NIV. NIV provides a certain positive pressure ventilation effect through the positive pressure formed by the closed mask. HFNO combined with intermittent short-term NIV (1–2 h) support may be useful to reduce respiratory power consumption and improve oxygenation. But NIV guidelines recommend the use of respiratory support therapy in hypoxemic respiratory failure or pandemic viral illness. Limited data showed a high failure rate of NIV in MERS patients. Invasive mechanical ventilation should be considered in case the ARDS still exists and even acutely deteriorates in NIV process (about 1 h). Patients with hemodynamic instability, multiple organ failure, or abnormal mental status should not receive NIV.