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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↗

PubMed1986

Electrical and mechanical activity of respiratory muscles during hypercapnia.

In nine anesthetized supine spontaneously breathing dogs, we compared moving average electromyograms (EMGs) of the costal diaphragm and the third parasternal intercostal muscles with their respective respiratory changes in length (measured by sonomicrometry). During resting O2 breathing the pattern of diaphragm and intercostal muscle inspiratory shortening paralleled the gradually incrementing pattern of their moving average EMGs. Progressive hypercapnia caused progressive increases in the amount and velocity of respiratory muscle inspiratory shortening. For both muscles there were linear relationships during the course of CO2 rebreathing between their peak moving average EMGs and total inspiratory shortening and between tidal volume and total inspiratory shortening. During single-breath airway occlusions, the electrical activity of both the diaphragm and intercostal muscles increased, but there were decreases in their tidal shortening. The extent of muscle shortening during occluded breaths was increased by hypercapnia, so that both muscles shortened more during occluded breaths under hypercapnic conditions (PCO2 up to 90 Torr) than during unoccluded breaths under normocapnic conditions. These results suggest that for the costal diaphragm and parasternal intercostal muscles there is a close relationship between their electrical and mechanical behavior during CO2 rebreathing, this relationship is substantially altered by occluding the airway for a single breath, and thoracic respiratory muscles do not contract quasi-isometrically during occluded breaths.

Animals↗

PubMed1987

Origins and regional distribution of blood flow to the respiratory muscles in conscious sheep.

The blood flow to the portions of the diaphragm (sternal, costal, and crural) and to the external and internal intercostal muscles was measured, using radio-labelled microspheres, in 12 young sheep breathing quietly. We calculated total blood flow and oxygen uptake of the diaphragm (VO2di). We also determined the proportion of diaphragmatic and intercostal muscle blood flow that arose from the descending aorta. Diaphragmatic blood flow (Qdi) was 0.62 +/- 0.04% of cardiac output (mean +/- SEM). VO2di was 1.53 +/- 0.15 ml X min-1 X 100 g-1, and was linearly related to Qdi. When standardized for weight Qdi was 28.3 +/- 1.5 ml X min-1 X 100 g-1, significantly greater than both external intercostal muscle blood flow (18.9 +/- 2.6 ml X min-1 X 100 g-1; P less than 0.05), and internal intercostal muscle blood flow (11.4 +/- 1.4 ml X min-1 X 100 g-1; P less than 0.01). Blood flow to the costal portion of the diaphragm was significantly less than blood flow to the crural portions. There was no difference between flow to these portions and to the sternal portion of the diaphragm. The blood supplying the dorsal-most regions of the diaphragm arose predominantly from the descending aorta. The results suggest that the crural portions work at a higher rate than the costal portions under resting conditions.

Animals↗

PubMed2002

Stage migration after biopsy of internal mammary chain lymph nodes in breast cancer patients.

BACKGROUND: Involvement of the internal mammary chain lymph nodes (IMNs) is associated with worsened prognosis in breast cancer. Use of lymphoscintigraphy to visualize sentinel nodes reveals that IMNs often receive lymph from the area containing the tumor. METHODS: We biopsied IMNs in 182 patients because there was radiouptake to the IMNs or because the tumor was located in the medial portion of the breast. After tumor removal, pectoralis major fibers were divided to expose intercostal muscle. A portion of intercostal muscle adjacent to the sternum was removed. Lymph nodes and surrounding fatty tissue in the intercostal space were freed, removed, and analyzed histologically. The pleural cavity was breached in four cases (2.2%), with spontaneous resolution. RESULTS: IMNs were found in 160 (88%) of 182 patients; 146 (94.4%) were negative and 14 (8.8%) were positive. The latter received internal mammary chain radiotherapy. The axilla was negative in 4 of 14 cases and positive in 10. CONCLUSIONS: IMNs can be quickly and easily removed via the breast incision with insignificant risk and no increase in postoperative hospitalization. The patients with a positive IMN migrated from N0 (4 cases) or N1 (10 cases) to N3, prompting modification of both local (radiotherapy to internal mammary chain) and systemic treatment; without IMN sampling, they would have been understaged.

Breast Neoplasms↗

PubMed1991

Mechanical properties of respiratory muscles in primates.

We examined the in-vitro mechanical characteristics of the diaphragm and parasternal intercostal muscles in adult baboons. At optimal length (Lo) the parasternal intercostal muscles were consistently faster than the diaphragm as judged by a shorter time-to-peak tension and a reduced twitch-to-tetanus ratio. However, maximal absolute force at Lo, corrected for cross-sectional area, revealed that the inherent strengths of both inspiratory muscles were identical (31.5 +/- 3.2 N/cm2 for diaphragm vs 29.5 +/- 1.1 N/cm2 for parasternal intercostals). Moreover, at submaximal stimulation rates, the parasternal intercostals produced significantly less tension at Lo than the diaphragm. At lengths less than Lo, however, the parasternal intercostal muscles generated significantly less tetanic tension than the diaphragm. These differences are similar to previously reported values in dogs (Farkas et al. (1985) J. Appl. Physiol. 59: 528-535). Thus, based on our findings, it appears that within a given species, the parasternal intercostals are quite different in mechanical terms from the diaphragm. Since both muscles are recruited at all levels of ventilation, including quiet breathing, these differences do not appear to be related to the activation levels. Moreover, since the present results were similar to those in dogs, the differences between both muscles do not appear to be affected or altered by body habitus.

Animals↗

PubMed1970

Cholinesterase activity of motor end plate in human skeletal muscle.

The activity and properties of cholinesterase of the motor end plate in human intercostal muscle were studied in the isolated muscle membrane. This preparation was used because cholinesterase activity of the membrane preparation was localized in the motor end plate without contamination of cholinesterase of other muscle components. Under the experimental conditions, cholinesterase in a human end plate hydrolyzed 1.21 x 10(8) molecules of acetylcholine per msec, which is smaller than hydrolysis of 2.69 x 10(8) by a motor end plate of rat intercostal muscle. Studies with cholinesterase inhibitors and specific substrates indicated that about 90% of cholinesterase of human motor endplates is acetylcholinesterase, and about 10% is pseudocholinesterase. The end plate cholinesterase had an optimal pH of 7.8 and a Michaelis-Menten constant of 4.15 mmoles/liter, and was stable at 4 degrees C for at least 4 wk. Motor end plates were estimated to contain only about 2% of the total cholinesterase activity of human intercostal muscle, compared with about 20% in rat tibialis anterior muscle. The difference is due to the lower cholinesterase activity of the motor end plate and higher cholinesterase activity of non-end plate components in human muscle than in rat muscle. The isolated muscle membrane provides a useful preparation for the study of the properties of motor end plate in human skeletal muscle.

Acetylcholine↗

PubMed1999

Traumatic intercostal hernia: presentation and diagnostic workup.

Intercostal herniation of lung caused by nonpenetrating thoracic trauma is rare in the pediatric population. An 11-year-old boy presented with such a hernia 4 years after the original injury. The hernia was increasing in size and was becoming more difficult to reduce. In view of possible future strangulation, a surgical repair was undertaken with prosthetic mesh closure of the intercostal muscle defect. Intercostal hernias are rare, but familiarity with the proper investigation and treatment to be provided is important.

Child↗

PubMed1996

Impaired reflex responses to airway occlusion in the inspiratory muscles of asthmatic subjects.

BACKGROUND: Asthmatic subjects have an impaired capacity to activate the diaphragm during attempted maximal inspiratory efforts. Limb muscles require reflex facilitation to achieve maximal force. The reflex responses of inspiratory muscles to airway occlusion in asthmatic subjects were measured and compared with those in non-asthmatic control subjects. METHODS: Nine healthy asthmatic subjects breathed at a constant inspiratory flow through a low resistance valve. Random inspirations were transiently occluded for 250 ms. Surface electromyographic activity (EMG) was recorded over the scalene muscles, parasternal intercostal muscles, and the lateral chest wall overlying the diaphragm. The asthmatic subjects were studied with and without bronchoconstriction. Responses were compared with data from a matched group of 12 control subjects. RESULTS: Compared with the reflex responses to airway occlusion in control subjects, the duration of the initial short latency inhibition of inspiratory muscles was prolonged by 50% in asthmatic subjects and the size of the subsequent excitation was reduced by 30%. Bronchoconstriction reduced the time to the peak of the excitatory response in asthmatic subjects, although the values remained longer than in the control subjects. CONCLUSIONS: This study reveals impaired reflex excitation of inspiratory motoneurones in asthmatic subjects which could contribute to the reduced ability of these subjects to drive the diaphragm during maximal volitional efforts.

Adolescent↗

PubMed1993

Persistence of tissue cysts in edible tissues of cattle fed Toxoplasma gondii oocysts.

Four 1-year-old steers were each inoculated orally with 10,000 Toxoplasma gondii oocysts of the GT-1 strain and euthanatized on postinoculation days (PID) 350, 539, 1191, and 1201. Samples (500 g) of tongue, heart, semimembranosus and semitendinosus muscles (roast), intercostal muscles (ribs), longismus muscles (tenderloin), brain, kidneys, liver, and small intestine were bioassayed for T gondii by feeding to cats and examination of cat feces for shedding of oocysts. Toxoplasma gondii was recovered by bioassays in cats for the 3 steers necropsied PID 350, 539, and 1191, but not from the steer euthanatized on PID 1201. Cats shed oocysts after ingesting tongue from 2 steers, heart from 3 steers, liver from 2 steers, and roast, ribs, brain, and intestines from 1 steer each. Toxoplasma gondii was not isolated from any of the other bovine tissues. In addition to tissues bioassayed in cats, homogenates of mesenteric lymph nodes, lungs, spinal cord, spleen, and eyes were bioassayed in mice for T gondii infection. Toxoplasma gondii was not recovered from the 135 mice inoculated with tissue from each of the 4 steers. All 4 inoculated steers developed high T gondii antibody titers (> or = 1:8,000) in the agglutination test, using formalin-fixed whole tachyzoites. In the steer euthanatized on PID 1201, agglutinating T gondii antibody titers decreased from 1:4,000 to 1:320 between 2 and 5 months after inoculation and to 1:20 by 19 months after inoculation.

Agglutination Tests↗

PubMed1993

Effect of free radical scavengers on endotoxin-induced respiratory muscle dysfunction.

Recent studies have suggested that free radicals contribute to the diaphragmatic dysfunction observed in sepsis. However, previous work has not determined which species of free radicals are responsible for producing these effects or whether the intercostal muscles are affected similarly during sepsis. The purpose of this study was to examine these issues using a hamster model of endotoxin-mediated sepsis in which diaphragm and intercostal muscle function was assessed on muscle strips excised from these animals after killing. Several groups of animals were studied, including animals injected with (1) saline, (2) endotoxin, (3) endotoxin plus active PEG-SOD, a superoxide scavenger, (4) endotoxin plus active PEG-catalase, a hydrogen peroxide scavenger, (5) endotoxin plus DMSO, a hydroxyl scavenger, and (6) endotoxin plus denatured PEG-SOD. We found that endotoxin administration elicited significant reductions in diaphragm and intercostal muscle contractility. In each of the three groups of animals to which active free radical scavengers were administered, the effects of endotoxin were attenuated. Denatured PEG-SOD did not protect the respiratory muscles from endotoxin-mediated dysfunction, however. These data indicate that both the diaphragm and intercostal muscles are affected similarly by sepsis; moreover, several free radical species (superoxide ions, hydrogen peroxide, and hydroxyl ions) play a role in mediating this type of injury.

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↗

PubMed1987

Respiratory changes in thoracic muscle length during bronchoconstriction.

The purpose of the present study was to assess the effects of bronchoconstriction on respiratory changes in length of the costal diaphragm and the parasternal intercostal muscles. Ten dogs were anesthetized with pentobarbital sodium and tracheostomized. Respiratory changes in muscle length were measured using sonomicrometry, and electromyograms were recorded with bipolar fine-wire electrodes. Administration of histamine aerosols increased pulmonary resistance from 6.4 to 14.5 cmH2O X l-1 X s, caused reductions in inspiratory and expiratory times, and decreased tidal volume. The peak and rate of rise of respiratory muscle electromyogram (EMG) activity increased significantly after histamine administration. Despite these increases, bronchoconstriction reduced diaphragm inspiratory shortening in 9 of 10 dogs and reduced intercostal muscle inspiratory shortening in 7 of 10 animals. The decreases in respiratory muscle tidal shortening were less than the reductions in tidal volume. The mean velocity of diaphragm and intercostal muscle inspiratory shortening increased after histamine administration but to a smaller extent than the rate of rise of EMG activity. This resulted in significant reductions in the ratio of respiratory muscle velocity of shortening to the rate of rise of EMG activity after bronchoconstriction for both the costal diaphragm and the parasternal intercostal muscles. Bronchoconstriction changed muscle end-expiratory length in most animals, but for the group of animals this was statistically significant only for the diaphragm. These results suggest that impairments of diaphragm and parasternal intercostal inspiratory shortening occur after bronchoconstriction; the mechanisms involved include an increased load, a shortening of inspiratory time, and for the diaphragm possibly a reduction in resting length.

Animals↗

PubMed1981

Function of the respiratory muscles in acute hemiplegia.

Electromyograms of the parasternal intercostal muscles and of the diaphragm were obtained with surface electrodes in 20 patients with early flaccid hemiplegia due to cerebrovascular accident. In most patients, a striking reduction in activity was observed during voluntary inspirations in both the intercostal muscles and the diaphragm on the side of the paresis. These findings suggest that in most persons the respiratory muscles are innervated primarily by decussated fibers. Dysfunction of the respiratory muscles might be implicated in the respiratory tract infections of patients with early hemiplegia.

Acute Disease↗

PubMed2006

Derangements in mitochondrial metabolism in intercostal and leg muscle of critically ill patients with sepsis-induced multiple organ failure.

Critically ill patients treated for multiple organ failure often develop muscle dysfunction. Here we test the hypothesis that mitochondrial and energy metabolism are deranged in leg and intercostal muscle of critically ill patients with sepsis-induced multiple organ failure. Ten critically ill patients suffering from sepsis-induced multiple organ failure and requiring mechanical ventilation were included in the study. A group (n = 10) of metabolically healthy age- and sex-matched patients undergoing elective surgery were used as controls. Muscle biopsies were obtained from the vastus lateralis (leg) and intercostal muscle. The activities of citrate synthase and mitochondrial respiratory chain complexes I and IV and concentrations of ATP, creatine phosphate, and lactate were analyzed. Morphological evaluation of mitochondria was performed by electron microscopy. Activities of citrate synthase and complex I were 53 and 60% lower, respectively, in intercostal muscle of the patients but not in leg muscle compared with controls. The activity of complex IV was 30% lower in leg muscle but not in intercostal muscle. Concentrations of ATP and creatine phosphate were, respectively, 40 and 34% lower, and lactate concentrations were 43% higher in leg muscle but not in intercostal muscle. We conclude that both leg and intercostal muscle show a twofold decrease in mitochondrial content in intensive care unit patients with multiple organ failure, which is associated with lower concentrations of energy-rich phosphates and an increased anaerobic energy production in leg muscle but not in intercostal muscle.

Adenosine Triphosphate↗

PubMed1990

[Histochemical analysis of respiratory muscles of patients with esophageal cancer--with special reference to the preoperative nutritional state].

Postoperative pulmonary complication and respiratory failure, frequently seen in undernourished patients such as those with esophageal cancer, were suspected to be due to respiratory muscle wasting caused by nutritional depletion. Based on this idea, the respiratory muscles obtained by biopsies during operation from diaphragm, external intercostal muscle, and rectus abdominis muscle were assessed histochemically in 32 patients. The specimens were stained for myosin ATPase to differentiate the types of muscle fibers, and then the size and distribution of the muscle fibers of each type were measured. In diaphragm muscle, cross-sectional areas of type 1 & 2 and the ratio of the area occupied by each fiber were usually the same; in external intercostal muscle, however, type 1 fibers were dominant and in rectus abdominis muscle, type 2 fibers were dominant. The cross-sectional area of each respiratory muscle fiber well correlated with certain anthropometrical indexes, and the nutritionally depleted cases, the muscle fibers were of a smaller size suggesting less respiratory muscle strength. The ratio of the area occupied by type 1 fibers in diaphragm muscle was linearly related to serum albumin, total cholesterol, and PNI (prognostic nutritional index). Type 2 fibers were dominant in malnourished patients, suggesting greater fatigue compared to well-nourished cases. Opposite findings were obtained in external intercostal muscle and rectus abdominis muscle, and the ratio of the area occupied by type 2 fibers was smaller in the undernourished cases, suggesting reduced maximum strength of these muscles.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1993

Respiratory muscle stiffness is age- and muscle-specific.

We investigated the possible contribution of respiratory muscles to the well documented increase in chest wall stiffness with age. Diaphragm and internal intercostal muscle strips were dissected from male Fischer 344 rats of 3, 6, 12, and 24 months of age. Muscles were subjected, in vitro, to stress-strain and yield point tests. Passive tension data from these tests were normalized to a reference length (Lr), which was defined in terms of absolute stress, 700 Pascals. In general, Lr of diaphragm was found to be 90% of the length (Lo) required for maximal tetanic tension. Within a range of stretch between Lr and 130% Lr, diaphragm muscles from adult rats (6-12 month) were more compliant than those of either young (3 month) or old (24 month) animals. In contrast, intercostal muscles from old rats were stiffer than those of young or adult rats. Yield strength of both muscles was constant with age, but diaphragm muscles were found to have a higher yield strength than intercostal muscles from any age. Thus, only some passive mechanical properties of respiratory muscles vary with age, and this variation in muscle-specific. A surprising finding of this study was that diaphragm muscles of adult animals were more compliant than those of either young or old rats.

Aging↗

PubMed1985

Altered breathing pattern elicited by stimulation of abdominal visceral afferents.

The effect of stimulation of afferent mesenteric nerves on tidal volume (VT), phrenic nerve, and external intercostal muscle activities was studied in anesthetized spontaneously breathing cats. Both mechanical distension of the small intestine and electrical stimulation of the mesenteric nerves resulted in an initial inspiratory inhibition of VT followed by a gradual recovery above the prestimulus controls. Changes in VT were accompanied by a depression of phrenic nerve activity and an excitation of external intercostal muscle activity. During the recovery phase of VT, the amplitude of phrenic nerve activity returned only partially, whereas the activity of the external intercostal muscle was greater than the prestimulus controls. In a second group of experiments, brief tetanic stimulation at the beginning of inspiration led to a complete and maintained inhibition of phrenic nerve activity but with a simultaneous excitation of external intercostal muscle activity and without any change in VT; whereas expiratory stimulation caused a decrease in expiratory abdominal muscle activity, without changing the peak amplitude of phrenic nerve activity. The respiratory changes observed with distension of the small intestine were abolished after denervation of the mesenteric plexus. It is concluded that activation of the visceral afferents of the mesenteric region reflexly changes diaphragmatic breathing to intercostal breathing. It is assumed that such a type of breathing pattern may occur in pregnancy and in pathophysiological situations involving splanchnic viscera.

Animals↗

PubMedDate not supplied

2-Deoxy-2-[18F] fluoro-D-glucose uptake in intercostal respiratory muscles on positron emission tomography/computed tomography: smokers versus nonsmokers.

PURPOSE: The purpose of this study was to determine the frequency of 2-deoxy-2-[18F]fluoro-D-glucose (FDG) uptake in the intercostal respiratory muscles (ICM) of smokers versus nonsmokers using positron emission tomography (PET). PROCEDURES: Ninety-six whole-body PET/computed tomography (CT) scans were retrospectively reviewed; 61 studies were from smokers and 35 from nonsmokers. The ICM uptake from the lung apices to the level of the carina was visually scored with respect to FDG intensity as follows: 0 = uptake less than or equal to lung uptake; 1 = greater than lung, but less than mediastinal blood pool; 2 = equal to mediastinal blood pool; and 3 = greater than mediastinal blood pool. RESULTS: In smokers, 30 out of 61 (49.2%) PET/CT scans had uptake that localized to ICM, compared to 3/35 (8.6%) studies in nonsmokers. Average ICM uptake was significantly different between smokers and nonsmokers (0.787 +/- 0.933 and 0.143 +/- 0.494, respectively; P < 0.01). CONCLUSION: Increased FDG uptake in ICM is a physiologic pattern of uptake that is frequently seen and is more common in smokers.

Adult↗