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The respiratory muscles encompass a variety of functions and roles, their action during exercise facilitates arterial blood-gas and pH regulation. Exercise hyperpnea is the first line of defense to meet increased metabolic demand. In so doing, the muscles of respiration encounter several challenges, which may lead to respiratory muscle fatigue and impaired exercise tolerance. The focus of this brief review is to summarize recent developments in the study of respiratory muscle mechanics, energetics, and fatigue during exercise. Advances in the field are highlighted and directions of potential future research identified.

Objectives: Pompe disease is a rare genetic disease produced by mutations in the GAA gene leading to progressive skeletal and respiratory muscle weakness. T1-weighted magnetic resonance imaging is useful to identify fatty replacement in skeletal muscles of late-onset Pompe disease (LOPD) patients. Previous studies have shown that replacement by fat correlates with worse results of muscle function tests. Our aim was to investigate if fat replacement of muscles involved in the ventilation process correlated with results of the spirometry and predicted respiratory muscle impairment in LOPD patients over time.Materials and Methods: We studied a cohort of 36 LOPD patients followed up annually in our center for a period of 4 years. We quantified muscle fat replacement using Mercuri score of the thoracic paraspinal and abdominal muscles and the pillars of the diaphragm. We correlated the combined Mercuri scores of these areas with spirometry results and the need of respiratory support.Results: We found a statistically significant correlation (Spearman test, p < 0.05; coefficient of correlation > 0.6) between forced vital capacity seated and lying and fat fraction score of all muscle groups studied. The group of patients who needed respiratory support had higher fat fraction scores than patients not requiring ventilatory support. Higher fat replacement in these areas correlated with worse progression in spirometry values over time.Conclusions: Fat replacement of paraspinal, abdominal, and trunk muscles correlates with results of spirometry and is able to predict worsening in respiratory muscle function tests that could lead to an emerging ventilatory dysfunction. Therefore, the identification of fat replacement in these muscle groups should lead to a closer monitorization of patients. Radiologic evaluation of diaphragm pillars in T1-weighted imaging axial sequences could also be helpful to predict respiratory insufficiency.

During a heavy exercise, energy requirement increases, causing insufficiency of inspiratory muscles to overcome the elastic recoil of the lungs. Respiratory accessory muscles are in charge during forced inspiration or expiration. Muscles elevating chest cage during respiration are referred to muscles of inspiration, while muscles depressing chest cage are termed as muscles of expiration. In case of high cervical spinal injury, sternocleidomastoid muscle remains intact and is the objective of physiotherapy. Expiratory muscle strength is significant in patients suffering chronic obstructive pulmonary disease. Involvement of bulbar muscles in patients with neuromuscular diseases presents a deterioration of the disease.

Minimizing the energy required for breathing muscles is based on the adaptation of the respiratory muscles which is reflected in the reduction of breathing frequency (BF) and tidal volume (VinfT/inf) increase. This may be influenced through a targeted BE and the quality of breathing may be linked to endurance performance. Aim of this study was assess dynamic ventilation parameters at different load intensities and their changes due to the systematic breathing exercise (BE).Study recruit 36 runners of both sexes with a mean age 16.8±1.6 years. A random distribution was performed. The intervention program consisted of a set of BE aimed at the activation of the diaphragm. We monitored the dynamics of ventilation parameters at intensities 2, 3, 4 W/kg during a stepped test on a bicycle ergometer.The BE was focused on the activation of the diaphragm for a 12.2±3.6 minutes per day, sixteen weeks. After eight weeks, there were significant changes in VinfT/infand BF (P0.05). After sixteen weeks there was a significant increase in VinfT/infof 5.7-18.3% (P0.01), depending on the load level, BF values decreased significantly by 5.4-14.4% (P0.01). VinfE/infand VOinf2/infvalues were without changes. There were no significant changes in the control group.It was confirmed that the two-month BE intervention focused on the activation of the diaphragm is sufficient and resulted in a significant change in the values of dynamic ventilation parameters. After four months of intervention, the changes are significantly greater compared with values found after a two-month intervention period.

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The primary function of the respiration is the gas exchange of oxygen and carbon dioxide between the lungs and the blood. Respiration includes ventilation, which takes place in the lungs within the interaction which sternum, ribs, vertebrae, and muscles surrounding the thorax. The nose, pharynx, and larynx are the parts of the upper airways. Upper airways are responsible for warming, moistening, and filtering of the air. The lower respiratory tract includes conducting airways and the respiratory zone. Thoracic cage expands, and the air enters into the lungs as the diaphragm, external intercostals, and the scalenes contract during quite inspiration. The expiration is passive during rest. Accessory muscles of respiration contract during forced expiration. Compliance, airway resistance, and surface tension affect ventilation. The children have different anatomical and physiological features of lungs and thorax compared to adults. The mechanical properties of the lungs and thoracic cage differ according to the diseases. In this chapter, the kinesiology of respiration is discussed.

Objectives: to evaluate the evolution of clinical indicators that characterize airway permeability in patients in the postoperative period of thoracoabdominal surgeries and to analyze their relationship with the occurrence of the diagnosis “ineffective airway clearance”. Methods: descriptive, quantitative, longitudinal research with 60 patients who were followed for five consecutive days. Eleven indicators of the nursing outcome “respiratory status: airway permeability” were used. Results: on the first day of evaluation, the most compromised indicators were: respiratory rate, cough, depth of breath and use of accessory muscles. During follow-up, most of the indicators presented a slight deviation from normal variation and, in the last evaluation, there was a predominance of indicators with some degree of impairment. Conclusions: with the aid of the Nursing Outcomes Classification, it was observed that patients submitted to thoracoabdominal surgeries may present compromised airway permeability even days after surgery.

The control of rate, rhythm and depth of different phases of respiration is required not only for exchange of gases but also during non-respiratory motor behaviours and emotional states. A network of rhythm-generating and pattern-generating neural groups in the ponto-medullary region of brain controls the activity of inspiratory, expiratory and accessory muscles of respiration. This network is intricately connected to the higher subcortical and cortical regions of the brain for state and behaviour-specific modulation respiration. The network also receives afferent information from periphery to modulate the ongoing respiratory activity to match the respiration with the metabolic needs. This chapter details the most recent information regarding neural substrate and models that underlie the control of respiration.

International audience; In this chapter, we evaluate the 3D tumor trajectories from patient-specific biomechanical model of the respiratory system, which takes into account the physiology of respiratory motion to simulate irregular motion. The behaviour of the lungs, driving directly by simulated actions of the breathing muscles, i.e. the diaphragm and the intercostal muscles (the rib cage). In this chapter, the lung model is monitored and controlled by a personalized lung pressure-volume relationship during a whole respiratory cycle. The lung pressure is patient specific and calculated by an optimization framework based on inverse finite element analysis. We have evaluated the motion estimation accuracy on two selected patients, with small and large breathing amplitudes (Patient 1 = 10.9 mm, Patient 10 = 26.06 mm). In this order, the lung tumor trajectories identified from 4D CT scan images were used as reference and compared with the 3D lung tumor trajectories estimated from finite element simulation during the whole cycle of breathing. Over all phases of respiration, the average mean error is less than 1.8 ± 1.3 mm. We believe that this model, despite of others takes into account the challenging problem of the respiratory variabilities and can potentially be incorporated effectively in Treatment Planning System (TPS) and as lung tumor motion tracking system during radiation treatment.

Key points Respiratory failure is a leading cause of mortality in Duchenne muscular dystrophy (DMD), but little is known about the control of breathing in DMD and animal models. We show that young (8 weeks of age) mdx mice hypoventilate during basal breathing due to reduced tidal volume. Basal CO2 production is equivalent in wild-type and mdx mice. We show that carotid bodies from mdx mice have blunted responses to hyperoxia, revealing hypoactivity in normoxia. However, carotid body, ventilatory and metabolic responses to hypoxia are equivalent in wild-type and mdx mice. Our study revealed profound muscle weakness and muscle fibre remodelling in young mdx diaphragm, suggesting severe mechanical disadvantage in mdx mice at an early age. Our novel finding of potentiated neural motor drive to breathe in mdx mice during maximal chemoactivation suggests compensatory neuroplasticity enhancing respiratory motor output to the diaphragm and probably other accessory muscles. Abstract Patients with Duchenne muscular dystrophy (DMD) hypoventilate with consequential arterial blood gas derangement relevant to disease progression. Whereas deficits in DMD diaphragm are recognized, there is a paucity of knowledge in respect of the neural control of breathing in dystrophinopathies. We sought to perform an analysis of respiratory control in a model of DMD, the mdx mouse. In 8-week-old male wild-type and mdx mice, ventilation and metabolism, carotid body afferent activity, diaphragm muscle force-generating capacity, and muscle fibre size, distribution and centronucleation were determined. Diaphragm EMG activity and responsiveness to chemostimulation was determined. During normoxia, mdx mice hypoventilated, owing to a reduction in tidal volume. Basal CO2 production was not different between wild-type and mdx mice. Carotid sinus nerve responses to hyperoxia were blunted in mdx, suggesting hypoactivity. However, carotid body, ventilatory and metabolic responses to hypoxia were equivalent in wild-type and mdx mice. Diaphragm force was severely depressed in mdx mice, with evidence of fibre remodelling and damage. Diaphragm EMG responses to chemoactivation were enhanced in mdx mice. We conclude that there is evidence of chronic hypoventilation in young mdx mice. Diaphragm dysfunction confers mechanical deficiency in mdx resulting in impaired capacity to generate normal tidal volume at rest and decreased absolute ventilation during chemoactivation. Enhanced mdx diaphragm EMG responsiveness suggests compensatory neuroplasticity facilitating respiratory motor output, which may extend to accessory muscles of breathing. Our results may have relevance to emerging treatments for human DMD aiming to preserve ventilatory capacity.

Respiratory muscles are located at multiple sites of the upper airway and are the effectors for the respiratory, alimentary, and communicative roles of the upper airway. The upper airway contains multiple muscles at each of five major sites. Their major respiratory functions are to optimize airway patency during inspiration, regulate the rate of airflow during expiration, and partition ventilation between nasal and oral routes. Accessory muscles of the neck act to assist the thoracic respiratory muscles mainly by stabilizing the upper rib cage. There are five groups of upper airway muscles, based on their anatomic location: regulating the pharynx, soft palate, larynx, nose, and mouth. The muscles of the upper airway are rhythmically active during the respiratory cycle, and have several influences on airflow under normal circumstances and in the presence of disease. An appreciation of the high prevalence of obstructive sleep apnea has led to a wealth of new information about the structural and contractile properties of pharyngeal muscles.

The lungs do not act in isolation, but rather are part of an integrated system that also involves the central nervous system (CNS), which controls the action of the muscles of respiration, and the appropriate response of the respiratory muscles to the signals they receive from the CNS. The respiratory generator, located in the medulla, also receives input from the cerebral cortex and higher levels of the brainstem, as well as feedback from central and peripheral chemoreceptors that is targeted to maintaining stable and acceptable levels of Po 2 and Pco 2 . This chapter provides an overview of the neural, muscular, and chest wall contributions to respiration. The anatomy of ventilatory control is presented, followed by a description of input that the control system receives from chemoreceptors as well as receptors from the lungs and chest wall. The action of the diaphragm, the main muscle of respiration, is described, including the importance of the zone of apposition and diaphragm length. This presentation of the anatomy and physiology of ventilatory control and the respiratory pump forms the background information for understanding the disorders of ventilatory control and disorders of the respiratory pump that will be presented in Chapters 18 and 19, respectively.

This study focused on how pulmonary function is affected by proprioceptive neuromuscular facilitation (PNF) of accessory respiratory muscles in the chronic post-stroke phase. The study involved patients who had had ischemic stroke 6 months or more before the PNF treatment investigated. The objective was to define the effect of PNF on bioelectrical resting and maximum activity of the accessory muscles. Patients were randomly assigned to PNF treatment and just positioning treatment as a reference for comparison; 30 patients each. Electromyography of accessory muscles was investigated before and after physiotherapeutic treatments. We found that there was a greater reduction in EMG activity in all muscles investigated after PNF compared to positioning treatment alone. A reduction of muscle activity due to PNF concerned both affected and unaffected body side, but it was greater on the affected side. We conclude that a reduction of the accessory respiratory muscle activity due to PNF treatment could be of benefit in chronic stoke patients in that it would help normalize breathing pattern and thereby prevent the development of hypoxia.

Background: Hypertension is recognized as a major health problem throughout the world leading to various life-threatening heart diseases. The higher the level of blood pressure in the long run, the more likely there is a complication of hypertension. Slow breathing exercises are one of the non-pharmacological therapies that can be used to control or reduce blood pressure and strengthening breathing muscles. This systematic review is to analyze the effectiveness of slow breathing training in blood pressure in patients with hypertension.Methods: Literature search is through Scopus, Pubmed, Proquest, Science Direct, and EBSCO. with the last 5 years (2014-2019). Criteria for inclusion in this review are as follows: studies involving hypertension, ages 18 years and over, patients who have received or are still receiving slow breathing exercises. Keyword in this review was Slow Breathing, Blood Pressure, and Hypertension.Results: There are 10 journals chosen. Total respondents in this review were 1757 hypertensive patients who received slow respiratory therapy. Slow breathing training provides many benefits for hypertensive patients. Subjects with hypertension, pre-hypertension, and antihypertensive drugs, were given slow breathing intervention that is inhaling as much as ≤10 breaths/minute carried out for ≥5 minutes. This exercise is carried out at ≥3 days/week; total duration of intervention ≥4 weeks; Slow breathing training reduces blood pressure at rest, the average using this slow breathing exercise, blood pressure drops 10 -15 mmHg in systole and diastole. Overall, slow breathing exercises decreased SBP by -5.62 mmHg [-7.86, -3.38] and DBP by -2.97 mmHg [-4.28, -1.66].Conclusion: Slow breathing training provides many benefits for hypertensive patients. Especially for patients with isolated systolic hypertension. This non-pharmacological therapy can be carried out by individuals independently in controlling the breathing rate so that they can reach breathing speed both during inspiration and expiration. Slow breathing exercises can also help increase baroreflex sensitivity, then affect blood pressure reduction.

[Purpose] This study aimed to determine the effects of different intensities of inspiratory muscle training on the relative respiratory muscle activity in healthy adults. [Subjects and Methods] Thirteen healthy male volunteers were instructed to perform inspiratory muscle training (0%, 40%, 60%, and 80% maximal inspiratory pressure) on the basis of their individual intensities. The inspiratory muscle training was performed in random order of intensities. Surface electromyography data were collected from the right-side diaphragm, external intercostal, and sternocleidomastoid, and pulmonary functions (forced expiratory volume in 1 s, forced vital capacity, and their ratio; peak expiratory flow; and maximal inspiratory pressure) were measured. [Results] Comparison of the relative activity of the diaphragm showed significant differences between the 60% and 80% maximal inspiratory pressure intensities and baseline during inspiratory muscle training. Furthermore, significant differences were found in sternocleidomastoid relative activity between the 60% and 80% maximal inspiratory pressure intensities and baseline during inspiratory muscle training. [Conclusion] During inspiratory muscle training in the clinic, the patients were assisted (verbally or through feedback) by therapists to avoid overactivation of their accessory muscles (sternocleidomastoid). This study recommends that inspiratory muscle training be performed at an accurate and appropriate intensity through the practice of proper deep breathing.

From a functional point of view, there are three groups of respiratory muscles: the diaphragm, the rib cage muscles and the abdominal muscles. Each group acts on the chest wall and its compartments, i.e. the lung-apposed rib cage, the diaphragm-­apposed rib cage and the abdomen. Contraction of the diaphragm expands the abdomen and the lower part of the rib cage (abdominal rib cage). The rib cage muscles, including the intercostals, the parasternals, the scalene and the neck muscles, mostly act on the upper part of the rib cage (pulmonary rib cage) and are both inspiratory and expiratory. The abdominal muscles act on the abdomen and the abdominal rib cage and are expiratory. When each muscle group contracts alone or the contraction is predominant compared to the other groups, undesirable effects (such as “paradoxical” inward or outward motion during inspiration and expiration, respectively) occur on at least one of the compartments. A highly coordinated recruitment of two or three muscle groups is required to avoid these effects. During breathing at rest, this is accomplished by the coordinated activity of the diaphragm and inspiratory rib cage muscles. Normally no expiratory muscles are used [1]., Although during exercise respiratory muscles are finely controlled, they can contribute to limit performance http://ow.ly/qYUc300m9uP

When lesions in the spinal cord occur, the neural activation of respiratory muscles is compromised (De Troyer and Heilporn, 1980; De Troyer et al., 1986, 1990; Estenne et al., 2000a) resulting in significant respiratory dysfunction (De Troyer and Heilporn, 1980; Linn et al., 2000, 2001; Yokoba et al., 2003). However the underlying mechanisms that contribute to this dysfunction remain unclear. The aims of this study were: (1) to investigate whether a correlation exists between pulmonary function and the International Standards for the Neurological Classification of Spinal Cord Injury (ISNCSCI) examination scores for sensory and motor function; (2) to evaluate whether compensatory muscle activation plays a role in pulmonary function after spinal cord injury (SCI). We recorded Forced Vital Capacity (FVC); Forced Expiratory Volume in 1s (FEV1); and electromyography (EMG) of respiratory muscles during maximum respiratory tasks in 36 with SCI and 15 neurologically intact participants. Results indicate that pulmonary function (FVC, FEV1) was strongly correlated with motor and sensory scores from the ISNCSCI exam and maximal expiratory pressure (MEP) was also significantly related to ISNCSCI sensory scores (ρ=0.73, p

Introduction: Diaphragmatic dysfunction (DD) is a frequently underdiagnosed condition mainly secondary to traumas or surgery that determines a restrictive syndrome with a decrease in vital capacity and it is often associated to respiratory symptoms, exercise intolerance and sleep disturbances. Inspiratory muscle training (IMT) is a technique used to increase strength or endurance of the diaphragm and accessory muscles of inspiration. Isocapnic hyperpnea is a type of IMT training approach that requires people to ventilate at a high proportion of their maximum voluntary ventilation for a fixed period. Aim: To evaluate the effects of a 4-weeks isocapnic hyperpnea training (ST-MEDICAL device) on lung function, dyspnea, exercise capacity and diaphragm motility and thickness. Materials and Methods: 10 patients with DD were enrolled. Spirometry and maximal inspiratory pressure (MIP), 6-minute walking test (6MWT) and diaphragm ultrasound were performed. METs were measured by Armband for 3 days. Patients started a 4-weeks training with ST-MEDICAL and were re-assessed after training. Results: Significant effects of ST-MEDICAL training were observed on MIP (7±3.12 vs. 8.9±2.7 cmH2O, P=0.005), modified Medical Research Council (mMRC) (2.7±0.86 vs. 1±0.5, P=0.001) and distance at 6MWT (357.5±5.1 vs. 412.5±8, P Conclusions: IMT with ST-MEDICAL elicits positive changes in terms of MIP and dyspnea but not significant changes in diaphragm thickness and motility in patients with DD.

Introduction: Mechanical ventilation (MV) induces respiratory muscle dysfunction, generating difficulties in the weaning process, especially in patients with prolonged ventilation. Recently, the timed inspiratory effort index (TIE) was able to assess inspiratory muscle strength (MIP) at the bedside, and was effective in predicting success at weaning. Surface electromyography (EMGs) allows measurement of respiratory muscle work. Objective: to analyze the mechanical relationships of the accessory and main muscular groups of the breathing during the procedure of measurement of the MIP with the method TIE, with the intention of understanding which muscular group is responsible for the MIP. Method: Prospective observational study with patients in prolonged MV apt for weaning. The EMGs variable will be RMS, in which it will be confronted with the MIP of the TIE method. Values of P Results: We analyzed 19 patients, 16 female, age 83 years, APACHE II of 42%, time of VM of 10 days, and 47% were successfully weaning. The median MIP as a function of time 0-20s, 21-40s, 41-60s were respectively: 34 (16.8 - 43.2), 36.5 (26.4 - 54.8), and 44.5 (35.8 – 60.0) ANOVA = 0.0002. RMS (microvolts/seconds) of accessory muscles according to the same time were: 1.6 (1.2 – 2.1), 1.8 (1.6 – 2.3), 2.3 (1.9 - 2.8) ANOVA = 0.001; and of the mainly muscles were: 1.5 (1.3 – 2.0), 1.55 (1.3 -1.7), 1.7 (1.1 - 1.8) ANOVA = 0.25. Conclusion: MIP is achieved after 40 seconds of airway occlusion, and the accessory muscles significantly influence to generate this pressure result.

Background: Cor pulmonale is a synonym for pulmonary heart disease. The term “cor pulmonale” if broken into its constituents “cor” (heart) and “pulmo” (lungs), means cardiac involvement due to pulmonary diseases. Chronic cor pulmonale is not a single disease entity but resulting secondary to many bronchopulmonary vascular diseases and also from thoracic cage abnormalities. Cor pulmonale accounts for 5-10% of all heart diseases, 20-30% of all admissions for heart failure and 9.2% in the cardiac autopsies.Methods: This was a hospital-based study carried among patients diagnosed with chronic cor pulmonale admitted to the medical wards of Karnataka institute of medical sciences, Hubli. during December 2011- November 2012 using simple random sampling method.Results: The following observations were made in 50 representative cases the age group of patients was between 24 to 85 years. Chronic cor pulmonale was commonly seen in middle and elderly age groups. Incidence below 35 years is very less. Almost every patient of chronic cor pulmonale presented with breathlessness and cough. All patients in the study had Tachypnoea, Diminished chest movements, Prominent use of accessory muscles of respiration, Cyanosis, Clubbing (in some patients), Crepitations and rhonchi on chest auscultation, Loud P2 and pansystolic murmur in Tricuspid area on cardiac auscultation.Conclusions: The peak incidence of chronic cor pulmonale was found to be in the middle and older age groups with high incidence during winter season. Smoking and dusty environment at the site of occupation were aggravating the primary lung disease. Breathlessness, cough and edema of the feet were the most common symptoms.

Purpose To identify the frequency of the nursing diagnoses, ineffective breathing pattern, impaired gas exchange and impaired spontaneous ventilation in newborns; and, to analyze the accuracy of diagnostic indicators identified for each of these diagnoses. Methods This was a cross-sectional study conducted with a nonprobability sample of 92 infants. Data collected were represented by demographic and clinical variables, clinical indicators of the three respiratory nursing diagnoses from NANDA International, and were analyzed according to frequency and agreement between pairs of expert nurses (Kappa). Findings Ineffective breathing pattern was identified in 74.5% of infants; impaired gas exchange was noted in 31.5%; impaired spontaneous ventilation was found in 16.8% of subjects. Use of accessory muscles to breathe showed the highest sensitivity for ineffective breathing pattern; abnormal blood gases had the best predictive value for impaired gas exchange. Use of accessory muscles to breathe had the highest sensitivity for impaired spontaneous ventilation. Conclusions Ineffective breathing pattern was the most frequently identified; use of accessory muscles, alteration in depth of breathing, abnormal breathing, and dyspnea were the most representative signs/symptoms. Implication for nursing practice Early recognition of respiratory conditions can support safe interventions to ensure appropriate outcomes.

Duchenne muscular dystrophy is a fatal neuromuscular disease associated with respiratory-related morbidity and mortality. Herein, we review recent work by our group exploring deficits and compensation in the respiratory control network governing respiratory homeostasis in a pre-clinical model of DMD, the mdx mouse. Deficits at multiple sites of the network provide considerable challenges to respiratory control. However, our work has also revealed evidence of compensatory neuroplasticity in the motor drive to breathe enhancing diaphragm muscle activity during increased chemical drive. The finding may explain the preserved capacity for mdx mice to increase ventilation in response to chemoactivation. Given the profound dysfunction in the primary pump muscle of breathing, we argue that activation of accessory muscles of breathing may be especially important in mdx (and perhaps DMD). Notwithstanding the limitations resulting from respiratory muscle dysfunction, it may be possible to further leverage intrinsic physiological mechanisms serving to compensate for weak muscles in attempts to preserve or restore ventilatory capacity. We discuss current knowledge gaps and the need to better appreciate fundamental aspects of respiratory control in pre-clinical models so as to better inform intervention strategies in human DMD.

Spectral analysis of the electromyogram (EMG) of different groups of respiratory muscles showed that exercise combined with resistive load caused a decrease in the maximum inspiratory pressure (MIP) and a shift in the EMG centroid frequency of parasternal, scalene, and sternocleidomastoid muscles towards the lower part of the spectrum. Changes in the EMG spectrum of the diaphragm were not observed. Thus, the decrease in the total power reserve of the respiratory muscles, observed after heavy load on the respiratory system, was caused by deterioration of the functional state of the thoracic and accessory inspiratory muscles rather than the diaphragm. The diaphragm is more resistant to fatigue. These data suggest that the reduction of the maximum inspiratory pressure in chronic obstructive pulmonary disease is also caused primarily by the weakening of accessory muscles, whereas the weakness of the diaphragm may develop in the later stages of the disease. The functional failure of accessory muscles is an additional factor, which, along with the additional breathing resistance, increases the load on the diaphragm, promoting its fatigue and reduced respiratory reserve.

Background Forward head posture (FHP) causes changes in the strengths and rigidities of cervical muscles. Objective The aim of this study was to investigate correlations between FHP and respiratory functions and the muscle activities of respiratory accessory muscles in young adults in their 20s. Methods A volunteer sample of 33 healthy young adults participated in this study. Craniovertebral angle (CVA), cranial rotational angle (CRA), vital capacity (VC), forced vital capacity (FVC), forced expiratory volume at 1 second (FEV1), peak expiratory flow (PEF), maximal voluntary ventilation (MVV), and sternocleidomastoid (SCM) and upper trapezius activity ratios were measured. Results Significant positive correlations were found between CVA and VC, FVC, FEV1, PEF, and MVV, and a significant negative correlation was found between CVA and SCM activity ratio. Significant negative correlations existed between CRA and VC and FVC, and significant positive correlations between CRA and SCM and upper trapezius activity ratios. Conclusion FHP may act to lower respiratory functions, and thus, the maintenance of correct head posture is required to prevent such functional reductions.

Craniomandibular electromyographic (EMG) studies frequently include several parameters, e.g. resting, chewing and tooth-clenching. EMG activity during these parameters has been recorded in the elevator muscles, but little is known about the respiratory muscles. The aim of this study was to compare EMG activity in obligatory and accessory respiratory muscles between subjects with different breathing types. Forty male subjects were classified according to their breathing type into two groups of 20 each: costo-diaphragmatic breathing type and upper costal breathing type. Bipolar surface electrodes were placed on the sternocleidomastoid, diaphragm, external intercostal and latissimus dorsi muscles. EMG activity was recorded during the following tasks: (i) normal quiet breathing, (ii) maximal voluntary clenching in intercuspal position, (iii) natural rate chewing until swallowing threshold, (iv) short-time chewing. Diaphragm EMG activity was significantly higher in the upper costal breathing type than in the costo-diaphragmatic breathing type in all tasks (P0·05). External intercostal EMG activity was significantly higher in the upper costal breathing type than in the costo-diaphragmatic breathing type in tasks 3 and 4 (P0·05). Sternocleidomastoid and latissimus dorsi EMG activity did not show significant differences between breathing types in the tasks studied (P0·05). The significantly higher EMG activity observed in subjects with upper costal breathing than in the costo-diaphragmatic breathing type suggests that there could be differences in motor unit recruitment strategies depending on the breathing type. This may be an expression of the adaptive capability of muscle chains in subjects who clinically have a different thoraco-abdominal expansion during inspiration at rest.

To compare electromyographic (EMG) activity in young-adult subjects with different breathing types.This study included 50 healthy male subjects with complete natural dentition, and no history of orofacial pain or craniomandibular-cervical-spinal disorders. Subjects were classified into two groups: upper costal breathing type, and costo-diaphragmatic breathing. Bipolar surface electrodes were located on sternocleidomastoid, diaphragm, external intercostal, and latissimus dorsi muscles. Electromyographic activity was recorded during the following tasks: (1) normal quiet breathing; (2) speaking the word 'Mississippi'; (3) swallowing saliva; and (4) forced deep breathing.Sternocleidomastoid and latissimus dorsi EMG activity was not significantly different between breathing types, whereas diaphragm and external intercostal EMG activity was significantly higher in the upper costal than costo-diaphragmatic breathing type in all tasks (P0·05; Wilcoxon signed rank-sum test).Diaphragm and external intercostal EMG activity suggests that there could be differences in motor unit recruitment strategies depending on the breathing type.

Introduction: This study aimed to evaluate the simultaneous and maximum activities ofthe sternocleidomastoid (SCM) and pectoralis major (PM) muscles, to determine how the two types of breathing patterns (normal and forced) can affect these activities , and to verify which of these muscles could be used to establish an evaluation protocol for patients undergoing mechanical ventilation. Methods: Eleven healthy men, aged 18 to 25 years, participated in this study. The individuals remained in supine position using a respiratory belt to monitor both inspiratory and expiratory phase during shifts in the rib cage, performing three repetitions for the normal and forced respiratory movements, while keeping the breathing rhythm with a standard metronome. Electromyographic signals were captured using bipolar surface electrodes placed on the lower third of the SCM muscle and on the lower PM muscle fibers. Electromyographic signals were analyzed and the root mean square (RMS) values were calculated for a complete respiratory cycle. The EMG values were analyzed using the Bonferroni test for multiple comparisons. The homogeneity of variances was verified using the logarithmic transformation (LOG). The level of statistical significance was set at 5% (SPSS 19.0). Results: The values showed that there are signiicant differences between the EMG values of the SCM muscle during normal and forced respiration and the EMG values of the ECM and PM muscles during forced respiration. Conclusion: These results showed that the SCM muscle can be an indicator for the development of parameters to be used in the analysis of patients with respiratory failure.

The upper airway is a complex muscular tube that is used by the respiratory and digestive systems. The upper airway is invested with several small and anatomically peculiar muscles. The muscle fiber orientations and their nervous innervation are both extremely complex, and how the activity of the muscles is initiated and adjusted during complex behaviors is poorly understood. The bulk of the evidence suggests that the entire assembly of tongue and laryngeal muscles operate together but differently during breathing and swallowing, like a ballet rather than a solo performance. Here we review the functional anatomy of the tongue and laryngeal muscles, and their neural innervation. We also consider how muscular activity is altered as respiratory drive changes, and briefly address upper airway muscle control during swallowing.

Background In Amyotrophic Lateral Sclerosis (ALS) weak cervical muscles are commonly found. These accessory muscles of respiration are innervated by medially spinal-located motor neurons close to phrenic nerve nuclei. A correlation between cervical strength and prognosis has been described. We investigate the association with respiratory function. Methods Consecutive ALS patients assessed with flexor/extensor cervical muscle strength, revised functional ALS rating scale (ALSFRS-R), phrenic nerve studies and forced vital capacity (FVC) within 3 months were included. Flexor/extensor strength were assessed respectively in dorsal decubitus/sitting and categorized as normal/abnormal (MRC = 5/MRC Results We included 281 patients (157 men, disease duration 16.216 months; meanFVC 80.424%; MeanPhrenAmpl 0.50.25 m). Weak cervical flexion/extension: 156/59 patients. Abnormal PhrenAmpl: 100 patients; Abnormal FVC: 45; Abnormal RofALSFRS-R: 108. Sensitivity, specificity, PPV, NPP of extensor muscles for PhrenAmpl, FVC and RofALSFRS-R: 31%-35.5%, 84.5%-85.2, 33.3–52.5%, 66.1%-86.1%, respectively. Sensitivity, specificity, PPV, NPP of flexor muscles for PhrenAmpl, FVC and RofALSFRS-R: 66.6%-73.3%, 51.5%-54.1%, 24.4%-46.8%, 70.7%-90.1%, respectively. Combined flexor/extensor sensitivity, specificity, PPV, NPP: 68.5%-77.7%, 48.5%-51.4%, 26%-46%, 70%-91.2%, respectively. AUC: 0.58–0.64. Conclusion Weak cervical muscles indicate higher probability of respiratory involvement. Weak extensors are a strong predictor (high specificity) of respiratory compromise in ALS, which should be regarded as a significant warning in clinical practice.

Background: Incentive spirometers (IS) are widely used in clinical practice and classified as flow-oriented (FIS) and volumetric (VIS). Until recently, the respiratory inductive plethysmography used to evaluate the effects of IS on chest wall mechanics presented limitations, which may explain why the impact of VIS and FIS remains poorly known. Objective: We compared the effects of the VIS and FIS on thoracoabdominal mechanics and respiratory muscular activity in healthy volunteers. Methods: This cross-sectional trial assessed 20 subjects, 60% female, aged between 20 and 40 years and with a body mass index (BMI) between 20 and 30 kg/m2. All participants performed 8 quiet and 8 deep breaths using both FIS and VIS in a randomized order. The outcomes measured were the thoracoabdominal kinematics (i.e., chest wall, upper and lower ribcage and abdominal volumes), assessed using Optoelectronic Plethysmography, and the muscular activity of the sternocleidomastoid and superior and inferior intercostal muscles, assessed using electromyography. The statistical analysis was performed with one-way repeated measures ANOVA, and the significance level was set to 5%. Results: VIS increased 17 the chest wall volume to a greater extent than the FIS (p=0.007) and induced a larger increase in the upper and lower ribcages and abdomen (respectively, 156%, 91% and 151% p

Introduction: Connective tissue laxity identifies in various sites throughout the body. Aim was to estimate the accessory RM using ultrasound scanner. Methods: We examined 34 young men (median age 19 yrs; BMI 22,3 kg/m 2 , smokers 41%, packs/yrs 0,75) and 41 young women (median age 20 yrs; BMI 20,2 kg/m 2 , smokers 7%, packs/yrs 0,13). The peak histograms of active expiration muscles (external and internal oblique abdominal (extOAM and intOAM), transverses and rectus abdominal and internal intercostals) and accessory muscles of inspiration were detected by ultrasonic scanner. We studied indices reflecting muscle tissue echogenicity: homogeneity (H), structural density (SD) and echogenicity (E). The Beighton (B) score was used for showing up hypermobility (the 1 st group (n=20 men) B score 1-3, the 2 nd group (n=14 men) B score 4-9, the 3 rd group (n=17 women) B score 1-3, the 4 th group (n=24 men) B score 4-9). Results: We identified significantly decreasing echogenicity of muscles (fall of the index E and growth of the indices H, SD) only in the 2 nd group of extOAM, intOAM, transverses abdominal and external intercostals in comparison with the 1 st group. The index E of extOAM was similar in the 3 rd group and in the 4 th group: 3,3 (2,9;4,4) and 3,2 (2,7; 4,3) respectively. The index H was 23 (21;27) in the 3 rd group and in the 4 th group of extOAM 24(20;29). So was SD 1661 (1280;1914) and 1408 (1159; 1929) respectively. Conclusions: Probably ascertained c hanges of accessory RM in young menwith hypermobility (B score 4-9) come out of hypotrophy muscle tissue. We did not find significant changes in the muscle tissue of young women with increasing joint hypermobility.

Este estudo objetivou avaliar o efeito da fisioterapia nos parâmetros ventilatórios e na dinâmica tóraco-abdominal de crianças respiradoras bucais. Dez crianças respiradoras bucais foram submetidas a um programa de reeducação respiratória e correção postural durante 20 sessões de exercícios de alongamento e fortalecimento muscular sobre a bola suíça, estimulação diafragmática e alongamento dos músculos acessórios da inspiração. Os dados coletados foram as medidas de pressões inspiratórias e expiratórias máximas (PIM e PEM), capacidade inspiratória (CI), pico de fluxo expiratório (PFE), mobilidade torácica por meio do coeficiente respiratório (Cr) nos níveis axilar (CrA), xifoide (CrX) e umbilical (CrU) e análise biofotogramétrica do ângulo de Charpy. Estes foram verificados antes e após 10 e 20 atendimentos. Os dados foram submetidos a uma análise de variância (ANOVA) e, nas diferenças encontradas entre as médias, aplicou-se o Teste de Tukey com nível de significância de 5% (p

We describe and discuss haemorrhages discovered in the back and auxiliary breathing muscles of a population of cases of suicidal death by hanging. Intramuscular haemorrhages were present in approximately 30% of the cases. Pre-existing illnesses with an increased tendency to bleed or an anticoagulant medication did not exist; corresponding skin and subcutaneous fatty tissue structures were intact in each case. In cases of death by hanging, the occurrence of muscle haemorrhages of this type may be explained pathophysiologically by the occurrence of increased respiratory exertions and/or seizures during the hanging process. Although the results of our study do not indicate an obligatory autopsy finding, evidence of internal haemorrhaging into the back and auxiliary breathing muscles may be called upon following consideration of differential diagnostic aspects as a further diagnostic indication of vital hanging.

Objectives In this study, we quantified the profiles of phasic activity in respiratory muscles (diaphragm, genioglossus and external intercostal) and non-respiratory muscles (neck and extensor digitorum) across REM sleep. We hypothesized that if there is a unique pontine structure that controls all REM sleep phasic events, the profiles of the phasic twitches of different muscle groups should be identical. Furthermore, we described how respiratory parameters (e.g., frequency, amplitude, and effort) vary across REM sleep to determine if phasic processes affect breathing. Methods Electrodes were implanted in Wistar rats to record brain activity and muscle activity of neck, extensor digitorum, diaphragm, external intercostal, and genioglossal muscles. Ten rats were studied to obtain 313 REM periods over 73 recording days. Data were analyzed offline and REM sleep activity profiles were built for each muscle. In 6 animals, respiratory frequency, effort, amplitude, and inspiratory peak were also analyzed during 192 REM sleep periods. Results Respiratory muscle phasic activity increased in the second part of the REM period. For example, genioglossal activity increased in the second part of the REM period by 63.8% compared to the average level during NREM sleep. This profile was consistent between animals and REM periods (η(2)=0.58). This increased activity seen in respiratory muscles appeared as irregular bursts and trains of activity that could affect rythmo-genesis. Indeed, the increased integrated activity seen in the second part of the REM period in the diaphragm was associated with an increase in the number (28.3%) and amplitude (30%) of breaths. Non-respiratory muscle phasic activity in REM sleep did not have a profile like the phasic activity of respiratory muscles. Time in REM sleep did not have an effect on nuchal activity (P=0.59). Conclusion We conclude that the concept of a common pontine center controlling all REM phasic events is not supported by our data. There is a drive in REM sleep that affects specifically respiratory muscles. The characteristic increase in respiratory frequency during REM sleep is induced by this drive.

The respiratory control system is not just reflexive, it is smart, it learns, and, in fact, it has a memory. The respiratory system listens to and carefully remembers how previous stimuli affect breathing. Respiratory memory is laid down by adjusting synaptic strength between respiratory neurons. For example, repeated hypoxic bouts trigger a form of respiratory memory that functions to strengthen the ability of respiratory motoneurons to trigger contraction of breathing muscles. This type of respiratory plasticity is known as long-term facilitation (LTF). Although chemical feedback, such as hypoxia, initiates LTF, it is unknown whether natural modulation of mechanical feedback (from vagal inputs) also causes motor plasticity. Here, we used reverse microdialysis, electrophysiology, neuropharmacology, and histology to determine whether episodic modulation of vagally mediated mechanical feedback is able to induce respiratory LTF in anesthetized adult rats. We show that repeated obstructive apneas disrupt vagal feedback and trigger LTF of hypoglossal motoneuron activity and genioglossus muscle tone. This same stimulus does not cause LTF of diaphragm activity. Hypoxic episodes do not cause apnea-induced LTF; instead, LTF is triggered by modulation of vagal feedback. Unlike hypoxia-induced respiratory plasticity, vagus-induced LTF does not require 5-HT2receptors but instead relies on activation of α1-adrenergic receptors on hypoglossal motoneurons. In summary, we identify a novel form of hypoxia- and 5-HT-independent respiratory motor plasticity that is triggered by physiological modulation of vagal feedback and is mediated by α1-adrenergic receptor activation on (or near) hypoglossal motoneurons.

The nervous control of expiratory muscles is less well understood than that of the inspiratory muscles, particularly in the rat. The patterns of respiratory discharges in adult rats were therefore investigated for the muscles of the caudal intercostal spaces, with hypercapnia and under either anaesthesia or decerebration. With neuromuscular blockade and artificial ventilation, efferent discharges were present for both inspiration and expiration in both external and internal intercostal nerves. This was also the case for proximal internal intercostal nerve branches that innervate only internal intercostal and subcostalis muscles. If active, this region of muscle in other species is always expiratory. Here, inspiratory bursts were almost always present. The expiratory activity appeared only gradually and intermittently, when the anaesthesia was allowed to lighten or as the pre-decerebration anaesthesia wore off. The intermittent appearance is interpreted as the coupling of a slow medullary expiratory oscillator with a faster inspiratory one. The patterns of nerve discharges, in particular the inspiratory or biphasic activation of the internal and subcostalis layers, were confirmed by observations of equivalent patterns of EMG discharges in spontaneously breathing preparations, using denervation procedures to identify which muscles generated the signals. Some motor units were recruited in both inspiratory and expiratory bursts. These patterns of activity have not previously been described and have implications both for the functional role of multiple respiratory oscillators in the adult and for the mechanical actions of the muscles of the caudal intercostal spaces, including subcostalis, which is a partly bisegmental muscle.

Purpose: Skeletal muscle damage occurs following high-intensity or unaccustomed exercise; however, it is difficult to monitor damage to the respiratory muscles, particularly in humans. The aim of this study was to use clinical measures to investigate the presence of skeletal muscle damage in the inspiratory muscles. Methods: Ten healthy subjects underwent 60 minutes of voluntary inspiratory threshold loading (ITL) at 70% of maximal inspiratory pressure. Maximal inspiratory and expiratory mouth pressures, delayed onset muscle soreness on a visual analogue scale and plasma creatine kinase were measured prior to ITL, and at repeated time points after ITL (4, 24 and 48 hours post-ITL). Results: Delayed onset muscle soreness was present in all subjects 24 hours following ITL (intensity = 22 ± 6 mm; significantly higher than baseline p = 0.02). Muscle soreness was reported primarily in the anterior neck region, and was correlated to the amount of work done by the inspiratory muscles during ITL (r = 0.72, p = 0.02). However, no significant change was observed in maximal inspiratory or expiratory pressures or creatine kinase. Conclusions: These findings suggest that an intense bout of ITL results in muscle soreness primarily in the accessory muscles of inspiration, however, may be insufficient to cause significant muscle damage in healthy adults.

To test the feasibility of implanting intramuscular electrodes (Permaloc, Synapse Biomedical Inc, Oberlin OH) with self-securing polypropylene anchors to stimulate upper-intercostal and abdominal muscles plus the diaphragm.In 6 anesthetized dogs, 12 Permaloc electrodes were implanted in the 3 respiratory muscles (4 in each muscle group). Tidal volume with diaphragmatic stimulation was 310 +/- 38 mL (mean +/- SE); with upper intercostal stimulation, it was 68 +/- 18 mL; and with combined diaphragm intercostal stimulation, it was 438 +/- 78 mL. By study design, stimulation in the upper intercostal muscles was limited to not more than slight/moderate contraction of the serratus and latissimus muscles overlying the ribs. Abdominal muscle stimulation produced exhaled volumes of 38 +/- 20 mL (this stimulation was limited by the maximal output of the stimulator of 25 milliamperes). Combined diaphragm intercostal stimulation followed by abdominal muscle stimulation increased exhaled volumes from 312 +/- 31 mL to 486 +/- 58 mL (P = 0.024).Permaloc electrodes can be successfully implanted in upper intercostal and abdominal muscles in addition to the diaphragm. Combined diaphragm intercostal stimulation followed by abdominal muscle stimulation increased the exhaled volumes recorded with diaphragmatic stimulation alone.

Respiratory distress (RD), a term utilised to summate a conglomeration of clinical features, including tachypnoea, use of accessory muscles of respiratory, lower chest wall indrawing, grunting, hypoxaemia and cyanosis, is useful in determining severity of illness in childhood. While these features commonly reflect pathology in the respiratory system, a condition accounting for the vast majority of the 10.8 million under-five childhood deaths occurring globally each year, dysfunction in other organ systems may also present with features of respiratory distress. The World Health Organization (WHO) has utilised some of these clinical findings to classify the severity of pneumonia and to advocate management under its programme of integrated management of childhood illness. The WHO has identified the following three essential steps that would help reduce mortality from pneumonia: (1) recognition of a sick child, (2) appropriate seeking of care, and (3) management of the underlying condition. Despite th...

Neuromuscular respiratory failure is the cause of death in the majority of patients with ALS. Respiratory muscle dysfunction impacts on quality of life and survival. Attentive management of respiratory muscle weakness is an important aspect of the management of the ALS patient. The respiratory muscles may be thought of as four functional groups: the inspiratory muscles, the expiratory muscles, the accessory muscles of respiration, and the upper airway muscles. This paper will review the structure and function of the neuromuscular respiratory system, and the evaluation and management of respiratory muscle dysfunction in ALS patients.

Several anatomical and physiological features of the respiratory system in infants (age ,1 yr) and young children render them susceptible to airway obstruction. The upper and lower airways are small, prone to occlusion by secretions, and susceptible to oedema and swelling. As resistance to laminar airflow increases in inverse proportion to the fourth power of the radius (Poiseuille’s law), a small decrease in the radius of the airway results in a marked increase in resistance to airflow and the work of breathing. The support components of the airway are less developed and more compliant than in the adult. The ribs are cartilaginous and perpendicular relative to the vertebral column, reducing the effect of the ‘bucket handle’ movement of the rib cage. In addition, the intercostal muscles and accessory muscles of ventilation are immature. As a result, children are more reliant on the diaphragm for inspiration. Increased respiratory effort causes subcostal and sternal recession, and the mechanical efficiency of the chest wall is reduced. Higher metabolic rate and increased oxygen demand mean children with airway compromise can deteriorate very quickly. Also, with a smaller functional residual capacity and fewer fatigueresistant fibres in the diaphragm, there is little respiratory reserve at times of stress.

Leith and Bradley's1 work in the 1970s first applied principles of strength and endurance training to the muscles of respiration. A considerable body of research into respiratory muscle training (RMT) has since accumulated. To date, most evidence supporting RMT is derived from healthy and athletic persons and from cardiorespiratory patient groups.2,3 A number of studies have also investigated RMT in patients with neurologic conditions, including stroke.4,5

2 ABSTRACT | Objective: To investigate the respiratory and postural adaptations associated with mouth and nasal breathing and to evaluate the associations of such adaptations in mouth breathers' self-perceived quality of life. Method: Cross- sectional study with mouth breathers (initial n=116 and final n=48) and nasal breathers (initial n=131 and final n=24) from elementary school, aged between 7 and 14 years. Chest expansion, using cirtometry, the breathing pattern and the use of accessory muscles, by means of clinical evaluations and photogrammetry, and flexibility tests were evaluated in both groups. Subsequently, the mouth breathers were asked to complete the quality of life questionnaire. Statistical tests: Chi-square, odds ratio, Mann-Whitney, and binomial tests were first applied followed by logistic regressions. Results: Thoracic breathing (p=0.04), using of accessory muscles (p=0.03) and reductions in flexibility ( p=0.001) increased the chances of an individual being a mouth breather when compared to nasal breathers. Subsequently, using of accessory muscles decreased the chances of snoring among mouth breathers (p=0.03); the presence of shoulder asymmetry reduced the chances of experiencing quiet sleep (p=0.05) and increased the chances of coughing or being tired when playing or running (p=0.008). Finally, forward head position reduced the chances of waking up at night (p=0.04) and experiencing shortness of breath (p=0.05). Conclusions: Respiratory and postural adaptations increased the chances of individuals persisting with mouth breathing. Additionally, these adaptations could be associated with mouth breathers' self-perceived quality of life.

This article provides a critical review of inspiratory muscle training (IMT) in chronic obstructive pulmonary disease (COPD). Although extensive research on IMT has accumulated, its benefits have been debated, primarily because of methodological limitations of studies. Using relevant key words, multiple databases were searchedfrom 1966. Selected studies used PI^sub max^ (maximal inspiratory pressure) as an outcome variable. Overall, research demonstrated that a standard protocol of 30% or higher for a duration of 20 to 30 minutes per day for 10 to 12 weeks improves dyspnea and inspiratory strength and endurance with either inspiratory resistive or inspiratory threshold training. Regardless of method, IMT protocols for people with COPD and inspiratory muscle weakness and dyspnea are generally safe, feasible, and effective. Patient selectivity and study of subgroups are recommended. Keywords: inspiratory muscle training; respiratory muscle dysfunction; respiratory muscle training Inspiratory muscle training (IMT), though not always by that name, has been evident in the literature since the mid-l970s. Various terms have been used to describe this intervention, including ventilatory, respiratory, and IMT, though the latter is currently predominant. Regardless of technique, which has also evolved over time, the purpose of IMT is to improve the performance of the inspiratory muscles, which may be limited in a variety of conditions. Interest in IMT as a means to treat respiratory muscle dysfunction has grown over the past two decades; recently, IMT was included in the Cochrane Database of Systematic Reviews (Bradley, Moran, & Greenstone, 2002; Ram, Picot, Barnes, & Polkey, 2002). IMT has been used in an increasingly wide range of clinical situations, but the benefits continue to be debated. One of the predominant reasons is related to methodological concerns of the studies conducted to date. The purpose of this article is to provide a comprehensive, critical review of IMT. No attempt will be made to address expiratory muscle training since the overwhelming majority of the research has been conducted in the area of IMT. Scientific knowledge is most extensive in the area of chronic obstructive pulmonary disease (COPD), yet many questions remain. This analysis will focus on the efficacy of IMT in relationship to specific outcomes, including inspiratory muscle strength and endurance, dyspnea, functional performance outcomes, and health-related quality of life (HRQOL). This paper will include a review of the pathophysiologic basis and clinical significance of respiratory muscle dysfunction, a rationale for and principles of training respiratory skeletal muscles, a mechanism of action and types of IMT, and a critical review of the research related to IMT in COPD. PATHOPHYSIOLOGIC BASIS OF RESPIRATORY MUSCLE DYSFUNCTION The muscles primarily responsible for inspiration include the diaphragm, the intercostal muscles, and the scalene, with accessory muscles recruited during increased ventilation levels (Reid, Clarke, & Wallace, 2001); exhalation is generally passive (Breslin, 1996). The respiratory muscles uniquely perform other nonventilatory functions as well. Reduced function of the respiratory muscles, which may be acute or chronic (Breslin, 1996), has been attributed to their weakness (Rochester, 1991) or fatigue (Roussos, Moxham,B fatigue occurs whenever energy demand exceeds supply (Roussos, 1985) and results in the inability to generate or maintain the forces needed for respiration (Larson & Kim, 1987a). This decline in force is related to both reduced central motor drive as well as peripheral muscle contractile failure (Roussos&Zakynthinos, 1996) that may be interdependent (Enoka&Stuart, 1992). …

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.

Changes in intrathoracic pressure produced by the various inspiratory intercostals are essentially additive, but the interaction between these muscles and the diaphragm remains uncertain. In the present study, this interaction was assessed by measuring the changes in airway opening (ΔPao) or transpulmonary pressure (ΔPtp) in vagotomized, phrenicotomized dogs during spontaneous inspiration (isolated intercostal contraction), during isolated rectangular or ramp stimulation of the peripheral ends of the transected C5 phrenic nerve roots (isolated diaphragm contraction), and during spontaneous inspiration with superimposed phrenic nerve stimulation (combined diaphragm-intercostal contraction). With the endotracheal tube occluded at functional residual capacity, ΔPao during combined diaphragm-intercostal contraction was nearly equal to the sum of the ΔPao produced by the two muscle groups contracting individually. However, when the endotracheal tube was kept open, ΔPtp during combined contraction was 123% of the sum of the individual ΔPtp ( P < 0.001). The increase in lung volume during combined contraction was also 109% of the sum of the individual volume increases ( P < 0.02). Abdominal pressure during combined contraction was invariably lower than during isolated diaphragm contraction. It is concluded, therefore, that the canine diaphragm and intercostal muscles act synergistically during lung expansion and that this synergism is primarily due to the fact that the intercostal muscles reduce shortening of the diaphragm. When the lung is maintained at functional residual capacity, however, the synergism is obscured because the greater stiffness of the rib cage during diaphragm contraction enhances the ΔPao produced by the isolated diaphragm and reduces the ΔPao produced by the intercostal muscles.

1. Divisao de Pneumologia, Instituto do Coracao, Hospital das Clinicas, Faculdade de Medicina, Universidade de Sao Paulo, Sao Paulo (SP) Brasil. Interstitial lung diseases (ILDs) are a heterogeneous group of parenchymal lung disorders characterized by permanent structural changes that result in mechanical modifications, notably a significant reduction in the elasticity of the lung parenchyma.(1) Among individuals with ILDs, dyspnea and lower exercise tolerance are quite common complaints, varying in severity and having psychosocial repercussions, as well as a negative impact on quality of life, affecting the patients and their families. (2) Many factors, alone or in combination, can contribute to those symptoms, including altered gas exchange, airflow limitation, pulmonary vascular involvement (usually by pulmonary capillary destruction and hypoxemia-induced vasoconstriction) and left ventricular dysfunction, as well as impairment of the respiratory musculature and accessory muscles,(1-8) together with possible mechanisms specifically related to the etiology of the ILD in question.

When extra-diaphragmatic muscles are activated progressively under approximately isometric conditions, we expect a corresponding increase in respiratory muscle output. Therefore, we examined relative recruitment shown as the latency to onset of EMG activity, and the relationship between mouth pressure and electromyogram activity of the neck accessory and transversus abdominis (TRANS) muscles during respiratory maneuvers against occlusion. Fine wire electrodes were inserted into the scalene (SCLN), sternocleidomastoid (STERNO), trapezius (TRAPZ) and TRANS in six awake, healthy subjects. Mouth pressure, raw and moving average EMG signals were recorded during gradual production of expiratory or inspiratory mouth pressure to maximum (MPmax) at FRC in the standing posture. Group mean linear regression lines of EMG activity versus mouth pressure were strongly significant for SCLN and TRANS, less for STERNO, and least for TRAPZ. The SCLN and STERNO showed EMG activities with low, and TRAPZ showed EMG activity only with high, mouth pressure. At 90% MPmax, TRAPZ was much less active compared with TRANS, SCLN, or STERNO. These results suggest that over a wide range of respiratory effort there is a significant difference in the relationship between mouth pressure and EMG activity in the accessory muscles, with differential recruitment of individual respiratory muscles.

SUMMARYThe axial muscles of terrestrial vertebrates serve two potentially conflicting functions, locomotion and lung ventilation. To differentiate the locomotor and ventilatory functions of the hypaxial muscles in mammals, we examined the locomotor and ventilatory activity of the trunk muscles of trotting dogs under two conditions: when the ventilatory cycle and the locomotor cycle were coupled and when they were uncoupled. Patterns of muscle-activity entrainment with locomotor and ventilatory events revealed (i)that the internal and external abdominal oblique muscles performed primarily locomotor functions during running yet their activity was entrained to expiration when the dogs were standing, (ii) that the internal and external intercostal, external oblique thoracic and transversus abdominis muscles performed both locomotor and respiratory functions simultaneously, (iii) that the parasternal internal intercostal muscle performed a primarily respiratory function (inspiration) and (iv) that the deep pectoralis and longissimus dorsi muscles performed only locomotor functions and were not active while the dogs were standing still. We conclude that the dual function of many hypaxial muscles may produce functional conflicts during running. The redundancy and complexity of the respiratory musculature as well as the particular pattern of respiratory—locomotor coupling in quadrupedal mammals may circumvent these conflicts or minimize their impact on respiration.