Short Term Effects of Early Respiratory Muscle Training on Respiratory Muscle Strength in Inpatient Acute Stroke

• High-Intensity Interval Inspiratory and Expiratory Muscle Training (H-IIIEMT) (Behavioral): High-intensity interval inspiratory and expiratory muscle training is performed using the BigBreathe Double Action IMT/PEP device, which provides resistance during inspiration and expiration. Participants perform the exercise in a semi-Fowler position using a mouthpiece with an airtight lip seal. Training is performed once daily for 5 consecutive days, with five 2-minute sets per session and approximately 1 minute of rest between sets. Inspiratory resistance is set at 50% of MIP and expiratory resistance at 30% of MEP.
• Control Group (Behavioral): Diaphragmatic Breathing Exercise for 15 minutes in a semi-Fowler position.

Primary outcomes

• Maximal Inspiratory Pressure [Baseline and Day 3]: Maximal inspiratory pressure (MIP) is used to assess inspiratory muscle strength. Participants perform a maximal inspiratory effort against an occluded airway starting from residual volume. MIP is recorded in centimeters of water (cmH₂O). A greater magnitude of MIP indicates greater inspiratory muscle strength.
• Maximal Expiratory Pressure [Baseline and Day 3]: Maximal expiratory pressure (MEP) is used to assess expiratory muscle strength. Participants perform a maximal expiratory effort against an occluded airway. MEP is recorded in centimeters of water (cmH₂O). Higher MEP values indicate greater expiratory muscle strength.

Secondary outcomes

• Thoracic Expansion [Baseline and Day 3]: Thoracic expansion is assessed as the difference in chest circumference between maximal inhalation and maximal exhalation. Chest circumference is measured using a measuring tape at a standardized thoracic level and is reported in centimeters (cm). A greater difference indicates greater chest wall expansion.
• Single-Breath Counting Test (SBCT) Score [Baseline and Day 3]: The Single-Breath Counting Test (SBCT) is a bedside assessment of respiratory function. After a maximal inspiration, participants count aloud sequentially for as long as possible during a single exhalation. The highest number reached during one breath is recorded as the SBCT score. A higher score indicates a greater ability to sustain phonation during a single breath.

Sex: All, ages: 18 Years to any

Inclusion Criteria:

* Male or female participants aged 18 years or older.
* First-ever acute ischemic stroke, with stroke onset 2 to 14 days before enrollment, confirmed by computed tomography (CT) or magnetic resonance imaging (MRI).
* National Institutes of Health Stroke Scale (NIHSS) score ≥5, with the presence of hemiparesis.
* Baseline maximal inspiratory pressure (MIP) <80 cmH₂O.
* Baseline maximal expiratory pressure (MEP) <68 cmH₂O.
* Able to understand instructions and participate in the respiratory muscle training program.
* Willing to comply with the study protocol and provide written informed consent.

Exclusion Criteria:

* Resting blood pressure >160/100 mmHg.
* Resting peripheral oxygen saturation (SpO₂) <92%.
* Resting heart rate <40 beats/min or >110 beats/min.
* Fever, defined as body temperature ≥37.5°C.
* Previous participation in or experience with a respiratory muscle training program.
* Presence of chronic pulmonary disease.
* Presence of a tracheostomy tube.
* Presence of unstable cardiac disease.
* Presence of another neurological disorder associated with respiratory dysfunction.
* Presence of an orthopedic or musculoskeletal condition that significantly interferes with respiratory function or the ability to perform respiratory muscle training.
* History of major thoracic or abdominal surgery within the previous 3 months.