Table 2 Types of critical respiratory events (modified Murphy’s criteria)

1. Upper airway obstruction: if the patient required an intervention such as:

   o Oral airway

   o Jaw thrust

   o Nasal airway

2. Mild-moderate hypoxaemia (SpO₂ of 93–90%)

3. Severe hypoxaemia (SpO₂ < 90%)

4. Signs of respiratory distress or impending ventilation failure:

   o Accessory muscle use

   o Tracheal tug

   o Respiratory rate > 20 breaths per minute

5. Patient could not breathe deeply whilst asked for by the PACU nursing staff

6. Patient complaining of upper airway muscle weakness or symptoms of respiratory:

   o Difficulty swallowing: ask the patient to swallow a sip of water

   o Difficulty speaking

   o Difficulty breathing

7. Patient requiring re-intubation in the PACU

8. Clinical evidence or suspicion of pulmonary aspiration after tracheal extubation (gastric contents observed in the oropharynx and hypoxaemia)