Effects of Non-Invasive Vagus Nerve Stimulation in Adolescent Burn Patients

Burn injuries may cause long-term physical and psychological symptoms in pediatric and adolescent patients, including pain, itching, sleep problems, anxiety, and changes in autonomic nervous system activity. These symptoms may negatively affect recovery and rehabilitation outcomes.

Non-invasive vagus nerve stimulation is a transcutaneous neuromodulation method that stimulates the auricular branch of the vagus nerve through electrodes placed on the external ear. This stimulation may influence autonomic nervous system regulation and may have potential effects on pain, sleep, anxiety, itching, and physiological recovery.

This study is designed as a randomized interventional study. Adolescents aged 12 to 18 years with burn injuries will be randomly assigned to an intervention group or a control group. The intervention group will receive non-invasive vagus nerve stimulation in addition to conventional physiotherapy. The control group will receive conventional physiotherapy only.

The non-invasive vagus nerve stimulation will be applied through electrodes placed on the tragus and concha regions of both ears. Stimulation will be delivered with a biphasic asymmetrical waveform, a pulse duration of 300 microseconds, and a frequency of 25 Hz. Each stimulation session will last 20 minutes. The stimulation intensity will be gradually increased in 0.1 mA steps until the participant's sensory threshold is reached. If the participant feels unwell during the stimulation, the procedure will be stopped.

Both groups will receive individualized conventional physiotherapy programs based on their clinical needs. These programs may include strengthening exercises, stretching exercises, balance exercises, active and passive range-of-motion exercises, and interventions for edema management. Conventional physiotherapy sessions will last approximately 45 minutes and will be applied 5 days per week for a total of 10 sessions.

Outcome assessments will be performed before the start of treatment and after completion of the 10-session treatment program. Anxiety will be assessed using the Beck Anxiety Inventory. Sleep-related symptoms will be assessed using the Adolescent Insomnia Scale. Pain will be assessed using the Visual Analog Scale. Itching severity will be assessed using the 12-Item Pruritus Severity Scale. Autonomic nervous system function will be evaluated using heart rate variability measurements recorded with a Polar H10 heart rate sensor and analyzed with Kubios HRV software.

The aim of the study is to determine whether non-invasive vagus nerve stimulation, when added to conventional physiotherapy, improves anxiety, sleep quality, pain, itching, and autonomic function in adolescents with burn injuries.

• Non-Invasive Vagus Nerve Stimulation (Device): Non-invasive vagus nerve stimulation will be applied using electrodes placed on the tragus and concha regions of both ears. Stimulation will be delivered with a biphasic asymmetrical waveform, a pulse duration of 300 microseconds, and a frequency of 25 Hz for 20 minutes. The stimulation intensity will be gradually increased in 0.1 mA steps until the participant's sensory threshold is reached. The intervention will be applied 5 days per week for a total of 10 sessions.
• Conventional Physiotherapy (Other): Participants will receive an individualized conventional physiotherapy program based on their clinical needs. The program may include strengthening exercises, stretching exercises, balance exercises, active and passive range-of-motion exercises, and interventions for edema management. Each session will last approximately 45 minutes and will be applied 5 days per week for a total of 10 sessions.

Primary outcomes

• Change in anxiety level [Baseline and after completion of the 10-session treatment program, approximately 2 weeks]: Anxiety level will be assessed using the Beck Anxiety Inventory. The scale consists of 21 items scored from 0 to 3, with a total score ranging from 0 to 63. Higher scores indicate higher anxiety severity.
• Change in sleep-related symptoms [Baseline and after completion of the 10-session treatment program, approximately 2 weeks]: Sleep-related symptoms will be assessed using the Adolescent Insomnia Scale. The scale includes 13 items and evaluates sleep onset, sleep maintenance, and sleep dissatisfaction/disturbances. Total scores range from 0 to 52, with higher scores indicating more severe insomnia symptoms.
• Change in pain intensity [Baseline and after completion of the 10-session treatment program, approximately 2 weeks]: Pain intensity will be assessed using the Visual Analog Scale. Participants will mark their pain level on a 100-mm line, where higher scores indicate greater pain intensity.
• Change in pruritus severity [Baseline and after completion of the 10-session treatment program, approximately 2 weeks]: Pruritus severity will be assessed using the 12-Item Pruritus Severity Scale. The scale evaluates the severity, frequency, duration, distribution, and impact of itching on daily life and sleep. Higher scores indicate more severe pruritus.
• Change in Root Mean Square of Successive Differences [Baseline and after completion of the 10-session treatment program, approximately 2 weeks]: Autonomic nervous system function will be assessed using the root mean square of successive differences between normal RR intervals derived from heart rate variability analysis. RR interval data will be recorded with a Polar H10 heart rate sensor during a 5-minute resting measurement and analyzed using Kubios HRV software. The root mean square of successive differences will be reported in milliseconds.
• Change in Standard Deviation of Normal-to-Normal Intervals [Baseline and after completion of the 10-session treatment program, approximately 2 weeks]: Autonomic nervous system function will be assessed using the standard deviation of normal-to-normal intervals derived from heart rate variability analysis. RR interval data will be recorded with a Polar H10 heart rate sensor during a 5-minute resting measurement and analyzed using Kubios HRV software. The standard deviation of normal-to-normal intervals will be reported in milliseconds.
• Change in Low-Frequency/High-Frequency Ratio [Baseline and after completion of the 10-session treatment program, approximately 2 weeks]: Autonomic nervous system function will be assessed using the low-frequency/high-frequency ratio derived from heart rate variability analysis. RR interval data will be recorded with a Polar H10 heart rate sensor during a 5-minute resting measurement and analyzed using Kubios HRV software. The low-frequency/high-frequency ratio will be reported as a ratio.

Sex: All, ages: 12 Years to 18 Years

Inclusion Criteria:

* Being between 12 and 18 years of age
* Having completed the acute phase after burn injury, with at least 1 month and at most 1 year since the burn injury
* Having second- or third-degree burns involving 5% to 30% of total body surface area
* Having at least one of the following complaints: anxiety, poor sleep quality, pain, or itching
* Written informed consent provided by the parent or legal guardian, and willingness of the participant to take part in the study
* Ability to read and understand Turkish

Exclusion Criteria:

* Infection, ulcer, or scar tissue on the auricle
* Burn injury in the head and neck region that prevents application of the device to the auricular vagus nerve area
* Metallic implant in the skull, excessive sensitivity in the ear, ear injury, or ear inflammation
* Chronic pulmonary and/or cardiac disease
* Heart rate below 60 beats per minute
* Presence of a pacemaker, cochlear implant, or similar implanted device
* Uncontrolled hypertension
* Lack of cooperation
* Refusal or inability of the parent or legal guardian to sign the informed consent form

• Sümeyye Akçay, Asst. Prof., Principal investigator, Fenerbahçe University