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Introduction: Forward head posture (FHP) is a very common problem among the working population. Being one of the most subconscious function in humans, respiratory function utilizes both the diaphragmand external intercostal muscles for quiet breathing. However during labored breathing, many other muscles will be recruited, and mostly these muscles have attachments in the cervical, thoracic ribcage,and even lumbar vertebrae. By the nature of attachments of these muscles on the cervical vertebra and thoracic cage, it is then plausible that FHP would affect the respiratory function. Methods: Thorough searches were done through international journals for the last ten years regarding the topic of FHP and its impacts to the respiratory biomechanics. Discussion: Previous studies have reported how prolonged FHP will result in kyphotic posture, reducing the mobility of ribcage, and modifies all respiratory muscular attachments such as sternocleidomastoids, intercostals, and to a certain extent, the diaphragm. All these result in a restrictive lung disorder, signified by reducing spirometry values, such as Forced Vital Capacity, Sniff Nasal Inspiratory Pressure, and Peak Flow Rate. Conclusion: Forward head posture disturb the respiratory biomechanics.

Background: Pectoral nerve (Pecs) block is one of the most promising regional analgesic techniques for breast surgery. However, Pecs II block may not provide analgesia of the medial aspect of the breast or the entire nipple-areolar complex. Objectives: The aim of the present study was to investigate the efficacy of combining the pectointercostal fascial block (PIFB) and Pecs II block for perioperative analgesia following modified radical mastectomy (MRM). Study Design: A prospective randomized study. Setting: An academic medical center. Methods: Sixty women undergoing unilateral MRM were randomly divided into 2 groups. The Pecs II group received Pecs II block using 20 mL bupivacaine 0.25% between the serratus anterior and the external intercostal muscles, and 10 mL bupivacaine 0.25% between the pectoralis major and minor muscles, together with sham PIFB using 15 mL normal saline solution in the interfascial plane between the pectoralis major muscle and the external intercostal muscle. PIFB-Pecs II group received the same Pecs II block combined with PIFB using 15 mL bupivacaine 0.25%. Results: The median (interquartile range [IQR]) time to the first morphine dose was significantly longer in the PIFB-Pecs II group (327.5 [266.3–360.0] minutes) than the Pecs II group (196 [163.8– 248.8] minutes) (P < 0.001, 95% confidence interval [CI] 79.98, 150.00).The median (IQR) cumulative morphine consumption was higher in the Pecs II group (14.0 [11.0–18.0] mg) than the PIFB-Pecs II group (8.0 [7.0–9.0] mg) (P < 0.001; CI, 4.0–8.0). Intraoperative consumption of fentanyl was significantly lower in PIFB-Pecs II group with a median (IQR) of 0 (0–15 μg) than the Pecs II group median 57.5 (0–75 μg) (P = 0.022, CI; 0–60). The Visual Analog Scale scores for the first 12 postoperative hours were lower in the PIFB-Pecs II group than the Pecs II group at rest and on moving the ipsilateral arm (P < 0.001). The dermatomal block on the lateral chest wall was comparable between the 2 studied groups. PIFB-Pecs II provided extensive sensory block on the anterior chest wall, whereas Pecs II block failed to achieve any sensory block. Limitations: This study was limited by its small sample size. Conclusions: The combination of Pecs II and PIFB provide better perioperative analgesia for MRM than Pecs II alone. Key Words: Pectoral nerves, postoperative pain, modified radical mastectomy

Aim . To identify features of changes in electrical activity of inspiratory muscles and their relationship with anthropometric indicators in different age groups. Materials and methods . There were examined 57 men with the same strength of respiratory muscles, aged 20 to 65 years old, who were divided into 3 groups. The 1st group included 26 young people, the 2nd group consisted of 20 middle-aged people, the 3rd group had 11 elderly patients. The examination included determination of anthropometric indicators, assessment of motor activity, inspiratory muscle strength, analysis of the electrical activity of inspiratory muscles when performing functional tests. Results. In young people compared with patients of groups 2 and 3, a significant difference in anthropometric indicators was revealed. In patients of group 1, the dynamics of electromyography (EMG) indices of inspiratory muscles was the greatest when performing functional tests. There was revealed correlation between age and dynamics of the EMG amplitude indicators of external intercostal muscles (r=0.48, p

The levator scapulae, rhomboideus, and serratus anterior muscles (as a group referred to the dorsal shoulder girdle muscles) and the scalenus muscles in mammals are usually innervated by cervical nerves. However, in koalas, the serratus anterior is additionally innervated by the lateral cutaneous branch of the first intercostal nerve. In cats, as in some other mammalian species, a part of the scalenus muscle (scalenus longus muscle) is innervated by the lateral cutaneous branches of the intercostal nerves. A precise comparison of the innervating nerves at the same segment in these two cases could clarify the homological relationship between the cervical and thoracic trunk muscles. In this context, the aim of this study was to follow the nerve fibers included in the nerves supplying the dorsal shoulder girdle and scalenus muscles up to the level of the spinal nerve roots in two koalas and two cats. The resultant observations revealed that both of the nerves to the serratus anterior in koalas and to the scalenus muscles in cats from the lateral cutaneous branch of the intercostal nerve occupy the same position in the spinal roots as the cervical nerve branches to the dorsal shoulder girdle muscles and the thoracic nerve branches to the external intercostal muscle. Based on these results, the axial trunk muscles in the cervico-thoracic region could be classified as follows: the scalenus and dorsal shoulder girdle muscles belong to the same lateral axial trunk muscle group as the external intercostal muscle, and are clearly distinguished from the medial group, such as the internal and innermost intercostal muscle.

Highlights • Rare case of bilateral scapulothoracic bursitis. • Collections verified by magnetic resonance. • Open surgical resection with good result., Introduction Scapulothoracic articulation has several bursae which allow a sliding movement of the scapulothoracic joint. The two major anatomical bursae are the supraserratus bursa and infraserratus bursa. Presentation of Case It was a case of a 59 year-old female patient with a professional load and a clinical finding of bilateral subscapular resistances of the thorax. The finding of bilateral collections in the intermuscular spaces between external intercostal muscles and heads of serratus anterior muscle was verified by magnetic resonance. Conclusion Due to progressively increasing bilateral findings an open surgical resection was implemented, with good result.

Introduction. Respiratory muscle stretching is useful in reducing chest wall rigidity, consequently increasing chest wall expansion and improving ventilatory patterns. There are few reports that have examined the effects of these techniques in relation to both minute ventilation and inspiratory muscle activities. The purpose of this study was to evaluate the acute effects of respiratory muscle stretching on ventilatory patterns and respiratory muscle activities in healthy persons. Methods. Ten healthy young men participated in the experiment. Subjects were placed in the Fowler’s position. The stretching of both bilateral neck and pectoralis major muscles by a physical therapist was performed throughout the expiratory phase, allowing inspiratory muscles to reach their maximum length during the relaxation time. Two sets of 10 consecutive stretches were performed for each muscle, with a 30 s interval between the series. The ventilatory pattern and inspiratory muscle activities (both sternocleidomastoid and external intercostal muscles) were evaluated through spirometry and electromyography before and immediately after each intervention. Both measurements were taken while the subject breathed at a rate of 30 times per minute. Muscle discharges were quantified using the root mean square to analyze the changes in the contraction levels. The study was performed according to the guidelines set by the Ethics Committee of Aomori University of Health and Welfare. All participants signed an informed consent form. Results. Respiratory muscle stretching promoted a significant acute increase in maximum voluntary ventilation, mean inspiratory flow, and inspiratory muscle activities during tachypnea compared with the control group. Conclusion. Acute effects of respiratory muscle stretching suggested increased respiratory muscle activities and/or improved expansion of ventilatory functions.

Background and aims The SPB/BRILMA block was described in 2013 as a good method for multimodal analgesia in non-reconstructive breast surgery. Methods A 94-year-old woman, ASA III, was listed for a left radical mastectomy because of an ulcerated breast cancer. It was a painful, infected and malodorous ulcer. She presented severe medical comorbidities and was under many medications. 2 mgr of midazolam were administrated before performing the BRILMA block under ultrasound vision, using a 50-mm ultra-plex needle (20 mL of bupivacaine 0.125% were introduced into the fascial plane between the serratus anterior muscle and the external intercostal muscle at the level of the 3rd, 4th and 5th ribs). After that, an intravenous induction with 70 mgr of propofol and 100 µgr of fentanyl was performed and an I-gel® LMA was placed. She received sevoflurane® (CAM 0.5) for the maintenance of anesthesia. Results The patient was successfully treated under BRILMA block. She maintained a good hemodynamic stability during the procedure and was extubated without any complications. She did not need any other analgesics during the surgery. During the first 24 hours the patient did not request opiates, and she just received alternately 1 gr of acetaminophen and 2 gr of metamizol as a part of our multimodal analgesic guideline. Conclusions The SPI/BRILMA block by ultrasound can be used for intra and post-operative analgesia for non-reconstructive surgery providing good postoperative pain control which allows a reduction of the use of opiates. It could be also used as an alternative to general anesthesia and loco-regional conventional techniques in high risk patients.

Background and aims A case report of the use bilateral subpectoral nerve catheters in a 57-year-old patient with severe acute pain secondary to a traumatic sternal fracture. the pain was opioid-resistant and unchanged by systemic analgesia. It was preventing the patient from mobilizing, deep breathing and coughing. Methods Consent was obtained. He was positioned supine. Aseptic technique was adhered to. a SonoSite® ultrasound high frequency linear probe was placed 2cm lateral to the sternum in the parasagittal plane and a Pajunk E-Cath nerve catheter needle was inserted in plane from caudal to cephalad in the fascial plane between pectoralis major and external intercostal muscle. 10 ml of 0.25% levobupivacaine was injected bilaterally, and the catheters were subsequently topped up every 12 hours. Results Within 5 minutes of a single dose of local anaesthetic the patient was pain free, able to deep breath, cough and mobilise. He was discharged home after 3 days of treatment. Conclusions In patients with isolated sternal fractures, severe pain is the most frequently reported complaint and this can lead to further complications, such as hospital-acquired pneumonia. Furthermore, high dose opioid therapy can lead to multiple adverse events and is often ineffective in chest wall fractures. This case highlights that subpectoral nerve catheters used in the management of sternal fractures can reduce pain. Further research if required to determine its role in reducing opioid-associated complications, incidence of pneumonia and inpatient length of stay.

AIMS Radical prostatectomy may cause stress urinary incontinence (SUI). We compared continent and incontinent men after radical prostatectomy, in regard to the change of the temporal pattern of pelvic floor activation during cough. METHODS Twenty-two patients were included in this prospective, multicentric study. All patients gave their informed consent. Simultaneous recordings of electromyographic activity of external anal sphincter (EAS EMG) and external intercostal muscle (EIC EMG) during cough were performed with a pair of pregelled surface electrodes. Cough effort caused an involuntary pelvic contraction. Intercostal muscles recording was chosen because they are one of the muscular components of cough initiation with diaphragm muscle. Twenty-four-hour pad-weighing test was used to quantify urinary incontinence. The primary endpoint was the latency between the onset of EIC EMG and EAS EMG (RT3), during a cough effort. We also measured the contraction time, the maximum EAS EMG activity, and the area under the curve. RESULTS All the patients were analyzed: 12 continent and 10 with SUI. The median age was 66 years old. Both groups were similar except in term of follow-up. Median latency was increased by -1.7 ms (-47.9; +34.2) to 55.8 ms (+47.5; +80) in patients with SUI (P = 0.0033; Table 2). The duration of the contraction, the maximum EAS EMG activity and the area under the curve were not different. CONCLUSIONS The latency between the onset of EIC EMG and EAS EMG is increased in patients with SUI after radical prostatectomy. It may be one of the reasons for SUI in these patients.

Unilateral bronchial occlusion, a complication of many lung diseases, causes dyspnea but the mechanism of this symptom is uncertain. In this study, electromyographic (EMG) activity in the parasternal and external intercostal muscles in the third intercostal space and inspiratory motion of the third rib on both sides of the thorax were assessed during occlusion of a main bronchus for a single breath in anesthetized dogs. Occlusion produced a 65% increase in external intercostal EMG activity in both hemithoraces without altering parasternal EMG activity. Concomitantly, the inspiratory cranial rib motion showed a 50% decrease on both sides of the thorax. These changes were unaffected by bilateral vagotomy. However, when an external, caudally oriented force was applied to the third rib on the right or left side so that its inspiratory cranial displacement was abolished, activity in the adjacent external intercostals showed a twofold increase, but rib motion and external activity in the contralateral hemithorax remained unchanged. It is concluded that during occlusion of a main bronchus, the increase in external intercostal activity is induced by the decrease in inspiratory cranial rib displacement in both hemithoraces, and that this decrease is determined by the increase in pleural pressure swings on both sides of the mediastinum. This mechanism, combined with the decrease in PaO2, induces similar alterations when unilateral bronchial occlusion is maintained for a series of consecutive breaths., SCOPUS: ar.j, info:eu-repo/semantics/published

Acute experiments on urethane-anesthetized rats were performed to study the respiratory effects of administration of 10–5, 10–8, and 10–10 M gastrin-releasing peptide into the solitary tract nucleus. Microinjections of this neuropeptide were found to lead to increases in respiratory volume and the amplitudes of volley activity in the diaphragm and external intercostal muscles, along with an increase in the duration of expiration. The most marked reactions were seen with 10–8 M gastrin-releasing peptide, while a concentration of 10–10 M was subthreshold and did not elicit changes in the pattern of respiration or the bioelectrical activity of the inspiratory muscles. Experiments in which the respiratory pattern was measured simultaneously with arterial blood pressure and heart rate showed that these parameters showed no reaction to microinjections of gastrin-releasing peptide into the study zone. These data, along with results on the distribution of specific gastrin-releasing peptide receptors in the brainstem, suggest that this peptide is involved in relating respiration at the level of the solitary tract nucleus.

The design of the respiratory pump is different from the design of the heart. The ribs carry compressive stresses that balance the pressure difference across the chest wall, and the rib cage provides a mechanism for transforming muscle shortening into chest wall expansion. The external intercostal muscles in the cranial-dorsal quadrant and the parasternal muscles have inspiratory actions and the internal intercostals in the caudal-dorsal quadrant and the triangularis sterni have expiratory actions. The diaphragm separates the pleural cavity and the abdomen, and the combined effect of diaphragm muscle tension and curvature balances the difference between abdominal pressure and pleural pressure. The inspiratory action of the diaphragm is the result of the descent of the diaphragm that accompanies muscle shortening and of the inspiratory forces that the diaphragm exerts on the lower ribs. Compartmental models provide simplified descriptions of the mechanics of the chest wall. The work of breathing is small compared to the work of the heart.

External intercostal muscle is considered as an inspiratory muscle. Its electromyographic (EMG) activity is exquisitely sensitive to proprioceptive afferents and is predominant in zones with the greatest respiratory effect. In the current series of studies, we assessed the contribution of segmental reflexes to this particular distribution of activity in anesthetized rabbits. We first established a parallel between gradients of activity and mechanical advantage. The sensitivity of external intercostal EMG activity to rib displacement was then assessed in the 3rd and 5th interspaces and in the dorsal, middle and ventral muscle bundles of the 3rd interspace. Finally, persistence of the dorso-ventral gradient was tested after a dorsal rhizotomy (interspaces 3-5). There were no differences in the sensitivity to rib motion in the studied positions. After rhizotomy, the dorso-ventral gradient of activity persisted at rest and with inspiratory resistive loading. We, therefore, conclude that the neuromechanical matching of respiratory drive in the external intercostal muscles is not the result of segmental reflexes.

The respiratory central pattern generator distributes rhythmic excitatory input to phrenic, intercostal, and hypoglossal premotor neurons. The degree to which this input shapes motor neuron activity can vary across respiratory muscles and motor neuron pools. We evaluated the extent to which respiratory drive synchronizes the activation of motor unit pairs in tongue (genioglossus, hyoglossus) and chest-wall (diaphragm, external intercostals) muscles using coherence analysis. This is a frequency domain technique, which characterizes the frequency and relative strength of neural inputs that are common to each of the recorded motor units. We also examined coherence across the two tongue muscles, as our previous work shows that, despite being antagonists, they are strongly coactivated during the inspiratory phase, suggesting that excitatory input from the premotor neurons is distributed broadly throughout the hypoglossal motoneuron pool. All motor unit pairs showed highly correlated activity in the low-frequency range (1–8 Hz), reflecting the fundamental respiratory frequency and its harmonics. Coherence of motor unit pairs recorded either within or across the tongue muscles was similar, consistent with broadly distributed premotor input to the hypoglossal motoneuron pool. Interestingly, motor units from diaphragm and external intercostal muscles showed significantly higher coherence across the 10–20-Hz bandwidth than tongue-muscle units. We propose that the lower coherence in tongue-muscle motor units over this range reflects a larger constellation of presynaptic inputs, which collectively lead to a reduction in the coherence between hypoglossal motoneurons in this frequency band. This, in turn, may reflect the relative simplicity of the respiratory drive to the diaphragm and intercostal muscles, compared with the greater diversity of functions fulfilled by muscles of the tongue.

Non-technical summary Normal breathing is controlled by specialized neurons in the central nervous system including the brainstem and spinal cord. Signals generated in the brainstem and transmitted to the major inspiratory muscles, including the diaphragm and intercostal muscles, are necessary to sustain life. However, we show that the specific pattern of intercostal muscle activation during breathing does not require input from the brainstem. In other words, the neural circuitry controlling this pattern of activation exists within the spinal cord. This knowledge furthers our understanding of the mechanisms that control breathing and has implications for patients with certain disease states such as cervical spinal cord injury.

We read with interest “Breast Augmentation and Augmentation-Mastopexy With Local Anesthesia and Intravenous Sedation,” by Colque and Eisemann.1 The article prompted us to share with your readers the novel ultrasound-guided anesthetic techniques we use in breast surgery. The intercostal nerve block (ICNB) is traditionally performed using surface anatomical landmarks. Although it is a “blind” technique, ICNB is technically simple to perform, has a high success rate, and has a relatively low overall complication rate. The use of ultrasonography in regional anesthesia allows for visualization of soft tissues and vessels, which in turn improves the accuracy of needle placement.2 We have been performing a relatively new regional anesthetic ultrasound-guided technique in patients who undergo major or minor breast surgery, which has led to decreased systemic perioperative pain, lower analgesic requirements, and improved patient satisfaction.3 In this letter, we introduce 2 new ultrasound-guided techniques. The first is the pecto-intercostal fascial block (PIFB), which consists of injecting a local anesthetic (LA) between the pectoralis major muscle (PMM) and the external intercostal muscle (EIM), in the interfascial plane where the anterior cutaneous branch emerges from the lateral side of the sternal bone. The second technique, known as the serratus intercostal …

The ultrasound-guided intercostal nerves (cutaneous branches) block in the mid-axillary line at the level of the 8th rib (modified BRILMA) is an analgesic technique described back in 2015. Four patients undergoing open gastrectomy (who are not candidates for epidural analgesia) are discussed. The patients underwent the above-mentioned bilateral block, with the administration of 15 mL of levobupivacaine 0.5% into the fascial plane, between the serratus anterior muscle and the external intercostal muscle, with the aim of blocking the intercostal nerves T6 to 11. Postoperative pain control was adequate, with low levels of opioids used. There were no complications associated with the technique.

Survival requires adequate pulmonary ventilation which, in turn, depends on adequate contraction of muscles acting on the chest wall in the presence of a patent upper airway. Bulbospinal outputs projecting directly and indirectly to 'obligatory' respiratory motoneurone pools generate the required muscle contractions. Recent studies of the phasic inspiratory output of populations of single motor units to five muscles acting on the chest wall (including the diaphragm) reveal that the time of onset, the progressive recruitment, and the amount of motoneuronal drive (expressed as firing frequency) differ among the muscles. Tonic firing with an inspiratory modulation of firing rate is common in low intercostal spaces of the parasternal and external intercostal muscles but rare in the diaphragm. A new time and frequency plot has been developed to depict the behaviour of the motoneurone populations. The magnitude of inspiratory firing of motor unit populations is linearly correlated to the mechanical advantage of the intercostal muscle region at which the motor unit activity is recorded. This represents a 'neuromechanical' principle by which the CNS controls motoneuronal output according to mechanical advantage, presumably in addition to the Henneman's size principle of motoneurone recruitment. Studies of the genioglossus, an obligatory upper airway muscle that helps maintain airway patency, reveal that it receives simultaneous inspiratory, expiratory and tonic drives even during quiet breathing. There is much to be learned about the neural drive to pools of human inspiratory and expiratory muscles, not only during respiratory tasks but also in automatic and volitional tasks, and in diseases that alter the required drive.

The respiratory muscles of patients with chronic obstructive pulmonary disease (COPD) display evidence of structural damage in parallel with signs of adaptation. We hypothesized that this can only be explained by the simultaneous activation of satellite cells. The aim of this study was to analyze the number and activation of those cells along with the expression of markers of microstructural damage that are frequently associated with regeneration.The study included 8 patients with severe COPD (mean [SD] forced expiratory volume in 1 second, 33% [9%] of predicted) and 7 control subjects in whom biopsies were performed of the external intercostal muscle. The samples were analyzed by light microscopy to assess muscle fiber phenotype, electron microscopy to identify satellite cells, and real-time polymerase chain reaction to analyze the expression of the following markers: insulin-like growth factor 1, mechano growth factor, and embryonic and perinatal myosin heavy chains (MHC) as markers of microstructural damage; Pax-7 and m-cadherin as markers of the presence and activation of satellite cells, respectively; and MHC-I, IIa, and IIx as determinants of muscle fiber phenotype.The patients had larger fibers than healthy subjects (54 [6] vs 42 [4] microm(2); P.01) with a similar or slightly increased proportion of satellite cells, as measured by ultrastructural analysis (4.3% [1%] vs 3.7% [3.5%]; P.05) or expression of Pax-7 (5.5 [4.1] vs 1.6 [0.8] arbitrary units [AU]; P.05). In addition, there was greater activation of satellite cells in the patients, as indicated by increased expression of m-cadherin (3.8 [2.1] vs 1.0 [1.2] AU; P=.05). This was associated with increased expression of markers of microstructural damage: insulin-like growth factor 1, 0.35 (0.34) vs 0.09 (0.08) AU (P.05); mechano growth factor, 0.45 (0.55) vs 0.13 (0.17) AU (P=.05).The intercostal muscles of patients with severe COPD show indirect signs of microstructural damage accompanied by satellite cell activation. This suggests the presence of ongoing cycles of lesion and repair that could partially explain the maintenance of the structural properties of the muscle.

Background: The external intercostal muscles are chronically exposed to increased inspiratory loading and to continuous hypoxia-reoxygenation cycles in patients with obstructive sleep apnoea syndrome (OSAS). It was therefore hypothesised that oxidative stress levels would be increased in these muscles, and that treatment with continuous positive airway pressure (CPAP) would modify the oxidative stress levels and improve muscle dysfunction. Methods: A case-control study and a case-case study were conducted on the external intercostal muscles of 12 patients with severe OSAS (before and after 6 months of treatment with CPAP) and 6 control subjects. Reactive carbonyl groups, malondialdehyde (MDA)-protein and hydroxynonenal (HNE)-protein adducts, antioxidant enzyme levels, 3-nitrotyrosine and fibre type proportions were measured using immunoblotting and immunohistochemistry. Results: Compared with controls, the intercostal muscles of patients with OSAS had higher levels of protein carbonylation (median values 3.06 and 2.45, respectively, p = 0.042), nitration (median values 1.64 and 1.05, respectively, p = 0.019) and proportions of type I fibres (median values 57% and 48%, respectively, p = 0.035) and reduced respiratory muscle endurance (median values 3.2 and 9.5 min, respectively, p = 0.001). Positive correlations were found between MDA-protein and HNE-protein adducts ( r = 0.641, p = 0.02 and r = 0.594, p = 0.05, respectively) and 3-nitrotyrosine ( r = 0.625, p = 0.03) and the apnoea-hypopnoea index (AHI) in all the patients with OSAS. Although treatment with CPAP significantly improved the AHI and oxygen desaturation, muscle oxidative stress levels and respiratory muscle endurance were not affected. Conclusions: This study suggests that inspiratory muscle performance is not completely restored after long-term treatment with CPAP.

Few studies focused on concomitant electromyographic recordings of pelvic floor muscles and muscles involved in cough initiation. The objective of this study was to investigate the temporal course of external anal sphincter activation during coughing. Informed consent was obtained from ten healthy volunteers and ten women presenting with stress urinary incontinence (SUI). Simultaneously, recordings of electromyographic activity of external intercostal muscles (EIC EMGi) and external anal sphincter (EAS EMGi) during coughing have been performed. It was chosen to study intercostals muscles because they are synchronous to diaphragmatic muscle during cough initiation. Median (interquartile range) latency between the onset of the EAS EMGi and the onset of the EIC EMGi was -210 ms (-398; -135) and 0 ms (-30; +111.7) in volunteers' group and in SUI group, respectively (p = 0.0009). Abnormal temporal course of external anal sphincter activation is observed during coughing in women presenting with SUI compared to healthy volunteers.

Background: Muscles of the human paraspinal region have been the focus of attention in patients with Adolescent Idiopathic Scoliosis (AIS). Despite the description of differences in muscle histology on the two sides of the scoliotic curve, there is no consensus on the significance of such findings. The purpose of this study was to assess changes in the thoracic wall muscles, including the paraspinal and the intercostal muscles (not previously described in the literature) in patients with AIS, and examine their relationship to the curvature. Methods: The paraspinal and external intercostal muscles on both sides of the scoliotic curve were biopsied in 29 patients with AIS. Tissues were studied under light microscopy and submitted to morphometric examination. Results: Both muscles on the concave side of the curve were characterized by a greater percentage of type 2 (fast twitch) fibers and a smaller mean fiber diameter than the contralateral muscles. Fiber diameter in the concavity, for both muscles, showed an inverse relationship to the Cobb angle. Conclusion: Patients with AIS present variations in the microstructure of both paraspinal and intercostals muscles, with similar changes. This suggests that the process of AIS is broadly based; it affects more than one muscle group in the thoracic wall, and is not confined to the paraspinal region. The new findings on the intercostal muscles may be related to the rotation component of the scoliotic curve. Results suggest the possibility that an imbalance between muscle and vertebral growth may lead to the deformity through a bowstring phenomenon.

A realistic two-dimensional (2D) model of the human trunk was developed for quantitative analysis of the relative contribution to breathing mechanics of seven groups of respiratory muscles. Along with noninvasive measurements of electromyography (EMG) signals from respiratory muscles near the skin surface, it provides predictions for the forces generated by inner respiratory muscles as well as the instantaneous work of each muscle. The results revealed that inspiratory muscles reach their maximal force towards the end of inspiration, while expiratory muscles reach their maximal force at mid-expiration. Inspiratory muscles contributed to the work of breathing even at low efforts, while that of the expiratory muscles was observed only at relatively high efforts. The study clearly showed that the diaphragm muscle generates forces, which are of the same order as those generated by other inspiratory muscles, but performed 60-80% of the inspiratory work. The contribution of the external intercostal muscle to inspiration was not negligible, especially at high breathing efforts.

The coupling between the ribs and the lung in dogs increases with increasing rib number in the cranial part of the rib cage and then decreases markedly in the caudal part. The hypothesis was raised that this non-uniformity is primarily related to differences between the areas of the lung subtended by the different ribs, and in the current study we tested this idea by assessing the effects of passive lung inflation. Thus, by causing a descent of the diaphragm, inflation would expand the area of the lung subtended by the caudal ribs and improve the coupling between these ribs and the lung. The axial displacements of the ribs and the changes in airway opening pressure (DeltaP(ao)) were measured in anaesthetized, pancuronium-treated, supine dogs while loads were applied in the cranial direction to individual rib pairs at functional residual capacity (FRC) and after passive inflation to 10 and 20 cm H(2)O transrespiratory pressure. In agreement with the hypothesis, inflation caused an increase in DeltaP(ao) for ribs 9 and 10. The most prominent alteration, however, was a marked decrease in DeltaP(ao) for ribs 2-8; at 20 cm H(2)O, DeltaP(ao) for these ribs was only 30% of the value at FRC. Additional measurements indicated that this decrease in DeltaP(ao) results partly from the increase in diaphragmatic compliance but mostly from the reduction in outward rib displacement. This alteration in the pattern of rib motion should add to the decrease in muscle length to reduce the lung expanding action of the external intercostal muscles at high lung volumes.

The muscular-hydrostat model of tongue function proposes a constant interaction of extrinsic (external bony attachment, insertion into base of tongue) and intrinsic (origin and insertion within the tongue) tongue muscles in all tongue movements (Kier WM and Smith KK. Zool J Linn Soc 83: 207-324, 1985). Yet, research that examines the respiratory-related effects of tongue function in mammals continues to focus almost exclusively on the respiratory control and function of the extrinsic tongue protrusor muscle, the genioglossus muscle. The respiratory control and function of the intrinsic tongue muscles are unknown. Our purpose was to determine whether intrinsic tongue muscles have a respiration-related activity pattern and whether intrinsic tongue muscles are coactivated with extrinsic tongue muscles in response to respiratory-related sensory stimuli. Esophageal pressure and electromyographic (EMG) activity of an extrinsic tongue muscle (hyoglossus), an intrinsic tongue muscle (superior longitudinal), and an external intercostal muscle were studied in anesthetized, tracheotomized, spontaneously breathing rats. Mean inspiratory EMG activity was compared at five levels of inspired CO2. Intrinsic tongue muscles were often quiescent during eupnea but active during hypercapnia, whereas extrinsic tongue muscles were active in both eupnea and hypercapnia. During hypercapnia, the activities of the airway muscles were largely coincident, although the onset of extrinsic muscle activity generally preceded the onset of intrinsic muscle activation. Our findings provide evidence, in an in vivo rodent preparation, of respiratory modulation of motoneurons supplying intrinsic tongue muscles. Distinctions noted between intrinsic and extrinsic activities could be due to differences in motoneuron properties or the central, respiration-related control of each motoneuron population.

Previous studies have shown that in normal humans the change in airway opening pressure (ΔPao) produced by all the parasternal and external intercostal muscles during a maximal contraction is approximately −18 cmH2O. This value is substantially less negative than ΔPao values recorded during maximal static inspiratory efforts in subjects with complete diaphragmatic paralysis. In the present study, therefore, the respiratory effects of the two prominent inspiratory muscles of the neck, the sternomastoids and the scalenes, were evaluated by application of the Maxwell reciprocity theorem. Seven healthy subjects were placed in a computed tomographic scanner to determine the fractional changes in muscle length during inflation from functional residual capacity to total lung capacity and the masses of the muscles. Inflation induced greater shortening of the scalenes than the sternomastoids in every subject. The inspiratory mechanical advantage of the scalenes thus averaged (mean ± SE) 3.4 ± 0.4%/l, whereas that of the sternomastoids was 2.0 ± 0.3%/l ( P < 0.001). However, sternomastoid muscle mass was much larger than scalene muscle mass. As a result, ΔPao generated by a maximal contraction of either muscle would be 3–4 cmH2O, which is about the same as ΔPao generated by the parasternal intercostals in all interspaces.

The external intercostal muscles in humans show marked regional differences in respiratory effect, and this implies that their action on the lung during breathing is primarily determined by the spatial distribution of neural drive among them. To assess this distribution, monopolar electrodes were implanted under ultrasound guidance in different muscle areas in six healthy individuals and electromyographic recordings were made during resting breathing. The muscles in the dorsal portion of the third and fifth interspace showed phasic inspiratory activity with each breath in every subject. However, the muscle in the ventral portion of the third interspace showed inspiratory activity in only three subjects, and the muscle in the dorsal portion of the seventh interspace was almost invariably silent. Also, activity in the ventral portion of the third interspace, when present, and activity in the dorsal portion of the fifth interspace were delayed relative to the onset of activity in the dorsal portion of the third interspace. In addition, the discharge frequency of the motor units identified in the dorsal portion of the third interspace averaged (mean +/- S.E.M.) 11.9 +/- 0.3 Hz and was significantly greater than the discharge frequency of the motor units in both the ventral portion of the third interspace (6.0 +/- 0.5 Hz) and the dorsal portion of the fifth interspace (6.7 +/- 0.4 Hz). The muscle in the dorsal portion of the third interspace started firing simultaneously with the parasternal intercostal in the same interspace, and the discharge frequency of its motor units was even significantly greater (11.4 +/- 0.3 vs. 8.9 +/- 0.2 Hz). These observations indicate that the distribution of neural inspiratory drive to the external intercostals in humans takes place along dorsoventral and rostrocaudal gradients and mirrors the spatial distribution of inspiratory mechanical advantage.

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.

To assess the respiratory function of the ribs, we measured the changes in airway opening pressure (Pao) induced by stimulation of the parasternal and external intercostal muscles in anesthetized dogs, first before and then after the bony ribs were removed from both sides of the chest. Stimulating either set of muscles with the rib cage intact elicited a fall in Pao in all animals. After removal of the ribs, however, the fall in Pao produced by the parasternal intercostals was reduced by 60% and the fall produced by the external intercostals was eliminated. The normal outward curvature of the rib cage was also abolished in this condition, and when the curvature was restored by a small inflation, external intercostal stimulation consistently elicited a rise rather than a fall in Pao. These findings thus confirm that the ribs play a critical role in the act of breathing by converting intercostal muscle shortening into lung volume expansion. In addition, they carry the compression that is required to balance the pressure difference across the chest wall.

Accounts of breathing in methodological books on singing are often confusing or inaccurate rather than helpful. This chapter provides an overview of the principles of respiration and how this is modified for singing. Inspiration results from an increase in thoracic dimensions caused by activity in the diaphragm and external intercostal muscles. At high lung volumes the sternocleidomastoids and scalenes also aid chest expansion. Subglottic pressure is created during expiration by the contraction of the abdominal wall, predominantly as a result of lateral abdominal muscle activity, which drives the relaxed diaphragm upwards while simultaneously the internal intercostals pull the ribs downwards. When the lungs are full and the inspiratory muscles release, elastic recoil forces alone can drive out the air and in order to regulate subglottic pressure these forces must be resisted by gradually reducing inspiratory muscle activity. How different patterns of activity in these and other muscles contribute to singing is described and the way in which similar ends can be achieved by different means in different singers is explained.

Idiopathic scoliosis causes respiratory muscles weakness and reduced exercise capacity. However, the mechanism of these symptoms is still unknown. The main objective of this study was to determine the intensity of respiratory muscle activity and exercise capacity in patients with idiopathic scoliosis in comparison with healthy people.In this study, 20 female patients with adult idiopathic scoliosis (10 mild and 10 moderate) as well as 10 healthy matched individuals with characteristics of the patients were selected.The subjects were fatigued through a maximal incremental cycle ergometry protocol. Meanwhile, the electromyography values of the external intercostal muscles and diaphragm were recorded bilaterally, and fatigue duration was determined.The root mean square of concave external intercostal muscles and concave diaphragm in patients with idiopathic scoliosis was significantly reduced during the fatiguing exercise protocol compared with healthy individuals. The median frequencies of the two sides differed significantly and were lower in patients with moderate scoliosis than healthy subjects. Fatigue duration (minutes) also was lower in patients with moderate scoliosis than healthy subjects.Scoliosis causes respiratory muscle weakness and reduced fatigue duration in response to mild physical activity compared with healthy subjects and these dysfunctions appear to be related to the severity of scoliosis curvature (moderatemild).

The ability to measure intercostal muscle blood flow in humans has implications for understanding blood flow distribution patterns and circulatory regulation during exercise. Accordingly, the advantage of performing actual muscle blood flow measurements is that it provides an insight into the “blood flow competition” theory, based on which it is proposed that the respiratory muscles compete with the locomotor muscles for the available blood flow. Until very recently it was impossible to measure respiratory muscle blood flow in humans during exercise owing to several difficulties. Near-infrared spectroscopy (NIRS) combined with indocyanine green dye (ICG) is a new valid and minimally invasive technique for measuring respiratory muscle blood flow during exercise in humans allowing for continuous and variable frequency data collection. On the basis of tracer principles of mass conservation, the NIRS–ICG technique makes it possible to quantify blood flow because the rate of accumulation of ICG in a given tissue reflects perfusion in the specified tissue of interest. Respiratory muscle blood flow measurements by NIRS–ICG technique primarily reflect the internal and external intercostal muscles and only to a lesser extent the costal part of the diaphragm. However, while the diaphragm acts as the primary flow generator during exercise, the role of the intercostal muscles is also important as they develop the necessary pressure to move the rib cage. This chapter focuses on the intercostal muscle perfusion measured by the NIRS–ICG technique in healthy individuals and patients with chronic obstructive pulmonary disease (COPD) during exercise who often experience greater work of breathing than healthy subjects both at rest and during exercise.

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.

High-frequency mechanical vibration of the rib cage reduces dyspnea, but the effect of this procedure on the respiratory muscles is largely unknown. In the present studies, we have initially assessed the electrical and mechanical response to vibration (40 Hz) of the canine parasternal and external intercostal muscles (third interspace) during hyperventilation-induced apnea. When the vibrator was applied to the segment investigated, prominent external intercostal activity was recorded in the seven animals studied, whereas low-amplitude parasternal intercostal activity was recorded in only four animals. Similarly, when the vibrator was applied to more rostral and more caudal interspaces, activity was recorded commonly from the external intercostal but only occasionally from the parasternal. The two muscles, however, showed similar changes in length. We next examined the response to vibration of the muscles in seven spontaneously breathing animals. Vibrating the rib cage during inspiration (in-phase) had no effect on parasternal intercostal inspiratory activity but induced a marked increase in neural drive to the external intercostals. For the animal group, peak external intercostal activity during the control, nonvibrated breaths averaged (mean +/- SE) 43.1 +/- 3.7% of the activity recorded during the vibrated breaths (p0.001). External intercostal activity during vibration also occurred earlier at the onset of inspiration and commonly carried on after the cessation of parasternal intercostal activity. Yet tidal volume was unchanged. Vibrating the rib cage during expiration (out-of-phase) did not elicit any parasternal or external intercostal activity in six animals. These observations thus indicate that the external intercostals, with their larger spindle density, are much more sensitive to chest wall vibration than the parasternal intercostals. They also suggest that the impact of this procedure on the mechanical behavior of the respiratory system is relatively small.

1. Inspiratory activity in the canine external intercostal muscles is exquisitely sensitive to the direction and amplitude of the inspiratory displacement of the ribs. This study was designed to investigate the role of muscle receptors, in particular the muscle spindles, in mediating this phenomenon. 2. External intercostal inspiratory activity showed a reflex increase when the normal cranial motion of the ribs and the normal shortening of the muscles was reduced, and showed a reflex decrease when the cranial motion of the ribs and the shortening of the muscles was augmented. However, clamping the two ribs making up the interspace and maintaining muscle length constant only moderately attenuated these responses. 3. These persistent responses remained unchanged after section of the levator costae muscles. 4. The responses were attenuated but still present after section of the external intercostals in the contiguous segments and denervation of the internal intercostals. 5. These reflex responses are therefore mediated in part by non-muscular receptors, which most likely lie within the costovertebral joints. These joint receptors might be a primary determinant of the load-compensating reflex.

We have previously shown in dogs that the ribs in flail chest move paradoxically inward during inspiration but continue to move cranially. We have also shown that flail elicits, probably via an increased activation of the muscle spindles, a threefold to fourfold increase in external intercostal inspiratory EMG activity without inducing any changes in parasternal intercostal activity. Therefore, the present studies were undertaken to test the hypothesis that the persistent cranial motion of the fractured ribs resulted primarily from the action of the external intercostals. A flail was induced in seven supine anesthetized animals by fracturing both dorsally and ventrally ribs 3 to 6 on the right side of the chest, after which the external intercostal muscles in interspaces 1 to 7 were severed. Severing the external intercostals caused a small increase in the inspiratory inward displacement of the fractured ribs, from 2.76 +/- 0.31 to 3.25 +/- 0.38 mm (p < 0.05), but it did not affect the parasternal intercostal EMG activity or the cranial rib displacement (before, 3.61 +/- 1.03 mm; after, 3.22 +/- 1.43 mm; NS). However, when the parasternal intercostals in interspaces 1 to 7 were also denervated, the inspiratory inward displacement of the ribs increased markedly to 5.95 +/- 0.48 mm (p < 0.01), and their inspiratory cranial displacement was reversed into a 1.05 +/- 0.58 mm inspiratory caudal displacement (p < 0.01). We conclude, therefore, that in dogs with flail chest the respiratory displacements of the ribs are still primarily determined, besides pleural pressure, by the action of the parasternal intercostals. These observations also suggest that in anesthetized dogs, spindle-induced excitation of the external intercostals has little impact on the mechanical behavior of the ribs.

1. A test was performed of the hypothesis that the motion of the ribs during inspiration modulates, via changes in spindle afferent activity, the activation of the inspiratory intercostal muscles. The electrical activity of the parasternal intercostal, external intercostal, and levator costae muscles in anaesthetized spontaneously breathing dogs was thus recorded during manipulation of the inspiratory displacement of the ribs over a wide range of rib motion. 2. In agreement with the hypothesis, the external intercostal and levator costae muscles lengthened and showed increased inspiratory activities when the normal inspiratory cranial motion of the lower rib was reduced or reversed into an inspiratory caudal motion. Conversely, the inspiratory activities decreased when the inspiratory cranial motion of the rib and the inspiratory shortening of the muscles was augmented. The inspiratory activity of the parasternal intercostal remained unchanged throughout. 3. However, when the two ribs making up the interspace were linked together so that the external intercostal muscle was constant in length, the relationship of muscle activity to rib motion was maintained. 4. In addition, when the upper rather than the lower rib of the interspace was manipulated, the relationship between the change in muscle length and inspiratory activity was reversed, so that activity decreased when the muscle was lengthened and increased when the muscle was shortened. The relationship of muscle activity to lower rib motion, however, was still maintained. 5. These observations thus indicate that rib motion triggers proprioceptive reflexes which, regardless of the changes in length of the individual muscles, make the external intercostal inspiratory activity exquisitely sensitive to the direction of rib displacement.

To study the interaction between postural and respiratory control of intercostal muscles, we used electromyography of intercostal muscles of the lateral chest wall in conscious humans. Bipolar fine-wire electrodes were placed in external and internal intercostal muscles in the midaxillary line of four subjects who sat on a bench and breathed through a pneumotachograph. They were instructed to hold their breath at end expiration, rotate their thorax to the right or left, and then hold the rotation while resuming breathing. Holding a rotation induces steady tonic activity in either internal or external intercostal muscles, depending on the direction of the rotation. The degree of rotation was varied from one run to the next, resulting in varied levels of tonic postural activity. When breathing resumes, internal intercostal muscles have their activity almost completely suppressed with each inspiration independently of whether the tonic postural tone is small or large. External intercostal muscles show inspiratory increases in activity superimposed on the postural tone, which apparently amplifies the effect of respiratory input to their motoneurons.

To test the hypothesis that the external intercostals and levator costae constitute an inspiratory reserve system, we have examined the response of these muscles to increased inertial loads. Weights were thus attached sequentially to the ribs in ten lightly anesthetized, spontaneously breathing dogs. As weights were attached, the ribs were progressively displaced caudally at end-expiration, so that the external intercostal muscles were lengthened. In addition, the cranial motion of the ribs during inspiration was gradually reduced, the inspiratory shortening of external intercostal disappeared, and the external intercostal and levator costae inspiratory EMG activities increased. The parasternal intercostal inspiratory activity, however, remained unchanged. Studies also showed that: (1) the increases in external intercostal activity appeared with the first loaded breath and disappeared as soon as the load was removed; (2) these increases were related to the suppression of the inspiratory muscle shortening, rather than to the increase in precontraction muscle length or to vagal inputs; and (3) denervation of the external intercostal caused inspiratory muscle lengthening but had little effect on the inspiratory motion of the ribs. These observations thus indicate that increased inertial loads on the ribs trigger reflexes, possibly spindle reflexes, which cause selective increases in external intercostal and levator costae inspiratory EMG activities. In that sense, the present findings are consistent with the idea that these two muscles constitute an inspiratory reserve system. However, it appears that the major effect of these increased activities is simply to prevent the muscles from lengthening during inspiration.

Although blunt chest injuries frequently lead to respiratory failure, the effects of flail chest on the mechanics of breathing have not been evaluated. In the present studies, we have measured the respiratory displacements of the ribs and sternum and the electromyograms (EMG) of the parasternal and external intercostal muscles in eight supine, anesthetized, spontaneously breathing dogs before and after the third to sixth ribs on the right side of the chest were fractured both dorsally and ventrally. After flail, the fractured ribs moved inward, rather than outward, during inspiration, but their inspiratory cranial displacement remained unchanged. The inspiratory outward and caudal displacement of the sternum, the inspiratory EMG activity of the parasternal intercostals, the pattern of breathing, and the arterial blood gases were also unaltered. However, the inspiratory EMG activity recorded from the external intercostals increased consistently to 327 +/- 101% of control (p < 0.05). These observations indicate that with flail chest, the disconnected segment of the rib cage shows paradoxical motion exclusively along the lateral axis; the increased external intercostal activation may account, at least in part, for the persistent inspiratory cranial motion of the ribs. These observations also suggest that the harmful effects of blunt chest injuries are related to pulmonary contusion and pain, rather than to flail chest per se.

This is the first reported detailed electrophysiological study of diaphragmatic myoclonus. An 86 year old woman had rapid, intermittent epigastric pulsations. Neurological examination and imaging studies of the brain and spinal cord were normal. Needle EMG showed rhythmic contractions of the diaphragm and external intercostal muscles at 4 to 5 Hz. These contractions were often associated with suppression of normal breathing and were capable of maintaining adequate ventilation. Both diaphragms were involved but showed considerable variability in their relative latencies. Automated interference pattern analysis suggested a change in recruitment order, with selective activation of large phrenic motoneurons. The supraspinal mechanisms mediating diaphragmatic myoclonus are different from that of voluntary and involuntary rhythmic breathing, and seem to be unrelated to palatal myoclonus. The generator source is likely related to respiratory centres in the rostral medulla.

To the Editor, Thoracic paravertebral block (PVB) provides excellent surgical anesthesia as well as postoperative analgesia for thoracic surgeries. Several ultrasound-guided PVB techniques have been described using either a transverse scan or a parasagittal scan in both the in-plane and the out-of-plane needle insertion approaches. The different approaches rely on the identification of one of two landmarks: 1) the superior costotransverse ligament (SCTL) or 2) the internal intercostal membrane (IICM). Learning to scan and identify the SCTL and IICM is possible on volunteers or patients, but, ideally, proficiency of hands-on needle insertion skills is acquired on phantoms prior to patient care given the potential risks of epidural or intrathecal spread, accidental pleural puncture, and pneumothorax associated with thoracic PVB. It is well known that phantom practice can shorten the learning curve, reduce complications, and result in changes in clinical practice. We have designed a pig carcass phantom which can be used to practice ultrasound-guided PVB. A pig weighing 50-60 kg is purchased from a local abattoir, sacrificed, shaved, decapitated, eviscerated, and washed as per regulations for human consumption. The carcass is then stored in the abattoir fridge at 4 C until use (not frozen). The carcass is placed prone for scanning and needle practice. Ultrasound images of the paravertebral space can be obtained using a 12 MHz transducer, and real-time longitudinal parasagittal views show the sonoanatomy of the transverse processes, pleura, and SCTL (Figs. 1, 2). Transverse views show the sonoanatomy of the transverse process, pleura, external intercostal muscle, and internal intercostal membrane. The phantom is useful not only for scanning but also for hands-on practice in needle insertion involving a particularly realistic tactile experience and practice in hand-eye coordination. A successful needle insertion and injection is indicated by downward displacement of the parietal pleura (a hyperechoic line visualized on ultrasound). The addition of methylene blue dye to the injectate permits localization of dye spread along the thoracic paravertebral space after injection, shown by viewing the pleura from the front (Figs. 3, 4). Unintentional pleural puncture is indicated by dye leakage beyond the parietal pleura when inspected from the front. Also, needle track marks are not seen in the flesh after repeated needle insertions. We recommend the pig carcass phantom for teaching and learning ultrasound-guided thoracic PVB because of the remarkable anatomical similarity of paravertebral space structures in pigs and humans. This is a potentially useful training model to gain competency in scanning and needle insertion for this technique as well as for ultrasound-guided intercostal blocks. F. W. Abdallah, MD V. W. Chan, MD (&) Toronto Western Hospital, University Health Network, University of Toronto, Toronto, ON, Canada e-mail: Vincent.Chan@uhn.on.ca

1. In this study, carbonic anhydrase III (CA-III) content in 18 equine muscles was determined by enzyme immunoassay. 2. It was found to differ in several muscles. 3. That in external intercostal muscle, rectus abdominis muscle and splenius muscle from four horses was very high. 4. Although the masseter muscle had only type I fibers, CA-III content was similar to that in mixed-fiber type muscles such as the biceps femoris muscle. 5. It thus appear that equine type I fibers can be further subgrouped.

Vomiting is a nonrespiratory behavior during which the major respiratory muscles contract in a characteristic pattern which generates changes in the intrathoracic and intra abdominal pressures that lead to expulsion of gastric content. During vomiting, the major inspiratory muscles (the diaphragm and the external intercostal) co-contract with the expiratory abdominal muscles in a series of activity bursts.The question arises whether brain stem respiratory neurons are involved in the control of these muscles during vomiting. In the present study, we undertook to determine whether bulbospinal inspiratory neurons in the dorsal respiratory group (DRG) and in the para-ambiguus region of the ventral respiratory group (VRG), together with the upper cervical inspiratory propriospinal neurons, are important for activation of the diaphragm and external intercostal muscles during vomiting. To analyze the behavior of these neurons, we elicited “fictive vomiting” using either emetic agents or electrical stimulation of the supradiaphragmatic vagal nerve afferents in decerebrate paralyzed cats. This fictive vomiting was identified by a characteristic series of bursts from coactivation of the phrenic nerve and some other nerves innervating abdominal muscles, which would be expected to produce an expulsion of gastric contents in nonparalyzed animals.Only a few (

1. The effects of tracheal occlusion on peak parasternal (PA) and external intercostal (EI) (3rd interspace) EMG activities were examined at different end-expiratory lung volumes both above and below functional reserve capacity (FCR) in anaesthetized, vagotomized and spontaneously breathing dogs. 2. Parasternal (PA) and external intercostal (EI) muscle lengths were monitored in situ. The difference in peak EMG activity between free and occluded breaths (test breaths) was related to the coincident peak change in intercostal muscle length (delta L) for each muscle, respectively. 3. At FRC, tracheal occlusion resulted in compensatory augmentation of peak EI, but little change in peak PA EMG activities. At lung volumes below FRC, airway occlusion resulted in augmentation of both PA and EI activities. Responses to airway occlusion at lung volumes above FRC were variable. The magnitude and duration of these changes in EMG, however, could be linearly related to the value of delta L. With delta L = 0, there was no change in peak EI or PA EMG; for values of delta L less than 0, there was attenuation of EI and PA EMG; for delta L greater than 0, there was enhancement of EI and PA EMG activation. 4. The magnitude of the changes in EMG activity in response to tracheal occlusion was more prominent for the EI muscle compared to the PA, the latter of which are known to have much fewer muscle spindles than EI muscle. 5. Our results suggest that a difference in end-inspiratory muscle length between the control and occluded breaths is a stimulus for the intercostal response to applied loads implicating muscle spindles as the predominant receptor moderating these responses. We hypothesize that when delta L = 0, no change in EMG occurs since the spindles sense no change in muscle length. When delta L less than 0 (i.e. peak muscle length during the occluded breath is shorter than control) muscle spindles would be disengaged, resulting in a disfacilitation of EMG activity. Where delta L greater than 0 (i.e. peak muscle length during the occluded breath is longer than control), muscle spindles are stimulated, resulting in enhancement of EMG activity. 6. Additional doses of Nembutal (20 mg), which produced significant changes in breathing pattern, did not affect the magnitude of the load compensatory responses.

A pair of anomalous supernumerary muscles has been found in a single cadaver which fit the classic description of the Musculus supracostalis anterior. The muscles took origin from the first rib deep to the two pectoral muscles and between the origins of the pectoralis minor and serratus anterior muscles. They were directed inferiorly to insert on the upper margin of the fourth rib. The nerve supply of one muscle of the pair was determined to be from the collateral branch of the second right intercostal nerve. This supports the theory that these rare muscles may be derived from a single external intercostal muscle which grew to span several intercostal spaces.

We used the histochemical stain for ATPase to compare the fiber-type composition of rat internal and external intercostal muscles from thoracic (T) segments 2-5, 8, and 11. At each level, type II fibers were more numerous than type I fibers, type II B fibers were more numerous than II A fibers, and type I fibers were more numerous in external than in internal intercostals. However, fiber type composition varied from segment to segment. For example, the proportion of type II A fibers increased in a rostrocaudal gradient in internal but not external intercostals, and type I fibers were more prevalent at rostral and caudal than at intermediate levels in both internal and external intercostals. These results provide a basis for interpreting previous physiological and molecular studies which have compared intercostal muscles from different segmental levels.