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At least 1,279 records · Page 71Linked to original sources
PubMed1990

Distribution of motor activity to expiratory muscles during sciatic nerve stimulation in the dog.

The present study examined the effect of increasing sensory input from the lower limbs (assessed from the response to electrical stimulation of the sciatic nerve) on the distribution of electrical activity to the expiratory muscles. Expiratory muscle response to sciatic nerve stimulation (SNS) was compared to the response of the inspiratory muscles, and to their response to hypercapnia. In 16 anesthetized dogs afferent SNS increased ventilation and augmented the integrated EMG of all six expiratory muscles studied. Increases in abdominal muscle electrical activity were not uniform, being greater in the transversus abdominis and external oblique as compared to the internal oblique and the rectus abdominis. Increases in thoracic expiratory and inspiratory muscle activity during SNS were similar in magnitude. SNS performed while dogs were breathing 7% CO2, produced increased neural activity similar to those observed during O2 breathing. During CO2 rebreathing, at equal levels of minute ventilation, expiratory muscle responses to SNS and to CO2 were similar. In contrast, the rate of rise of the inspiratory muscle EMGs was greater during SNS. The present study indicates that the abdominal muscles participate in the respiratory response to afferent neural drive from skeletal muscles. The magnitude of their response is independent of their pre-stimulation level of activity and is similar to that observed during CO2 stimulated breathing.

Abdominal Muscles↗
PubMed1990

Electrical control of gastric emptying in denervated and reinnervated canine stomach: a pilot study.

Gastric emptying of solids is abnormally slow after vagotomy. To determine whether it was possible to accelerate emptying by electrical stimulation either of the gastric wall directly or of a "foreign" nerve brought in to reinnervate the stomach, eight dogs underwent truncal vagotomy (TV); five of the dogs received intercostal nerve muscle pedicle (NMP) implants. Gastric atony was demonstrated postoperatively in all animals up to 4 months later by means of radiological contrast studies. After allowing time for neurotization to occur (mean 78 days), the cervical vagi were stimulated to confirm that TV was complete. Gastric peristalsis, intraluminal pressures, and emptying were assessed during stimulation of the NMPs and of the gastric wall, followed by sacrifice for histologic study. Neither reinnervation alone nor stimulation of the NMPs improved emptying. Although viable somatic nerve was found in the gastric wall, nerve sprouting was not. By contrast, stimulation of the gastric wall with trains of pulses (20 Hz, 2-10 ms, 2-5 mA) evoked peristalsis in all animals. We conclude that somatic nerve tissue cannot produce functional reinnervation of a visceral organ; however, direct muscular stimulation can accelerate gastric emptying after TV.

Abdominal Muscles↗
PubMedDate not supplied

Cournand lecture: Mechanical action of the abdominal muscles.

The abdominal muscles, by causing a rise in abdominal pressure and a cranial displacement of the diaphragm, 1--deflate the lungs (minimize the increase in FRC which normally occurs when adopting the standing posture), 2--exert an expanding force on the lower rib cage, which may counterbalance or even dominate the insertional (expiratory) force they exert on the lower ribs by way of their insertions, 3--improve the pressure-generating ability of the diaphragm. In addition, because they prevent the diaphragmatic dome from descending during inspiration, they also improve the rib cage expanding action of the diaphragm.

Abdominal Muscles↗
PubMedDate not supplied

[Detection of the bioelectric activity of respiratory musculature in clinically healthy persons of various ages].

We studied the amplitude of the integrated electromyogram of three sets of muscles, which have an active part in the respiratory movements, for senile changes. Bipolar 50-mm2 electrodes with an interelectrode spacing of 20 mm were used to produce the electromyograms. A "Mediator" electromyograph equipped with an amplitude and frequency analyzer and synchronized to a "Medikor" spirograph was used. The electrodes were placed at precisely determined locations. 164 clinically healthy persons, 85 men and 79 women, aged between 18 to 89 years, were included in the study. The amplitude of the pectoral muscles decreases significantly in case of accelerated exspiration. The amplitude of cervical muscles increases in case of women respirating regularly, whereas that of the abdominal muscles decreases significantly in case of deep respiration and accelerated exspiration. This applies to women only for accelerated inspiration. The amplitude response to a number of respiratory movements is lower in old age, particularly in women.

Abdominal Muscles↗
PubMed1980

[Resistive loading and mechanisms regulating respiration].

In experiments on anesthetized cats, switch on of additional inelastic respiration resistance (resistive load) produced, apart from slowing of the respiratory flows, an increase in the activity of motoneurons and inspiratory intrathoracic pressure. Bilateral vagotomy resulted in disappearance of resistive load-induced elevation of the phrenic nerve activity, but did not abolish the growth of the inspiratory effort. Analysis of the evidence obtained indicates that activation of phrenic motoneurons associated with increased respiration resistance is underlain by prolongation of the inspiratory phase that is consequent on relaxation of the inspiratory inhibition. It is suggested that, in addition to the mechanism depicted, the compensatory reaction to the resistive load involves, apart from diaphragm participation, other inspiratory muscles as well as enhanced contractions of respiratory muscles provided by the properties of muscular fiber.

Abdominal Muscles↗
PubMed1987

Tubular musculopleural pedicle grafting of esophageal long gaps in dogs.

Direct anastomosis of the esophagus is the treatment of choice in patients with esophageal atresia. If, however, a long esophageal gap exists, the anastomosis is performed under tension or a staged procedure is anticipated. The aim of this study was to prove that a pedicle musculopleural graft can be used to bridge the two esophageal ends. In 14 dogs through a right thoracotomy, the periosteum of the fifth rib was mobilized and the rib was excised. An intercostal musculopleural flap was created leaving the muscle attached to its vascular pedicle posteriorly with the intercostal vessels and nerve carefully preserved. A tube-like portion including pleural and intercostal muscles was formed from the free part of the graft. A 5 cm segment of the esophagus was excised and the tubular graft was interimposed. Animals were studied 1 month postoperatively with a barium meal that showed free passage through the esophageal neolumen. Peristaltic activity was studied with strain gauges above, below, and at the grafted area. Histologic examination revealed good healing at both anastomotic sites, while esophageal squamous epithelium covered the lumen all over the graft. Survival of the musculopleural pedicle graft seems to be feasible providing that its vascular supply is preserved. It is, thus, suggested that this technique might offer an alternative method in bridging long gaps in esophageal surgery.

Animals↗
PubMed1982

Inspiratory muscle activity during rebreathing in intact and vagotomized rabbits.

The relation between relative peak 'integrated' diaphragmatic (Adi) and cranial (u) or caudal (1) inspiratory intercostal activity (Aic) was assessed in intact and vagotomized rabbits during rebreathing. During unloaded rebreathing Aic increased markedly more than Adi, and Aicu more than Aicl, independently of intact vagi. Vagal signals facilitated inspiratory intercostals, since vagotomy or vagal blocks increased Adi more than Aic without changing diaphragm activity time course, and delta Aic/delta Adi in the same range of Adi values was greater before than after vagotomy. Reflexes from the chest wall were not involved since phrenic block after vagotomy modified rib cage motion without changing Aic, independently of chemical drive. Possibly chemical and vagal dependent changes in fusimotor activity contribution to VT, as the latter increases. Obstruction at FRC shifted postvagotomy Aic vs. Adi relationship upwards, suggesting reflex facilitation of intercostals by chest wall receptors. The strength of this reflex was largely independent of intact vagi, since pre- and postvagotomy Aic vs. Adi relations coincided, and of chemical drive, since postvagotomy delta Aic/delta Adi for obstructed and unimpeded rebreathing were similar.

Airway Obstruction↗