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At least 19 recordsLinked to original sources
PubMed1977

Interaction of lung volume and chemical drive on respiratory muscle EMG and respiratory timing.

The effect of increased FRC on the change in respiratory muscle electrical activity (EMG) and the duration of inspiration (Ti) and expiration (Te) produced by increases in chemical drive (i.e., progressive hypercapnia and isocapnic hypoxia) was assessed in 15 anesthetized, spontaneously breathing dogs. FRC was raised by applying continuous positive pressure (4 and 8 cmH2O) to the airway. Progressive hypercapnia and hypoxia were produced by rebreathing techniques. At any PCO2 or PO2, increases in FRC decreased diaphragm EMG (D); increased abdominal muscle EMG (AB); and prolonged Te without affecting Ti. The effect of increased FRC on D, AB, and Te diminished as PCO2 increased or PO2 decreased. The effect of sustained increases in lung volume in the absence of phasic changes was assessed by performing airway occlusion for a single inspiration during rebreathing at both control and increased FRC. The effects of increases in FRC were present during airway occlusion but were eliminated by vagotomy. We conclude, therefore, that tonic vagal stimulation produced by increases in FRC modified the change in respiratory muscle electrical activity and timing produced by increasing chemical drive.

Animals↗
PubMed1978

Myelinated nerve fiber supply and muscle spindles in the respiratory muscles of cat: quantitative study.

The present study was undertaken to provide quantitative data on the myelinated fibers of the phrenic and intercostal nerves and the number of spindles in the main respiratory muscles of the cat. The myelinated component of the phrenic and intercostal nerves was studied in the cat. Histograms of sequency distributions as a function of nerve fiber diameter were established for normal nerves. Certain nerves were then examined 35 to 40 days after excision of the dorsal spinal ganglia. The muscle spindles of the corresponding muscles were counted and localized, and, on the basis of several morphological criteria, were classified with those usually described in the interosseous muscles. The study of the nerves, as that of the spindles, demonstrates clear differences of proprioceptive innervation among the respirator muscles. The lateral part of the diaphragm and the Triangularis sterni have practically no spindles. The external muscles of the first thoracic spaces are very rich in spindles. Respiratory muscles can be ranged in an almost continuous manner between these two extremes.

Animals↗
PubMed1977

Respiratory muscle fatigue: a cause of respiratory failure?

1. The question whether respiratory muscle fatigue ever causes respiratory failure is over 40 years old, but we still have no definitive answer to this question. Skeletal muscle fatigue occurs when the rate of energy consumption of the muscle is greater than the energy supplied, so that energy stores are utilized and eventually become depleted. 2. Five factors which are important in the development of muscle fatigue (a, the tension developed by the muscle; b, the maximum tension the muscle can develop; c, the energy stored within the muscle; d, the energy supplied to the muscle; e, the efficiency of the muscle). These can be affected in many diseases, so disposing to fatigue, thus respiratory muscle fatigue is likely to be a common occurrence. 3. Respiratory muscle fatigue can in principle easily be diagnosed at the bedside by application of a simple electromyographic technique used to detect fatigue in other skeletal muscles.

Electromyography↗
PubMed1977

Histochemical studies of respiratory muscles of chicken.

The histochemical profiles of myofibrillar adenosine triphosphatase (ATPase), nicotinamide adenine dinucleotide diaphorase (NADDase), and phosphorylase (Pase) activities were studied in the respiratory muscles of the chicken. Most respiratory muscles contained fibers exhibiting 18 possible combinations of staining reactions (dark or light ATPase; dark, intermediate, or light NADDase; dark, intermediate, or light Pase). Fibers that stained light for ATPase constituted as little as 10% of the total population in rectus abdominis, but as much as 32% of the total in costosternalis pars major. Those fibers did not tend to be smaller than fibers that stained dark for ATPase in the respiratory muscles as a group. Assuming these staining characteristics are correlated with functional properties of the fibers, as they are in mammals, the majority of the fibers should contract rapidly (dark ATPase) and be fatigue resistant (dark and intermediate NADDase).

Adenosine Triphosphatases↗
PubMed1977

The distribution of blood flow, oxygen consumption, and work output among the respiratory muscles during unobstructed hyperventilation.

An animal model was developed to describe respiratory muscle work output, blood flow, and oxygen consumption during mechanical ventilation, resting spontaneous ventilation, and the increased unobstructed ventilatory efforts induced by CO2 rebreathing. Almost all of the work of breathing was inspiratory work at all ventilatory levels; thus, only blood flows to the diaphragm and external intercostals increased in the transition from mechanical to spontaneous ventilation, and they further increased linearly as ventilatory work was incrementally augmented ninefold by CO2 rebreathing. No other muscles of inspiration manifest increased blood flows. A small amount of expiratory work was measured at high ventilatory volumes during which two expiratory muscles (transverse abdominal and intercostals) had moderate increases in blood flow. Blood pressure did not change, but cardiac output doubled. Arterial-venous oxygen content difference across the diaphragm increased progressively, so oxygen delivery was augmented by both increased blood flow and increased oxygen extraction at all work loads. Oxygen consumption increased linearly as work of breathing increased, so efficiency did not change significantly. The mean efficiency of the respiratory muscles was 15.5%. These results differ significantly from the patterns previously observed by us during increased work of breathing induced by inspiratory resistance, suggesting a different distribution of work load among the various muscles of respiration, a different fractionation of oxygen delivery between blood flow and oxygen extraction, and a higher efficiency when shortening, not tension development, of the muscle is increased.

Animals↗
PubMedDate not supplied

The influence of chronic cerebellar stimulation on respiratory muscle coordination in a patient with cerebral palsy.

The effect of chronic cerebellar stimulation on respiratory muscle coordination has been evaluated using a relatively simple and objective target breathing test on one patient. Seven normal subjects were used as controls. Magnetometer recordings were used to determine whether abdominal and rib cage expansion were in phase. Subjects were asked to match their breathing frequency to a metronome signal. Their ability to control respiratory timing voluntarily was assessed in terms of the coefficient of variation (CV) of inspiratory time (Ti) and of expiratory time (Te). The CV's of Ti and Te were much greater in the patient in the absence of cerebrellar stimulation than they were in normal subjects. Both at 3 weeks and 6 months after implantation of the stimulator, a significant improvement in the performance of the patient was demonstrable with the stimulator on, although normal values were never achieved. This demonstrable influence of chronic cerebellar stimulation on respiratory muscle coordination has important implications for both the avoidance of respiratory complications and the potential improvement of speech in patients with cerebral palsy.

Adolescent↗
PubMed1979

Relationship of static respiratory muscle pressure and maximum voluntary ventilation in normal subjects.

40 normal subjects performed spirometry, maximum voluntary ventilation (MVV), and tests of static inspiratory (Pi max) and expiratory (Pe max) respiratory muscle pressure. Forced expiratory volumes in 0.5 (FEV0.5), in 0.75 (FEV0.75), and 1 sec (FEV1) correlated significantly with MVV (r = 0.805, 0.804, 0.779, respectively). When Pi max was considered as a second independent variable, the probability of predicting MVV from timed forced expiratory volumes was enhanced (r = 0.914, 0.900 and 0.872 for FEV0.5, FEV0.75, and FEV1, respectively). Statistical analysis indicated that multiple regression with Pi max was superior to regression with timed forced expiratory volume alone in the prediction of MVV. For any given FEV1, however, Pi max was widely dispersed (range: -60 to -200 cm H2O). MVV values, expressed as percentage difference between largest and smallest value, varied less than did Pi max. Pe max, vital capacity, height and age did not enhance the ability of timed forced expiratory volumes to predict MVV. These data indicate that while respiratory muscle strength is important for sustaining maximal ventilation, the MVV is not a sensitive indicator of respiratory muscle strength.

Adult↗
PubMed1976

Histochemical localization of acid mucopolysaccharide in the respiratory muscles of a fresh-water air-breathing siluroid fish, Clarias batrachus (Linn.).

Respiratory muscles involved in gill ventilation (= irrigation) of an amphibious siluroid fish, Clarias batrachus (Linn.) were studied by phase contrast and light microscopy after the treatment with PAS. Alcian Blue at pH 2.5 and 1.0, dialyzed iron and Toludine Blue. The transverse muscle bands lightly stained with PAS, Alcian Blue at pH 2.5 and 1.0 and Dialyzed Iron suggesting that the mucopolysaccharide occured in relatively low concentrations. Phase contrast microscopy indicated that the transverse bands stained by the above mentioned reagents correspond to the I-bands. Methylation for 4 hours at 60 degrees C prevented I-band staining with Alcian Blue in the muscles studied. Saponification alone left I-band alcianophilia intact. These findings reveal that myofibrillar I-bands of respiratory muscles contain sulphated acid mucosubstances.

Animals↗
PubMed1978

Regulation of the activity of respiratory muscles during sleep.

This review concerns studies on the electrograms of respiratory muscles carried out in unrestrained sleeping cats. The respiratory unit discharges of the diaphragm and intercostal muscles undergo only quantitative changes from quiet wakefulness to synchronized sleep. Intercostal postural activity is also evident whereas such activity is practically absent in diaphragmatic electrograms. During desynchronized sleep the activity, both postural and respiratory, of intercostal muscles is tonically depressed and highly irregular, while diaphragmatic electrograms are scarcely affected, except for random disturbances related to the phasic events of this stage of sleep (rems, muscle twitches). The changes in the activity of intercostal muscles do not depend on modifications of the activity of respiratory centres as phrenic motor neurones are not tonically depressed. Only strong phasic influences of non-respiratory brain stem structures may affect phrenic motor neurones during desynchronized sleep. The depression of intercostal respiratory activity during this stage of sleep rather depends on the tonic inhibitory influences of brain stem structures on spinal motor neurones affecting also intercostal postural activity. The respiratory frequency during desynchronized sleep increases and decreases above eupneic and below polypneic values of synchronized sleep, respectively. Such a phenomenon cannot be related to the tonic brain stem inhibition of spinal motor neurones occurring during desynchronized sleep as it is unlikely that the same influence may elicit two opposite effects. These effects can be better explained on the basis of a release of respiratory centres from higher controls, particularly hypothalamic. In conclusion, the clear dichotomy in respiratory motor innervation between synchronized and desynchronized sleep reveals a basic change in respiratory regulation whose functional significance is still obscure.

Animals↗
PubMed1977

Respiratory muscle EMG in newborns: a non-intrusive method.

A non-intrusive method of recording the EMG of respiratory muscles with electronic suppression of the ECG artifact and averaging with a running window was employed in newborn infants at term to study respiratory patterns in different behavioural states. There are clear state-related differences in the diphragmatic and intercostal activity patterns. During most of the time in state 1 (quiet sleep) sustained tonic activity is found in the diaphragm as well as in intercostal muscles, but is virtually absent during state 2 (active sleep). During state 1 intercostal activity slightly precedes diaphragmatic activity whereas in state 2 both muscles contract about synchronously and vary widely in their amplitude. During periodic breathing the inspiratory EMG activity is absent in the pauses, but tonic activity may be present during periodic breathing in state 1. Isolated respiratory pauses with silence in the respiratory muscles occur in state 1 after sighs and starties with deep inspirations. During state 2 many respiratory pauses accompany gross movements and simultaneous laryngeal muscle activity suggests upper airway occlusion. Respiratory pauses without movements cannot be due to general alpha-motoneuron inhibition, because chin muscle activity may be seen at the same time. Gross movements often act as a reset mechanism for increase or decrease in tonic activity and phasic respiratory activity. Some speculations on the neural mechanisms of respiratory control based on the preliminary findings from the EMG recordings are mentioned.

Apnea↗
PubMed1975

Skeletal muscle respiratory capacity, endurance, and glycogen utilization.

This study was undertaken to evaluate the relationship between physical performance capacity and the mitochondrial content of skeletal muscle. Four groups of rats were trained by means of treadmill running 5 days/wk for 13 wk. One group ran 10 min/day, a second group ran 30 min/day, a third group ran 60 min/day, and a fourth group ran 120 min/day. The magnitude of the exercise-induced adaptive increase in gastrocnemius muscle respiratory capacity varied over a twofold range in the four groups. There were significant correlations between the levels of three mitochondrial markers (cytochrome c, citrate synthase, respiratory capacity) in the animals' gastrocnemius muscles and the duration of a run to exhaustion. There was also a significant correlation between the amounts of glycogen remaining in liver and skeletal muscle after a 30-min-long exercise test and the respiratory capacity of the animal's leg muscles. These findings are compatible with the interpretation that a close relationshiop exists between skeletal muscle mitochondrial content and the capacity to perform endurance exercise.

Adenosine Diphosphate↗
PubMed1977

The relationship of respiratory failure to the oxygen consumption of, lactate production by, and distribution of blood flow among respiratory muscles during increasing inspiratory resistance.

An animal model was developed to determine if blood flow to the respiratory muscles limits oxygen delivery and thus work output during inspiratory resistance. With incremental increases in the rate of work of breathing to 15 times the resting level, blood flow to the diaphragm rose exponentially 26-fold. Blood flow to other inspiratory and a few expiratory muscles increased to a much smaller extent, often only at the greater work loads. Cardiac output and blood pressure did not change. Arterial-venous oxygen content difference across the diaphragm became maximal at low work rates and thereafter all increases in oxygen delivery during higher work rates were accomplished by increments in blood flow. Oxygen consumption of the respiratory musculature calculated by blood flow times oxygen extraction increased exponentially with increasing work of breathing and was less than the increase in total body oxygen consumption at each work load. Hypoxemia and respiratory acidosis occurred when the animals inspired through the highest resistance; blood flow and oxygen consumption were even higher than that observed during previous resistances and there was no evidence of a shift to anaerobic metabolsim in blood lactate and pyruvate levels. Respiratory failure did not appear to be a consequence of insufficient blood flow in this model.

Airway Resistance↗
PubMed1977

Cervical accessory respiratory muscle function in a patient with a high cervical cord lesion.

The function of the accessory respiratory muscles (ARM) of the neck were studied in a quadriplegic patient suffering from a C2-3 lesion of the cervical spinal cord. Subtotal expiratory paralysis resulted in an essentially complete loss of expiratory reserve volume such that residual volume and functiona residual capacity were equal (RV=FRC). Tidal volume and vital capacity were severely reduced. Being extrinsic to the chest, the ARM of the neck functioned independently of changes in thoracic gas volume; however, their performance appeared posture-dependent, and was less efficient in the sitting position. Despite the fact that the ARM preferentially expanded the upper part of the ribcage, significant V/Q mismatch did not seem to occur. Voluntary use of glossopharynegeal breathing (GPB) greatly enhanced the patient's ventilatory capability. Flow volume data during GPB documented the efficiency of the glossopharyngeal muscles, which function as a positive pressure pump to force air into the lungs.

Adult↗
PubMed1976

Electromyographic response of respiratory muscles during elastic loading.

The response of respiratory motor neurons to graded elastic loading was assessed in anesthetized dogs by recording the electromyogram (EMG) from the diaphragm (ED) and the intercostal muscle (EIC). Elastic loads were applied for 1-20 breaths. The effects of changes in PCO2 on respiratory motor neuron output was assessed by applying loads during the course of CO2 rebreathing. On the first loaded breath, ED and EIC increased reflexly due chiefly to prolongation of inspiration. Vagotomy or vagal cooling to block the Hering-Breuer reflex eliminated the increase in ED and diminished the increase in EIC. During the second to fifth breath, the level of EMG activity was disproportionately high for the level of PCO2, suggesting an additional reflex component over and above the reflex activity present on the first loaded breath.

Animals↗
PubMedDate not supplied

[Respiratory muscle activity in newborn children during sleep and wakefulness].

Two types of electrical activity - inspiratory and tonic (postural) ones - have been registered in the external intercostal muscles and diaphragm. Both types of the activity decrease during orthodoxical sleep as compared with the period of quiet awakefulness. During the transition of orthodoxical sleep into paradoxical one, tonic activity is completely inhibited, while inspiratory activity in the intercostal muscles remains unchanged, being increased in the diaphragm. In the period of rapid eye movements inspiratory activity of the intercostal muscles is reduced. The decreased tone of the intercostal muscles accounts for changes in respiratory movements and for the onset of asynchoronous thoracic and abdominal respiratory movements during paradoxical sleep.

Diaphragm↗