Effect of Transcutaneous Auricular Vagus Nerve Stimulation Application on Respiratory Functions in Stroke Patients

Introduction Stroke is one of the leading causes of morbidity and long-term disability worldwide. Respiratory muscle weakness is a common complication in stroke patients, leading to respiratory dysfunction, increased aspiration risk, and higher mortality. Post-stroke, reduced vital capacity, maximum inspiratory and expiratory pressure, and low expiratory reserve volume significantly affect respiratory muscle function.

Objective This study aims to investigate the effects of Transcutaneous Auricular Vagus Nerve Stimulation (TAVSS) on respiratory parameters in chronic stroke patients.

Participants and Methods

The study included 50 chronic stroke patients in their 1st to 3rd year post-stroke, meeting specific motor levels in Brunnstrom Staging.

Participants were randomized equally into experimental (TAVSS + conventional physiotherapy) and control (sham TAVSS + conventional physiotherapy) groups.

Treatment Protocol

Experimental Group: TAVSS and conventional physiotherapy were applied three times per week for a total of 10 sessions. TAVSS was delivered for 20 minutes using a biphasic asymmetric waveform.

Control Group: Sham TAVSS (without current) and conventional physiotherapy were applied with the same frequency and duration.

Both groups received individualized physiotherapy protocols, including strengthening, stretching, balance exercises, electrotherapy, and neurodevelopmental treatment.

Measurements and Evaluation

Chest circumference measurements were taken at the axillary, epigastric, and subcostal regions during deep inspiration and expiration using a tape measure.

Respiratory function parameters (Maximum Inspiratory Pressure, Maximum Expiratory Pressure, Forced Expiratory Volume in 1 Second, Forced Vital Capacity, Forced Expiratory Volume in 1 Second to Forced Vital Capacity Ratio) were measured using the Minispir 2 spirometer before treatment and after the 10th session.

Conclusion and Recommendations The study aims to evaluate the impact of TAVSS on improving respiratory muscle strength and function, presenting an alternative approach in stroke rehabilitation. TAVSS is expected to support respiratory function and positively influence rehabilitation outcomes in stroke patients

Inclusion criteria

• Being a chronic stroke patient with an ischemic or hemorrhagic stroke diagnosis made 1-3 years ago
• Having been diagnosed with stroke for the first time
• Ability to understand and follow simple verbal instructions
• Being between the ages of 40 and 80
• No conditions affecting perioral muscles, such as facial paralysis or swallowing disorders
• No visual, auditory, or communication problems
• No cardiopulmonary disorders
• No additional neurological, cardiovascular, orthopedic, or similar conditions causing balance problems
• Mini Mental State Examination (MMSE) score ≥24
• No surgical operations or Botox applications in the last 6 months
• Scoring 2 or below on the Modified Ashworth Scale

Exclusion criteria

• Presence of infection, ulcer, or scar on the auricle
• Metallic implants in the skull, hypersensitivity, injury, or inflammation inside the ear
• Chronic pulmonary and/or cardiac diseases
• Resting heart rate below 60 beats per minute
• Devices such as pacemakers or cochlear implants
• Uncontrolled hypertension
• Chronic obstructive pulmonary disease (COPD) or asthma unrelated to stroke
• History of surgical operation or Botox application within the last 6 months
• Presence of aphasia, apraxia, or neglect syndrome
• History of 2 or more strokes (SVO)
• Comorbid conditions affecting respiratory functions (e.g., Multiple Sclerosis, Parkinson's, spinal cord injury, contractures, deformities after fractures, active upper or lower respiratory infections, etc.)
• Lack of cooperation