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

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%). 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:

* 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.

Conditions

• Heart Failure
• Heart Failure and Reduced Ejection Fraction
• Heart Failure and Mildly Reduced Ejection Fraction
• Muscle Weakness
• Inspiratory Muscle Weakness

Interventions

DEVICE

Mechanical Pressure-Threshold IMT Device

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.

DEVICE

PowerBreathe KH2 Electronic IMT Device

An electronic flow-resistive device that delivers automated, dynamic, and electronically controlled resistance throughout the entire inspiratory phase to optimize muscle loading.

DEVICE

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

Sponsors & Collaborators

• Universidad Nacional Andres Bello

  lead OTHER

Principal Investigators

• Gabriel I Garrido Cerda, PhD(c) · university Andrés Bello

Study Design

Allocation

RANDOMIZED

Purpose

TREATMENT

Masking

DOUBLE

Model

PARALLEL

Eligibility

Min Age

18 Years

Sex

ALL

Healthy Volunteers

No

Timeline & Regulatory

Start

2026-06-17

Primary Completion

2026-09-30

Completion

2027-12-31

Countries

• Chile

Study Locations