The first question is always: is the airway patent, and is the patient able to protect it? In many ICU patients the airway will already have been secured before admission, and the focus shifts to confirming correct endotracheal tube (ETT) position, checking the cuff pressure (target 20–30 cmH2O — too low allows aspiration, too high causes tracheal ischaemia), and ensuring there is no obstruction from secretions or kinking.

For patients admitted without a secured airway, rapid assessment is required. A GCS of 8 or below is the conventional threshold at which the ability to protect the airway is considered unreliable, and these patients should be considered for rapid sequence intubation (RSI). However, this is a guideline, not an absolute rule — a patient with a GCS of 10 who is vomiting and obtunded may be at higher aspiration risk than a calm patient with a GCS of 7. Clinical judgement must always supersede the number.

Rapid sequence intubation in the ICU is typically performed with a pre-oxygenation phase (bag-mask ventilation or high-flow nasal oxygen — HFNO — can extend the safe apnoea time considerably), induction with ketamine or propofol depending on haemodynamic status, and rocuronium or suxamethonium as the neuromuscular blocking agent. Ketamine is preferred when the patient is haemodynamically unstable because it preserves sympathetic tone and maintains blood pressure; propofol is a vasodilator and can cause significant hypotension in the sick patient. After intubation, ETT position should be confirmed with waveform capnography and a chest radiograph.