This randomized controlled trial was designed to investigate the effects of fascial mobilization along the course of the vagus nerve on acute physiological parameters in individuals with obstructive sleep apnea syndrome (OSAS). Patients diagnosed with moderate to severe OSAS by polysomnography at Mardin Training and Research Hospital Sleep Laboratory will be included in the study. Participants will be randomly assigned to mobilization or control groups. In the mobilization group, 16 minutes of manual fascial mobilization will be applied to fascial regions associated with the vagus nerve, starting from the occipitomastoid suture and extending through the cervical, thoracic, and abdominal regions. The control group will rest in the supine position for the same duration. Heart rate, systolic and diastolic blood pressure, and peripheral oxygen saturation (SpO₂) will be recorded before and after the intervention. This study is expected to demonstrate the effectiveness of fascial mobilization as a non-invasive, low-cost, and innovative approach in the treatment of OSAS, contributing to clinical practice.

Inclusion Criteria:

• Patients diagnosed with moderate to severe obstructive sleep apnea syndrome (OSAS) confirmed by polysomnography (PSG) according to international criteria (AASM - American Academy of Sleep Medicine) with an apnea-hypopnea index (AHI ≥15/hour).

Patients aged between 18 and 65 years.

Patients able to comply with PSG procedures and the manual mobilization protocol.

Patients with stable cardiac and respiratory status.

Patients without acute exacerbations or decompensated disease.

Patients who have not received CPAP, BiPAP, oral appliance therapy, or surgical treatment previously, or who discontinued such treatments at least 3 months prior to enrollment.

Patients not taking medications that directly affect sleep patterns or autonomic nervous system function (e.g., sedatives, hypnotics, anticholinergics).

Patients who provide written informed consent to participate in the study.

Exclusion Criteria:

• Patients with uncontrolled hypertension.

Patients with advanced heart failure, severe arrhythmia, or asthma.

Patients with coronary artery disease.

Patients with a history of cerebrovascular disease.

Patients with chronic obstructive pulmonary disease (COPD).

Patients with interstitial lung disease.

Patients with epilepsy, Parkinson's disease, or dementia.

Patients with major depressive disorder or anxiety disorder.

Patients with a body mass index (BMI) > 40 kg/m².

Patients with a history of major surgery in the cervical region (e.g., thyroidectomy, cervical disc surgery) or vagus nerve injury.

Patients with acute infection, skin lesions, or inflammatory disease in the neck/thoracic region.

Patients currently using CPAP, BiPAP, or oral appliances.

Patients with narcolepsy, insomnia, or parasomnia.

Patients with alcohol use or taking sedative/hypnotic medications.

Patients with night-shift work schedules or irregular sleep patterns.

Pregnant or breastfeeding women.

Patients with cognitive impairment preventing adherence to the study protocol.

Patients with severe musculoskeletal limitations (e.g., in the cervical/thoracic region) that would prevent mobilization.

The decision will depend on journal requirements and ethical committee approval

Outcome assessors were blinded to group allocation. Physiotherapists performing the mobilization were not involved in the measurement process. A different physiotherapist, who was unaware of the participants' group assignments, recorded heart rate, blood pressure, and oxygen saturation before and after the intervention.