What is the goal of ICU oxygen supplementation?

• A. Improve SpO2 to 100% regardless of FiO2
• B. Increase FiO2 to maximum
• C. Improve P/F ratio rather than isolated SpO2 improvement
• D. Achieve normal PaO2 at any FiO2

Answer: (C)

The goal of ICU oxygen therapy is to improve how efficiently oxygen moves from the lungs into the blood, not merely to push the saturation up to 100% or to flood the patient with oxygen. The key measure is the P/F ratio (PaO2 divided by FiO2), which reflects the lungs’ ability to transfer oxygen for a given amount of inspired oxygen. When this ratio improves, it indicates better alveolar gas exchange and more effective oxygen delivery to tissues for the same or even less oxygen support.

Chasing a normal PaO2 at any FiO2 isn’t realistic or always safe, since lung disease and ventilation–perfusion problems prevent perfect oxygen transfer. Likewise, simply maximizing FiO2 can cause oxygen toxicity and other complications without guaranteeing better tissue oxygenation. And aiming for SpO2 of 100% regardless of FiO2 can mask underlying issues and isn’t necessary for optimal outcomes.

So, improving the P/F ratio best captures the intended goal: enhancing oxygen transfer efficiency through the lungs while using the minimum effective amount of inspired oxygen.