Heart FailureIMT-HF-COMPARENCT07688863

Comparative Effects of Different Inspiratory Muscle Training Modalities in Patients With Heart Failure.

A study testing Mechanical Pressure-Threshold IMT Device and PowerBreathe KH2 Electronic IMT Device in people with Heart Failure and Heart Failure and Reduced Ejection Fraction, run by Universidad Nacional Andres Bello at 1 site in Chile.

Enrolling by invitation

Enrolling by invitation. The study team selects and invites participants, usually from an existing group of patients.

Sites and contacts

Official record

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Trial summary

The purpose of this study is to compare the effects of three different modalities of inspiratory muscle training (IMT) in patients diagnosed with chronic heart failure who exhibit reduced or mid-range left ventricular ejection fraction (LVEF < 50%). Read more about this study

Who is it for?: Ages 18 years and older
Conditions the study is for: Heart Failure, Heart Failure and Reduced Ejection Fraction, Heart Failure and Mildly Reduced Ejection Fraction
What is being tested?: Mechanical Pressure-Threshold IMT Device and PowerBreathe KH2 Electronic IMT Device
Type of treatment: Medical device
Could I receive a placebo?: Yes, some participants may receive a placebo
How many people: 60 participants
Where: 1 siteChile
Study dates: 17 Jun 2026to Dec 2027
Phase: Interventional
Are there results?: Not yet: the study is under way

Key requirements

Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.

Ages 18 years and older
All sexes
No healthy volunteers
Adult, Older adult

Who may be able to join

Documented clinical diagnosis of chronic Heart Failure with Reduced Ejection Fraction (HFrEF) according to the European Society of Cardiology (ESC) guidelines.
Left Ventricular Ejection Fraction (LVEF) less than or equal to 40% documented by echocardiography within the last 12 months.
Clinically stable condition for at least 3 months prior to enrollment, with no hospitalizations or major changes in optimized medical therapy.
New York Heart Association (NYHA) functional class I to IV.
Evidence of inspiratory muscle weakness, defined as a baseline Maximal Inspiratory Pressure (MIP) < 70% of the predicted value for age and sex.
Age greater than or equal to 18 years.
Patient must be capable of understanding the protocol instructions and must provide signed written informed consent.

Who cannot join

Presence of primary severe pulmonary or respiratory diseases (e.g., Chronic Obstructive Pulmonary Disease [COPD] GOLD stage III or IV, active asthma, severe pulmonary hypertension, or restrictive lung disease).
Recent myocardial infarction, unstable angina, or coronary artery bypass graft (CABG) surgery within the last 6 months.
Severe uncorrected valvular heart disease or complex, uncontrolled ventricular arrhythmias.
Orthopedic, neurological, or musculoskeletal limitations that prevent the safe execution of an incremental cardiopulmonary exercise test on a cycle ergometer or the performance of the isometric handgrip protocol.
Cognitive impairment or psychological conditions that limit the ability to follow instructions, maintain correct diaphragmatic breathing technique, or properly seal the training device mouthpiece.
Current participation in another structured physical rehabilitation or formal sports training program that could confound the systemic results of the intervention.
Any acute infectious, inflammatory, or medical condition that, in the investigator's opinion, poses a safety risk during high-intensity training.

Trial locations and contacts

1 site in 1 country. Contact the study team or a site near you to ask about taking part.

Chile1 site

Universidad Andrés Bello, Campus Viña del Mar
Viña del Mar, Valparaiso, 2520000

Other trials in Chile

About this study

Official title: Effects of Inspiratory Muscle Training on Maximal Inspiratory Pressure, Cardiopulmonary Capacity, and Quality of Life in Patients With Heart Failure

The study has a total duration of 8 weeks and is divided into two distinct phases. During the first 2 weeks, participants will undergo a familiarization phase to learn the proper breathing techniques with the devices and to complete baseline resting and functional clinical evaluations. The following 6 weeks will comprise the effective training phase, consisting of 3 weekly sessions of high-intensity inspiratory training.

Participants will be randomly assigned to one of three parallel groups:

Group 1 (Pressure-Threshold IMT): Participants will train using a mechanical pressure-threshold device at an initial high-intensity load of 60% of their baseline maximal inspiratory pressure (MIP).
Group 2 (Electronic Flow-Resistive IMT): Participants will train at a high-intensity load of 60% of their baseline MIP utilizing the PowerBreathe KH2 electronic device, which provides a dynamic, flow-dependent automated resistance.
Group 3 (Control / Sham IMT): Participants will perform the same breathing protocol but using a mechanical device set at a low, non-training intensity of 15% of their baseline MIP.

For all three groups, training volume is standardized to 5 sets of 8 repetitions (40 inspiratory efforts per session). To ensure progressive overload, training intensity will be increased by 10% of the initial baseline MIP value every 2 weeks.

The main outcomes to be evaluated before and immediately after the 8-week period include maximal inspiratory muscle strength, structural changes in respiratory muscles (diaphragmatic and parasternal intercostal thickening fraction measured via ultrasound), cardiac autonomic balance (heart rate variability), and health-related quality of life. Additionally, dynamic responses such as respiratory and locomotor muscle oxygenation (measured continuously via Near-Infrared Spectroscopy [NIRS] during a respiratory metabolic reflex provocation test) and overall cardiopulmonary exercise capacity (measured via an incremental cycle ergometer test) will be analyzed.

This study aims to determine which training modality provides the most effective physiological adaptations to optimize rehabilitation in this population.

Read the detailed description

This clinical trial aims to explore the underlying physiological mechanisms and comparative systemic adaptations of mechanical pressure-threshold versus electronic flow-resistive inspiratory muscle training (IMT) in patients with Heart Failure with Reduced Ejection Fraction (HFrEF). Patients with HFrEF frequently exhibit respiratory muscle weakness, which triggers an early activation of the inspiratory muscle metaboreflex. This reflex increases sympathetic vasoconstrictor drive to active locomotor muscles, accelerating peripheral fatigue, exacerbating dyspnea, and limiting overall exercise tolerance.

To systematically address these mechanisms, the protocol is structured into a precise multi-stage timeline distributed over 8 consecutive weeks:

Methodological Familiarization and Baseline Testing (Weeks 1-2): To eliminate the confounding "learning effect" and ensure internal data validity, the first two weeks are exclusively dedicated to patient technical habituation. Participants will learn proper diaphragmatic breathing techniques, device interface seal (using flanged mouthpieces and nose clips), and device manipulation under submaximal loads. Concurrently, baseline clinical profiling will be conducted, including spirometry, maximal inspiratory pressure (MIP), resting cardiac autonomic balance through Heart Rate Variability (HRV), and central vascular stiffness via Pulse Wave Velocity (PWV).
High-Intensity Standardized Intervention (Weeks 3-8): The formal training phase lasts 6 weeks with a frequency of 3 supervised sessions per week, totaling 18 effective sessions. To preserve biomechanical quality and prevent disproportionate dyspnea or early neuromuscular fatigue in this clinical population, the training volume is strictly set to 5 sets of 8 repetitions (40 breathing efforts per session), separated by standardized resting intervals. The progression scheme utilizes a linear model based on the initial baseline MIP, preventing the logistical friction of constant maximum re-testing in fragile patients:

Weeks 3-4: 60% of baseline MIP (Groups 1 and 2) or 15% (Group 3).
Weeks 5-6: Progression to 70% of baseline MIP (Groups 1 and 2) or 15% (Group 3).
Weeks 7-8: Progression to 80% of baseline MIP (Groups 1 and 2) or 15% (Group 3).

Advanced Dynamic Evaluations:

Muscle Oxygenation and Metaboreflex Provocation (NIRS): Peripheral blood flow redistribution and tissue oxygen saturation kinetics (SmO2) will be tracked continuously via three percutaneous Near-Infrared Spectroscopy sensors (Moxy Monitor®) placed simultaneously on the right intercostal space (respiratory pump), vastus lateralis of the quadriceps (locomotor reference), and the dominant forearm flexor mass (non-locomotor control). The provocation protocol includes an inspiratory resistive load test at 60% MIP until task failure (inability to sustain target pressure for three consecutive breaths), followed immediately by an isometric Handgrip peripheral fatigue protocol (12 repetitions of 10-second maximal voluntary contractions with 30-second rests).
Cardiopulmonary Exercise Testing (CPET): Maximal oxygen consumption (VO2max) and ventilatory efficiency (VE/VCO2 slope) will be evaluated using a cycle ergometer under an incremental ramp protocol. Following the recommendations of Tuesta et al. (2023), the workload increase rate will be individually tailored based on the patient's NYHA functional class: 5 W/min for Class IV, 6-7 W/min for Class III, 8-9 W/min for Class II, and 9 W/min or more for Class I, targeting an optimal test duration between 8 and 12 minutes to peak exhaustion.

Conditions: Heart Failure, Heart Failure and Reduced Ejection Fraction, Heart Failure and Mildly Reduced Ejection Fraction, Muscle Weakness, Inspiratory Muscle Weakness
Being tested: Mechanical Pressure-Threshold IMT Device, PowerBreathe KH2 Electronic IMT Device, Sub-therapeutic Mechanical IMT Device (Sham)
Keywords: inspiratory muscle training, Heart Failure, Quality of Life, Maximal Inspiratory Pressure, Metaboreflex, Near-Infrared Spectroscopy, Cardiopulmonary Exercise Testing, Diaphragmatic Ultrasound
Medical subject headings: Heart Failure, Heart Failure, Systolic, Muscle Weakness

What participants receive

What participants receive. In a randomised study each person is assigned to one group by chance.

Mechanical Pressure-Threshold IMT DeviceDevice
A mechanical threshold loading device used to deliver high-intensity inspiratory muscle training. Resistance is load-dependent, requiring the participant to generate sufficient negative pressure to open the valve.
PowerBreathe KH2 Electronic IMT DeviceDevice
An electronic flow-resistive device that delivers automated, dynamic, and electronically controlled resistance throughout the entire inspiratory phase to optimize muscle loading.
Sub-therapeutic Mechanical IMT Device (Sham)Device
The same mechanical threshold loading device model, but configured with a sub-therapeutic, low-resistance load to serve as a physiological control without training effect

Study groups in NCT07688863
Study group	Role	What they receive
Mechanical Pressure- Threshold 60% IMT	Experimental	High-intensity inspiratory muscle training utilizing a mechanical pressure-threshold device. The training protocol consists of 3 supervised sessions per week for 6 weeks (18 sessions total), with a standardized volume of 5 sets of 8 repetitions per session. The training load is established based on the patient's initial baseline Maximal Inspiratory Pressure (MIP). To ensure progressive overload, intensity is specifically structured as follows: 60% of baseline MIP during weeks 1-2, progressing to 70% during weeks 3-4, and reaching 80% during weeks 5-6. Receives: Device: Mechanical Pressure-Threshold IMT Device
Electronic Flow-Resistive 60% IMT	Experimental	High-intensity inspiratory muscle training utilizing the PowerBreathe KH2 electronic flow-resistive device, which delivers automated, dynamic resistance throughout the breath. The protocol consists of 3 supervised sessions per week for 6 weeks (18 sessions total), with a standardized volume of 5 sets of 8 repetitions per session. The training load is calibrated based on the initial baseline Maximal Inspiratory Pressure (MIP), using a progressive overload scheme: 60% of baseline MIP during weeks 1-2, advancing to 70% during weeks 3-4, and reaching 80% during weeks 5-6. Receives: Device: PowerBreathe KH2 Electronic IMT Device
Sham Control IMT	Sham comparator	Low-intensity inspiratory muscle training serving as a sham control, utilizing a mechanical pressure-threshold device set to a sub-therapeutic load. To simulate the active treatment arms, the protocol consists of 3 supervised sessions per week for 6 weeks (18 sessions total), with the exact same standardized volume of 5 sets of 8 repetitions per session. The training load is based on the initial baseline Maximal Inspiratory Pressure (MIP) but kept intentionally low to avoid true physiological conditioning: 15% of baseline MIP during 6 weeks Receives: Device: Sub-therapeutic Mechanical IMT Device (Sham)

What is being measured

The primary outcome is the main question the study is designed to answer.

Change in Maximal Inspiratory Pressure (MIP)
Maximal Inspiratory Pressure (MIP) will be assessed from residual volume using a calibrated digital manometer according to standardized international guidelines. The highest value obtained from at least three reproducible maneuvers (varying less than 10%) will be recorded to quantify changes in volitional inspiratory muscle strength
Measured: Baseline (Week 0) and post-intervention (Week 9).
Change in Peak Oxygen Consumption (VO2 peak)
Peak oxygen consumption will be evaluated during a incremental symptom-limited cardiopulmonary exercise test (CPET) on a cycle ergometer using a breath-by-breath metabolic cart to assess changes in aerobic capacity.
Measured: Baseline (Week 0) and post-intervention (Week 9).
Change in Health-Related Quality of Life via Minnesota Living with Heart Failure Questionnaire (MLHFQ)
Changes in disease-specific health-related quality of life will be assessed using the unabbreviated Minnesota Living with Heart Failure Questionnaire (MLHFQ). The total score ranges from 0 to 105, where a higher score indicates a worse health-related quality of life and greater symptom limitation.
Measured: Baseline (Week 0) and post-intervention (Week 9).

Secondary outcomes (4)

Change in Ventilatory Efficiency (VE/VCO2 slope)
The VE/VCO2 slope will be calculated via linear regression from the initiation of exercise to the respiratory compensation point during the cardiopulmonary exercise test, reflecting changes in ventilatory efficiency and ventilation-perfusion matching.
Measured: Baseline (Week 0) and post-intervention (Week 9).
Change in Multi-Muscle Tissue Oxygen Saturation Kinetics (SmO2)
Multi-muscle tissue oxygen saturation (SmO2) kinetics will be continuously monitored via Near-Infrared Spectroscopy (NIRS) using three simultaneous Moxy sensors (intercostal space, vastus lateralis, and dominant forearm flexors). The assessment will follow a strict sequential protocol: first, patients will perform an inspiratory resistive load challenge at 60% MIP until task failure to induce respiratory muscle fatigue and trigger the metaboreflex; immediately following, they will execute a peripheral isometric handgrip protocol (12 repetitions of 10-second maximal voluntary contractions with 30-second rests) to evaluate the specific systemic vasoconstrictor impact and blood flow redistribution across respiratory, locomotor, and non-locomotor beds.
Measured: Baseline (Week 0) and post-intervention (Week 9).
Change in Diaphragmatic and Parasternal Intercostal Ultrasound Parameters
B-mode ultrasound will be used to evaluate respiratory muscle morphology. Diaphragmatic thickness will be measured at the zone of apposition at end-expiration and end-inspiration to calculate the thickening fraction. Concurrently, the thickness and thickening fraction of the parasternal intercostal muscles will be assessed in the second intercostal space during quiet and maximal breathing to quantify structural adaptations and accessory muscle recruitment changes.
Measured: Baseline (Week 0) and post-intervention (Week 9).
Change in Inspiratory Muscle Endurance Time
Inspiratory muscle endurance will be quantified as the total time (in seconds) sustained during the constant-load resistive breathing challenge at 60% of baseline MIP until task failure (defined as the inability to overcome the target pressure for three consecutive breaths).
Measured: Baseline (Week 0) and post-intervention (Week 9).

Timeline

From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.

17 Jun 2026Dec 2027

First posted7 Jul 2026
Study start17 Jun 2026
Primary completionSep 2026 (estimated)
Study completionDec 2027 (estimated)

Resources

Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
Publications (10)Papers the sponsor has linked to this study.
Other trials for Heart FailureStudies of the same condition, open and under way.
What the trial phases meanHow a treatment moves from first tests in people to approval.

More details

For doctors and researchers: how the study is designed, who runs it, and its registry IDs.

Study design

Study type: Interventional
Phase: Phase N/A
Primary purpose: Treatment
Allocation: Randomised
Intervention model: Parallel groups
Model description: A randomized, parallel-group, single-blind clinical trial. Eligible participants will be randomly allocated in a 1:1:1 ratio into one of three parallel arms: Group 1 (High-Intensity Pressure-Threshold IMT), Group 2 (High-Intensity Electronic Flow-Resistive IMT using the PowerBreathe KH2), or Group 3 (Low-Intensity Sham Control IMT). All interventions will run concurrently over a total span of 8 weeks. This duration includes a 2-week baseline testing and technical familiarization period, followed by a 6-week progressive training protocol consisting of 18 effective sessions. Outcomes will be assessed by an external investigator blinded to group allocations (single-blind design). Statistical analysis will be executed using coded identifiers for each arm to maintain allocation concealment until the processing of all respiratory, metabolic, and tissue oxygenation variables is finalized in R.
Masking: Double blind
Who is masked: Care provider, Outcomes assessor
Enrolment: 60 participants (estimated)

IDs, dates and publications

ClinicalTrials.gov ID: NCT07688863
Sponsor's protocol ID: 17B2025
Acronym: IMT-HF-COMPARE
Status last verified: Jun 2026
First submitted: 24 Jun 2026
Last updated: 7 Jul 2026
Results posted: No
Data monitoring committee: No
FDA-regulated drug: No
FDA-regulated device: No
Individual data sharing: Yes: De-identified individual participant data (IPD) including baseline characteristics, maximal inspiratory pressure (MIP) values, diaphragmatic and parasternal intercostal ultrasound measurements, and breath-by-breath metabolic cart parameters (VO2, VCO2, VE) will be shared. Relative tissue oxygenation kinetics (SmO2) from the intercostal, vastus lateralis, and forearm sensors during the resistive load and handgrip protocols will also be available. Data will be shared upon reasonable request after formal publication of the primary trial results.

Publications

Zacarias Rondinel T, Bocchi L, Cipriano Junior G, Chiappa GRDS, Martins GS, Mateus SRM, Cahalin LP, Cipriano GFB. Diaphragm thickness and mobility elicited by two different modalities of inspiratory muscle loading in heart failure participants: A randomized crossover study. PLoS One. 2024 May 24;19(5):e0302735. doi: 10.1371/journal.pone.0302735. eCollection 2024.
PubMed 38787839
Kabbadj K, Taiek N, El Hjouji W, El Karrouti O, El Hangouche AJ. Cardiopulmonary Exercise Testing: Methodology, Interpretation, and Role in Exercise Prescription for Cardiac Rehabilitation. US Cardiol. 2024 Dec 20;18:e22. doi: 10.15420/usc.2024.37. eCollection 2024.
PubMed 39872828
Bilbao A, Escobar A, Garcia-Perez L, Navarro G, Quiros R. The Minnesota living with heart failure questionnaire: comparison of different factor structures. Health Qual Life Outcomes. 2016 Feb 17;14:23. doi: 10.1186/s12955-016-0425-7.
PubMed 26887590
Tuesta M, Alvarez C, Pedemonte O, Araneda OF, Manriquez-Villarroel P, Berthelon P, Reyes A. Average and Interindividual Effects to a Comprehensive Cardiovascular Rehabilitation Program. Int J Environ Res Public Health. 2022 Dec 24;20(1):261. doi: 10.3390/ijerph20010261.
PubMed 36612584
Bosnak-Guclu M, Arikan H, Savci S, Inal-Ince D, Tulumen E, Aytemir K, Tokgozoglu L. Effects of inspiratory muscle training in patients with heart failure. Respir Med. 2011 Nov;105(11):1671-81. doi: 10.1016/j.rmed.2011.05.001. Epub 2011 May 31.
PubMed 21621993
Juarez M, Castillo-Rodriguez C, Soliman D, Del Rio-Pertuz G, Nugent K. Cardiopulmonary Exercise Testing in Heart Failure. J Cardiovasc Dev Dis. 2024 Feb 20;11(3):70. doi: 10.3390/jcdd11030070.
PubMed 38535093
American Thoracic Society/European Respiratory Society. ATS/ERS Statement on respiratory muscle testing. Am J Respir Crit Care Med. 2002 Aug 15;166(4):518-624. doi: 10.1164/rccm.166.4.518. No abstract available.
PubMed 12186831
Rittayamai N, Marinpong V, Chuaychoo B, Tscheikuna J, Brochard LJ. Ultrasound Evaluation of Parasternal Intercostal, Diaphragm Activity, and Their Ratio in Male Patients with Chronic Obstructive Pulmonary Disease. Am J Respir Crit Care Med. 2024 Apr 15;209(8):1016-1018. doi: 10.1164/rccm.202310-1769LE. No abstract available.
PubMed 38319129
Heidenreich PA, Bozkurt B, Aguilar D, Allen LA, Byun JJ, Colvin MM, Deswal A, Drazner MH, Dunlay SM, Evers LR, Fang JC, Fedson SE, Fonarow GC, Hayek SS, Hernandez AF, Khazanie P, Kittleson MM, Lee CS, Link MS, Milano CA, Nnacheta LC, Sandhu AT, Stevenson LW, Vardeny O, Vest AR, Yancy CW; ACC/AHA Joint Committee Members. 2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2022 May 3;145(18):e895-e1032. doi: 10.1161/CIR.0000000000001063. Epub 2022 Apr 1.
PubMed 35363499
Azambuja ACM, de Oliveira LZ, Sbruzzi G. Inspiratory Muscle Training in Patients With Heart Failure: What Is New? Systematic Review and Meta-Analysis. Phys Ther. 2020 Dec 7;100(12):2099-2109. doi: 10.1093/ptj/pzaa171.
PubMed 32936904

Interested in taking part?

The sponsor has not listed a contact. The official record may have more details.

Talk to your doctor first and take this page with you. Only the study team can confirm whether you can join.

Questions to ask the study team

What is the study trying to find out?
What would I need to do, and how often would I visit?
Could I receive a placebo instead of the treatment?
What are the possible risks and benefits for me?
Will it cost me anything? Are travel or time paid for?
Can I keep seeing my own doctor during the study?
What happens when the study ends?

See sites and contacts

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Not yet recruitingPhase 2
A Study of Bimagrumab in Participants With HFpEF
Heart Failure, Diastolic, Diastolic Heart Failure
Recruiting
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Heart Failure
Active, not recruiting
Assessment of Combined CCM and ICD Device in HFrEF
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Not yet recruiting
RELIEVE-HFrEF TRIAL: REducing Lung congestIon Symptoms Using the v-wavE Shunt in adVancEd Heart Failure With Reduced EF
Heart Failure and Reduced Ejection Fraction, Heart Failure Chronic

All Heart Failure trials

Study at a glance

From the registry record, last updated by the sponsor on 7 Jul 2026. Recruitment status is as the sponsor reported it: confirm with the study team.

Official title: Effects of Inspiratory Muscle Training on Maximal Inspiratory Pressure, Cardiopulmonary Capacity, and Quality of Life in Patients With Heart Failure
ClinicalTrials.gov ID: NCT07688863
Acronym / sponsor ID: IMT-HF-COMPARE / 17B2025
Conditions: Heart Failure, Heart Failure and Reduced Ejection Fraction, Heart Failure and Mildly Reduced Ejection Fraction, Muscle Weakness, Inspiratory Muscle Weakness
Keywords: inspiratory muscle training, Heart Failure, Quality of Life, Maximal Inspiratory Pressure, Metaboreflex, Near-Infrared Spectroscopy, Cardiopulmonary Exercise Testing, Diaphragmatic Ultrasound
Study type: Interventional
Recruitment status: Enrolling by invitation
Enrolment: 60 participants (estimated)
Lead sponsor: Universidad Nacional Andres BelloUniversity, hospital or other
Study start: 17 Jun 2026 (actual)
Primary completion: Sep 2026 (estimated)
Study completion: Dec 2027 (estimated)
First posted: 7 Jul 2026 (actual)
Results: Not posted in the source record

Clinical summary

The research question as the sponsor registered it. This describes what the study plans to test, not what it found.

Participants will be randomly assigned to one of three parallel groups:

Group 1 (Pressure-Threshold IMT): Participants will train using a mechanical pressure-threshold device at an initial high-intensity load of 60% of their baseline maximal inspiratory pressure (MIP).
Group 2 (Electronic Flow-Resistive IMT): Participants will train at a high-intensity load of 60% of their baseline MIP utilizing the PowerBreathe KH2 electronic device, which provides a dynamic, flow-dependent automated resistance.
Group 3 (Control / Sham IMT): Participants will perform the same breathing protocol but using a mechanical device set at a low, non-training intensity of 15% of their baseline MIP.

This study aims to determine which training modality provides the most effective physiological adaptations to optimize rehabilitation in this population.

Detailed description

To systematically address these mechanisms, the protocol is structured into a precise multi-stage timeline distributed over 8 consecutive weeks:

Methodological Familiarization and Baseline Testing (Weeks 1-2): To eliminate the confounding "learning effect" and ensure internal data validity, the first two weeks are exclusively dedicated to patient technical habituation. Participants will learn proper diaphragmatic breathing techniques, device interface seal (using flanged mouthpieces and nose clips), and device manipulation under submaximal loads. Concurrently, baseline clinical profiling will be conducted, including spirometry, maximal inspiratory pressure (MIP), resting cardiac autonomic balance through Heart Rate Variability (HRV), and central vascular stiffness via Pulse Wave Velocity (PWV).
High-Intensity Standardized Intervention (Weeks 3-8): The formal training phase lasts 6 weeks with a frequency of 3 supervised sessions per week, totaling 18 effective sessions. To preserve biomechanical quality and prevent disproportionate dyspnea or early neuromuscular fatigue in this clinical population, the training volume is strictly set to 5 sets of 8 repetitions (40 breathing efforts per session), separated by standardized resting intervals. The progression scheme utilizes a linear model based on the initial baseline MIP, preventing the logistical friction of constant maximum re-testing in fragile patients:

Weeks 3-4: 60% of baseline MIP (Groups 1 and 2) or 15% (Group 3).
Weeks 5-6: Progression to 70% of baseline MIP (Groups 1 and 2) or 15% (Group 3).
Weeks 7-8: Progression to 80% of baseline MIP (Groups 1 and 2) or 15% (Group 3).

Advanced Dynamic Evaluations:

Muscle Oxygenation and Metaboreflex Provocation (NIRS): Peripheral blood flow redistribution and tissue oxygen saturation kinetics (SmO2) will be tracked continuously via three percutaneous Near-Infrared Spectroscopy sensors (Moxy Monitor®) placed simultaneously on the right intercostal space (respiratory pump), vastus lateralis of the quadriceps (locomotor reference), and the dominant forearm flexor mass (non-locomotor control). The provocation protocol includes an inspiratory resistive load test at 60% MIP until task failure (inability to sustain target pressure for three consecutive breaths), followed immediately by an isometric Handgrip peripheral fatigue protocol (12 repetitions of 10-second maximal voluntary contractions with 30-second rests).
Cardiopulmonary Exercise Testing (CPET): Maximal oxygen consumption (VO2max) and ventilatory efficiency (VE/VCO2 slope) will be evaluated using a cycle ergometer under an incremental ramp protocol. Following the recommendations of Tuesta et al. (2023), the workload increase rate will be individually tailored based on the patient's NYHA functional class: 5 W/min for Class IV, 6-7 W/min for Class III, 8-9 W/min for Class II, and 9 W/min or more for Class I, targeting an optimal test duration between 8 and 12 minutes to peak exhaustion.

Study design

Primary purpose: Treatment
Allocation: Randomised
Intervention model: Parallel groups
Masking: Double blind (care provider, outcomes assessor)
Number of arms: 3
Model description: A randomized, parallel-group, single-blind clinical trial. Eligible participants will be randomly allocated in a 1:1:1 ratio into one of three parallel arms: Group 1 (High-Intensity Pressure-Threshold IMT), Group 2 (High-Intensity Electronic Flow-Resistive IMT using the PowerBreathe KH2), or Group 3 (Low-Intensity Sham Control IMT). All interventions will run concurrently over a total span of 8 weeks. This duration includes a 2-week baseline testing and technical familiarization period, followed by a 6-week progressive training protocol consisting of 18 effective sessions. Outcomes will be assessed by an external investigator blinded to group allocations (single-blind design). Statistical analysis will be executed using coded identifiers for each arm to maintain allocation concealment until the processing of all respiratory, metabolic, and tissue oxygenation variables is finalized in R.

Arm	Type	Receives
Mechanical Pressure- Threshold 60% IMT	Experimental	Device: Mechanical Pressure-Threshold IMT DeviceHigh-intensity inspiratory muscle training utilizing a mechanical pressure-threshold device. The training protocol consists of 3 supervised sessions per week for 6 weeks (18 sessions total), with a standardized volume of 5 sets of 8 repetitions per session. The training load is established based on the patient's initial baseline Maximal Inspiratory Pressure (MIP). To ensure progressive overload, intensity is specifically structured as follows: 60% of baseline MIP during weeks 1-2, progressing to 70% during weeks 3-4, and reaching 80% during weeks 5-6.
Electronic Flow-Resistive 60% IMT	Experimental	Device: PowerBreathe KH2 Electronic IMT DeviceHigh-intensity inspiratory muscle training utilizing the PowerBreathe KH2 electronic flow-resistive device, which delivers automated, dynamic resistance throughout the breath. The protocol consists of 3 supervised sessions per week for 6 weeks (18 sessions total), with a standardized volume of 5 sets of 8 repetitions per session. The training load is calibrated based on the initial baseline Maximal Inspiratory Pressure (MIP), using a progressive overload scheme: 60% of baseline MIP during weeks 1-2, advancing to 70% during weeks 3-4, and reaching 80% during weeks 5-6.
Sham Control IMT	Sham comparator	Device: Sub-therapeutic Mechanical IMT Device (Sham)Low-intensity inspiratory muscle training serving as a sham control, utilizing a mechanical pressure-threshold device set to a sub-therapeutic load. To simulate the active treatment arms, the protocol consists of 3 supervised sessions per week for 6 weeks (18 sessions total), with the exact same standardized volume of 5 sets of 8 repetitions per session. The training load is based on the initial baseline Maximal Inspiratory Pressure (MIP) but kept intentionally low to avoid true physiological conditioning: 15% of baseline MIP during 6 weeks

Who may qualify

Ages: 18 years and older
Sex: All
Healthy volunteers: Not accepted
Age groups: Adult, Older adult

Key inclusion criteria (7 listed)

Documented clinical diagnosis of chronic Heart Failure with Reduced Ejection Fraction (HFrEF) according to the European Society of Cardiology (ESC) guidelines.
Left Ventricular Ejection Fraction (LVEF) less than or equal to 40% documented by echocardiography within the last 12 months.
Clinically stable condition for at least 3 months prior to enrollment, with no hospitalizations or major changes in optimized medical therapy.
New York Heart Association (NYHA) functional class I to IV.
Evidence of inspiratory muscle weakness, defined as a baseline Maximal Inspiratory Pressure (MIP) < 70% of the predicted value for age and sex.

Key exclusion criteria (7 listed)

Presence of primary severe pulmonary or respiratory diseases (e.g., Chronic Obstructive Pulmonary Disease [COPD] GOLD stage III or IV, active asthma, severe pulmonary hypertension, or restrictive lung disease).
Recent myocardial infarction, unstable angina, or coronary artery bypass graft (CABG) surgery within the last 6 months.
Severe uncorrected valvular heart disease or complex, uncontrolled ventricular arrhythmias.
Orthopedic, neurological, or musculoskeletal limitations that prevent the safe execution of an incremental cardiopulmonary exercise test on a cycle ergometer or the performance of the isometric handgrip protocol.
Cognitive impairment or psychological conditions that limit the ability to follow instructions, maintain correct diaphragmatic breathing technique, or properly seal the training device mouthpiece.

Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.

Interventions

Intervention	Type	Arms
Mechanical Pressure-Threshold IMT DeviceA mechanical threshold loading device used to deliver high-intensity inspiratory muscle training. Resistance is load-dependent, requiring the participant to generate sufficient negative pressure to open the valve.	Device	Mechanical Pressure- Threshold 60% IMT
PowerBreathe KH2 Electronic IMT DeviceAn electronic flow-resistive device that delivers automated, dynamic, and electronically controlled resistance throughout the entire inspiratory phase to optimize muscle loading.	Device	Electronic Flow-Resistive 60% IMT
Sub-therapeutic Mechanical IMT Device (Sham)The same mechanical threshold loading device model, but configured with a sub-therapeutic, low-resistance load to serve as a physiological control without training effect	Device	Sham Control IMT

Primary outcome

Change in Maximal Inspiratory Pressure (MIP)
Time frame: Baseline (Week 0) and post-intervention (Week 9).
Maximal Inspiratory Pressure (MIP) will be assessed from residual volume using a calibrated digital manometer according to standardized international guidelines. The highest value obtained from at least three reproducible maneuvers (varying less than 10%) will be recorded to quantify changes in volitional inspiratory muscle strength
Change in Peak Oxygen Consumption (VO2 peak)
Time frame: Baseline (Week 0) and post-intervention (Week 9).
Peak oxygen consumption will be evaluated during a incremental symptom-limited cardiopulmonary exercise test (CPET) on a cycle ergometer using a breath-by-breath metabolic cart to assess changes in aerobic capacity.
Change in Health-Related Quality of Life via Minnesota Living with Heart Failure Questionnaire (MLHFQ)
Time frame: Baseline (Week 0) and post-intervention (Week 9).
Changes in disease-specific health-related quality of life will be assessed using the unabbreviated Minnesota Living with Heart Failure Questionnaire (MLHFQ). The total score ranges from 0 to 105, where a higher score indicates a worse health-related quality of life and greater symptom limitation.

4 secondary outcomes

Change in Ventilatory Efficiency (VE/VCO2 slope)
Time frame: Baseline (Week 0) and post-intervention (Week 9).
Change in Multi-Muscle Tissue Oxygen Saturation Kinetics (SmO2)
Time frame: Baseline (Week 0) and post-intervention (Week 9).
Change in Diaphragmatic and Parasternal Intercostal Ultrasound Parameters
Time frame: Baseline (Week 0) and post-intervention (Week 9).
Change in Inspiratory Muscle Endurance Time
Time frame: Baseline (Week 0) and post-intervention (Week 9).

Results and safety

This study is still under way. Results are not available in the source record yet.

Research links

Official record on ClinicalTrials.govLast updated by the sponsor 7 Jul 2026.
Background: PubMed 38787839Zacarias Rondinel T, Bocchi L, Cipriano Junior G, Chiappa GRDS, Martins GS, Mateus SRM, Cahalin LP, Cipriano GFB. Diaphragm thickness and mobility elicited by two different modalities of inspiratory muscle loading in heart failure participants: A randomized crossover study. PLoS One. 2024 May 24;19(5):e0302735. doi: 10.1371/journal.pone.0302735. eCollection 2024.
Background: PubMed 39872828Kabbadj K, Taiek N, El Hjouji W, El Karrouti O, El Hangouche AJ. Cardiopulmonary Exercise Testing: Methodology, Interpretation, and Role in Exercise Prescription for Cardiac Rehabilitation. US Cardiol. 2024 Dec 20;18:e22. doi: 10.15420/usc.2024.37. eCollection 2024.
Background: PubMed 26887590Bilbao A, Escobar A, Garcia-Perez L, Navarro G, Quiros R. The Minnesota living with heart failure questionnaire: comparison of different factor structures. Health Qual Life Outcomes. 2016 Feb 17;14:23. doi: 10.1186/s12955-016-0425-7.
Background: PubMed 36612584Tuesta M, Alvarez C, Pedemonte O, Araneda OF, Manriquez-Villarroel P, Berthelon P, Reyes A. Average and Interindividual Effects to a Comprehensive Cardiovascular Rehabilitation Program. Int J Environ Res Public Health. 2022 Dec 24;20(1):261. doi: 10.3390/ijerph20010261.
Background: PubMed 21621993Bosnak-Guclu M, Arikan H, Savci S, Inal-Ince D, Tulumen E, Aytemir K, Tokgozoglu L. Effects of inspiratory muscle training in patients with heart failure. Respir Med. 2011 Nov;105(11):1671-81. doi: 10.1016/j.rmed.2011.05.001. Epub 2011 May 31.
Background: PubMed 38535093Juarez M, Castillo-Rodriguez C, Soliman D, Del Rio-Pertuz G, Nugent K. Cardiopulmonary Exercise Testing in Heart Failure. J Cardiovasc Dev Dis. 2024 Feb 20;11(3):70. doi: 10.3390/jcdd11030070.
Background: PubMed 12186831American Thoracic Society/European Respiratory Society. ATS/ERS Statement on respiratory muscle testing. Am J Respir Crit Care Med. 2002 Aug 15;166(4):518-624. doi: 10.1164/rccm.166.4.518. No abstract available.
Background: PubMed 38319129Rittayamai N, Marinpong V, Chuaychoo B, Tscheikuna J, Brochard LJ. Ultrasound Evaluation of Parasternal Intercostal, Diaphragm Activity, and Their Ratio in Male Patients with Chronic Obstructive Pulmonary Disease. Am J Respir Crit Care Med. 2024 Apr 15;209(8):1016-1018. doi: 10.1164/rccm.202310-1769LE. No abstract available.
Background: PubMed 35363499Heidenreich PA, Bozkurt B, Aguilar D, Allen LA, Byun JJ, Colvin MM, Deswal A, Drazner MH, Dunlay SM, Evers LR, Fang JC, Fedson SE, Fonarow GC, Hayek SS, Hernandez AF, Khazanie P, Kittleson MM, Lee CS, Link MS, Milano CA, Nnacheta LC, Sandhu AT, Stevenson LW, Vardeny O, Vest AR, Yancy CW; ACC/AHA Joint Committee Members. 2022 AHA/ACC/HFSA Guideline for the Management of Heart Failure: A Report of the American College of Cardiology/American Heart Association Joint Committee on Clinical Practice Guidelines. Circulation. 2022 May 3;145(18):e895-e1032. doi: 10.1161/CIR.0000000000001063. Epub 2022 Apr 1.
Background: PubMed 32936904Azambuja ACM, de Oliveira LZ, Sbruzzi G. Inspiratory Muscle Training in Patients With Heart Failure: What Is New? Systematic Review and Meta-Analysis. Phys Ther. 2020 Dec 7;100(12):2099-2109. doi: 10.1093/ptj/pzaa171.
Individual participant dataSharing planned: Yes. De-identified individual participant data (IPD) including baseline characteristics, maximal inspiratory pressure (MIP) values, diaphragmatic and parasternal intercostal ultrasound measurements, and breath-by-breath metabolic cart parameters (VO2, VCO2, VE) will be shared. Relative tissue oxygenation kinetics (SmO2) from the intercostal, vastus lateralis, and forearm sensors during the resistive load and handgrip protocols will also be available. Data will be shared upon reasonable request after formal publication of the primary trial results.

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Referral and contact

AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.

Gabriel I Garrido Cerda, PhD(c) principal investigator

university Andrés Bello

1 site in 1 country: see every site and its status.

Questions about this trial

What is this clinical trial studying?

The full registered description is in the About this study section and the official record.

Who may be eligible to take part?

The sponsor lists 7 inclusion and 7 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.

Is this clinical trial currently recruiting?

The record says: enrolling by invitation, as of the sponsor's last update on 7 Jul 2026. Status can change between updates, so confirm with the study contact before making plans.

Where is the study taking place?

The record lists 1 site in Chile. Whether a site is taking part right now should be confirmed with that site. See every site.

What are the possible benefits and risks?

They depend on the study and the treatment, and no study can promise a benefit. Some participants in this study may receive a placebo. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.

Are results available for this study?

This study is still under way. Results are not available in the source record yet.

How can a doctor refer a patient or contact the research team?

The record lists no contact. The official record names the sponsor, who can be asked directly. AzTrials does not enrol participants or take referrals.

What does the primary outcome measure?

Change in Maximal Inspiratory Pressure (MIP) (time frame: Baseline (Week 0) and post-intervention (Week 9).). The study lists 3 primary outcomes in all. It is what the study was designed to measure, not a finding.

Where can I read the original study information?

On the ClinicalTrials.gov record for NCT07688863, which also lists 10 linked publications.

Does a listing mean the treatment is approved or proven to work?

No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.

How often is this information updated?

AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 7 Jul 2026.