Use Scale 2 only for patients with target sats 88-92% (known Type 2 respiratory failure / chronic CO₂ retainers). Otherwise Scale 1.
Any form of supplemental O₂ at the time of vitals. Adds 2 points and changes Scale 2 SpO2 scoring above the target window.
AVPU + new-onset Confusion (NEWS2 2017 addition). Anything other than Alert scores 3.