Inclusion Criteria:  invasive mechanical ventilation > 48 hours acute hypoxemic respiratory failure(PaO2/FiO2 < 300 mmHg) as a main cause of invasive mechanical ventilation. planned extubation & already passed a spontaneous breathing trial (SBT)  Exclusion Criteria:  < 20 years of ages refusal to re-intubation with terminal cancer pregnant women with a tracheal stoma or tracheostomy tube in situ not feasible for high-flow nasal cannula(decided by the primary care team) must required to use non-invasive ventilation immediately after extubation (decided by the primary care team)