnemius muscles during surgery. They had a low WOBLA (83 +/- 6 W, mean +/- 1 S.E.M), WOBLA corresponded to 79 +/- 4% (% WOBLA) of WSL (symptom limited or 'maximal' capacity = 111 +/- 11 W). Peak blood lactate concentration averaged 2.9 mmol x l-1. Muscle fibre composition disclosed a depressed percent slow twitch (ST or 'red') muscle fibres in the vastus lateralis and intercostal muscles (%ST). The diaphragm and gastrocnemius muscles had normal %ST. Intercostal muscles had elevated values for the fast twitch muscle fibre (FT) subgroup FTa indicative of endurance adaptation. The vastus lateralis, gastrocnemius and diaphragm muscles had normal muscle ubiquinone (UQ) contents, whereas the intercostals were depleted. Plasma contents of the antioxidants UQ and alpha-tocopherol were low as compared to healthy man.

Aged↗
PubMed1987

The labile respiratory activity of ribcage muscles of the rat during sleep.

1. Sleep-waking states of chronically implanted rats were identified polygraphically while recording the integrated electromyogram (e.m.g.) of extrinsic (scalenus medius and levator costae) and intrinsic (external and internal interosseous intercostal and parasternal) muscles of the thoracic cage. Rats breathed air, air enriched in CO2 (5%) or air deficient in O2 (10% O2 in N2) and were free to adopt any desired posture. 2. In non-rapid eye movement (non-r.e.m.) sleep, the scalenus medius and intercostal muscles of the cephalic spaces were always inspiratory; intercostal muscles of the mid-thoracic spaces were commonly expiratory while the more caudal ones were only occasionally expiratory. Expiratory activity, when present in quiet wakefulness, extended for a variable period of time into non-r.e.m. sleep and always disappeared in r.e.m. sleep regardless of the ribcage muscle under study. 3. Inspiratory activity, when present in non-r.e.m. sleep, was unaffected, partially attenuated or abolished at entry into r.e.m. sleep. The peak integrated e.m.g. activity of ribcage muscles was measured as a function of posture, gas mixture breathed and ribcage site: (a) the greater the degree of curled-up posture, the greater the respiratory activity of scalenus medius, an effect augmented by CO2 but depressed by hypoxia, and (b) the more caudally placed ribcage muscles exhibited respiratory activity which was essentially unaffected by posture and gas mixture inspired. 4. The presence or absence of tonic activity in ribcage respiratory muscles during non-r.e.m. sleep was unrelated to posture. When tonic activity was present, it always disappeared in r.e.m. sleep. When expiratory activity was present in non-r.e.m. sleep, it too always disappeared in r.e.m. sleep. Inspiratory activity present in non-r.e.m. sleep was variably affected at entry into r.e.m. sleep; it was unchanged, partially attenuated or abolished. 5. It is concluded that thoracic cage muscles exhibit marked variability in their respiratory activity depending on posture, sleep-waking states and gas mixture breathed. It is postulated that the presence of tonic and/or expiratory activity in ribcage muscles during non-r.e.m. sleep reflects an increase in functional residual capacity (F.R.C.).

Air↗
PubMed1991

Free muscle transplantation combined with intercostal nerve crossing for reconstruction of elbow flexion and wrist extension in brachial plexus injuries.

Complete paralysis due to traumatic brachial plexus injury is extremely difficult to treat when the injury affects whole nerve roots and when motor function fails to show any signs of recovery. Seddon has suggested that arthrodesis of the shoulder and amputation at the humerus, combined with the use of a functional upper extremity prosthesis, was the most practical procedure available. Since 1965, in cases of irreparable lesions such as complete root avulsion type injuries, we have performed direct intercostal nerve crossing to the musculocutaneous nerve without free nerve graft to achieve elbow flexion. However, it is necessary to operate on the patient within 6 months following the injury to obtain good results. In the past there was no procedure for dealing with delayed cases of complete brachial plexus palsy. However, with the advent of microsurgical techniques, new approaches have become open to us. Since 1978, we have reconstructed the elbow flexor by the combined surgery of free muscle transplantation with intercostal nerve crossing in delayed cases of complete paralysis. This article introduces the operative technique and the results we have obtained.

Adolescent↗
PubMed2000

Clinical applications of the posterior rectus sheath-peritoneal free flap.

Soft-tissue injuries involving the dorsum of the hand and foot continue to pose complex reconstructive challenges in terms of function and contour. Requirements for coverage include thin, vascularized tissue that supports skin grafts and at the same time provides a gliding surface for tendon excursion. This article reports the authors' clinical experience with the free posterior rectus sheath-peritoneal flap foil dorsal coverage in three patients. Two patients required dorsal hand coverage; one following acute trauma and another for delayed reconstruction 1 year after near hand replantation. A third patient required dorsal foot coverage for exposed tendons resulting from skin loss secondary to vasculitis. In all three patients, the flap was harvested through a paramedian incision at the lateral border of the anterior rectus sheath. After opening the anterior rectus sheath, the rectus muscle was elevated off of the posterior rectus sheath and peritoneum. When elevating the muscle, the attachments of the inferior epigastric vessels to the posterior rectus sheath and peritoneum were preserved while ligating any branches of these vessels to the muscle. Segmental intercostal innervation to the muscle was preserved. The deep inferior epigastric vessels were then dissected to their origin to maximize pedicle length and diameter. The maximum dimension of the flaps harvested for the selected cases was 16 X 8 cm. The anterior rectus sheath was closed primarily with non-absorbable suture. Mean follow-up was 1 year, and all flaps survived with excellent contour and good function in all three patients. Complications included a postoperative ileus in one patient, which resolved after 5 days with nasogastric tube decompression.

Adult↗