Effects of Left and Bilateral Transcutaneous Auricular Vagus Nerve Stimulation on Pain, Mood, and Autonomic Function in Female Fibromyalgia Patients

Fibromyalgia Impact Questionnaire is a scale consisting of 10 questions, displaying physical function, absence from work, feeling well, fatigue, difficulty at work, pain, stillness, morning fatigue, anxiety, and depression. Apart from feeling well, low scores indicate recovery or being slightly affected by the disease. The maximum score of each subheading is 10 and the total score is 100. FIQ score was evaluated as being slightly affected under 50 points, moderately affected between 50-69, and heavily affected at 70 and more.

Pain severity was assessed with the Visual Analog Scale (VAS), which is scored between 0 and 10, and is used to evaluate pain. 0 denotes no pain and 10 denotes unbearably severe pain. Participants were asked to mark the pain they felt on a 10 cm straight line and the value found was recorded in cm.

The PNS Index was used to measure ANS activity, indicating the evaluation of a person's parasympathetic nervous system activity compared to normal resting values. (https://www.kubios.com/publications/) The PNS index serves as a quantitative indicator of ANS function by reflecting the activity levels of its branches. This measures play a crucial role in heart rate variability (HRV) analysis, offering valuable insights into an individual's stress levels and recovery capacity. For PNS activity reduces heart rate and enhances HRV. HRV changes in pathological conditions (ischemic heart disease etc.), and decreased variability is a predictor of worse outcomes. Cyclical fluctuations in heart rate reveal changes in the ANS. The e-motion Faros device has been classified as a Class II medical device by Health Canada. After recording the R-R intervals of heart rate by e-motion Faros, the data were transferred to Kubios software for interpretation of HRV.

The SNS Index was used to measure ANS activity, indicating the evaluation of a person's sympathetic nervous system activity compared to normal resting values. (https://www.kubios.com/publications/) The SNS index serves as a quantitative indicator of ANS function by reflecting the activity levels of its branches. This measures play a crucial role in heart rate variability (HRV) analysis, offering valuable insights into an individual's stress levels and recovery capacity. A heightened SNS index is often associated with increased sympathetic activity, commonly linked HRV changes in pathological conditions (ischemic heart disease etc.), and decreased variability is a predictor of worse outcomes. Cyclical fluctuations in heart rate reveal changes in the ANS. The e-motion Faros device has been classified as a Class II medical device by Health Canada. After recording the R-R intervals of heart rate by e-motion Faros, the data were transferred to Kubios software for interpretation of HRV.

Autonomic nervous system (ANS) activity, including both sympathetic (SNS) and parasympathetic (PNS) indices, is assessed using the eMotion Faros device. The device continuously records electrocardiographic (ECG) signals via a single-lead chest electrode setup. It is classified as a Class II medical device by Health Canada.

The collected ECG data are analyzed using proprietary Kubios HRV Premium software, which computes time-domain, frequency-domain, and nonlinear heart rate variability (HRV) parameters. SNS and PNS indices are derived using Kubios' built-in algorithms that combine spectral analysis (e.g., LF/HF ratio), stress index, and other HRV-derived metrics to estimate autonomic balance.

Higher SNS index values indicate increased sympathetic activity, while higher PNS index values reflect enhanced parasympathetic tone.

The Beck Depression Index (BDI) is an evaluation questionnaire that assesses, behavioral signs of depression in adolescents and adults. The total score ranges from 0 to 63. It is interpreted as Minimal =0-9, Mild=10-16, Moderate=17-29 and Severe=30-63.

The Beck Anxiety Inventory (BAI) is suggested as a tool for evaluating clinical anxiety and distinguishing between anxious and non-anxious diagnostic groups. It is a 21-item Likert-type scale, scored from 0 to 3. The total score ranges from 0 to 63, with the following classifications: mild <21, moderate: 22-35, and severe>36