Insp O2 Tension

Used to estimate inspired oxygen pressure (PIO2) to guide oxygen titration when adjusting FiO2 or interpreting hypoxemia. Indicated for acute hypoxemic respiratory failure, post–cardiac arrest oxygen targeting (avoid hypoxemia/hyperoxemia per ILCOR 1 [Level I evidence]), and ventilated ICU patients requiring PaO2/FiO2 assessment. Clinically useful for setting appropriate FiO2, evaluating oxygenation deficits, and standardizing oxygenation indices (e.g., PaO2/FiO2, SpO2/FiO2).

Avoid excessive FiO₂ because high inspired O₂ tension increases oxidative stress and organ injury risk (JAMA Surgery RCT in cardiac surgery showed greater oxidative injury with hyperoxia 1 [Level I evidence]). Maintain normoxemia to prevent hyperoxemia‑associated mortality seen in meta‑analyses of acutely ill adults 2 [Level I evidence]. Caution in brain or post–cardiac arrest patients, where hyperoxia worsens neurologic outcomes 3 [Level II evidence].