Inclusion Criteria:

1. Age between 18 and 75 years, with BMI <30 kg/m².

2. Cervical SCI involving levels C1-C5 for at least 2 weeks.

3. Respiratory failure defined by one or more of the following:

   • Peripheral oxygen saturation <90% on room air;
   • Arterial oxygen tension (PaO₂) <60 mmHg;
   • Respiratory acidosis (PaCO₂ >45 mmHg with pH <7.35);
   • Requirement for mechanical ventilation.

4. Maximum inspiratory pressure (MIP) >-15 cmH₂O.

5. Judged by the treating physician to be unable to tolerate continuous ventilator weaning for ≥48 hours due to SCI.

6. Written informed consent provided by the participant or legally authorized representative.

Exclusion Criteria:

1. Active infection at the planned electrode implantation site, severe systemic infection, or existing implanted neurostimulation devices.
2. Respiratory failure primarily caused by severe pneumonia, pulmonary contusion, pneumothorax, hemothorax, chronic obstructive pulmonary disease, or requirement for home oxygen therapy within the previous 6 months.
3. New York Heart Association (NYHA) class III or IV heart failure or implanted cardiac pacemaker.
4. Severe hepatic or renal dysfunction (Child-Pugh class C liver disease or estimated glomerular filtration rate ≤30 mL/min/1.73 m²) or dialysis dependence.
5. Generalized seizures, traumatic brain injury, intracranial hypertension, intracranial aneurysm with Glasgow Coma Scale score ≤12, or neuromuscular disorders affecting respiratory function.
6. Expected survival <72 hours or refusal of life-sustaining treatment.
7. Pregnancy or breastfeeding.
8. Any other condition considered by the investigator to make study participation inappropriate.