Inspiratory Muscle Training in Hospitalized Heart Failure Patients

Effects of Inspiratory Muscle Training on Inspiratory Muscle Strength in Hospitalized Heart Failure Patients: A Randomized Clinical Trial

Introduction Exercise intolerance is the most common symptom in patients with heart failure (HF), significantly impacting their quality of life and functional capacity. Muscle metabolism may be impaired due to sympathetic hyperactivation, systemic inflammation, and neurohormonal alterations, contributing to ventilatory inefficiency and exercise intolerance. Inspiratory muscle training (IMT) has been shown to improve inspiratory muscle strength and endurance, reducing fatigue and the sensation of dyspnea.

There is a gap in the evidence regarding the use of IMT in hospitalized settings, particularly concerning short-term gains in inspiratory muscle strength and the safety of the intervention. This study aims to evaluate the effects of IMT on inspiratory muscle strength, hemodynamic and functional outcomes, as well as the safety of the IMT protocol in hospitalized patients with HF.

Methods A randomized, controlled clinical trial will be conducted in the Cardiac Intensive Care Unit of the University Hospital Pedro Ernesto. The study will include individuals of both sexes, aged 18 years or older, who are hospitalized due to heart failure.

Exclusion criteria will include: pregnancy; head trauma and/or brain injury; motor disability; signs and/or symptoms of low cardiac output; acute coronary syndrome; advanced HF with left ventricular ejection fraction (LVEF) below 20%; presence of untreated tachyarrhythmias or bradyarrhythmias; use of high-dose inotropes or vasopressors or an increase in their dose within the past 24 hours.

Primary outcomes will include inspiratory muscle strength, safety, functional status, length of stay in the ICU, and hospital readmission within 90 days. After randomization, the intervention group will undergo IMT with a load between 30% and 50% of maximal inspiratory pressure (MIP), while the control group will perform IMT without load.

It is expected that IMT will be safe and lead to improvements in inspiratory muscle strength and functional status, without significant hemodynamic repercussions.

In hospitalized patients, the use of inspiratory muscle training (IMT) may be particularly beneficial to mitigate muscle strength loss caused by hospitalization, reduce length of stay, and optimize the transition to post-discharge rehabilitation. Thus, the implementation of IMT in the hospital setting can be a safe intervention capable of improving the functional capacity of patients with heart failure.

Despite the known benefits, to date there are no studies conducted with heart failure patients admitted to intensive care units that evaluate gains in inspiratory muscle strength and their hemodynamic and functional effects.

After recruitment, patients will be randomized (using the website random.org) into an Intervention group, which will perform inspiratory muscle training (IMT), and a Control group, which will perform a sham IMT (IMTsham). Both groups will follow the institutional ICU rehabilitation protocol.

The IMT protocol will involve the use of the Power Breath® linear resistor device, classic light model (Anvisa Registration: 81001390001). The IMT group will perform the protocol with a load between 30% and 50% of maximal inspiratory pressure (MIP). Two daily sessions of 30 repetitions each will be conducted, starting with a minimum load of 30%, with a 10-minute interval between sessions, and with a proposed weekly load increase according to patient tolerance.

For training load progression, patient effort will be considered, aiming to maintain a perceived exertion level between light and moderate fatigue (BORG scale less than 4).

Inclusion Criteria:

• Diagnosis of heart failure;
• age over 18 years;
• hospital admission due to heart failure;
• clinical and hemodynamic stability defined as: heart rate > 40 bpm and < 130 bpm; systolic blood pressure (SBP) > 90 mmHg and < 180 mmHg; mean arterial pressure (MAP) > 60 mmHg and < 110 mmHg; respiratory rate > 5 breaths per minute and < 40 breaths per minute; peripheral oxygen saturation > 88%; absence of psychomotor agitation or somnolence

Exclusion Criteria:

• pregnancy;
• head trauma and/or brain injury;
• motor incapacity preventing participation in the institutional rehabilitation protocol of the Cardiointensive Care Unit (ICU);
• signs and/or symptoms of low cardiac output (such as sweating, hypotension, hyperlactatemia, nausea);
• acute coronary syndrome;
• advanced heart failure with left ventricular ejection fraction (LVEF) less than 20%
• presence of untreated tachyarrhythmias or bradyarrhythmias;
• use of inotropes or vasopressors at high doses or dose escalation in the last 24 hours (dobutamine above 15 mcg/kg/min, milrinone above 0.5 mcg/kg/min, norepinephrine above 0.3 mcg/kg/min).