Intubation(mechanical ventilation) Blood oxygen level below 90% Breathing rate equal to 30 or more per minute Allergic reaction to drugs Shortness of breath caused by cardiogenic pulmonary edema Pregnancy and lactation History of oxygen therapy at home Patients with end stage, lung, malignant, G6PD deficiency, diabetic ketoacidosis, cardiac arrhythmia

Intubation(mechanical ventilation) Blood oxygen level below 90% Breathing rate equal to 30 or more per minute Allergic reaction to drugs Shortness of breath caused by cardiogenic pulmonary edema Pregnancy and lactation History of oxygen therapy at home Patients with end stage, lung, malignant, G6PD deficiency, diabetic ketoacidosis, cardiac arrhythmia