Analysis and applications of respiratory surface EMG: report of a round table meeting

Surface electromyography (sEMG) can be used to measure the electrical activity of the respiratory muscles. The possible applications of sEMG span from patients suffering from acute respiratory failure to patients receiving chronic home mechanical ventilation, to evaluate muscle function, titrate ventilatory support and guide treatment. However, sEMG is mainly used as a monitoring tool for research and its use in clinical practice is still limited-in part due to a lack of standardization and transparent reporting. During this round table meeting, recommendations on data acquisition, processing, interpretation, and potential clinical applications of respiratory sEMG were discussed. This paper informs the clinical researcher interested in respiratory muscle monitoring about the current state of the art on sEMG, knowledge gaps and potential future applications for patients with respiratory failure.

Normal values for maximal respiratory pressures in children and adolescents: A systematic review with meta-analysis

BACKGROUND

The non-invasive assessment of maximal respiratory pressures (MRP) reflects the strength of the respiratory muscles.

OBJECTIVE

To evaluate the studies which have established normative values for MRP in healthy children and adolescents and to synthesize these values through a meta-analysis.

METHODS

The searches were conducted until October 2023 in the following databases: ScienceDirect, MEDLINE, CINAHL, SciELO, and Web of Science. Articles that determined normative values and/or reference equations for maximal inspiratory pressure (MIP) and maximal expiratory pressure (MEP) in children and adolescents published in English, Portuguese, or Spanish regardless of the year of publication were included. Two reviewers selected titles and abstracts, in case of conflict, a third reviewer was consulted. Articles that presented sufficient data were included to conduct the meta-analysis.

RESULTS

Initially, 252 studies were identified, 28 studies were included in the systematic review and 19 in the meta-analysis. The sample consisted of 5798 individuals, and the MIP and MEP values were stratified by sex and age groups of 4-11 and 12-19 years. Values from females 4-11 years were: 65.8 cmH2O for MIP and 72.8 cmH2O for MEP, and for males, 75.4 cmH2O for MIP and 84.0 cmH2O for MEP. In the 12-19 age group, values for females were 82.1 cmH2O for MIP and 90.0 cmH2O for MEP, and for males, they were 95.0 cmH2O for MIP and 105.7 cmH2O for MEP.

CONCLUSIONS

This meta-analysis suggests normative values for MIP and MEP in children and adolescents based on 19 studies.

Impact of high-intensity interval hyperpnea on aerobic energy release and inspiratory muscle fatigue

Respiratory muscle endurance training reportedly has beneficial effects on whole-body endurance performance. We produced a novel high-intensity interval (HII) protocol and characterized the associated physiological responses and respiratory muscle fatigue. Peak oxygen uptake of respiratory muscle (V̇O2peakRM) was estimated during the respiratory incremental test. The HII session consisted of five 3-minute hyperpnea periods at 100%V̇O2peakRM interspersed with 2-minute periods at 40%V̇O2peakRM (25 min total). The high-intensity continuous (HIC) session involved a single time-to-end bout of hyperpnea at 100%V̇O2peakRM. The moderate-intensity continuous (MIC) session involved 25 min of hyperpnea at 60% of maximal voluntary ventilation. V̇O2RM was recorded continuously, and maximal inspiratory pressure (PImax) was assessed before and after the sessions. HII session: V̇O2RM gradually increased as the sets proceeded, whereas PImax decreased significantly. HIC session: V̇O2RM increased progressively, and the time to end was 6.5 ± 0.5 min. PImax decreased significantly. MIC session: V̇O2RM did not change for 25 min, and PImax remained unchanged. The duration of V̇O2RM at near- and supra-maximal levels in the HII session (10 ± 1 min) was longer than that in the HIC session (4 ± 1 min). The decrease in PImax was larger in the HII session (-12 ± 3 %) than MIC session (-4 ± 3 %). The HII protocol is characterized by a longer time to maximally stimulate the aerobic energy system of respiratory muscle than the HIC protocol and greater inspiratory muscle fatigue than the traditional MIC protocol. These results suggest that the HII protocol could enhance the efficacy of respiratory muscle training programs.

Ultrasound assessment of diaphragm and quadriceps muscles and its relationship with handgrip and respiratory muscle strength in patients with systemic sclerosis: a cross-sectional study

BACKGROUND

Muscle dysfunction may cause disability and reduce the quality of life of patients with systemic sclerosis (SSc) when compared to healthy individuals. However, the literature on the topic is scarce and uses several criteria for assessing muscle dysfunction in this population.

OBJECTIVES

To compare diaphragm and quadriceps muscle thickness, diaphragm mobility, and handgrip strength between patients with SSc and healthy individuals.

METHOD

This cross-sectional study included 16 patients with SSc and 16 self-reported healthy individuals matched for age. We assessed quadriceps and diaphragm thickness and diaphragmatic mobility (ultrasound), handgrip strength (hand-held dynamometer), and respiratory muscle strength (manovacuometer). Patients also responded to the Health Assessment Questionnaire Disability Index and the International Physical Activity Questionnaire.

RESULTS

Patients with SSc presented lower quadriceps thickness (p < 0.0001), diaphragmatic mobility (p = 0.01), handgrip (p < 0.0001), and respiratory muscle strength (p < 0.0001) than healthy individuals. A moderate positive correlation was observed between handgrip strength and quadriceps thickness in patients with SSc (rho = 0.576; p = 0.02).

CONCLUSIONS

Patients with SSc presented reduced quadriceps thickness, diaphragmatic mobility, handgrip, and respiratory muscle strength when compared to healthy individuals Also, handgrip strength was correlated with quadriceps thickness in patients with SSc, suggesting that loss of muscle mass accompanies loss of peripheral muscle strength group of patients. Key Points • SSc patients presented reduced quadriceps thickness and diaphragmatic mobility • SSc patients have reduced handgrip and respiratory muscle strength • Lower handgrip muscle strength correlated with lower quadriceps thickness.

Electromyogram Power Spectrum and Cardiac Function Changes After Combined Aerobic Interval Training and Inspiratory Muscle Training in Chronic Heart Failure Patients

Exercise intolerance and dyspnea are the major symptoms of patients with chronic heart failure (CHF) and are associated with a poor quality of life. In addition to impaired central hemodynamics, symptoms may be attributed to changes in peripheral skeletal muscles. This study aimed to evaluate the effects of aerobic interval training (AIT) combined with inspiratory muscle training (IMT) on cardiac and skeletal muscle function and on functional capacity and dyspnea in patients with CHF and inspiratory muscle weakness.Left ventricle ejection fraction was improved significantly after AIT and AIT & IMT with a high percentage of amelioration (17%, P < 0.042) in the combined group compared to the control group. Therefore, we showed a significant improvement in maximal voluntary isometric force, isometric endurance time, root mean square, and frequency median in both strength and endurance manipulations in the aerobic and combined group; however, the improvement was superior in the combined group compared to the control group. Significant amelioration was proved in functional capacity and dyspnea after all types of training but was performed at 18% higher in 6 minutes' walk test and 43% lower in dyspnea for the combined group compared to the control group.Combining AIT to IMT had optimized exercise training benefits in reversing the cardiac remodeling process and improving skeletal muscle function, functional capacity, and dyspnea in patients with CHF.

Effects of body postures on respiratory muscle force and coughing in healthy people

The respiratory muscle force determines the intensity of cough force. A greater cough force for cleaning the airways is essential for preventing and managing pneumonia. Body posture can affect the onset of aspiration pneumonia. However, the effects of body posture on the respiratory muscle and cough forces remain unclear. Thus, we aimed to explore the influence of the four body postures on respiratory muscle force, cough pressure, subjective ease of coughing, and pulmonary function in healthy individuals. Twenty healthy individuals were included in this study. Body postures were 0-degree supine, 30- and 60-degree semi-recumbent, and 90-degree sitting. The maximal inspiratory and expiratory pressures, maximal cough pressure, subjective ease of coughing, and pulmonary function, including peak expiratory flow, were evaluated. We set the measured values in the supine posture to 100% and showed the relative values. The 60-degree posture showed stronger inspiratory (125.1 ± 3.9%, mean ± standard error [SE]) and expiratory (116.4 ± 3.0%) muscle force, cough pressure, more subjective ease of coughing, and greater peak expiratory flow (113.4 ± 3.0%) than the supine posture. The sitting posture also showed greater inspiratory muscle force and peak expiratory flow than the supine posture. The correlation coefficient for the 60-degree posture showed that the maximal inspiratory pressure was moderately correlated with the maximal expiratory pressure (r = 0.512), cough pressure (r = 0.495), and peak expiratory flow (r = 0.558). The above findings suggest the advantage of keeping a 60-degree posture and avoiding the supine posture to generate a greater cough force in the prevention and management of pneumonia.

Preoperative respiratory muscle training reduces the risk of pulmonary complications and the length of hospital stay after cardiac surgery: a systematic review

QUESTIONS

What is the effect of preoperative respiratory muscle training (RMT) on the incidence of postoperative pulmonary complications (PPCs) after open cardiac surgery? What is the effect of RMT on the duration of mechanical ventilation, postoperative length of stay and respiratory muscle strength?

DESIGN

Systematic review of randomised trials with meta-analysis.

PARTICIPANTS

Adults undergoing elective open cardiac surgery.

INTERVENTION

The experimental groups received preoperative RMT and the comparison groups received no intervention.

OUTCOME MEASURES

The primary outcomes were PPCs, length of hospital stay, respiratory muscle strength, oxygenation and duration of mechanical ventilation. The methodological quality of studies was assessed using the PEDro scale and the overall certainty of the evidence was assessed using the GRADE approach.

RESULTS

Eight trials involving 696 participants were included. Compared with the control group, the respiratory training group had fewer PPCs (RR 0.51, 95% CI 0.38 to 0.70), less pneumonia (RR 0.44, 95% CI 0.25 to 0.78), shorter hospital stay (MD -1.7 days, 95% CI -2.4 to -1.1) and higher maximal inspiratory pressure values at the end of the training protocol (MD 12 cmH2O, 95% CI 8 to 16). The mechanical ventilation time was similar in both groups. The quality of evidence was high for pneumonia, length of hospital stay and maximal inspiratory pressure.

CONCLUSION

Preoperative RMT reduced the risk of PPCs and pneumonia after cardiac surgery. The training also improved the maximal inspiratory pressure and reduced hospital stay. The effects on PPCs were large enough to warrant use of RMT in this population.

REGISTRATION

CRD42021227779.

Effects of pulmonary rehabilitation in hematopoietic stem cell transplantation recipients: a randomized controlled study

PURPOSE

During hematopoietic stem cell transplantation (HSCT), patients' exercise capacity and quality of life (QOL) are impaired. Exercise training is recommended to preserve cardiorespiratory fitness during the compelling HSCT period. However, studies investigating the effects of pulmonary rehabilitation (PR) in HSCT recipients are limited. Therefore, this study aimed to investigate the effects of two different PR programs on maximal exercise capacity, respiratory muscle strength and endurance, pulmonary function, and QOL.

METHODS

This is a prospective, randomized, controlled, triple-blinded study. Thirty hospitalized patients undergoing HSCT were randomized to the pulmonary rehabilitation plus inspiratory muscle training (PR + IMT) group and the PR group. PR group performed upper extremity aerobic exercise training (AET) and progressive resistance exercise training (PRET), PR + IMT group performed IMT in addition to the upper extremity AET and PRET. Maximal exercise capacity (cardiopulmonary exercise testing), respiratory muscle strength (mouth pressure device, (MIP and MEP)) and respiratory muscle endurance (threshold loading test), pulmonary function (spirometry), and QOL (European Organization for Research and Treatment of Cancer (EORTC QLQ-C30) were evaluated before HSCT and after discharge.

RESULTS

Changes in pulmonary function, respiratory muscle strength and endurance, and QOL were similar within groups (p > 0.05). The MEP, peak oxygen consumption, and oxygen pulse significantly decreased in both groups (p < 0.05).

CONCLUSION

Pulmonary function, inspiratory muscle strength and endurance, and QOL preserved after HSCT. Expiratory muscle strength and maximal exercise capacity decreased even though PR during HSCT. Breathing reserve and restriction improved in the PR + IMT group. In addition, minute ventilation and dyspnea were preserved in the PR + IMT group, while these values were worsened during two structured PR programs. Therefore, PR should be applied in accordance with the patient's current clinical and hematologic status to patients undergoing HSCT.

CLINICALTRIALS

gov (19/07/2018, NCT03625063).

Relationship between walking speed, respiratory muscle strength, and dynamic balance in community-dwelling older people who required long-term care or support and used a daycare center

Background

Focusing on the relationship between frail older people and gait speed is vital to minimize the need for long-term care or increased support. The relationship between gait speed, respiratory muscle strength, and dynamic balance, is not well understood in older people requiring long-term care or support. Therefore, this study aimed to provide new insights into the relationship between gait speed, respiratory muscle strength, and dynamic balance in community-dwelling older people who required long-term care or support and used a daycare center.

Methods

This was a cross-sectional study of 49 community-dwelling older people (21 men, 28 women) aged ≥65 years who were certified as requiring long-term care or support under the Japanese system. The participants' maximal inspiratory pressure (PImax), maximal expiratory pressure (PEmax), walking speed (maximal and normal walking speed), and maximal double-step length test (MDST) results were recorded. The measurement data were evaluated using Pearson's correlation coefficient and multiple regression analysis.

Results

Pearson's correlation coefficient revealed correlations between PImax and the following: maximal walking speed (r = 0.606, p < 0.001), normal walking speed (r = 0.487, p < 0.001), and MDST (r = 0.435, p = 0.002). Correlations were also observed between PEmax and the following: maximal walking speed (r = 0.522, p < 0.001), normal walking speed (r = 0.467, p < 0.001), and MDST (r = 0.314, p = 0.028). Moreover, a correlation was found between MDST and both maximal walking speed and (r = 0.684, p < 0.001) and normal walking speed (r = 0.649, p < 0.001). The effect size was 0.379. Multiple regression analysis using a forced entry method with maximal walking speed as the dependent variable showed that maximal walking speed was significantly associated with MDST (p < 0.001) and PEmax (p = 0.036), with an effect size of 0.272. The model's adjusted coefficient of determination was 0.593 (p < 0.001). Multiple regression analysis using a forced entry method with normal walking speed as the dependent variable showed that normal walking speed was significantly associated with MDST (p < 0.001) and PEmax (p = 0.021), with an effect size of 0.272. The model's adjusted coefficient of determination was 0.497 (p < 0.001). Multiple regression analysis using a forced entry method with MDST as the dependent variable showed that MDST was significantly associated with PImax (p < 0.025), with an effect size of 0.243. The model's adjusted coefficient of determination was 0.148 (p = 0.017).

Conclusions

Respiratory muscle strength and dynamic balance were related to walking speed in older people requiring long-term care or support.

Maximal Respiratory Pressure Reference Equations in Healthy Adults and Cut-off Points for Defining Respiratory Muscle Weakness

INTRODUCTION

Maximal inspiratory and expiratory pressures (PImax/PEmax) reference equations obtained in healthy people are needed to correctly interpret respiratory muscle strength. Currently, no clear cut-off points defining respiratory muscle weakness are available. We aimed to establish sex-specific reference equations for PImax/PEmax in a large sample of healthy adults and to objectively determine cut-off points for respiratory muscle weakness.

METHODS

A multicentre cross-sectional study was conducted across 14 Spanish centres. Healthy non-smoking volunteers aged 18-80 years stratified by sex and age were recruited. PImax/PEmax were assessed using uniform methodology according to international standards. Multiple linear regressions were used to obtain reference equations. Cut-off points for respiratory muscle weakness were established by using T-scores.

RESULTS

The final sample consisted of 610 subjects (314 females; 48 [standard deviation, SD: 17] years). Reference equations for PImax/PEmax included body mass index and a squared term of the age as independent variables for both sexes (p<0.01). Cut-off points for respiratory muscle weakness based on T-scores ≥2.5 SD below the peak mean value achieved at a young age were: 62 and 83cmH2O for PImax and 81 and 109cmH2O for PEmax in females and males, respectively.

CONCLUSION

These reference values, based on the largest dataset collected in a European population to date using uniform methodology, help identify cut-off points for respiratory muscle weakness in females and males. These data will help to better identify the presence of respiratory muscle weakness and to determine indications for interventions to improve respiratory muscle function.

Reliability of maximal respiratory nasal pressure tests in healthy young adults

INTRODUCTION

Sniff nasal inspiratory (SNIP) and expiratory pressure (SNEP) may complement the assessment of respiratory muscle strength. Thus, specifying their reliability is relevant to improving the clinical consistency of both tests.

OBJECTIVE

To assess the reliability of SNIP and SNEP in healthy young adults.

METHODS

This cross-sectional study included self-reported healthy aged 18 to 29 years. SNIP was performed using a plug to occlude one nostril, while SNEP was conducted using a facemask. Participants performed 20 SNIP and SNEP maneuvers with 30-second intervals in between. The intraclass correlation coefficient (ICC), standard error of measurement (SEM), and minimum detectable change (MDC) assessed the reliability of SNIP and SNEP. Analyses were conducted between the highest peak pressure and the first reproducible maneuver in men and women.

RESULTS

The total sample comprised 32 participants: 16 men and 16 women. The ICC, SEM, and MDC for SNIP maneuvers were 0.994 (95%CI 0.988 to 0.997), 1.820 cmH2O, and 5.043 cmH2O, respectively. For SNEP, these parameters were 0.950 (95%CI 0.897 to 0.976), 6.03 cmH2O, and 16.716 cmH2O. The SNIP and SNEP in men showed ICC of 0.992 (95%CI 0.977 to 0.997) and 0.877 (95%CI 0.648 to 0.957), SEM of 2.07 and 7.66 cmH2O, and MDC of 5.74 and 21.23 cmH2O. In women, SNIP and SNEP presented ICC of 0.992 (95%CI 0.977 to 0.997) and 0.957 (95%CI 0.878 to 0.985), SEM of 1.15 and 6.11 cmH2O, and MDC of 3.19 and 16.95 cmH2O. Also, 60% of the highest SNIPs occurred among the 11th and 20th maneuvers in men and women. In men, 55% of the highest SNEPs occurred among the 11th and 20th maneuvers; this value was 50% in women.

CONCLUSION

SNIP and SNEP showed excellent reliability. The reliability of SNIP and SNEP in men was good and excellent, respectively, whereas both tests had excellent reliability in women. Also, women reached the highest peak pressure faster than men in both tests.

Investigation of the relationship between spinal posture and mobility to respiratory muscle strength and pulmonary functions in unilateral breast cancer surgery survivors: a cross-sectional study

PURPOSE

Despite the research on structural and functional changes that may occur in breast cancer survivors, no study has investigated the relationship between spinal characteristics and the respiratory system. Therefore, we aimed to investigate the relationship between spinal posture and mobility to respiratory muscle strength and pulmonary functions in breast cancer patients who have completed their treatment METHODS: This cross-sectional study included 38 female breast cancer surgery survivors. Participants underwent the following evaluations: Chest wall mobility with a tapeline; postural assessments (spinal curvature, spinal mobility, and spinal inclination) with a non-invasive, computer-assisted electromechanical device; and pulmonary function test and respiratory muscle strength with a portable digital spirometer device. The relationship between spinal posture and mobility to respiratory muscle strength and pulmonary functions was analyzed by the bivariate correlation analysis.

RESULTS

Increased thoracic curvature angle was associated with decreased FEV1 (r=-0.360, p=0.026) and decreased subcostal mobility (r=-0.385, p=0.017), and the increase in thoracic frontal mobility was associated with decrease in PEF (r=-0.342, p=0.036). Increased lumbar mobility was associated with increased FVC (r=0.324, p=0.047), and increased total spinal inclination mobility was associated with decreased MIP (r=-0.396, p=0.017). Chest wall mobility was associated with postural assessments at varying rates (the r value ranged from -0.357 to 0.661, p<0.05).

CONCLUSION

The changes in spinal posture and mobility of women who have undergone unilateral breast cancer surgery were associated with respiratory parameters and thoracic cage mobility. These patients' spinal posture and mobility should be taken into account in conjunction with respiratory functions for a comprehensive assessment.

Time-efficient, high-resistance inspiratory muscle strength training increases cerebrovascular reactivity in midlife and older adults

Aging is associated with increased risk for cognitive decline and dementia due in part to increases in systolic blood pressure (SBP) and cerebrovascular dysfunction. High-resistance inspiratory muscle strength training (IMST) is a time-efficient, intensive respiratory training protocol (30 resisted inspirations/day) that lowers SBP and improves peripheral vascular function in midlife/older adults with above-normal SBP. However, whether, and by what mechanisms, IMST can improve cerebrovascular function is unknown. We hypothesized that IMST would increase cerebrovascular reactivity to hypercapnia (CVR to CO2), which would coincide with changes to the plasma milieu that improve brain endothelial cell function and enhance cognitive performance (NIH Toolbox). We conducted a 6-wk double-blind, randomized, controlled clinical trial investigating high-resistance IMST [75% maximal inspiratory pressure (PImax); 6×/wk; 4 females, 5 males] vs. low-resistance sham training (15% PImax; 6×/wk; 2 females, 5 males) in midlife/older adults (age 50-79 yr) with initial above-normal SBP. Human brain endothelial cells (HBECs) were exposed to participant plasma and assessed for acetylcholine-stimulated nitric oxide (NO) production. CVR to CO2 increased after high-resistance IMST (pre: 1.38 ± 0.66 cm/s/mmHg; post: 2.31 ± 1.02 cm/s/mmHg, P = 0.020). Acetylcholine-stimulated NO production increased in HBECs exposed to plasma from after vs. before the IMST intervention [pre: 1.49 ± 0.33; post: 1.73 ± 0.35 arbitrary units (AU); P < 0.001]. Episodic memory increased modestly after the IMST intervention (pre: 95 ± 13; post: 103 ± 17 AU; P = 0.045). Cerebrovascular and cognitive function were unchanged in the sham control group. High-resistance IMST may be a promising strategy to improve cerebrovascular and cognitive function in midlife/older adults with above-normal SBP, a population at risk for future cognitive decline and dementia.NEW & NOTEWORTHY Midlife/older adults with above-normal blood pressure are at increased risk of developing cognitive decline and dementia. Our findings suggest that high-resistance inspiratory muscle strength training (IMST), a novel, time-efficient (5-10 min/day) form of physical training, may increase cerebrovascular reactivity to CO2 and episodic memory in midlife/older adults with initial above-normal blood pressure.

[Research advances on neurally adjusted ventilatory assist]

Mechanical ventilation has, since its introduction into clinical practice, undergone a major evolution from controlled ventilation to diverse modes of assisted ventilation. Conventional mechanical ventilators depend on flow sensors and pneumatic pressure and controllers to complete the respiratory cycle. Neurally adjusted ventilatory assist (NAVA) is a new form of assisted ventilation in recent years, which monitors the electrical activity of the diaphragm (EAdi) to provide an appropriately level of pressure support. And EAdi is the best available signal to sense central respiratory drive and trigger ventilatory assist. Unlike other ventilation modes, NAVA breathing instructions come from the center. Therefore, NAVA have the synchronous nature of the breaths and the patient-adjusted nature of the support. Compared with traditional ventilation mode, NAVA can efficiently unload respiratory muscles, relieve the risk of ventilator-induced lung injury (VILI), improve patient-ventilator coordination, enhance gas exchange, increase the success rate of weaning, etc. This article reviews the research progress of NAVA in order to provide theoretical guidance for clinical applications.

Effects of high intensity interval-based inspiratory muscle training in patients with heart failure: A single-blind randomized controlled trial

BACKGROUND

Given the promising effects of inspiratory muscle training (IMT), determining the most appropriate IMT protocol will optimize the training benefits.

OBJECTIVES

The objective of this study was to determine the effects of high intensity interval-based inspiratory muscle training (H-IMT) on cardiovascular, pulmonary, physical, and psychosocial functions in patients with heart failure and reduced ejection fraction (HFrEF).

METHODS

Thirty-four patients with HFrEF were randomly assigned to the H-IMT or control group for 3 days/week, 8 weeks training period. The H-IMT group performed IMT at least 70% of the maximal inspiratory pressure, whereas the control group performed unloaded IMT. Each session occurred 7 sets with a total of 21 min consisting of 2-min training and 1-min interval. Heart rate variability (HRV), arterial stiffness, respiratory muscle strength and endurance, diaphragm thickness, quadriceps strength, functional capacity, frailty, dyspnea, fatigue, disease-specific health-related quality of life (HRQoL), and generic HRQoL were evaluated at baseline and after 8 weeks training period by blinded assessors.

RESULTS

Statistically significant between-group differences were observed in the time domain parameters of HRV, arterial stiffness, inspiratory and quadriceps muscle strength, respiratory muscle endurance, diaphragm thickness, functional capacity, frailty, dyspnea, fatigue, and disease-specific HRQoL in favor of the H-IMT group (p<0.05).

CONCLUSIONS

H-IMT is an effective protocol for improving cardiac autonomic function, arterial stiffness, inspiratory and quadriceps muscle strength, respiratory muscle endurance, diaphragm thickness, functional capacity, frailty, dyspnea, fatigue, and disease-specific quality of life in patients with HFrEF.

CLINICAL TRIAL REGISTRATION

NCT04839211.

The therapeutic role of inspiratory muscle training in the management of asthma: a narrative review

Asthma is a disorder of the airways characterized by chronic airway inflammation, hyperresponsiveness, and variable recurring airway obstruction. Treatment options for asthma include pharmacological strategies, whereas nonpharmacological strategies are limited. Established pharmacological approaches to treating asthma may cause unwanted side effects and do not always afford adequate protection against asthma, possibly because of an individual's variable response to medications. A potential nonpharmacological intervention that is most available and cost effective is inspiratory muscle training (IMT), which is a technique targeted at increasing the strength and endurance of the diaphragm and accessory muscles of inspiration. Studies examining the impact of IMT on asthma have reported increases in inspiratory muscle strength and a reduction in the perception of dyspnea and medication use. However, because of the limited number of studies and discordant methods between studies more evidence is required to elucidate in individuals with asthma the efficacy of IMT on inspiratory muscle endurance, exercise capacity, asthma control, symptoms, and quality of life as well as in adolescents with differing severities of asthma. Large randomized controlled trials would be a significant step forward in clarifying the effectiveness of IMT in individuals with asthma. Although IMT may have favorable effects on inspiratory muscle strength, dyspnea, and medication use, the current evidence that IMT is an effective treatment for asthma is inconclusive.

Reference Respiratory Muscle Strength Values and a Prediction Equation Using Physical Functions for Pulmonary Rehabilitation in Korea

BACKGROUND

In Korea, tests for evaluating respiratory muscle strength are based on other countries' clinical experience or standards, which can lead to subjective evaluations. When evaluating respiratory function based on the standards of other countries, several variables, such as the race and cultures of different countries, make it difficult to apply these standards. The purpose of this study was to propose objective respiratory muscle strength standards and predicted values for healthy Korean adults based on age, height, weight, and muscle strength, by measuring maximal inspiratory pressure (MIP), maximal expiratory pressure (MEP), and peak cough flow (PCF).

METHODS

This cross-sectional study analyzed MIP, MEP, and PCF in 360 people, each group comprising 30 adult men and women aged 20-70, diagnosed as healthy after undergoing medical check-ups at a general hospital. Hand grip strength (HGS) and the five times sit-to-stand test (FTSST) results were also recorded. Correlations among respiratory muscle strength, participant demographics, and overall muscle strength were evaluated using Pearson's correlation analysis. The predicted values of respiratory muscle strength were calculated using multiple regression analysis.

RESULTS

Respiratory muscle strength differed from the values reported in studies from other countries. In the entire samples, both MIP and MEP had the highest correlations with peak HGS (r = 0.643, r = 0.693; P < 0.05), while PCF had the highest correlation with forced expiratory volume in 1 s (r = 0.753; P < 0.05). Age, body mass index, peak HGS, and FTSST results were independent variables affecting respiratory muscle strength. A predictive equation for respiratory muscle strength was developed using the multiple regression equation developed in this study.

CONCLUSION

Respiratory muscle strength index may differ by country. For more accurate diagnoses, standard values for each country are required. This study presents reference values for Korea, and a formula for estimation is proposed when no respiratory muscle strength measurement equipment is available.

TRIAL REGISTRATION

Clinical Research Information Service Identifier: KCT0006778.

Heterogeneous Treatment Effects after Inspiratory Muscle Training during Recovery from Postacute COVID-19 Syndrome

PURPOSE

The objective of this study is to investigate whether heterogeneous treatment effects occur for changes in inspiratory muscle strength, perceived dyspnea, and health-related quality of life after 8 wk of unsupervised home-based inspiratory muscle training (IMT) in adults with postacute coronavirus disease 2019 (COVID-19) syndrome.

METHODS

In total, 147 adults with self-reported prior COVID-19 either completed an 8-wk home-based IMT intervention ( n = 111, 92 females, 48 ± 11 yr, 9.3 ± 3.6 months postacute COVID-19 infection) or acted as "usual care" wait list controls ( n = 36, 34 females, 49 ± 12 yr, 9.4 ± 3.2 months postacute COVID-19 infection).

RESULTS

Applying a Bayesian framework, we found clear evidence of heterogeneity of treatment response for inspiratory muscle strength: the estimated difference between standard deviations (SD) of the IMT and control groups was 22.8 cm H 2 O (75% credible interval (CrI), 4.7-37.7) for changes in maximal inspiratory pressure (MIP) and 86.8 pressure time units (75% CrI, 55.7-116.7) for sustained MIP (SMIP). Conversely, there were minimal differences in the SD between the IMT and the control group for changes in perceived dyspnea and health-related quality of life, providing no evidence of heterogeneous treatment effects. Higher cumulative power during the IMT intervention was related to changes in MIP ( β = 10.9 cm H 2 O (95% CrI, 5.3-16.8) per 1 SD) and SMIP ( β = 63.7 (32.2-95.3) pressure time units per 1 SD), clearly indicating an IMT dose response for changes in inspiratory muscle strength. Older age (>50 yr), a longer time postacute COVID-19 (>3 months), and greater severity of dyspnea at baseline were also associated with smaller improvements in inspiratory muscle strength.

CONCLUSIONS

Heterogeneous individual responses occurred after an 8-wk home-based IMT program in people with postacute COVID-19 syndrome. Consistent with standard exercise theory, larger improvements in inspiratory muscle strength are strongly related to a greater cumulative dose of IMT.

Similar effects on exercise performance following different respiratory muscle training programs in healthy young men

Both respiratory muscle endurance training (RMET) and inspiratory resistive training (IMT) seem to increase whole-body exercise performance, but direct comparisons between the two are scarce. We hypothesized that the similarity of RMET to exercise-induced ventilation would induce larger improvements compared to IMT. Twenty-six moderately-trained men performed either 4 weeks of RMET, IMT or SHAM training. Before and after the interventions, respiratory muscle endurance, 3-km running time-trial performance and leg muscle fatigue after intense constant-load cycling (assessed with femoral nerve magnetic stimulation) were measured. Both RMET (+ 59%) and IMT (+ 38%) increased respiratory muscle endurance (both p < 0.01 vs. SHAM) but only IMT increased inspiratory strength (+ 32%, p < 0.001 vs. SHAM). 3-km time improved showing a main effect of training (p = 0.026), however with no differences between groups. Leg fatigue after cycling was not attenuated with training (p = 0.088 for group-training interaction). All groups showed a significant (~ 0.3 l) increase in average tidal volume during cycling exercise combined with a concomitant reduction in respiratory exertion. While RMET and IMT improved specific aspects of respiratory muscles performance, no benefits beyond SHAM were seen during whole-body exercise. Changes in respiratory sensations might be a result of altered breathing pattern.

Effects of Inspiratory Muscle Training in Patients With Pulmonary Hypertension

The study aimed to examine the effects of inspiratory muscle training (IMT) in patients with pulmonary hypertension (PH). A total of 24 patients with PH were included in the randomized controlled evaluator-blind study. IMT was performed at 40% to 60% of the maximal inspiratory pressure for 30 min/d, 7 d/wk (1 day supervised) for 8 weeks. Respiratory muscle strength, dyspnea, diaphragm thickness (DT), pulmonary functions, 24-hour ambulatory blood pressure (BP), arterial stiffness, exercise capacity, upper extremity functional exercise capacity, physical activity levels, fatigue, anxiety-depression levels, activities of daily living (ADL), and quality of life were evaluated. A total of 24 patients (treatment = 12, control = 12) completed the 8-week follow-up. There was no significant difference between the patient groups in terms of demographic and clinical characteristics (p >0.05). Considering the change between the groups in the treatment and control groups, brachial and central BP, dyspnea, respiratory muscle strength, DT in total lung capacity, knee extension muscle strength, functional exercise capacity, upper extremity functional exercise capacity, physical activity, ADL, fatigue, anxiety, and quality of life improved in favor of the IMT group (p <0.05). In conclusion, IMT has improved brachial and central BP, dyspnea, respiratory muscle strength, DT in total lung capacity, knee extension muscle strength, functional exercise capacity, upper extremity functional exercise capacity, physical activity, ADL, fatigue, anxiety, and quality of life compared with the control group. IMT is an effective method in cardiopulmonary rehabilitation for patients with PH.

A Systematic Review of Methods Used to Determine the Work of Breathing during Exercise

INTRODUCTION

Measurement of the work of breathing (Wb) during exercise provides useful insights into the energetics and mechanics of the respiratory muscles across a wide range of minute ventilations. The methods and analytical procedures used to calculate the Wb during exercise have yet to be critically appraised in the literature.

PURPOSE

The aim of this systematic review was to evaluate the quality of methods used to measure the Wb during exercise in the available literature.

METHODS

We conducted an extensive search of three databases for studies that measured the Wb during exercise in adult humans. Data were extracted on participant characteristics, flow/volume and pressure devices, esophageal pressure (P oes ) catheters, and methods of Wb analysis.

RESULTS

A total of 120 articles were included. Flow/volume sensors used were primarily pneumotachographs ( n = 85, 70.8%), whereas the most common pressure transducer was of the variable reluctance type ( n = 63, 52.5%). Esophageal pressure was frequently obtained via balloon-tipped catheters ( n = 114, 95.0%). Few studies mentioned calibration, frequency responses, and dynamic compensation of their measurement devices. The most popular method of measuring the Wb was pressure-volume integration ( n = 51, 42.5%), followed by the modified Campbell ( n = 28, 23.3%) and Dean & Visscher diagrams ( n = 26, 21.7%). Over one-third of studies did not report the methods used to process their pressure-volume data, and the majority (60.8%) of studies used the incorrect Wb units and/or failed to discuss the limitations of their Wb measurements.

CONCLUSIONS

The findings of this systematic review highlight the need for the development of a standardized approach for measuring Wb, which is informative, practical, and accessible for future researchers.

Effects of Sprint Interval and Endurance Respiratory Muscle Training on Postcycling Inspiratory and Quadriceps Fatigue

PURPOSE

We investigated whether a 4-wk period of respiratory muscle endurance training (RMET) or respiratory muscle sprint interval training (RMSIT) would lead to an attenuation of inspiratory muscle and quadriceps fatigue after a bout of high-intensity cycling compared with a placebo intervention (PLAT), as predicted by the respiratory metaboreflex model.

METHODS

Thirty-three active, young healthy adults performed RMET, RMSIT, or PLAT. Changes in inspiratory muscle and quadriceps twitches in response to a cycling test at 90% of peak work capacity were assessed before and after training. EMG activity and deoxyhemoglobin (HHb, via near-infrared spectroscopy) of the quadriceps and inspiratory muscles were also monitored during the cycling test, along with cardiorespiratory and perceptual variables.

RESULTS

At pretraining, cycling reduced the twitch force of the inspiratory muscles (86% ± 11% baseline) and quadriceps (66% ± 16% baseline). Training did not attenuate the drop in twitch force of the inspiratory muscles (PLAT, -3.5 ± 4.9 percent-points [p.p.]; RMET, 2.7 ± 11.3 p.p.; RMSIT, 4.1 ± 8.5 p.p.; group-training interaction, P = 0.394) or quadriceps (PLAT, 3.8 ± 18.6 p.p.; RMET, -2.6 ± 14.0 p.p.; RMSIT, 5.2 ± 9.8 p.p.; group-training interaction P = 0.432). EMG activity and HHb levels during cycling did not change after training for either group. Only RMSIT showed a within-group decrease in the perception of respiratory exertion with training.

CONCLUSIONS

Four weeks of RMET or RMSIT did not attenuate the development of exercise-induced inspiratory or quadriceps fatigue. The ergogenic effects of respiratory muscle training during whole-body exercise might be related to an attenuation of perceptual responses.

Comparison of two inspiratory muscle training protocols in people with spinal cord injury: a secondary analysis

STUDY DESIGN/SETTING

Secondary analysis.

OBJECTIVES

To compare the change in maximal inspiratory pressure (PImax) over the first 4 weeks of two different inspiratory muscle training (IMT) protocols and explore if either method is more effective for people with spinal cord injury.

METHODS

Data originated from two published studies. Participants completed flow-resistive IMT (F-IMT) at 80% daily PImax, 7 days/week (supervised weekly), or threshold IMT (T-IMT) at 30-80% weekly PImax, twice-daily, 5 days/week (supervised every session). Seven participants from each trial were matched by training adherence, level of spinal cord injury, impairment grade (A-C), and height. Differences between F-IMT and T-IMT groups in training intensity, breaths taken, inspiratory work, and the change in the PImax from baseline at the end of week four were analysed.

RESULTS

Over 4 weeks, there was no difference in the change in PImax between groups (Absolute change in PImax (cmH2O): p = 0.456, Percent change in PImax relative to baseline: p = 0.128). F-IMT participants trained at a higher intensity (median: 77 vs 22 cmH2O, p = 0.001 and 80% baseline vs 61% baseline, p = 0.038) but took fewer breaths (840 vs 1404 breaths, p = 0.017) than T-IMT participants. Inspiratory work was similar between groups (64,789 vs 65,910 (% PImax × number of breaths), p = 0.535).

CONCLUSIONS

Our findings support both methods of IMT as the change in PImax and inspiratory work were similar between groups. However, daily high-intensity F-IMT with intermittent supervision, required fewer breaths and less participant and therapist time. Future studies should examine optimal dosage and supervision required to achieve increased PImax.

Evaluation of the possible effect of inspiratory muscle training on inflammation markers and oxidative stress in childhood asthma

Airway inflammation characterized as asthma is one of the most common chronic diseases in the world. The aim of this study was to evaluate the possible effect of inspiratory muscle training on inflammation markers and oxidative stress levels in childhood asthma. A total of 105 children (age range 8-17 years), including 70 asthmatics and 35 healthy children, participated in the study. The 70 asthma patients were randomly assigned to the inspiratory muscle training (IMT) group (n = 35) and control group (n = 35), and healthy children were assigned to the healthy group (n = 35). The IMT group was treated with the threshold IMT device for 7 days/6 weeks at 30% of maximum inspiratory pressure. Respiratory muscle strength was evaluated with a mouth pressure measuring device, and respiratory function was evaluated with a spirometer. In addition, CRP, periostin, TGF-β, and oxidative stress levels were analyzed. The evaluation was performed only once in the healthy group and twice (at the beginning and end of 6 weeks) in asthma patients. In the study, there were significant differences between asthma patients and the healthy group in terms of MIP and MEP values, respiratory function, oxidative stress level, periostin, and TGF-β. Post-treatment, differences were observed in the oxidative stress level, periostin, and TGF-β of the IMT group (p < .05).

CONCLUSION

After 6 weeks of training, IMT positively contributed to reducing the inflammation level and oxidative stress. This suggests that IMT should be used as an alternative therapy to reduce inflammation and oxidative stress. (Trial Registration: The clinical trial protocol number is NCT05296707).

WHAT IS KNOWN

• It is known that adjunctive therapies given in addition to pharmacological treatment contribute to improving symptom control and quality of life in individuals with asthma.

WHAT IS NEW

• There are no studies about the effect of respiratory physiotherapy on biomarkers in asthmatic children. The sub-mechanism of improvement in individuals has not been elucidated. • In this context, inspiratory muscle training has a positive effect on inflammation and oxidative stress levels in children with asthma and IMT should be used as an alternative treatment for childhood asthma.

Reduced peripheral and respiratory muscle strength in pediatric patients after kidney transplantation

INTRODUCTION

Reduced muscle strength and low-exercise capacity are well documented in adults, but there are few studies examining those impairments in children and adolescents after kidney transplantation. The objective of this study was to evaluate peripheral and respiratory muscle strength and the association with submaximal exercise capacity in children and adolescents after kidney transplant.

METHODS

Forty-seven patients between six and 18 years of age clinically stable after transplantation were included. Peripheral muscle strength (isokinetic and hand-grip dynamometry), respiratory muscle strength (maximal inspiratory and expiratory pressure), and submaximal exercise capacity (six-minute walk test - 6MWT) were assessed.

RESULTS

Patients had a mean age of 13.1 ± 2.7 years and an average of 34 months had elapsed since the transplantation. Flexors of the knee showed a significant reduction in muscle strength (77.3% of predicted) and knee extensors had normal values (105.4% of predicted). Hand-grip strength and maximal respiratory pressures (inspiratory and expiratory) also were significantly lower than expected (p < 0.001). Although distance walked in the 6MWT was significantly lower than predicted (p < 0.001), no significant correlation was found with peripheral and respiratory muscle strength.

CONCLUSION

Children and adolescents after kidney transplantation have reduced peripheral muscle strength of knee flexors, hand-grip, and maximal respiratory pressures. No associations were found between peripheral and respiratory muscle strength and submaximal exercise capacity.