The Murray score combines four measures of lung injury severity into a single averaged score, historically used to help decide whether an ARDS patient is sick enough to be referred for ECMO.
No lung injury.
Mild lung injury.
Mild-to-moderate lung injury.
Severe lung injury — referenced in ECMO candidacy.
It's largely been supplemented by simpler criteria like the Berlin ARDS PF-ratio staging, but it remains referenced in ECMO-candidacy discussions and older literature.
Four components — chest X-ray quadrants involved, PaO₂/FiO₂, PEEP level, and static compliance — are each scored 0–4, then averaged to give the final score.
0 means no lung injury, 0.1–2.5 indicates mild-to-moderate injury, and above 2.5 indicates severe lung injury.
Averaging keeps the score on a consistent 0–4 scale regardless of how many components are available, making values comparable across patients and over time.