An interventional study of Mechanical Pressure-Threshold IMT Device and PowerBreathe KH2 Electronic IMT Device in Heart Failure, Heart Failure and Reduced Ejection Fraction and Heart Failure and Mildly Reduced Ejection Fraction, sponsored by Universidad Nacional Andres Bello. Enrolling by invitation at 1 site in Chile. Open to participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-07-07.
Sponsored by Universidad Nacional Andres Bello · Not applicable, Interventional, and Treatment
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%). Patients will be recruited from cardiac rehabilitation programs and must be clinically stable before entering the protocol.
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:
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.
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:
Advanced Dynamic Evaluations:
6,331 studies on the registry are indexed under Heart Failure; 1,396 are open to participants now.
This study's planned enrollment of 60 is below the median of 76 across 4,049 interventional studies indexed under Heart Failure.
Browse Heart Failure studies →Universidad Nacional Andres Bello is the lead sponsor of 23 studies on the registry; 10 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Chronic obstructive pulmonary disease: long-term lung disease that makes it hard to breathe out, including emphysema and chronic bronchitis.
LVEF (left ventricular ejection fraction)
The share of blood the heart’s main pumping chamber (the left ventricle) pushes out with each beat, measured by an echocardiogram (heart ultrasound) or a MUGA scan. About 50–70% is normal.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
NYHA class (heart failure)
The New York Heart Association’s four classes of how much heart failure limits physical activity.
Studies set their own limit — many outside heart failure leave out class III–IV, while heart failure studies may ask for a particular class. Check the class this study names.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Informed consent
Before you join, the study team explains what taking part involves — its purpose, what happens, the risks and possible benefits — and answers your questions, so you can decide freely. Consent is usually recorded on a form (the informed consent form, ICF) signed by you or, where the law allows, by someone legally authorised to decide for you.
You can keep asking questions during the study, you are told of new information that matters, and you can choose to leave at any time.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
COPD
Chronic obstructive pulmonary disease: long-term lung disease that makes it hard to breathe out, including emphysema and chronic bronchitis.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
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.
Device: Mechanical Pressure-Threshold IMT Device
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.
Device: PowerBreathe KH2 Electronic IMT Device
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
Device: Sub-therapeutic Mechanical IMT Device (Sham)
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.
An electronic flow-resistive device that delivers automated, dynamic, and electronically controlled resistance throughout the entire inspiratory phase to optimize muscle loading.
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
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
Time frame: 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.
Time frame: 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.
Time frame: Baseline (Week 0) and post-intervention (Week 9).
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.
Time frame: 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.
Time frame: 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.
Time frame: 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).
Time frame: Baseline (Week 0) and post-intervention (Week 9).
Plan to share: 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.
Supporting information: Study protocol, Statistical analysis plan
Time frame: Data and supporting documents will be available beginning 6 months after the primary publication of the trial results and will remain accessible for a period of 36 months.
Access criteria: Data will be shared exclusively with qualified academic researchers who submit a methodologically sound research proposal that aligns with the scope of this trial. To gain access, interested parties must submit their proposal and statistical analysis plan directly to the Principal Investigator via email. Requests are subject to formal approval by the investigator and require a signed formal Data Sharing Agreement to ensure compliance with participant confidentiality and ethical standards.
Started Jun 2026 (actual). Primary completion is estimated for Sep 2026, 3 months after the start.
Of 1,118 non-industry interventional studies with no phase under Heart Failure, half reached primary completion within 29 months of starting (the median), counting those still running; a quarter within 16 and three quarters within 50. This study's planned 3 months is below that.
Counting every sponsor, half of 1,354 studies reached it within 31 months; a quarter within 16 and three quarters within 52.
How these figures are worked out, and which studies are left out of them.
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