This study will involve 70 adult patients with Guillain-Barré syndrome who have severe breathing problems. It will compare two types of breathing support: high-velocity nasal cannula (HVNC) (which delivers heated and humidified air at 35-60 L/min) and bi-level noninvasive ventilation (NIV) (which uses two pressure levels: inspiratory positive airway pressure (IPAP) 10-16 cmH₂O and expiratory positive airway pressure (EPAP) 5-8O). The main goal is to see how many patients can stop using non-invasive support without needing a breathing machine by Day 30. Other goals include how long it takes to stop using support, how comfortable patients feel, how long they stay in the ICU or hospital, how many days they can breathe on their own, and the number of deaths in 30 days. The main goal is to see how many patients can stop using non-invasive support without needing invasive ventilation by Day 30, while also looking at other factors like how long it takes to stop assistance, how comfortable patients are, how long they stay in the hospital, how many days they can breathe on their own, the number of deaths within 30 days, and their overall health.

Guillain-Barré Syndrome (GBS) is an acute autoimmune disorder characterized by rapid-onset muscle weakness due to peripheral nerve damage. A significant complication in GBS is respiratory failure, occurring in approximately 25% of cases, necessitating timely and effective respiratory support to prevent morbidity and mortality.

Non-invasive ventilation (NIV) is a standard intervention for managing acute respiratory failure, particularly in conditions such as chronic obstructive pulmonary disease (COPD). NIV delivers positive pressure ventilation through interfaces such as oronasal masks, providing support without the need for endotracheal intubation. While effective, NIV can be associated with patient discomfort, skin breakdown, and challenges in secretion management, potentially leading to intolerance or failure of the therapy.

High-flow nasal cannula (HFNC) therapy has emerged as an alternative respiratory support modality. HFNC delivers heated and humidified oxygen at high flow rates through nasal prongs, offering several physiological benefits:

Enhanced Oxygenation: By delivering high flow rates, HFNC can meet or exceed the patient's inspiratory demand, ensuring consistent oxygen delivery.

Reduction in Work of Breathing: The continuous flow can generate a low level of positive airway pressure, decreasing the effort required for breathing.

Enhanced Secretion Clearance: Humidified gas supports mucociliary function, facilitating the clearance of secretions.

Patient Comfort: The nasal interface is generally better tolerated than masks used in non-invasive ventilation (NIV), potentially improving adherence to therapy.

Recent studies have explored the efficacy of HFNC compared to NIV in various forms of respiratory failure. While NIV remains the first-line treatment in many scenarios, HFNC has shown promise in improving patient comfort and reducing the need for escalation to invasive mechanical ventilation in specific patient populations.

Inclusion Criteria:

• Age ≥ 18 years
• GBS per Brighton criteria (clinical ± cerebrospinal fluid (CSF)/electrodiagnostics)
• Moderate acute respiratory failure (vital capacity (VC) 15-20 mL/kg and/or arterial partial pressure of carbon dioxide (PaCO₂) > 45 mmHg or arterial partial pressure of oxygen (PaO₂) < 70 mmHg on room air (RA) and/or respiratory rate (RR) > 24 /min)
• Hughes Grade 3-4, The Erasmus Guillain-Barré Syndrome Respiratory Insufficiency Score (EGRIS) 1-3, Medical Research Council (MRC) sum score 20-40
• Glasgow Coma Scale (GCS) ≥ 13, intact cough/gag, stable hemodynamics
• Onset of respiratory symptoms ≤ 7 days

Exclusion Criteria:

• Chronic respiratory disease (COPD, interstitial lung diseases (ILD), persistent asthma)
• Immediate need for invasive ventilation (VC < 10 mL/kg, unresponsive severe gas-exchange derangement)
• Severe bulbar dysfunction or prior intubation for the current illness
• Contraindications to HVNC/NIV (facial trauma, untreated pneumothorax, agitation, vomiting)
• Pregnancy
• Severe comorbidity limiting prognosis.
• Declined consent

De-identified individual participant data supporting the primary and secondary outcomes, along with accompanying data dictionaries and the statistical analysis plan, will be made available by Assiut University's institutional data-sharing policies. Data will be accessible 6-36 months after publication to qualified researchers upon submission of a study proposal, approval by the University Research Ethics Committee, and execution of a data-use agreement.

6-36 months after publication

Qualified researchers must submit a study proposal, obtain approval from the University Research Ethics Committee, and execute a data-use agreement.

Outcome assessor blinding involves masking only those individuals who measure or adjudicate study endpoints, while participants and treating clinicians remain aware of treatment allocation. This approach reduces detection bias in outcome measurement without the logistical challenges of fully double-blinded designs.