Hypoxic respiratory failure and severe ARDS. Give oxygen therapy immediately to patients with ARDS, and closely monitor them for signs of clinical deterioration, such as rapidly progressive respiratory failure. Consider severe hypoxemic respiratory failure when standard oxygen therapy fails. When patients have increased frequency of breathing (> 30 times/min) and hypoxemia (SpO2 < 90% or PaO2 < 60 mmHg) even with oxygen delivered via a face mask and reservoir bag (gas flow of 10~15 L/min, FiO2 0.60–0.95), it may be considered as hypoxic respiratory failure.