Novel methods of inspiratory muscle training via the Test of Incremental Respiratory Endurance (TIRE)

Functional Sitting Balance and Anthropometric Measures Are Related to Inspiratory Muscle Performance in People with Spinal Cord Injury

Background

Respiratory complications are a leading cause of mortality post spinal cord injury (SCI). Along with breathing, respiratory muscles have a role in maintaining seated balance. Postinjury breathing influences respiratory muscle function. Preliminary evidence indicates a relation between respiratory muscle function and seated balance in people with chronic SCI dwelling in the community, but the relationship between balance and body habitus has not been explored.

Objectives

To explore the relationships among inspiratory muscle function, functional seated balance (FSB), and body habitus in people with SCI.

Methods

A convenience sample of inpatients with SCI (C5-T12) aged 18 to 60 years who were using a wheelchair was recruited from November 2022 to March 2023. Those with additional neurological disorders or respiratory support were excluded. Respiratory muscle function measures included maximal inspiratory pressure (MIP), sustained MIP (SMIP), and Fatigue Index Test (FIT). FSB was scored using the Function in Sitting Test (FIST). Body habitus was assessed using the axillary: umbilical (A:U) ratio. Spearman correlations explored the relationships.

Results

Thirty-eight of 42 screened participants were eligible and participated (male, 32). Levels of injury ranged from C5 to T12. The mean (SD) age and duration of injury of the sample was 25.61 (6.68) years and 31.03 (28.69) months, respectively. SMIP and FIT correlated significantly with FSB (r s= .441, p = .01, and r s= .434, p = .006, respectively). A significant correlation between SMIP and A:U ratio (r s= -.330, p = .043) was observed.

Conclusion

We observed a significant correlation between inspiratory pressure parameters and both functional seated balance and body habitus, adding to evidence on postural role of respiratory muscles.

Effectiveness of Respiratory Muscles Training by Voluntary Isocapnic Hyperpnea Versus Inspiratory Threshold Loading on Intercostales and Vastus Lateralis Muscles Deoxygenation Induced by Exercise in Physically Active Adults

Respiratory muscle training (RMT) improves physical performance, although it is still debated whether this effect depends on the type of training. The purpose of this study was to compare the effects of two different types of RMT, i.e., voluntary isocapnic hyperpnea (VIH) and inspiratory threshold loading (ITL), on the deoxygenation of intercostal (ΔSmO₂-m. intercostales) and vastus lateralis (ΔSmO₂-m. vastus lateralis) muscles during exercise. Twenty-four participants performed eight weeks of RMT by: (i) VIH (3 days·week^-1 for 12 min at 60% maximal voluntary ventilation) or (ii) ITL (5 sets·week^-1 of 30 breaths·minute^-1 at 60% maximal inspiratory pressure). Cardiopulmonary exercise testing (CPET) included ΔSmO₂ (the change from baseline to end of test) of intercostal and vastus lateralis muscles. After RMT, both groups showed decreased ΔSmO₂-m. intercostales (VIH = 12.8 ± 14.6%, p = 0.04 (effect size, ES = 0.59), and ITL = 8.4 ± 9.8%, p = 0.04 (ES = 0.48)), without a coincident change of ∆SmO_2-m. vastus lateralis. ITL training induced higher V˙O_2-peak absolute values than VIH (mean Δ post-pre, ITL = 229 ± 254 mL·min^-1 [95% CI 67-391] vs. VIH, 39 ± 153 mL·min^-1 [95% CI -58-136.0], p = 0.01). In conclusion, both RMT improved the balance between supply and oxygen consumption levels of m. intercostales during CPET, with ITL also inducing an increase of aerobic capacity.

Adherence to and impact of home-based high-intensity IMT in people with spinal cord injury: a pilot study

Study design

The pilot study was completed in 5 phases (Control and 4 phases of IMT) incorporating assessments at Baseline 1 (BL1), BL2, Follow-up 1 (F1), F2, F3, and F4.

Objective

To assess the adherence and impact of a daily high-intensity (80% of max) inspiratory muscle training (IMT) home program with once weekly supervision for people with spinal cord injury (SCI).

Setting

Assessments: research institution or zoom. IMT: participant’s home.

Methods

Participants completed daily IMT in IMT Phase 1 and 2, once weekly in IMT Phase 3, self-selected frequency in IMT Phase 4. All phases had one weekly supervised session except IMT Phase 4. Primary outcomes included adherence and a difficulty score [DS (0- not difficult to 10- the most difficult)]. Secondary outcomes included respiratory function and seated balance.

Results

Data from 10 people with chronic SCI (>1 year) (Cervical level of injury: 6, AIS: A-B, injury duration: 10.9 years 95% CI [3.9, 18.1]) were used in the analysis. Participants completed 69% of their training days in IMT Phase 1 and 65% overall reporting an average DS of 7.4 ± 1.4. Only one participant completed training during IMT Phase 4. One participant’s training load was reduced due to suspected overtraining. Maximal inspiratory pressure (MIP), sustained MIP (SMIP), and total power (TP), improved significantly (p < 0.05) from BL2 to F1.

Conclusion

Our data suggest that people with SCI can perform high-intensity IMT at home to improve inspiratory performance. It is strongly recommended that participants be intermittently monitored for adherence and safety.

ClinicalTrials.gov Registration number: NCT04210063.

The effects of COVID-19 on respiratory muscle performance: making the case for respiratory muscle testing and training

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection results in multiorgan damage primarily mediated by viral infiltration via angiotensin-converting enzyme-2 receptors on the surface of cells. A primary symptom for many patients is exertional dyspnoea which may persist even beyond recovery from the viral infection. Respiratory muscle (RM) performance was hypothesised as a contributing factor to the severity of coronavirus disease 2019 (COVID-19) symptoms, such as dyspnoea, and outcomes. This was attributed to similarities between patient populations at elevated risk for severe COVID-19 symptoms and those with a greater likelihood of baseline RM weakness and the effects of prolonged mechanical ventilation. More recent evidence suggests that SARS-CoV-2 infection itself may cause damage to the RM, and many patients who have recovered report persistent dyspnoea despite having mild cases, normal lung function or undamaged lung parenchyma. These more recent findings suggest that the role of RM in the persistent dyspnoea due to COVID-19 may be more substantial than originally hypothesised. Therefore, screening for RM weakness and providing interventions to improve RM performance appears to be important for patients with COVID-19. This article will review the impact of SARS-CoV-2 infection on RM performance and provide clinical recommendations for screening RM performance and treatment interventions.

Inspiratory Muscle Performance Is Related to Seated Balance Function in People With Spinal Cord Injury: An Observational Study

OBJECTIVE

To examine the relationship between inspiratory muscle performance (IMP) and functional sitting balance (FSB) in persons with chronic spinal cord injury (SCI). We hypothesized that a moderate correlation would be found between IMP and FSB and that individuals with better balance would have better IMP.

DESIGN

The SCI-specific modification of the Function in Sitting Test (FIST-SCI) measured FSB. The IMP measures included (1) maximal inspiratory pressure (MIP), (2) sustained MIP (SMIP), and (3) inspiratory duration. Upper extremity motor score (UEMS) and level of injury (LOI) were taken from International Standards for Neurological Classification of Spinal Cord Injury examinations. Spearman correlational analyses assessed relationships among these factors in the sample (N=37). Mann-Whitney U tests explored differences between 2 comparison group pairs (tetraplegia group [TG] vs paraplegia group [PG]; independent transfer group [ITG] vs assisted transfer group [ATG]). Regression analysis examined variables predictive of FSB in the TG.

SETTING

Research facility.

PARTICIPANTS

Volunteers with tetraplegia (n=21, American Spinal Injury Association Impairment Scale (AIS) A=8, B=7, C=6) and paraplegia (n=16, AIS A=9, B=4, C=3) (N=37).

INTERVENTION

Not applicable.

MAIN OUTCOME MEASURES

IMP, LOI, UEMS, FIST-SCI.

RESULTS

UEMS, MIP, SMIP, and LOI had moderate to high correlations with FIST-SCI scores (ρ=0.720 (P<.001), 0.480 (P=.003), 0.467 (P=.004), 0.527 (P=.001), respectively). UEMS, MIP, and FIST-SCI scores were higher in the PG and ITG than the TG and ATG, respectively (PG vs. TG P values=<.001, .008, .002, respectively, and ITG vs. ATG P values=<.001, .032, <.001, respectively). Further, SMIP and UEMS predicted FIST-SCI balance scores in the TG, accounting for 55% of total variance (P<.001) (FIST-SCI=11.88+0.03 [SMIP]+0.425 [UEMS]).

CONCLUSIONS

The relationship between IMP and balance appears preserved after SCI. FSB was predicted, in part, via UEMS and SMIP in the TG. Future research should focus on the effect of SCI-based breathing interventions on FSB.

Sex-Differences in the Oxygenation Levels of Intercostal and Vastus Lateralis Muscles During Incremental Exercise

This study aimed to examine sex differences in oxygen saturation in respiratory (SmO₂-m.intercostales) and locomotor muscles (SmO₂-m.vastus lateralis) while performing physical exercise. Twenty-five (12 women) healthy and physically active participants were evaluated during an incremental test with a cycle ergometer, while ventilatory variables [lung ventilation ( V . E), tidal volume (Vt), and respiratory rate (RR)] were acquired through the breath-by-breath method. SmO₂ was acquired using the MOXY^® devices on the m.intercostales and m.vastus lateralis. A two-way ANOVA (sex × time) indicated that women showed a greater significant decrease of SmO₂-m.intercostales, and men showed a greater significant decrease of SmO₂-m.vastus lateralis. Additionally, women reached a higher level of ΔSmO₂-m.intercostales normalized to V . E (L⋅min^-1) (p < 0.001), whereas men had a higher level of ΔSmO₂-m.vastus lateralis normalized to peak workload-to-weight (watts⋅kg^-1, PtW) (p = 0.049), as confirmed by Student's t-test. During an incremental physical exercise, women experienced a greater cost of breathing, reflected by greater deoxygenation of the respiratory muscles, whereas men had a higher peripheral load, indicated by greater deoxygenation of the locomotor muscles.

Inspiratory Muscle Performance and Anthropometric Measures-Novel Assessments Related to Pulmonary Function in People with Spinal Cord Injury: A Pilot Study

OBJECTIVE

To investigate the feasibility and validity of using the novel axillary:umbilical (A:U) ratio and sustained maximal inspiratory pressure (SMIP) as supplementary measures in the assessment of respiratory function in people with spinal cord injury.

DESIGN

Pilot study with a single day of data collection. All measurements were taken with participants in their personal wheelchairs to best represent normal functioning and positioning for each individual.

SETTING

Research institution.

PARTICIPANTS

A convenience sample of 30 community dwelling volunteers with chronic spinal cord injury (C2-T12, American Spinal Injury Association Impairment Scale A-D) participated.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Participants underwent anthropometric measurements (trunk height, abdominal circumference, axillary circumference) and assessment of inspiratory muscle performance, incluidng maximal inspiratory pressure, SMIP, and inspiratory duration, as well as standard pulmonary function tests.

RESULTS

The A:U ratio and SMIP were recorded for all participants. The SMIP was significantly related to more respiratory performance measures than the maximal inspiratory pressure (P<.05) and the A:U ratio was significantly related to more respiratory performance measures than any other anthropometric measure (P<.05). Additionally, an A:U ratio cutoff point detected individuals with a peak expiratory flow ≥ 80% of their predicted value with a sensitivity and specificity of 85.7% and 91.3%, respectively (area under the curve: 0.92).

CONCLUSIONS

It is feasible to capture the A:U Ratio and SMIP in individuals with spinal cord injury. Further, the strong significant relationships of SMIP and the A:U ratio to respiratory performance measures suggests their clinical importance in the pulmonary assessment and risk stratification of people with chronic spinal cord injury.

The Effect of a High-Intensity PrO2Fit Inspiratory Muscle Training Intervention on Physiological and Psychological Health in Adults with Bronchiectasis: A Mixed-Methods Study

Bronchiectasis is characterised by airflow obstruction and hyperinflation resulting in respiratory muscle weakness, and decreased exercise capacity. Inspiratory muscle training (IMT) is potentially an alternative treatment strategy to enhance respiratory muscle strength and endurance. Therefore, the aim was to investigate the effects of IMT on those with bronchiectasis. Eighteen participants (10 bronchiectasis) took part in an eight-week, three times a week IMT programme at 80% sustained maximal inspiratory pressure (SMIP). Lung function, respiratory muscle strength and endurance, exercise capacity, physical activity and self-determination theory measures were taken. Participants also took part in a semi-structured interview to assess their perceptions and experience of an IMT intervention. After eight weeks of IMT, bronchiectasis and healthy participants exhibited significant increases in MIP (27% vs. 32%, respectively), SMIP (16% vs. 17%, respectively) and inspiratory duration (36% vs. 30%, respectively). Healthy participants exhibited further improvements in peak expiratory flow and maximal oxygen consumption. Bronchiectasis participants reported high levels of perceived competence and motivation, reporting higher adherence and improved physical ability. Eight weeks of IMT increased inspiratory muscle strength and endurance in those with bronchiectasis. IMT also had a positive effect on perceived competency and autonomy, with bronchiectasis participants reporting improved physical ability and motivation, and high adherence.

Moderate- and High-Intensity Inspiratory Muscle Training Equally Improves Inspiratory Muscle Strength and Endurance-A Double-Blind Randomized Controlled Trial

BACKGROUND AND OBJECTIVE

Inspiratory muscle training (IMT) produced outstanding results in the physical performance of active subjects; however, little is known about the best training intensity for this population. The objective was to investigate the impact of an IMT of high intensity, using the critical inspiratory pressure (CIP), on inspiratory muscle strength (IMS), inspiratory muscle endurance (IME), peak power, and oxygen uptake of recreational cyclists; and to compare these results with moderate-intensity IMT (60% of maximal inspiratory pressure [MIP]).

METHODS

Thirty apparently healthy male recreational cyclists, 20-40 years old, underwent 11 weeks of IMT (3 times per week; 55 min per session). Participants were randomized into 3 groups: sham group (6 cmH2O; n = 8); 60% MIP (MIP60; n = 10) and CIP (n = 12). All participants performed the IMS test and incremental IME test at the first, fifth, ninth, and 13th weeks of the experimental protocol. Cardiopulmonary exercise testing was performed on an electromagnetic braking cycle ergometer pre-IMT and post-IMT. Data were analyzed using a 2-way repeated measures ANOVA (group and period factors).

RESULTS

IMS increased in CIP and MIP60 groups at the ninth and 13th weeks compared with the sham group (P < .001; β = 0.99). Regarding IME, there was an interaction between the CIP and MIP60 groups in all periods, except in the initial evaluation (P < .001; β = 1.00). Peak power (in watts) increased after IMT in CIP and MIP60 groups (P = .01; β = 0.67). Absolute oxygen uptake did not increase after IMT (P = .49; β = 0.05). Relative oxygen uptake to lean mass values did not change significantly (P = .48; β = 0.05).

CONCLUSION

High-intensity IMT is beneficial on IMS, IME, and peak power, but does not provide additional gain to moderate intensity in recreational cyclists.

Respiratory Muscle Performance Screening for Infectious Disease Management Following COVID-19: A Highly Pressurized Situation

The 2019-2020 coronavirus pandemic elucidated how a single highly infectious virus can overburden health care systems of even highly economically developed nations. A leading contributor to these concerning outcomes is a lack of available intensive care unit (ICU) beds and mechanical ventilation support. Poorer health is associated with a higher risk for severe respiratory complications from the coronavirus. We hypothesize that impaired respiratory muscle performance is an underappreciated factor contributing to poor outcomes unfolding during the coronavirus pandemic. Although impaired respiratory muscle performance is considered to be rare, it is more frequently encountered in patients with poorer health, in particular obesity. However, measures of respiratory muscle performance are not routinely performed in clinical practice, including those with symptoms such as dyspnea. The purpose of this article is to discuss the potential role of respiratory muscle performance from the perspective of the coronavirus pandemic. We also provide a theoretical patient management model to screen for impaired respiratory muscle performance and intervention, if identified, with the goal of unburdening health care systems during future pandemic crises.

Novel versus Traditional Inspiratory Muscle Training Regimens as Home-Based, Stand-Alone Therapies in COPD: Protocol for a Randomized Controlled Trial

BACKGROUND

Subjects with COPD frequently develop considerable weakness and deconditioning of the inspiratory musculature, which can be corrected with inspiratory muscle training (IMT). While rehabilitation centers may be able to provide IMT as part of the rather complex management of COPD, there is currently a lack of rehabilitation services in the Czech Republic. Remote IMT may then benefit subjects with COPD who are unable to attend or do not have access to rehabilitation programs. We aim at evaluating the utility of the test of incremental respiratory endurance (TIRE) as an at-home IMT method in subjects with COPD, while comparing the effectiveness of this novel training approach to the outcomes of traditional, threshold loading IMT protocols.

METHODS/DESIGN

This prospective, randomized controlled trial will comprise 8 weeks of at-home IMT sessions with remote supervision followed by 4 months of unsupervised, independent IMT. Eligible subjects will be randomly assigned to one of the following three distinct home-based IMT protocols: (1) TIRE, (2) Threshold loading, and (3) Sham training. Subjects allocated to the TIRE group will train once daily using an advanced IMT electronic system (PrO2), while the other two groups will receive threshold devices. Study outcomes will include measures of inspiratory muscle strength and endurance, pulmonary function, COPD-specific symptomatology, functional exercise capacity, surrogate markers of mortality risk, mental health status and health-related quality of life.

DISCUSSION

While we acknowledge the value of threshold loading IMT protocols, we believe that the TIRE training method has the potential to provide additional clinical benefits in COPD given its sophisticated remote tracking system and ability to modulate all aspects of muscular performance, including not only strength but also endurance, power and work capacity, allowing users to achieve considerably higher inspiratory pressures throughout the full range of inspiration when compared to other more traditionally used IMT methods.

Inspiration for the Future: The Role of Inspiratory Muscle Training in Cystic Fibrosis

Cystic fibrosis (CF) is an inherited, multi-system, life-limiting disease characterized by a progressive decline in lung function, which accounts for the majority of CF-related morbidity and mortality. Inspiratory muscle training (IMT) has been proposed as a rehabilitative strategy to treat respiratory impairments associated with CF. However, despite evidence of therapeutic benefits in healthy and other clinical populations, the routine application of IMT in CF can neither be supported nor refuted due to the paucity of methodologically rigorous research. Specifically, the interpretation of available studies regarding the efficacy of IMT in CF is hampered by methodological threats to internal and external validity. As such, it is important to highlight the inherent risk of bias that differences in patient characteristics, IMT protocols, and outcome measurements present when synthesizing this literature prior to making final clinical judgments. Future studies are required to identify the characteristics of individuals who may respond to IMT and determine whether the controlled application of IMT can elicit meaningful improvements in physiological and patient-centered clinical outcomes. Given the equivocal evidence regarding its efficacy, IMT should be utilized on a case-by-case basis with sound clinical reasoning, rather than simply dismissed, until a rigorous evidence-based consensus has been reached.

The BODE index and inspiratory muscle performance in COPD: Clinical findings and implications

Objectives

The Test of Incremental Respiratory Endurance is a novel testing method that provides a unique examination of one's inspiratory muscle strength, work and endurance. Little is known about the relationship between inspiratory muscle performance and mortality risk in obstructive lung disease. We examined the relationship between the Test of Incremental Respiratory Endurance measures and the Body-mass index, airflow Obstruction, Dyspnea and Exercise index in chronic obstructive pulmonary disease.

Methods

In all, 70 males with mild-to-very severe chronic obstructive pulmonary disease (mean ± standard deviation of 70.2 ± 5.9 years) underwent measurements of body-mass index, spirometry, dyspnea and a 6-min walk test from which the Body-mass index, airflow Obstruction, Dyspnea and Exercise score was calculated. The Test of Incremental Respiratory Endurance provided measures of maximal inspiratory pressure, sustained maximal inspiratory pressure and inspiratory duration.

Results

All Test of Incremental Respiratory Endurance parameters inversely correlated with the Body-mass index, airflow Obstruction, Dyspnea and Exercise score: maximal inspiratory pressure (r = -0.355, p = 0.00), sustained maximal inspiratory pressure (r = -0.426, p = 0.00) and ID (r = -0.278, p = 0.02), with sustained maximal inspiratory pressure displaying the highest correlation. Independent significant correlations were also observed between the sustained maximal inspiratory pressure and all Body-mass index, airflow Obstruction, Dyspnea and Exercise score components, except for body-mass index. Finally, sustained maximal inspiratory pressure was significantly different among the Body-mass index, airflow Obstruction, Dyspnea and Exercise index quartiles.

Discussion

The significant association between the Body-mass index, airflow Obstruction, Dyspnea and Exercise score and inspiratory muscle performance, in particular sustained maximal inspiratory pressure, suggests that these measures may have a potential prognostic value in the evaluation of chronic obstructive pulmonary disease.

Reliability and validity of the test of incremental respiratory endurance measures of inspiratory muscle performance in COPD

Purpose

The Test of Incremental Respiratory Endurance (TIRE) provides a comprehensive assessment of inspiratory muscle performance by measuring maximal inspiratory pressure (MIP) over time. The integration of MIP over inspiratory duration (ID) provides the sustained maximal inspiratory pressure (SMIP). Evidence on the reliability and validity of these measurements in COPD is not currently available. Therefore, we assessed the reliability, responsiveness and construct validity of the TIRE measures of inspiratory muscle performance in subjects with COPD.

Patients and methods

Test-retest reliability, known-groups and convergent validity assessments were implemented simultaneously in 81 male subjects with mild to very severe COPD. TIRE measures were obtained using the portable PrO2 device, following standard guidelines.

Results

All TIRE measures were found to be highly reliable, with SMIP demonstrating the strongest test-retest reliability with a nearly perfect intraclass correlation coefficient (ICC) of 0.99, while MIP and ID clustered closely together behind SMIP with ICC values of about 0.97. Our findings also demonstrated known-groups validity of all TIRE measures, with SMIP and ID yielding larger effect sizes when compared to MIP in distinguishing between subjects of different COPD status. Finally, our analyses confirmed convergent validity for both SMIP and ID, but not MIP.

Conclusion

The TIRE measures of MIP, SMIP and ID have excellent test-retest reliability and demonstrated known-groups validity in subjects with COPD. SMIP and ID also demonstrated evidence of moderate convergent validity and appear to be more stable measures in this patient population than the traditional MIP.