Accessory Inspiratory Muscles Research Articles

Features of inspiratory muscles’ functional state in chronic heart failure with preserved ejection fraction

BACKGROUND: It is known that chronic heart failure contributes to the development of multiple organ pathology, including skeletal muscle pathology. AIM: To determine the strength and electrical activity of the inspiratory muscles in patients with chronic heart failure with preserved left ventricular ejection fraction. MATERIAL AND METHODS: The study involved 80 patients of both sexes aged 45 to 74 years, who were divided into three groups: the first group consisted of 24 patients with stage IIA chronic heart failure, the second group consisted of 20 patients with stage I chronic heart failure, and the third group (control group) consisted of 36 patients without chronic heart failure. All patients underwent serum N-terminal fragment of natriuretic brain propeptide determination, 6-minute walk test, measurement of inspiratory muscle strength, and surface electromyography of the inspiratory muscles using three exercise tests. The statistical significance of differences between the groups was assessed using the Mann–Whitney test and Pearson χ2. RESULTS: It was found that when dividing the groups by gender, the maximum inspiratory pressure in women of the first group was lower than in women of the control group by 31.5% (p=0.006). In patients of the first group, a smaller increase in the amplitude of the diaphragm electromyogram was recorded in the 1st test — with maintaining an inspiratory effort of 30% power for 15 s by 27.9% (p=0.010), 26.1% (p=0.025) and 40.7% (p=0.033) at the 5th, 10th and 15th seconds, respectively, in the 2nd test — with maintaining an inspiratory effort of 50% power for 5 s, by 32.6% (p=0.041) at the 5th second, in the 3rd test — with maintaining an inspiratory effort of 70% power for 5 s, by 42.8% (p=0.009) at the 5th second compared to the control group. At the same time, a more pronounced decrease in the electromyogram frequency was noted in the 1st sample — by 24.2% (p=0.048), 24.7% (p=0.030) compared to the control group, which serves as a sign of fatigue. On the accessory inspiratory muscles, the amplitude increase was higher in patients of the first group compared to the control group, which indicates activation of additional motor units: on the external intercostal muscles in the 1st sample — by 31.7% (p=0.032), 37.9% (p=0.044), in the 2nd sample — by 28.9% (p=0.048), 43.1% (p=0.036); on the sternocleidomastoid muscle in the 1st sample — by 66.1% (p=0.033), 49.4% (p=0.043), in the 2nd sample — by 128.6% (p=0.032). CONCLUSION: In patients with chronic heart failure stage IIA, surface electromyography using stress tests revealed diaphragm fatigue and increased activity of accessory inspiratory muscles.

Differences of ventilatory muscle recruitment and work of breathing in COPD and interstitial lung disease during exercise: a comprehensive evaluation.

COPD and interstitial lung disease (ILD) are significant chronic respiratory disorders, impacting quality of life. Respiratory muscle roles and differences remain not entirely clear. The objective of the present study was to evaluate the degree of recruitment of the respiratory muscles and the work of breathing in COPD and ILD during exercise. We compared the sensory-mechanical relationships in COPD, ILD and healthy controls (n=20 each). They performed pulmonary function, noninvasive and invasive respiratory muscle strength, surface electromyography and work-of-breathing assessments. COPD and ILD did not show lower static muscle strength compared to controls, but did show poor performance in the exercise test with increased transdiaphragmatic pressure (P di). In ILD, there was a higher increase in oesophageal pressure and a lower gastric pressure (P ga) on inspiration; in COPD, there was a significant increase in P ga on inspiration. In ILD, there is greater recruitment of accessory inspiratory muscles, whereas in COPD, there is marked use of both inspiratory and expiratory muscles. The neuromechanical inefficiency (increased neural respiratory drive without the corresponding tidal volume) was found in both diseases. In COPD, there is a considerable increase in elastic work to overcome intrinsic positive end-expiratory pressure (PEEPi) and expiratory work of breathing, whereas in ILD, non-PEEPi elastic work of breathing is the highest part of the total work of breathing. Early and increased activity of the respiratory muscles and work-of-breathing components significantly contribute to dyspnoea, exercise intolerance and neuromechanical inefficiency of ventilation in COPD and ILD. The mechanisms of P di generation were different between diseases.

Effect of tone normalizing massage on stiffness of accessory inspiratory muscles in patients with COPD

The aim of this study was to evaluate the effect of medical massage on inspiratory accessory muscle function and sensory sensitivity in patients with chronic obstructive pulmonary disease. The participants were divided into two groups: group II (22 patients with COPD in the stable period), and group II (II: 17 participants with no respiratory disorders). Each group was subjected to a series of five massages. The treatment was performed for the sternocleidomastoid, levator scapulae, and the descending part of the trapezius muscle. The parameters of muscle frequency and stiffness were measured using a Myoton Pro Digital device. The compression sensitivity was measured using a Force algometer. The results obtained showed significant differences in the stiffness parameters of the muscles studied between the groups, which indicates a positive effect of massage on muscle function in patients with COPD. The greatest significant differences were found in the patient’s sensitivity parameters. The application of the massage series significantly improved the parameters of frequency and decreased stiffness of inspiratory accessory muscles in patients with COPD compared to the group of healthy participants. This massage is an effective method to normalize muscle tone and thus improve the functional status of patients with COPD.

Abstract P342: Acute Nasal Breathing Lowers Blood Pressure And Increases Parasympathetic Contributions To Heart Rate Variability In Young Adults

Introduction: Interest is growing in how breathing pace, pattern, and training (e.g., device-assisted or -resisted breathing) affect prognostic cardiovascular variables (e.g., blood pressure (BP)). Nasal breathing increases bronchodilation via airway epithelium nitric oxide production, increases diaphragmatic movement, and reduces accessory inspiratory muscle recruitment. Despite these changes, the effect of nasal compared with oral breathing (i.e., breathing route) on prognostic cardiovascular variables is unclear. Hypothesis: We hypothesized that nasal compared with oral breathing would acutely lower BP and improve heart rate variability (HRV) metrics. Methods: We tested 20 young healthy adults in this study (13 Female/7 Male; age: 18 [1] years, median [IQR]; body mass index: 23 ± 2 kg•m -2 , screening systolic / diastolic BP 116 ± 12 / 67 ± 7 mmHg mean ± SD). Participants self-selected their breathing rate during a five-minute ‘run-in’ period. Using a metronome, their breathing rate was fixed during two subsequent (random order) five-minute resting periods with nasal and oral breathing while we measured brachial BP and HRV metrics via ECG. We compared data between conditions using a Wilcoxon signed-rank paired test (data presented as median [IQR]) or using paired, two-tailed t-tests (data presented as mean ± SD). We set the significance to p <0.05. Results: Nasal breathing lowered mean (nasal: 84 ± 7 vs. oral: 86 ± 5 mmHg, p =0.006, Cohen’s d =0.70) and diastolic (nasal: 68 [8] vs. oral: 72 [5] mmHg, p <0.001, Rank-biserial correlation=0.89), but not systolic (nasal: 116 ± 11 vs. oral: 117 ± 9 mmHg, p =0.48, Cohen’s d =0.16) BP. Nasal breathing also raised the High-Frequency contribution to HRV (nasal: 59 ± 19 vs. oral: 52 ± 21 %, p =0.04, Cohen’s d =0.50) and lowered the Low-Frequency to High-Frequency ratio (nasal: 0.9 ± 0.8 vs. oral: 1.2 ± 0.9, p =0.04, Cohen’s d =0.49), suggesting a greater parasympathetic contribution to HRV. There were no differences between conditions for heart rate ( p= 0.90) or time-domain HRV metrics ( ps ≥0.07; e.g., the standard deviation of NN intervals). Conclusion: These data suggest that nasal compared with oral breathing acutely lowers mean and diastolic BP as well as potentially increases parasympathetic contributions to HRV.

Effects of high-intensity inspiratory muscle warm-up on inspiratory muscle strength and accessory inspiratory muscle activity

This study aimed to determine the effects of work-matched moderate-intensity and high-intensity inspiratory muscle warm-up (IMW) on inspiratory muscle strength and accessory inspiratory muscle activity. Eleven healthy men performed three IMWs at different intensities, namely, placebo, moderate-intensity, and high-intensity, set, respectively, at 15 %, 40 %, and 80 % of maximal inspiratory mouth pressure (MIP). MIP was measured before and after IMW. Electromyography (EMG) was recorded for the sternocleidomastoid muscle (SCM) and intercostal muscles (IC) during IMW. MIP increased significantly in the moderate-intensity condition (104.2 ± 5.1 %, p < 0.05) and high-intensity condition (106.5 ± 6.2 %, p < 0.01) after IMW. The EMG amplitudes of the SCM and IC during IMW were significantly higher in the order of high-intensity, moderate-intensity, and placebo conditions. There was a significant correlation between changes in MIP and EMG amplitude of the SCM (r = 0.60, p < 0.01) and IC (r = 0.47, p < 0.01) during IMW. These findings suggest that high-intensity IMW increases neuromuscular activity in the accessory inspiratory muscles, which may improve inspiratory muscle strength.

Expiratory and inspiratory action of transversus abdominis during eupnea and hypercapnic ventilation

BackgroundRecently, there is interest in the clinical importance of monitoring abdominal muscles during respiratory failure. The clinical interpretation relies on the assumption that expiration is a passive physiologic process and, since diaphragm and abdomen are arranged in series, any inward motion of the abdominal wall represents a sign of diaphragm dysfunction. However, previous studies suggest transversus abdominis might be active even during eupnea and is preferentially recruited over the other abdominal muscles. Objective1) Is transversus abdominis normally recruited during eupnea? 2) What is the degree of activation of transversus abdominis during hypercapnia? 3) Does the end-inspiratory length of transversus abdominis change during hypercapnia, while diaphragm function is normal? MethodsIn 30 spontaneously breathing canines, awake without confounding anesthetic, we measured directly both electrical activity and corresponding mechanical length and shortening of transversus abdominis during eupnea and hypercapnia. ResultsTransversus abdominis is consistently recruited during eupnea. During hypercapnia, transversus abdominis recruitment is progressive and significant. Throughout hypercapnia, transversus abdominis baseline end-inspiratory length is not constant: baseline length decreases progressively throughout hypercapnia.After expiration, into early inspiration, transversus abdominis shows a consistent neural mechanical post -expiratory expiratory activity (PEEA) at rest, which progressively increases during hypercapnia. ConclusionTransversus abdominis is an obligatory expiratory muscle, reinforcing the fundamental principle expiration is not a passive process. Beyond expiration, during hypercapnic ventilation, transversus abdominis contributes as an “accessory inspiratory muscle” into the early phase of inspiration. Clinical monitoring of abdominal wall motion during respiratory failure may be confounded by action of transversus abdominis.

Functional Condition Of Inspiratory Muscles In Obstructive Sleep Apnea Patients

Background — Recurrent upper airway obstruction during the sleep is a key feature of obstructive sleep apnea (OSA). In patients with OSA, an intermittent upper airway obstruction yields an increase in inspiratory effort and, consequently, an augmented impact on inspiratory muscles (IM). However, the issue of IM fatigue development in OSA patients is still controversial. Objective — to investigate the functional condition of IM in patients with OSA of various degrees of severity. Material and Methods — Were examined 82 men (30-65 years old), who were distributed among four groups depending on the OSA severity. Cardiorespiratory monitoring was performed to detect OSA. IM electrical activity was detected via surface electromyography (EMG) while holding the breath (during the inhalation). Results — In the course of our study, we detected a reduction in the frequency of EMG of accessory IM, specifically sternocleidomastoid muscle (SCMM) and external intercostal muscles (EIM), accompanied by a simultaneous increase in the amplitude of EMG of SCMM, EIM, and diaphragm (D), while holding the breath (during the inhalation), in the group of patients without OSA. In patients with mild OSA, when holding the breath during the inhalation, the frequency of EMG of SCMM and EIM decreased, while the amplitude of SCMM and EIM increased. In patients with moderate OSA, when holding the breath during the inhalation, a decrease in the frequency of SCMM EMG with a simultaneous increase in the amplitude of the EIM EMG were revealed. Same maneuver in the group of patients with severe OSA yielded no significant changes in the frequency and amplitude of EMG of respiratory muscles. Conclusion — Periodic obstruction of the upper airways with OSA leads to the development of fatigue resistance in accessory IM.

The Role of Diaphragmatic Rapid Shallow Breathing Index and Maximum Inspiratory Pressure in Predicting Outcome of Weaning From Mechanical Ventilation

Abstract Background Mechanical ventilation is the defining event of intensive care unit (ICU) management. It is a lifesaving intervention in patients with acute respiratory failure and whose spontaneous ventilation is inadequate for subsequent development of life threatening hypoxia and/or respiratory acidosis. Many physicians simply look at the patient’s ability to tolerate a spontaneous breathing trial (SBT) without distress through the respiratory rate (RR) and TV during the SBT. The RR/TV ratio, i.e., the rapid shallow breathing index (RSBI), one of the most used clinical indices to predict weaning outcome, reflects the balance between mechanical load posed on the inspiratory muscles and the inspiratory muscles ability to face it during the weaning attempt. However, RSBI was found to have both variable sensitivity and specificity for predicting weaning outcome. Although the diaphragm plays a fundamental role in generating TV in healthy subjects, if the diaphragmatic efficiency is impaired the accessory inspiratory muscles mild contribute to the ventilation for a limited period of time, for example during a SBT. However, since they are by far less efficient and more fatigable than the diaphragm, their exhaustion was likely lead to weaning failure in subsequent hours. Hence, the contribution of the accessory muscles to TV could compromise the diagnostic accuracy of the RSBI by masking the underlying diaphragmatic dysfunction. Aim of the Work To assess the accuracy of Diaphragmatic Rapid shallow breathing index and Maximum inspiratory pressure in predicting the outcome of weaning from mechanical ventilation. Patients and Methods The study was conducted at Ain Shams University Hospitals over 6 months on Patients who were mechanically ventilated for more than 48 hrs who were ready for weaning. Inclusion Criteria Patients intubated &amp; mechanically ventilated for more than 48 hrs. Patients at their first SBT.Patients with adequate cough reflex. Patients fulfilling criteria of readiness for weaning from mechanical ventilation after resolution of cause of respiratory failure: Patients with score ranging between -1 and +1 on the Richmond Agitation and sedation scale (RASS). Exclusion criteria Age &amp;lt; 18 yrs. Patients with thoracotomy, pneumothorax, or pneumomediastinum. Patients with presence of flail chest or rib fractures. Patients with neuromuscular disease. Use of muscle-paralyzing agents within 48 hours before the study. History or new detection of paralysis or paradoxical movement of a single hemi diaphragm on diaphragmatic ultrasonography. Pregnant females. Unconscious noncooperative patients. Patients with intra-abdominal hypertension, Long term steroid therapy. Results I- Distribution of the studied patients regarding final outcome. II- Demographic data. III. Causes of MV. IV- Days on MV. V- Patients’ data and characteristics before start of weaning trial. VI- SBT Ventilator Breathing pattern after 30 min. VII- Study predictors. Conclusion D-RSBI is a new and promising tool that is superior to the traditional RSBI in predicting weaning outcome also MIP provides appreciated data with greater accuracy to assess inspiratory muscle strength and predicting weaning success in mechanically ventilated patients. Recommendations We could recommend the measurement of MIP and DRSBI as weaning predictors should be an integral part of evaluation of patients plan for weaning from MV. All intensivists should be acquitted with the use of U/S in the evaluation of diaphragmatic function.

Hemodynamics of the sternocleidomastoid measured with frequency domain near-infrared spectroscopy towards non-invasive monitoring during mechanical ventilation.

Mechanical ventilation (MV) is used to assist spontaneous breathing in critically ill patients in the intensive care unit (ICU). MV is a cornerstone of critical care medicine but it is now known that inspiratory muscle dysfunction due to injury, disuse, and/or atrophy during MV plays a major role in outcomes for these patients. For example, prolonged MV is strongly correlated with dysfunction of the sternocleidomastoid (SCM), an accessory inspiratory muscle that has been linked to weaning failure from MV. Hemodynamic monitoring of the SCM may provide an important non-invasive and real-time means to monitor MV. In this work, we first conducted multi-layer Monte Carlo simulations to confirm the ability of near infrared light to detect changes in the oxygenation of the SCM over wide ranges of skin tones and adipose layer thicknesses. We then optimized a custom digital frequency domain near-infrared spectroscopy (FD-NIRS) system for continuous 10 Hz measurements of the SCM at 730 nm and 850 nm. A healthy volunteer study was conducted (N=10); subjects performed sets of isometric neck flexions of the SCM. Substantial changes in oxyhemoglobin + oxymyoglobin (oxy[Hb + Mb]), deoxyhemoglobin + deoxymyoglobin (deoxy[Hb + Mb]), and total hemoglobin + myoglobin (total[Hb + Mb]) were observed during sustained and intermittent isometric flexions. There were notable sex differences observed in the magnitude of hemodynamic changes (∼2x larger changes in males for oxy[Hb + Mb] and deoxy[Hb + Mb]). The magnitude of hemodynamic changes when taking into account µs' changes during flexions was ∼ 2-2.5x larger as compared to assuming constant scattering (CS), which is a common assumption used for continuous wave (CW) NIRS methods. This study suggests that FD-NIRS provides improved accuracy for hemodynamic monitoring of the SCM compared to CW-NIRS, and that FD-NIRS may provide value for SCM monitoring during MV.

Utilization of pectoralis minor accessory inspiratory muscles in a rodent model of respiratory motor neuron loss

Ventilatory failure, and ultimately death, occurs in patients with neuromuscular diseases due to the loss of respiratory motor neurons (e.g., phrenic and intercostal). Prior to ventilatory failure, patients are able to maintain breathing potentially via recruitment of accessory inspiratory muscles (e.g., pectoralis minor, which are responsible for lifting the ribs upward and outward to move the chest wall following increased ventilatory demand). Since genetic rodent models of motor neuron loss develop global symptoms (e.g., dysphagia, etc.), we have developed an inducible model of only respiratory motor neuron death in order to study how breathing is impacted, and to ultimately develop targeted therapeutic interventions. Briefly, adult male rats are intrapleurally injected with cholera toxin B conjugated to saporin (CTB-SAP) that is retrogradely transported to the spinal cord, resulting in selective elimination of phrenic and intercostal motor neurons. Despite deficits in maximal ventilatory capacity and diaphragmatic output following intrapleural CTB-SAP, eupnea is maintained at 7 days (d) and 28d post-injection. Thus, we hypothesize that pectoralis minor accessory inspiratory muscle activity is increased to maintain eupnea over the course of respiratory motor neuron loss in CTB-SAP rats. To test our hypothesis, we intrapleurally injected adult male rats with bilateral CTB-SAP or control (CTB unconjugated to SAP), and 7d and 28d later studied: 1) pectoralis minor motor neuron survival using immunohistochemistry; and 2) pectoralis minor output at baseline and in response to a maximal ventilatory challenge (hypercapnia + hypoxia; max) in anesthetized, spontaneously breathing rats (n=15/group) via electromyography. Thus far, our data suggests that although the pectoralis minor motor nucleus is in close proximity to the phrenic motor nucleus, these pools are exclusive from each other and pectoralis minor motor neuron survival is unaffected following intrapleural CTB-SAP (p>0.05). Additionally, pectoralis minor muscle amplitude is significantly increased in 7d and 28d intrapleurally injected CTB-SAP rats vs. controls (p<0.05) and in 28d vs. 7d CTB-SAP rats at baseline and max (p<0.05). To test whether pectoralis minor muscles are necessary for maintaining eupnea, we evaluated breathing via whole-body plethysmography in unanesthetized adult male rats following bilateral intrapleural and intramuscular pectoralis minor muscle CTB-SAP injections vs. controls (n=3/group). Our preliminary data suggests that eupneic frequency is increased, but tidal volume is decreased in 7d CTB-SAP rats vs. controls, and our 28d experiments are currently being conducted. In conclusion, our data suggests that the pectoralis minor muscles have an independent motor pool that can become recruited to assist in maintaining eupnea following intrapleural CTB-SAP-induced respiratory motor neuron loss. This study furthers our understanding of the contribution of the pectoralis minor muscles to maintaining eupnea following respiratory motor neuron loss, and suggests that these muscles could potentially be further stimulated and harnessed to significantly prolong and/or improve breathing in patients with neuromuscular disease.

A Review on the Effect of Kinesiotaping on Lung Function and Perception of Dyspnea in COPD Patients

Background: Chronic Obstructive Pulmonary Disease (COPD) is complicated by the presence of frequent and recurrent acute exacerbations. The patients are asymptomatic and stable in the early stages. They develop weakness of primary respiratory muscles and use accessory muscles, which lead to postural changes. The forward head posture is very common in COPD patients due to increased usage of accessory muscles and aging changes. Kinesiotaping application has been used to correct posture and lung function recently. Objective: The aim of this paper is to review the evidence on the effect of Kinesiotaping on lung function and posture in COPD patients. Methods: The research articles published in the major databases including Web of Science, Pubmed, and Google Scholar, were searched from January 2010 to January 2021 to be included in the review. Twenty-one articles were retrieved and six articles were selected for the review based on the inclusion criteria. Results: The studies indicate that Kinesiotaping of the thoracic wall in COPD patients has an immediate effect on accessory inspiratory muscle activity, chest expansion, pulmonary function, and postural alignment. Further research is required to determine the long-term effects of this special taping method in comparison with conventional therapy in COPD patients. Conclusion: The application of kinesiotaping as an adjunct to conventional breathing exercises in COPD patients helps in improving lung function, posture and reduces the perception of dyspnea.

Unilateral diaphragmatic paralysis: inspiratory muscles, breathlessness and exercise capacity.

BackgroundPatients with unilateral diaphragmatic paralysis (UDP) may present with dyspnoea without specific cause and limited ability to exercise. We aimed to investigate the diaphragm contraction mechanisms and nondiaphragmatic inspiratory muscle activation during exercise in patients with UDP, compared with healthy individuals.MethodsPulmonary function, as well as volitional and nonvolitional inspiratory muscle strength were evaluated in 35 patients and in 20 healthy subjects. Respiratory pressures and electromyography of scalene and sternocleidomastoid muscles were continuously recorded during incremental maximal cardiopulmonary exercise testing until symptom limitation. Dyspnoea was assessed at rest, every 2 min during exercise and at the end of exercise with a modified Borg scale.Main resultsInspiratory muscle strength measurements were significantly lower for patients in comparison to controls (all p<0.05). Patients achieved lower peak of exercise (lower oxygen consumption) compared to controls, with both gastric (−9.8±4.6 cmH2O versus 8.9±6.0 cmH2O) and transdiaphragmatic (6.5±5.5 cmH2O versus 26.9±10.9 cmH2O) pressures significantly lower, along with larger activation of both scalene (40±22% EMGmax versus 18±14% EMGmax) and sternocleidomastoid (34±22% EMGmax versus 14±8% EMGmax). In addition, the paralysis group presented significant differences in breathing pattern during exercise (lower tidal volume and higher respiratory rate) with more dyspnoea symptoms compared to the control group.ConclusionThe paralysis group presented with exercise limitation accompanied by impairment in transdiaphragmatic pressure generation and larger accessory inspiratory muscles activation compared to controls, thereby contributing to a neuromechanical dissociation and increased dyspnoea perception.

Effects of Inspiratory Muscles Training Plus Rib Cage Mobilization on Chest Expansion, Inspiratory Accessory Muscles Activity and Pulmonary Function in Stroke Patients

After stroke, limited ribcage movement may lead to impaired respiratory function. Combining threshold inspiratory muscle training with rib cage joint mobilization has been shown to enhance the recovery of respiratory function in patients with stroke. The present study investigated whether the combination of rib cage joint mobilization and inspiratory muscle training would improve chest expansion, inspiratory muscle activity, and pulmonary function after stroke. Thirty stroke patients were recruited and randomly assigned to one of the two groups, namely 6-week rib cage joint mobilization with inspiratory muscle training (experimental group) or inspiratory muscle training alone (control group). Outcome measures included upper and lower chest expansion, activity of accessory inspiratory muscles (latissimus dorsi (LD) and upper trapezius (UT)), and pulmonary function (forced vital capacity (FVC), forced expiratory volume in 1 s (FEV1), and peak expiratory flow (PEF)). All evaluations were conducted at baseline and after 6 weeks of inspiratory muscle training. Significant increases were observed in upper and lower chest expansion, LD and UT muscle activity, FVC, FEV1, and PEF in both the groups. Upper and lower chest expansion and muscle activity of UT and LD were significantly higher in the experimental group than in the control group. No significant differences were observed in FVC, FEV1, and PEF between the groups. Inspiratory muscle training is effective in improving chest expansion, inspiratory muscle activity, and pulmonary function after stroke. The addition of rib cage joint mobilization further increases chest expansion and inspiratory muscle activity.

The Effect of Breathing Exercise Using Visual Feedback on Muscle Activation of Accessory Inspiratory Muscles

The Effect of Breathing Exercise Using Visual Feedback on Muscle Activation of Accessory Inspiratory Muscles

Pectoralis Minor Activity in a Rodent Model of Respiratory Motor Neuron Loss

Patients with neuromuscular diseases experience loss of respiratory motor neurons (i.e., phrenic and intercostal) resulting in ventilatory failure, and ultimately death. No treatment is currently available to significantly prolong and/or improve breathing in these diseases. Since genetic rodent models of motor neuron loss develop global symptoms (e.g., dysphagia, limb paralysis, etc.), we have developed an inducible model of only respiratory motor neuron death in order to study how motor neuron loss impacts respiration and to develop therapeutic interventions. Briefly, adult rats are intrapleurally injected with cholera toxin B conjugated to saporin (CTB‐SAP) that is retrogradely transported to the phrenic and intercostal motor nuclei of the spinal cord, which results in selective elimination of phrenic and intercostal motor neurons. Despite deficits in maximal ventilatory capacity following CTB‐SAP, eupneic ventilation is maintained. Our preliminary data suggest that one way eupnea may be maintained in CTB‐SAP rats is via the recruitment of G‐coupled protein receptor‐dependent pathways to cause respiratory plasticity in the phrenic motor nucleus over the course of phrenic motor neuron death. However, our preliminary data also indicate that diaphragmatic amplitude appears to be decreased at baseline in CTB‐SAP rats vs. controls; thus, phrenic respiratory plasticity may only account for a portion of the maintenance of eupneic ventilation. We speculate that eupnea is also maintained through the recruitment of accessory inspiratory muscles (e.g., the pectoralis minor muscles) in the face of respiratory motor neuron loss. Pectoralis minor muscles are not normally utilized for eupnea, but have been shown to increase their activity to actively elevate the ribs upward and outward to move the chest wall following increased ventilatory demand (e.g., in response to disease or injury including spinal cord injury and bilateral diaphragmatic paralysis). Thus, we hypothesize that pectoralis minor activity is increased over the course of respiratory motor loss in CTB‐SAP rats vs. controls. To test our hypothesis, we are studying pectoralis minor output via electromyography in anesthetized, spontaneously breathing control and CTB‐SAP adult rats. Our preliminary data indicate that pectoralis minor activity appears to be increased in CTB‐SAP rats vs. controls (n=4/group). Thus, we conclude that the pectoralis minor muscles may also be recruited to maintain eupneic ventilation in the face of respiratory motor neuron death. Future studies will evaluate the recruitment of other accessory inspiratory muscles (e.g., scalenes, sternocleidomastoid, etc.) over the course of respiratory motor neuron loss, and whether these muscles (including the pectoralis minor) are necessary for eupnea in CTB‐SAP rats. This study furthers our understanding of the potential contribution accessory inspiratory muscles, specifically the pectoralis minor, have on the maintenance of eupneic ventilation following respiratory motor neuron loss. Lastly, if our hypothesis is correct, these muscles could potentially be further stimulated and harnessed to significantly prolong and/or improve breathing in patients with neuromuscular disease.Support or Funding InformationMissouri Spinal Cord Injury/Disease Research Program

Effect of inspiratory resistive training on diaphragm shear modulus and accessory inspiratory muscle activation.

This study aimed to elucidate changes in diaphragm and accessory inspiratory muscle (sternocleidomastoid (SCM) muscle and intercostal muscle (IC)) function after a 6-week training program. Nineteen male elite collegiate swimmers were assigned to either a control group (n = 9) or training group (n = 10). The subjects in the training group performed 30 maximum inspirations at a load resistance of 50% of maximum inspiratory mouth pressure (PImax) using an inspiratory muscle training device. These were conducted twice per day and 6 days per week. At baseline and after 6 weeks, PImax, shear modulus of the diaphragm, and electromyograms (EMG) of the SCM and IC during a maximal inspiratory maneuver were evaluated. Relative change in PImax was greater in the training group than in controls. The shear modulus during a PImax maneuver had increased significantly in both groups after 6 weeks. EMG amplitudes of the SCM increased in the training group after 6 weeks, but not in the control group. EMG amplitudes of the IC did not change after 6 weeks in either group. These results suggest that 6-week inspiratory resistive training significantly improves the activation of the SCM, which could be one of the major mechanisms behind increases in inspiratory muscle strength after resistive training. Novelty Six-week inspiratory resistive training increased diaphragm stiffness during maximal inspiration maneuver. Six-week inspiratory resistive training increased electromyogram amplitudes of the sternocleidomastoid during maximal inspiration maneuver.

Acute Effects of the 6-Minute Pegboard and Ring Test in COPD.

There are few reports in the literature supporting the understanding of the physiological mechanisms of intolerance in patients with COPD to perform unsupported upper limb activities. The aims of this study were to quantify the electrical activity and oxygenation of inspiratory and upper limb muscles, and to investigate whether electromyographic manifestations of muscle fatigue are related to upper limb function as assessed by the 6-min pegboard and ring test (6PBRT) in subjects with COPD and in healthy subjects. Thirty subjects with COPD (FEV1 42.1 ± 16.4% predicted; 68.0 ± 7.6 y old) comprised the COPD group, and 34 healthy subjects (66.8 ± 8.0 y old) comprised the control group. Both groups were assessed for body composition with dual-energy radiograph absorptiometry and spirometry. The 6PBRT was performed with simultaneous assessment of electromyography, near-infrared spectroscopy, and gas analyses (expiratory minute volume). Differences were observed between groups for performance (number of rings) in the 6PBRT, with the COPD group achieving lower values than the control group (P < .001). The ventilatory demand (expiratory minute volume/maximum voluntary ventilation) and root mean square amplitude of the sternocleidomastoid muscle were higher in the COPD group than in the control group (P < .04). Lower values for oxyhemoglobin and total hemoglobin were found in intercostal muscles of the COPD group compared to the control group. The root mean square amplitude of the intercostal muscles was lower in the COPD group, while it was similar between groups for anterior deltoid and trapezius muscles. Median frequency of anterior deltoid muscles presented a decreased in both groups. Our results indicate that the 6PBRT was performed at a higher electrical activity in the accessory inspiratory muscles, such as the sternocleidomastoid muscle, and a lower oxygenation profile in the intercostal muscles in subjects with COPD compared with healthy controls, but without muscle fatigue signs. These findings suggest that the higher ventilatory demand presented in subjects with COPD could have contributed to the worse performance in this group without signals of peripheral muscle limitation.

Severe diaphragmatic dysfunction with preserved activity of accessory respiratory muscles in a critically ill child: a case report of failure of neurally adjusted ventilatory assist (NAVA) and successful support with pressure support ventilation (PSV)

BackgroundNeurally adjusted ventilatory assist (NAVA) is an alternative to pressure support ventilation (PSV) potentially improving patient-ventilator interaction. During NAVA, diaphragmatic electrical activity (EAdi) is used to trigger the ventilator and perform a proportional respiratory assistance. We present a case in which the presence of severe bilateral diaphragmatic dysfunction led to a failure of NAVA. On the contrary, the preserved activity of the accessory inspiratory muscles allowed a successful respiratory assistance using PSV.Case presentationA 10-year-old girl developed quadriplegia after neurological surgery. Initially, no spontaneous breathing activity was present and volume controlled ventilation was necessary. Two months later spontaneous inspiratory efforts were observed and a maximal negative inspiratory force of − 20 cmH2O was recorded. In addition, a NAVA nasogastric tube was placed. The recorded EAdi signal, despite showing a phasic activity, had a very low amplitude (1–2 μV). Two brief (15 min) breathing trials to compare PSV (pressure support = 8 cmH2O) with NAVA (Gain = 5 cmH2O/μV, inspiratory trigger = 0.3 μV) were performed. On PSV, the patient was well adapted with stable tidal volumes, respiratory rates, minute ventilation, end-tidal and venous carbon dioxide levels. When switched to NAVA, her breathing pattern became irregular and she showed clear sign of increased work of breathing and distress: tidal volume dropped and respiratory rate rose, leading to an increase in total minute ventilation. Nevertheless, end-tidal and venous carbon dioxide rapidly increased (from 49 to 55 mmHg and from 52 to 57 mmHg, respectively). An electromyographic study documented an impairment of the diaphragm with preserved activity of the accessory inspiratory muscles.ConclusionsWe document the failure of mechanical assistance performed with NAVA due to bilateral diaphragmatic dysfunction in a critically ill child. The preserved activity of some accessory respiratory muscles allowed to support the patient effectively with pressure support ventilation, i.e. by applying a pneumatic trigger. The present case underlines (i) the importance of the integrity of the respiratory centers, phrenic nerves and diaphragm in order to perform NAVA and (ii) the possible diagnostic role of EAdi monitoring in complex cases of weaning failure.

Primary Versus Accessory Respiratory Muscles Response to Kinesio Tape in Normal Subjects

AbstractBackground: Kinesio Tape is claimed to have the effect of increasing muscular strength.Aim of Study: Was to find the effect of the Kinesio tape as a muscle technique applied to the primary respiratory muscles and accessory respiratory muscles on Maximum Inspiratory Pressure (MIP) and Maximum Expiratory Pressure (MEP).Material and Methods: Sixty normal individuals their ages ranged from 20 to 30 years old. They were recruited from under & post graduate students at Faculty of Physical Therapy, Cairo University. The subjects were randomly divided into 2 groups equal in number, Group A included 30 subjects, the Kinesio tape was applied to the primary inspiratory muscles (diaphragm and scaleni) of the subjects. Group B included 30 subjects, the Kinesio tape was applied to the sternocleido-mastoid (as accessory inspiratory muscle) and to the external abdominal oblique and internal abdominal oblique (as acces-sory expiratory muscles). The Kinesio tape application session was once every 4 days for a total study program of three weeks.Results: There was a significant increase in the MIP in the group (A) compared with that of group (B) after the study program and there was a significant increase in the MEP in the group (B) compared with that of group (A) after the study program.Conclusion: The results of this study support the impor-tance of applying Kinesio tape over respiratory muscles to improve their functions.

Sex differences in diaphragmatic fatigue and the metaboreflex following inspiratory pressure-threshold loading.

Sex differences in diaphragmatic fatigue and the metaboreflex following inspiratory pressure-threshold loading.