Does FiO2 pertain to breathing patients only?

FiO2, or the fraction of inspired oxygen, primarily pertains to patients who are breathing, as it measures the concentration of oxygen in the air they inhale. However, it can also be relevant in the context of mechanically ventilated patients, where the FiO2 setting determines the oxygen concentration delivered through a ventilator. In both cases, understanding FiO2 is crucial for managing oxygen therapy effectively.