Inspiratory Muscle Activity Research Articles

Effects of diaphragmatic control on multiparametric analysis of the sniff nasal inspiratory pressure test and inspiratory muscle activity in healthy subjects.

BackgroundWe investigated the influence of diaphragmatic activation control (diaphC) on the relaxation rate, contractile properties and electrical activity of the inspiratory muscles of healthy subjects. Assessments were performed non-invasively using the sniff inspiratory pressure test (SNIP) and surface electromyography, respectively.MethodsTwenty-two subjects (10 men and 12 women) performed 10 sniff maneuvers in two different days: with and without diaphC instructions. For the SNIP test with diaphC, the subjects were instructed to perform intense activation of the diaphragm. The tests with the best SNIP values were used for analysis.ResultsThe maneuver with diaphC when compared to the maneuver without diaphC exhibited significant lower values for: SNIP (p <0.01), maximum relaxation rate (MRR) (p <0.01), maximum rate of pressure development (MRPD) (p <0.01), contraction times (CT) (p = 0.02) and electrical activity of the sternocleidomastoid (SCM) (p <0.01), scalene (SCL) (p = 0.01) and intercostal (CI) (p = 0.03) muscles. In addition, the decay constant (tau, τ) and relaxation time (½ RT) did not present any changes.ConclusionThe diaphragmatic control performed during the SNIP test influences the inspiratory pressure and the contractile properties of inspiratory muscles. This occurs due to changes in the pattern of muscle recruitment, which change force velocity characteristics of the test. Thus, instruction on diaphC should be encouraged for better performance of the SNIP test and for evaluation targeting the diaphragm muscle activity.

P-NE015. Acute effects of respiratory muscle stretching on ventilatory patterns and respiratory muscle activity

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

Difference in Muscle Activity of Respiratory Muscle During Maximum Inspiration and Expiration Due to Position Change and Tool Use

Purpose : In this study, we aimed to measure how respiratory muscle activity changes as posture changes. We also aimed to measure the inspiratory sternocleidomastoid (SCM) and upper trapezius (UT) muscle activities as well as expiratory rectus abdominis (RA) and oblique abdominis (OA) muscle activities in healthy male and female university students in their twenties. Methods : Using the percentage of reference voluntary contraction (% RVC) with electromyography, we measured the SCM, UT, RA, and OA muscle activities in 16 healthy male and female university students in their 20s according to position change and breather tool use. Results : We found that the average value of inspiratory and expiratory muscle activities by posture was highest when using the breather tool. When using the tool with 10-mm and 2-mm straws for standard breathing at rest in the sitting position, a statistically significant increase in SCM, UT, and OA activities occurred (p < 0.05). For standard breathing at rest in the supine position, a statistically significant increase in SCM, RA, and OA activities occurred (p < 0.05). Conclusion : In clinical application, it may be better to use a respiratory muscle-strengthening tool to increase the activity of inspiratory and expiratory muscles.

Changes in electromyographic activity, mechanical power, and relaxation rates following inspiratory ribcage muscle fatigue

Muscle fatigue is a complex phenomenon enclosing various mechanisms. Despite technological advances, these mechanisms are still not fully understood in vivo. Here, simultaneous measurements of pressure, volume, and ribcage inspiratory muscle activity were performed non-invasively during fatigue (inspiratory threshold valve set at 70% of maximal inspiratory pressure) and recovery to verify if inspiratory ribcage muscle fatigue (1) leads to slowing of contraction and relaxation properties of ribcage muscles and (2) alters median frequency and high-to-low frequency ratio (H/L). During the fatigue protocol, sternocleidomastoid showed the fastest decrease in median frequency and slowest decrease in H/L. Fatigue was also characterized by a reduction in the relative power of the high-frequency and increase of the low-frequency. During recovery, changes in mechanical power were due to changes in shortening velocity with long-lasting reduction in pressure generation, and slowing of relaxation [i.e., tau (τ), half-relaxation time (½RT), and maximum relaxation rate (MRR)] was observed with no significant changes in contractile properties. Recovery of median frequency was faster than H/L, and relaxation rates correlated with shortening velocity and mechanical power of inspiratory ribcage muscles; however, with different time courses. Time constant of the inspiratory ribcage muscles during fatigue and recovery is not uniform (i.e., different inspiratory muscles may have different underlying mechanisms of fatigue), and MRR, ½RT, and τ are not only useful predictors of inspiratory ribcage muscle recovery but may also share common underlying mechanisms with shortening velocity.

Sex differences in post‐inspiratory inspiratory activity and evolution of net respiratory muscle pressures during incremental exercise

The respiratory muscle pressure (Pmus) waveform allows observation of net inspiratory andexpiratory muscle recruitment under a wide variety of conditions, including mechanical ventilation, spontaneous breathing, and during exercise. Observation of the Pmus waveform during incremental and constant work rate cycling reveals that inspiratory and expiratory muscle recruitment systematically increase with rising minute ventilations. Additionally, measuring Pmus allows one to assess the post-inspiratory inspiratory muscle activity (PIIA), whereby the inspiratory muscles “brake” some or all of expiration to allow for a smoother transition in muscle recruitment. In recent years, it has become increasingly evident that the work of breathing is systematically higher for women compared with men at a given minute ventilation during exercise. It is possible that a greater evolution of net respiratory pressures, as well as longer PIIA duration, may be a contributing factor to the greater work of breathing observed in women during exercise. However, to date, no study has examined the potential sex differences in Pmus, nor PIIA, during exercise. Thus, a comprehensive assessment of the Pmus and PIIA during exercise between sexes is warranted. PURPOSE To compare PIIA and inspiratory and expiratory Pmus between men and women during incremental cycling. METHODS Fifteen women (21 ± 2 yrs; 167 ± 7 cm; 62 ± 7 kg) and 19 men (24 ± 4 yrs; 182 ± 5 cm; 81 ± 10 kg) visited the laboratory on two separate occasions. The first occasion was used to obtain informed consent and to screen participants for normal pulmonary function (>85% age-predicted). On the second visit, participants were instrumented with an esophageal balloon catheter to estimate variations in pleural pressure (Ppl). Quasi-static relaxation curves were obtained to measure chest wall recoil pressure (Pcw). Participants then completed an incremental cycling protocol until volitional exhaustion. Pmus was calculated at given minute ventilations during the exercise protocol as follows: Pmus = Pcw – Ppl. RESULTS Total Pmus (sum of average inspiratory and expiratory Pmus) was greater in women than men (P < 0.05). Peak inspiratory Pmus was similar between sexes, but peak expiratory Pmus was greater in women. The average rates of change (slope) in Pmus during inspiration and expiration were significantly faster in women than men at a given minute ventilation (P < 0.05). Finally, the duration of PIIA (expressed as a fraction of expiratory time) gradually decreased with increasing minute ventilation during exercise in both sexes (P < 0.05), but the decrease was comparable between sexes (P > 0.05). CONCLUSION The primary finding of this study was that the pattern of respiratory muscle recruitment was different between sexes during incremental cycling, given that women displayed systematically faster rates, and greater magnitude, of net inspiratory and expiratory pressure-development compared with men at matched ventilations. Additionally, the duration of PIIA was similar in both women and men, which implies no difference in the pattern of transition from inspiration to expiration between sexes.

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.

The Usefulness of Modified Mallampati Score and CT Upper Airway Volume Measurements in Diagnosing OSA among Patients with Breathing-Related Sleep Disorders

Background: Obstructive sleep apnea (OSA) is a condition causing restriction of the airflow through the upper airways during sleep, despite preserved inspiratory muscle activity. This may lead to the development of secondary hypertension, ischemic heart disease, myocardial infarction, and arrhythmia. Moreover, the prevalence of OSA is on the rise. Methods: Comparison of scores from the Berlin Questionnaire, modified Mallampati scores (MMP), pulse oximetry readings and Upper Airway Volume (UAV) data obtained from CBCT (Cone Beam Computed Tomography). The study group of 129 patients of both sexes reporting sleep-related breathing problems completed the Berlin Questionnaire, had their oxygen saturation (SpO2) measured with a PO40 pulse oximeter, and oropharyngeal tissues assessed according to MMP. CBCT scans were put into 3D Amira TM 3D computer analysisto obtain UAV values. Results: Snoring was associated with significantly higher BMI compared to non-snoring patients. Furthermore, snoring patients had higher heart rate, modified Mallampati score, and lower UAV than the non-snoring group. The multifactorial analysis showed MMP as a useful indicator of the risk of snoring (OR = 7.468 (3863–14, 507, p &lt; 0.001)). Conclusions: The composition of MMP together with UAV and the Berlin questionnaire might be reliable indicators to assess the risk of snoring.

Investigation of inspiratory intercostal muscle activity in patients with spinal cord injury: a pilot study using electromyography, ultrasonography, and respiratory inductance plethysmography.

[Purpose] The respiratory function in patients with cervical spinal cord injury is influenced by inspiratory intercostal muscle function. However, inspiratory intercostal muscle activity has not been conclusively evaluated. We evaluated the inspiratory intercostal muscle activity in patients with cervical spinal cord injury by using inspiratory intercostal electromyography, respiratory inductance plethysmography, and ultrasonography. [Participants and Methods] Three patients with cervical spinal cord injury were assessed. The change in mean amplitude (rest vs. maximum inspiration) was calculated by using intercostal muscle electromyography. Changes in intercostal muscle thickness (resting expiration and maximum inspiration) were also evaluated on ultrasonography. The waveform was converted to spirometry ventilation with respiratory inductance plethysmography, and the waveform at the xiphoid was considered to determine the rib cage volume. Each index was compared with the inspiratory capacities in each case. [Results] Intercostal muscle electromyography failed to measure the notable myoelectric potential in all the patients. The rib cage volume was higher at higher inspiratory capacities. The changes in muscle thickness were not significantly different between the patients. [Conclusion] The rib cage volume (measured with inductance plethysmography) was greater in the patients with cervical spinal cord injury when inspiratory intercostal muscle activity was high. Respiratory inductance plethysmography can capture inspiratory intercostal muscle function in patients with cervical spinal cord injury.

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.

Computational Modeling of Spinal Cord Stimulation for Inspiratory Muscle Activation and Chronic Pain Management

Computational Modeling of Spinal Cord Stimulation for Inspiratory Muscle Activation and Chronic Pain Management

The condition of the respiratory muscles in obstructive sleep disordered breathing according to electromyographic data

Aim . To study functional state of respiratory muscles in patients with obstructive sleep-disordered breathing (oSDB) of varying severity based on changes in electrical activity when using a stepwise-increasing respiratory load. Materials and methods . According to results of cardiorespiratory monitoring, the examined patients were divided into 4 groups. Group 1 included 16 patients without oSDB, group 2 – 16 patients with mild oSDB, group 3 – 8 patients with moderate oSDB, group 4 – 8 patients with severe oSDB. The assessment of electrical activity of inspiratory muscles and expiratory muscles was carried out using electromyography (EMG) when performing tests with a stepwise-increasing inspiratory and expiratory load. Results . During inspiratory test, a decrease in EMG frequency was observed, indicating respiratory muscles fatigue development, with a simultaneous increase in EMG amplitude due to the involvement of additional motoneurons in muscle contraction. In all cases, degree of increase in EMG amplitude prevailed over degree of decrease in EMG frequency. In patients of groups 3 and 4, there were no signs of diaphragm fatigue. Results of expiratory test in group 1, degree of increase in EMG amplitude prevailed over degree of decrease in EMG frequency. In the groups of patients with oSDB, prevalence of decrease in the EMG frequency over increase in EMG amplitude was observed, which indicates development of neuromuscular fatigue of expiratory muscles. Conclusion . Changes in functional state of respiratory muscles are associated with severity of oSDB and are characterized by different dynamics of the electrical activity of inspiratory and expiratory muscles in response to a functional test.

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

Recruitment pattern of the diaphragm and extradiaphragmatic inspiratory muscles in response to different levels of pressure support

BackgroundInappropriate ventilator assist plays an important role in the development of diaphragm dysfunction. Ventilator under-assist may lead to muscle injury, while over-assist may result in muscle atrophy. This provides a good rationale to monitor respiratory drive in ventilated patients. Respiratory drive can be monitored by a nasogastric catheter, either with esophageal balloon to determine muscular pressure (gold standard) or with electrodes to measure electrical activity of the diaphragm. A disadvantage is that both techniques are invasive. Therefore, it is interesting to investigate the role of surrogate markers for respiratory dive, such as extradiaphragmatic inspiratory muscle activity. The aim of the current study was to investigate the effect of different inspiratory support levels on the recruitment pattern of extradiaphragmatic inspiratory muscles with respect to the diaphragm and to evaluate agreement between activity of extradiaphragmatic inspiratory muscles and the diaphragm.MethodsActivity from the alae nasi, genioglossus, scalene, sternocleidomastoid and parasternal intercostals was recorded using surface electrodes. Electrical activity of the diaphragm was measured using a multi-electrode nasogastric catheter. Pressure support (PS) levels were reduced from 15 to 3 cmH2O every 5 min with steps of 3 cmH2O. The magnitude and timing of respiratory muscle activity were assessed.ResultsWe included 17 ventilated patients. Diaphragm and extradiaphragmatic inspiratory muscle activity increased in response to lower PS levels (36 ± 6% increase for the diaphragm, 30 ± 6% parasternal intercostals, 41 ± 6% scalene, 40 ± 8% sternocleidomastoid, 43 ± 6% alae nasi and 30 ± 6% genioglossus). Changes in diaphragm activity correlated best with changes in alae nasi activity (r2 = 0.49; P < 0.001), while there was no correlation between diaphragm and sternocleidomastoid activity. The agreement between diaphragm and extradiaphragmatic inspiratory muscle activity was low due to a high individual variability. Onset of alae nasi activity preceded the onset of all other muscles.ConclusionsExtradiaphragmatic inspiratory muscle activity increases in response to lower inspiratory support levels. However, there is a poor correlation and agreement with the change in diaphragm activity, limiting the use of surface electromyography (EMG) recordings of extradiaphragmatic inspiratory muscles as a surrogate for electrical activity of the diaphragm.

Effects of Inspiratory Load on Chest Wall Kinematics, Breathing Pattern, and Respiratory Muscle Activity of Mouth-Breathing Children.

We sought to evaluate the acute effects of different inspiratory loads using nasal and oral interfaces on the volumes of the chest wall and its compartments, breathing pattern, and respiratory muscle activation in children with mouth-breathing syndrome. Children with mouth-breathing syndrome were randomized into 2 groups, one with an inspiratory load intensity 20% of maximum inspiratory pressure (n = 14), and the other with an inspiratory load intensity 40% of maximum inspiratory pressure (n = 15). The chest wall volumes and electromyography of sternocleidomastoid, rectus abdominis, scalene, and internal intercostal muscles were used to analyze respiration against the 2 load intensities and using 2 interfaces (ie, nasal and oral). A total of 72 children with mouth-breathing syndrome were recruited, and 29 were evaluated in this study. The use of inspiratory load promoted improvement in the components of the breathing pattern: breathing frequency (P = .039), inspiratory time (P = .03), and total respiratory time (P = .043); and increases in tidal volume (P < .001), end-inspiratory volume (P < .001), and electrical activity of scalene muscles and sternocleidomastoid muscles (P < .001) when compared to quiet breathing. The load imposed via a nasal interface versus an oral interface provided an increase in tidal volume (P = .030), end-inspiratory volume (P = .02), and electrical activity of scalene muscles (P < .001) and sternocleidomastoid muscles (P = .02). The use of acute inspiratory loads improved the breathing pattern and increased lung volume and electrical activity of inspiratory muscles. This work brings new perspective to the investigation of using nasal interfaces during the application of inspiratory loads. The nasal interface was more effective compared to the oral interface commonly used in clinical practice.

A Computational Model of Upper Thoracic High‐Frequency Spinal Cord Stimulation to Optimize Inspiratory Muscle Activation

BackgroundHigh‐frequency spinal cord stimulation (HFSCS) has been previously shown to elicit physiological activation of the diaphragm and inspiratory intercostal muscles via spinal cord pathways in canines. It was previously hypothesized that during upper thoracic HF‐SCS, the phrenic motoneuron pools are activated via spinal pathways located in the ventro‐lateral funiculus (VLF).ObjectiveThe aim of the present study was to develop a computational model of ventral HFSCS to optimize stimulation parameters and electrode configurations for activation of the inspiratory muscles.MethodsWe created a computer model of an anatomically‐accurate finite element model (FEM) of the canine spinal cord and surrounding anatomy, along with an implanted HFSCS electrode array. From this FEM, we calculated extracellular voltages generated by SCS and applied them to multicompartment cable models of axons within the VLF. Model analysis compared activation thresholds for several unique electrode designs, configurations, and electrode placements in order to optimize activation of these VLF fibers to maximize inspiratory muscle activation.ResultsFor initial model parameterization, we performed experimental measurements testing various electrode configurations and designs. We then used our computer model to evaluate several additional stimulation configurations (e.g. monopolar, bipolar) on VLF fiber selectivity. We then evaluated the effect of wider or narrow lateral lead spacing, contact spacing, and contact size. Finally, we considered several SCS waveform settings, such as rectangular waveforms and ramped waveforms, to potentially generate muscle activation more similar to natural inspiration.ConclusionsWe used our model to optimize electrode configurations, placements and novel stimulation waveforms of HFSCS to target fibers within the VLF. In particular, we found that wider lateral spacing between percutaneous electrodes better targets VLF fibers as opposed to the narrower spacing initially tested. We also show that ramped stimulation slowly recruits VLF fibers over time, which could improve naturalistic inspiratory muscle activation. In future work, we will perform experimental measurements in an animal model of HFSCS to confirm the ability of these optimized electrode designs and waveform parameters to better recreate normal inspiration.DisclosureDr. DiMarco is a founder of and has a significant financial interest in Synapse BioMedical, a manufacturer of diaphragm pacing systems and holds patents for spinal cord stimulation to restore cough and respiration (5,678,535; 5,911,218; 5,999,855; 8,751,004). Drs. DiMarco and Kowalski hold the U.S. patents for technology related to the content of this manuscript: Respiratory Muscle Activation by Spinal Cord Stimulation (8,352,036).Support or Funding InformationThis work is supported by NIH‐NINDS (R01NS064157).

Respiratory Muscle Activity during Maximal Efforts in ALS Patients and Healthy Controls

Amyotrophic lateral sclerosis (ALS) is a type of neurodegenerative disease involving upper and lower motor neuron loss. ALS patients usually die of respiratory failure due to breathing muscle weakness from motor neuron death. It is important to better understand how breathing changes in ALS to design effective treatments to target breathing insufficiency. Breathing capacity is preserved until late stages of disease in the SOD1G93A rodent model of ALS. Possible mechanisms preserving breathing in ALS rats include: 1) spinal synaptic plasticity; 2) neuromuscular junction plasticity; and 3) transition in balance from more affected muscles (eg. diaphragm) to less affected accessory respiratory muscles. If these mechanisms also exist in humans with ALS, we predict that characteristic patterns of altered respiratory muscle activity would precede ventilatory failure, assessed via traditional pulmonary function tests. Thus, using surface EMGs (sEMG) in ALS patients, we tested the hypothesis that ALS patients exhibit differential recruitment patterns of inspiratory muscle activity during a maximal inspiratory pressure (MIP) test versus healthy age‐ and sex‐ matched controls. EMG electrodes (Bagnoli surface electrode, Delsys, Massachusetts, USA) were bilaterally placed on the diaphragm, 2nd parasternal, scalene and sternocleidomastoid muscles. Subjects (8 patients and 8 controls) were instructed to perform the MIP test. The test was repeated until 3 measurements were obtained within 10% variability. RMS EMG amplitude of MIP testing was calculated using a 100ms sliding window with MATLAB v.9.2., and relationships between MIP and EMG activity were evaluated using a linear regression. A moderate relationship (r=0.65) was seen between parasternal muscle activity and MIP in ALS patients, while the controls showed moderate correlations between neck muscle activity (sternocleidomastoid and scalene) and MIP (rSCM= 0.56 and rscalene=0.69). Moreover, MIP‐generated parasternal (r=0.76) and diaphragm (r=0.7) activity corresponded strongly with disease severity of patients, as measured by the ALS‐FRS scale. Interestingly, we did not see a clear relationship between diaphragm surface EMG activity and MIP in either patients or controls. Several factors could account for this, including the use of surface electrodes and the mass‐effort nature of the MIP test. Further analyses are underway to assess respiratory muscle activity during other inspiratory challenges and compare the amount of sEMG output distribution between controls and ALS patients. These preliminary results support the idea that ALS patients use a different pattern of muscle activity during maximal breathing effort from controls.Support or Funding InformationSupported by: UF Clinical and Translational Science Institute (supported byNIH UL1TR001427), UF “Moonshot” grant initiative, and UF McKnight Brain Institute

Comparison of Wire and Disc Leads to Activate the Inspiratory Muscles in Dogs

ObjectiveHF‐SCS is a unique method of inspiratory muscle activation which results in coincident activation of the diaphragm and inspiratory intercostal muscles via spinal cord pathways and has the potential to provide respiratory support in ventilator dependent persons with spinal cord injury (SCI). The purpose of the present study was to examine the effectiveness of wire leads, which can be placed using minimally invasive techniques, to activate the inspiratory muscles.MethodsIn 5 anesthetized dogs, in separate trials, disc and wire leads were inserted onto the ventral epidural space at the T1–T4 spinal cord levels. The effects of electrical stimulation with disc, single wire, and two wire leads placed in parallel were compared.Outcome measuresAirway pressure generation following stimulation with disc and various configurations of wire leads were compared.ResultsSeveral different configurations of wire leads resulted in airway pressures that were similar to those generated with monopolar stimulation with disc leads (D). For example, monopolar stimulation (3mA, 300Hz, 0.2ms) with parallel wire leads in which each of the electrode contacts at the T2 were connected together and functioned as a common cathode (Y‐connection) and monopolar stimulation (separate cathode) at T2 both with a remote ground resulted in airway pressures that were 91±6 and 92±4%, respectively, of those achieved with D (NS for both). Bipolar stimulation (3mA, 300Hz, 0.2ms) with parallel wire leads using Y‐connection and with a separate cathode at the T2 and T3 level resulted in airway pressures that were 96 ± 4 and 94 ± 4%, respectively, of the pressures achieved with D (NS for both).ConclusionThese results suggest that specific configurations of wire leads, which can be placed via minimally invasive techniques, result in comparable activation of the inspiratory muscles compared to disc leads and may be a useful technique to restore ventilatory support in persons with SCI.Support or Funding InformationSupportNIH‐NINDS (R01NS064157)DisclosureDr. DiMarco is a founder of and has a significant financial interest in Synapse BioMedical, a manufacturer of diaphragm pacing systems and holds patents for spinal cord stimulation to restore cough and respiration (5,678,535; 5,911,218; 5,999,855; 8,751,004). Drs. DiMarco and Kowalski hold the U.S. patents for technology related to the content of this manuscript: Respiratory Muscle Activation by Spinal Cord Stimulation (8,352,036).

Features of electrical activity of inspiratory muscles in different age groups

Aim . To identify features of changes in electrical activity of inspiratory muscles and their relationship with anthropometric indicators in different age groups. Materials and methods . There were examined 57 men with the same strength of respiratory muscles, aged 20 to 65 years old, who were divided into 3 groups. The 1st group included 26 young people, the 2nd group consisted of 20 middle-aged people, the 3rd group had 11 elderly patients. The examination included determination of anthropometric indicators, assessment of motor activity, inspiratory muscle strength, analysis of the electrical activity of inspiratory muscles when performing functional tests. Results. In young people compared with patients of groups 2 and 3, a significant difference in anthropometric indicators was revealed. In patients of group 1, the dynamics of electromyography (EMG) indices of inspiratory muscles was the greatest when performing functional tests. There was revealed correlation between age and dynamics of the EMG amplitude indicators of external intercostal muscles (r=0.48, p&lt;0.05), sternocleidomastoid muscles (r=-0.41, p&lt;0.05) and diaphragm (r=-0.63, p&lt;0.05); dynamics of EMG amplitude indicators of diaphragm and circumference of the chest on the inspiration (r=-0.77, p&lt;0.05) and expiration (r=-0.73, p&lt;0.05), dynamics of EMG amplitude indicators of sternocleidomastoid muscles and circumference of chest on inspiration (r=-0.61, p&lt;0.05) and expiration (r=-0.59, p&lt;0.05). Conclusion. There is a negative relationship between dynamics of EMG amplitude indicators of inspiratory muscles when performing functional tests with age and chest circumference on inspiration and expiration. The main feature of electrical activity of inspiratory muscles in young people when performing functional tests is revealed in active participation of auxiliary muscles, in particular, the sternocleidomastoid muscle. In middle-aged and elderly people, dynamics of indicators of electrical activity of inspiratory muscles during performance of functional tests was the same.

Absence of inspiratory premotor potentials during quiet breathing in cervical spinal cord injury.

A premotor potential, or Bereitschaftspotential (BP), is a low-amplitude negativity in the electroencephalographic activity (EEG) of the sensorimotor cortex. It begins ~1 s prior to the onset of inspiration in the averaged EEG. Although normally absent during quiet breathing in healthy, younger people, inspiration-related BPs are present in people with respiratory disease and healthy, older people, indicating a cortical contribution to quiet breathing. People with tetraplegia have weak respiratory muscles and increased neural drive during quiet breathing, indicated by increased inspiratory muscle activity. Therefore, we hypothesized that BPs would be present during quiet breathing in people with tetraplegia. EEG was recorded in 17 people with chronic tetraplegia (14M, 3 female; 22-51 yr; C3-C7, American Spinal Injury Association Impairment Scale A-D; >1 yr postinjury). They had reduced lung function and respiratory muscle weakness [FEV1: 54 ± 19% predicted, FVC: 59 ± 22% predicted and MIP: 56 ± 24% predicted (mean ± SD)]. Participants performed quiet breathing and voluntary self-paced sniffs (positive control condition). A minimum of 250 EEG epochs during quiet breathing and 60 epochs during sniffs, time-locked to the onset of inspiration, were averaged to determine the presence of BPs at Cz, FCz, C3, and C4. Fifteen participants (88%) had a BP for the sniffs. Of these 15 participants, only one (7%) had a BP in quiet breathing, a rate similar to that reported during quiet breathing in young able-bodied participants (12%). The findings suggest that, as in young able-bodied people, a cortical contribution to quiet breathing is absent in people with tetraplegia despite higher neural drive.NEW & NOTEWORTHY People with tetraplegia have weak respiratory muscles, increased neural drive during quiet breathing, and a high incidence of sleep-disordered breathing. Using electroencephalographic recordings, we show that inspiratory premotor potentials are absent in people with chronic tetraplegia during quiet breathing. This suggests that cortical activity is not present during resting ventilation in people with tetraplegia who are awake and breathing independently.