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.