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PubMed2002

Effects of prolonged mechanical ventilation on respiratory muscle ultrastructure and mitochondrial respiration in rabbits.

OBJECTIVE: To investigate in rabbits whether prolonged mechanical ventilation (PMV) leads to ultrastructural changes in respiratory muscles and alters diaphragm mitochondrial respiration. DESIGN AND SETTING: Experimental prospective study in a university laboratory. ANIMALS AND INTERVENTIONS: We studied respiratory muscles of seven rabbits after 49+/-1 h of controlled mechanical ventilation. Ten nonventilated rabbits were used as a control group. MEASUREMENTS AND RESULTS: After mechanical ventilation electron-microscopic observations of the diaphragm and the external intercostal muscles revealed disrupted myofibrils, increased number of lipid vacuoles in the sarcoplasm, and smaller mitochondria with focal membrane disruptions. Volumetric and numerical densities of the mitochondria were significantly lower in the PMV group than the control group. Mitochondrial respiration was quantified in isolated diaphragm muscle-cell mitochondria using two respiratory substrates. There was no difference in oxygen consumption values in the three states of mitochondrial respiration between the two groups except for state 2 (basal state) with pyruvate/malate parameter (53.5+/-20 for the ventilated group vs. 33.8+/-10.2 nmol atom O/mg per minute for the control group). There was no significant difference between groups in ADP/O ratio or respiratory control ratio. CONCLUSIONS: PMV leads to respiratory muscle cell degeneration and minor changes in oxidative phosphorylation coupling in diaphragmatic mitochondria. These phenomena may mediate part of damage of respiratory muscles after inactivity related to PMV.

Animals↗
PubMed2002

Effects of controlled mechanical ventilation on respiratory muscle contractile properties in rabbits.

OBJECTIVE: We examined in rabbits the effects of more than 48 h of mechanical ventilation on the contractile properties and fiber type adaptations of the respiratory muscles. DESIGN AND SETTING: Experimental prospective study in a university laboratory. ANIMALS AND INTERVENTIONS: Nineteen rabbits were randomly allocated to two groups: control (n=10) or mechanically ventilated (MV; n=9) for 51+/-3 h. MEASUREMENTS AND RESULTS: Respiratory muscles contractile properties were analyzed before and after a fatigue protocol using in vivo isometric 1-s tetanic contraction characteristics in both muscles: peak tetanic force, contraction time, relaxation time, and total contraction time. Both muscle fiber type proportions, diameter, and cross-sectional areas were measured using ATPase staining. The MV rabbits showed significant weight loss in both muscles, accompanied by a reduced peak tetanic force (9.96+/-3.2 vs. 7.44+/-2.2 N for diaphragm of control and MV animals respectively), fatigue resistance index, and increased relaxation time (57.5+/-8.7 vs. 85.8+/-9.4 ms for diaphragm of control and MV animals) and contraction time. These impairments in the MV group worsened after the fatigue runs. Both muscle showed a significant atrophy of type IIa and IIb fibers but a stability in type I fibers cross-sectional area. CONCLUSIONS: Mechanical ventilation in rabbits produces alterations in contractile properties of the diaphragm and 5th external intercostal muscle, increases both muscles fatigue, and promotes atrophy of type II fibers.

Animals↗
PubMed1998

An increase in the threshold of citric acid-induced cough during chest wall vibration in healthy humans.

This study tested the hypothesis that the afferent input from the respiratory muscles may be involved in the neural mechanisms inducing cough responses. Coughing was evoked in conscious healthy humans by the inhalation of citric acid aerosol of several concentrations either during or not during chest wall vibration (100 Hz) at the right second intercostal space or during vibration of the right thigh. The mean threshold citric acid concentration to induce coughing was significantly higher during chest wall vibration (geometric mean, 131.8 mg/ml) than without vibration (75.9 mg/ml). Vibration after topical anesthesia of the chest wall skin did not significantly change the threshold concentration of citric acid. The threshold citric acid concentration during vibration of the right thigh did not significantly differ from that without vibration. We concluded that inputs from the chest wall afferent, presumably from the intercostal muscle or costovertebral joint, may have an inhibitory effect on the initiation of coughing at the higher neural structure in conscious humans.

Administration, Inhalation↗
PubMed1984

[Changes in the respiratory muscles and their microcirculatory bed during exposure of the body to chronic hypoxia and its aftereffects].

Changes of the respiratory muscles have been studied under the effect of a rarefied atmosphere when the pressure is 560 mm Hg (2,500 m), 405 mm Hg (5,000 m), 286 mm Hg (7,500 m) and during the period of their aftereffect. The experimental group consists of 260 and the control group--of 130 white rats. Adaptation of the respiratory muscles to the effect of the rarefied atmosphere at the pressure of 560 mm Hg takes place mainly at the expense of certain functional changes of the microcirculatory bed and hypertrophy of the muscle fibers. The period of aftereffect is characterized with normalization of these phenomena. Adaptation of the respiratory muscles at the pressure of 405 mm Hg takes place at the expense of hypertrophy of the muscle fibers, small destructive changes and a complex rearrangement of the microcirulatory bed. During the period of aftereffect, by the 40th day no destructive changes are noted in the muscle tissue. The capillary bed undergoes some rearrangements by the 42d -56th day with increasing quantitative indices per area unit. This results in improvement of the muscles nutrition. In the respiratory muscles at the pressure 286 mm Hg, atrophic changes in the muscle fibers take place at certain stages of the experiment. Essential destructive changes are observed, rearrangement of the microcirculatory bed with decreasing convolution of the longitudinal capillaries and a decreasing number of the transversal capillaries are noted by the end of the experiment. During the period of aftereffect, by the 56th day, the external and internal intercostal muscles completely restore their structure, and in the diaphragm the destructive changes remain. By the same time, the microcirculatory bed becomes more rare at the expense of decreasing capillarization of the muscle fibers and a decreasing number of the transversal capillaries.

Animals↗
PubMed1975

Chronic myopathy associated with coxsackievirus type A9. A combined electron microscopical and viral isolation study.

Virus-like crystalline structures in human skeletal muscles have been observed by many electron microspists, but no viruses have been isolated and identified in such cases. An 11-year-old girl who had had muscular weakness and physical retardation since early infancy died of pneumonia due to atrophy of diaphragmatic and intercostal muscles. Electron microscopy of these muscles revealed a heavy infiltration of picornavirus-like particles that measured 19 to 23 nm in diameter. Subsequent inoculation of primary human-amnion cells with a sonic-treated suspension of the patient's diaphragmatic muscle induced an enterovirus-like cytopathic effect. The isolate was identified with use of Lim-Benyesh--Meinick enterovirus typing serum pools as coxsackievirus Type A-9. This viral isolation supports the belief that the organized electron-dense particles in human muscle are indeed virions.

Animals↗
PubMed2005

Combined intercostal and diaphragm pacing to provide artificial ventilation in patients with tetraplegia.

OBJECTIVE: To evaluate the usefulness of combined intercostal and diaphragm pacing to maintain independence from mechanical ventilation. DESIGN: A prospective trial. SETTING: Clinical research center at a large tertiary hospital. PARTICIPANTS: Four ventilator-dependent subjects with spinal cord injury with only unilateral phrenic nerve function. INTERVENTION: During an initial surgical procedure, a multipolar epidural disk electrode was positioned on the ventral surface of the upper-thoracic spinal cord via a hemilaminectomy to activate the inspiratory intercostal muscles. A phrenic nerve electrode was implanted unilaterally via the thoracic approach. MAIN OUTCOME MEASURES: Inspired volume production and duration that subjects could be comfortably maintained when off mechanical ventilatory support. RESULTS: Initial maximum inspired volumes from combined intercostal and diaphragm stimulation ranged between .23 and .93L and significantly increased over the course of reconditioning period to between 0.55 and 1.31L; subjects could be maintained off mechanical ventilation between 16 and 24 hours a day. CONCLUSIONS: Combined intercostal and unilateral diaphragm pacing may be a useful therapeutic modality capable of maintaining long-term ventilatory support in patients with only unilateral phrenic nerve function.

Diaphragm↗
PubMed1998

The effect of nitrous oxide on chest wall function in humans and dogs.

UNLABELLED: The purpose of this study was to determine the effects of nitrous oxide (N2O) on the chest wall of anesthetized humans and dogs. Six human subjects and six mongrel dogs were studied during 1 minimum alveolar anesthetic concentration halothane anesthesia before and during the substitution of 70% N2O for 70% N2 in the inspired gas mixture. On a separate occasion, measurements also were made in pentobarbital-anesthetized dogs. Respiratory muscle activity was measured using electromyographic (EMG) electrodes. Chest wall configuration was determined by using fast three-dimensional computed tomography in dogs and by using respiratory impedance plethysmography in humans. N2O consistently decreased inspiratory ribcage displacement, a decrease attributable in dogs to decreased inspiratory activation of parasternal intercostal muscles; parasternal intercostal activity was not present in anesthetized humans. The decrease in ribcage motion decreased the tidal volume in humans, but not in dogs, because displacement of the diaphragm was better preserved in dogs, in association with changes in diaphragm EMG activation. N2O significantly increased phasic expiratory muscle activity in halothane-anesthetized humans and pentobarbital-anesthetized dogs. Thus, as has been demonstrated for other anesthetics, the actions of N2O are caused by alterations in the distribution and timing of neural drive to the respiratory muscles, rather than by a global depression of respiratory motoneuron drive. IMPLICATIONS: In this study, we examined the effects of nitrous oxide on breathing in halothane-anesthetized dogs and humans. Nitrous oxide affected breathing by changing the distribution and timing of neural drive to the respiratory muscles in a species-dependent manner, rather than by causing a global depression of their activity.

Animals↗
PubMed1977

Contributions of changing rib cage--diaphragm interactions to the ventilatory depression of halothane anesthesia.

The ventilatory response to CO2 was subdivided into that portion due to increasing rib cage expansion, and that due to increased diaphragmatic descent. Five children were studied, awake, and anesthetized with halothane, 0.8-0.9%. During anesthesia there was a 67+/-8% reduction (mean+/-SE) in the slope of the response of overall ventilation to an increase in CO2. This was primarily due to an 89+/-8% reduction in the recruitment of rib cage ventilation (P less than .001). There was no significant change in the slope of the diaphragmatic response (anesthetized value 19+/-21% less than control), although the response curve was shifted to the right so that a higher CO2 concentration was needed to stimulate a given level of diaphragmatic excursion. Additional measurements of the inspiratory intercostal electromyogram in three adult subjects documented a rapid, profound depression of intercostal activity with halothane anesthesia that was associated with a marked decrease in rib cage ventilation. The authors conclude that a major component of the ventilatory depression associated with halothane anesthesia results from the preferential suppression of intercostal muscle function with relative sparing of diaphragmatic activity.

Adolescent↗
PubMed1998

Acquired slow-channel syndrome: a form of myasthenia gravis with prolonged open time of the acetylcholine receptor channel.

A 32-year-old female presented with a 2-year history of fluctuating generalized weakness including extraocular, bulbar, and limb muscles, suggesting myasthenia gravis, but with poor response to pyridostigmine and unusual electromyographic findings. After rest, power increased on repeated maximal contractions, followed by progressive weakness. There were decremental responses at low-frequency stimulation, but incremental responses at high frequencies, and single stimuli evoked repetitive compound muscle action potentials. Plasmapheresis was ineffective. In a conventional assay, antibodies against acetylcholine receptors (AChRs) were borderline. However, in an assay using cells expressing mainly adult-type human AChRs, the patient's serum was positive. Thymectomy revealed a hyperplastic thymus. An intercostal muscle specimen revealed small miniature end-plate potentials, 0.22+/-0.02 mV instead of 0.56+/-0.05 mV in controls. The number of 125I-alpha-bungarotoxin binding sites was normal. The decay time constant of end-plate potentials was increased from 5.3+/-0.6 msec in controls to 23+/-3.6 msec in the patient. Ultrastructurally, there was no destruction of the end plate. Transfer of the patient's plasma to mice in vivo produced similar physiological changes in their diaphragms. We conclude that the patient has an immune-mediated disorder, in which an antibody specific to the adult form of the AChRs alters the channel properties, reducing total current and slowing the closure. We propose the name "acquired slow-channel syndrome" for this variant of myasthenia gravis.

Adult↗
PubMed1982

Activation of the parasternal intercostals during breathing efforts in human subjects.

We have tested the possibility that the electromyographic (EMG) activity present in the parasternal intercostal muscles during quiet inspiration was reflexive, rather than agonistic, in nature. Using concentric needle electrodes we measured parasternal EMG activity in four normal subjects during various inspiratory maneuvers. We found that 1) phasic inspiratory activity was invariably present in the parasternal intercostals during quiet breathing, 2) the parasternal EMG activity was generally increased during attempts to perform the tidal breathing maneuver with the diaphragm alone, 3) parasternal EMG activity was markedly decreased or suppressed in the presence of rib cage distortion during diaphragmatic isovolume maneuvers, and 4) that EMG activity could not be voluntarily suppressed during breathing unless the inspired volume was trivial. We conclude that the parasternal EMG activity detected during quiet inspiration in the normal subjects depends on a central involuntary mechanism and is not related to activation of intercostal mechanoreceptors.

Adult↗
PubMed1999

Response of respiratory muscles to intravenous nicotine challenge in anaesthetized cats.

The effects of an intravenous nicotine challenge on the ventilation and activity of rib cage muscles were studied in 33 pentobarbitone-chloralose anaesthetized cats. Bolus injection of nicotine (200 microg) into the right femoral vein evoked in 19 of the intact animals prompt, short-lived apnoea, or prolongation of the first expiration after the drug, the occurrence of which was significantly reduced by midcervical vagotomy (P < 0.001). In breaths that followed the apnoea, peak activity of the parasternal intercostal muscles increased from a baseline of 3.1 +/- 0.8 to 9.2 +/- 1.8 arbitrary units (P < 0.001). Nicotine produced a similar increase in peak phrenic ENG (7.0 +/- 0.5 to 14.5 +/- 1.2 arbitrary units; P < 0.001). Peak triangularis sterni muscle EMG was reduced from 8.9 +/- 1.2 to 6 +/- 1.7 arbitrary units (P < 0.05) and the onset of response was delayed to 30 s after the challenge. The changes of respiratory effectors induced by nicotine were independent of vagal integrity. The results show that post-nicotine apnoea is to large extent vagally dependent though the response of the respiratory muscles is mediated by non-vagal influences.

Anesthesia↗
PubMed1976

Blood flow to respiratory, cardiac, and limb muscles in dogs during graded exercise.

The distribution of cardiac output was analyzed in six dogs, with the animals at rest and running on a level treadmill for 3 min at 3-4 mph (mild exercise) and 3 min at 6-8 mph (moderate exercise). Organ flows were measured using 25-mug-diam radioactive microspheres. Cardiac output averaged 2.5, 4.6, and 5.7 liters/min, for rest, mild exercise, and moderate exercise, respectively. The greatest change was in diaphragmatic flow which increased by 275% with mild exercise and 500% with moderate exercise. Flow to intercostal muscles increased by 160 and 186%, to the exercising gastrocnemius muscle by 153 and 224%, and to cardiac muscle by 57 and 109% during mild and moderate exercise, respectively. Renal and cerebral flows did not change significantly. Significant decreases in flow occurred in the small and large intestines during moderate exercise. It is concluded that the increase in cardiac output during submaximal exercise was redistributed in a manner which limited flow to the brain, intestines, and kidneys and increased flow flow to the diaphragm, heart, and limb muscles.

Animals↗
PubMed1978

Motion of the rib cage and the abdomen in tetraplegic patients.

1. We have studied the motion of the abdomen and the rib cage in patients with a transection of the lower cervical spinal cord during normal breathing both in the supine and sitting posture, and compared it with that of normal subjects. 2. In the supine posture the rib cage of a patient moves paradoxically inward, therefore his chest wall is deformed, which explains the high work of breathing. 3. During expiration, beside the recoil of the respiratory system, there is also the recoil of the deformed chest wall, toward its passive configuration, with an expansion of the rib cage above its resting position during the first part of expiration and an alteration of the expiratory flow profile. 4. In a sitting 'relaxed' posture the paradoxical inward motion disappears in the lower rib cage, and it is reduced but still present in the higher rib cage. 5. We conclude that contraction of the diaphragm constricts the 'passive rib cage', either directly through its insertions or indirectly through the reduction of intrathoracic pressure. In seated subjects the diaphragm causes some expansion of the rib cage at its lower level. Therefore the motion of the rib cage is not only related to the balance between the forces developed by the diaphragm and the intercostal muscles, but also to the diaphragm dome configuration, the geometry of the rib cage and the lung volume.

Abdomen↗
PubMedDate not supplied

Intercostal pedicle flap for thoracic oesophageal perforations.

Oesophageal perforations are associated with a high mortality and morbidity. Intrathoracic perforations especially are associated with mediastinitis and sepsis. The repair of these perforations may be difficult, particularly when there has been a delay to diagnosis. We report our use of a method to repair or buttress the suture line after repair with a vascularized intercostal muscle flap, having used it successfully in two patients with intrathoracic oesophageal perforations.

Aged↗
PubMed1999

Reflex inhibition of canine inspiratory intercostals by diaphragmatic tension receptors.

1. Electrical stimulation of phrenic afferent fibres in the dog elicits a reflex inhibition of efferent activity to the inspiratory intercostal muscles. However, electrical stimulation has a poor selectivity, so the sensory receptors responsible for this inhibition were not identified. 2. In the present studies, cranial forces were applied during spontaneous inspiration to the abdominal surface of the central, tendinous portion of the canine diaphragm to activate tension mechanoreceptors in the muscle. Vagal afferent inputs were eliminated by vagotomy. 3. The application of force to the central tendon caused a graded, reflex reduction in inspiratory intercostal activity, especially in external intercostal activity. This reduction was commonly associated with a decrease in inspiratory duration and was invariably attenuated after section of the cervical dorsal roots. 4. In contrast, no change in inspiratory intercostal activity was seen when high frequency mechanical vibration was applied to the central tendon to stimulate diaphragmatic muscle spindles. 5. These observations provide strong evidence that tension receptors in the diaphragm, but not muscle spindles, induce reflex inhibition of inspiratory intercostal activity. The expression of this reflex probably involves supraspinal structures.

Animals↗
PubMed1986

Novel antigens at the neuromuscular junction.

Three novel components of neuromuscular junctions have been identified by use of monoclonal antibodies (McAb) against glycoproteins obtained from a mouse neuroblastoma X human dorsal root ganglion cell hybrid line. Antigen distribution was assessed by fluorescent immunohistochemistry on frozen sections of human intercostal muscle counterstained with labeled alpha-bungarotoxin to identify neuromuscular junctions. Antigen SOS 6 stained exclusively in the neuromuscular junction, whereas antigens SOS 5 and SOS 13 were highly enriched in the junction but also stained extrasynaptic regions. These antigens can be distinguished from previously described components of the neuromuscular junction by their molecular weights, insensitivity to collagenase treatment, and solubility in 0.1% Triton X-100. Indirect evidence suggests that these species-specific antigens are located in the postsynaptic muscle membrane, but location in the junctional basal lamina or subsarcolemmal region cannot be excluded.

Acetylcholinesterase↗
PubMed1979

Traumatic intercostal hernia due to a nonpenetrating injury in a child.

Herniation of the lung is a recognized, though rare, complication of thoracotomy and penetrating chest injury. Closed chest injury is usually associated with rib fractures, laceration of the lung, and rupture of the diaphragm, bronchus, and aorta. It is unusual for the intercostal muscles to be ruptured in a closed chest injury. In this case, herniation of the lung may result.

Child↗