FiO2
Pronunciation: FEE-oh-two
Also written as: FiO2 — Fraction of Inspired Oxygen
The percentage of oxygen concentration in the gas mixture delivered to a patient's lungs.
Full Definition
Fraction of Inspired Oxygen (FiO2) is a fundamental parameter in respiratory care and mechanical ventilation, expressed as a decimal (0.21-1.0) or percentage (21-100%). Room air has an FiO2 of 0.21 (21%), while supplemental oxygen delivery can increase this up to 1.0 (100%). In surgical critical care, FiO2 is carefully titrated to maintain adequate oxygenation while minimizing oxygen toxicity. The PaO2/FiO2 ratio is a key metric for assessing oxygenation efficiency and defining acute lung injury severity. Goal-directed oxygen therapy aims for the lowest FiO2 that maintains acceptable oxygen saturation, typically targeting SpO2 88-92% in COPD patients or 94-98% in others, to avoid hyperoxia complications.
Usage
Usage note: Express as decimal (0.21-1.0) in formal documentation, though percentage may be used in some contexts.
In Context
- "The ventilator FiO2 was titrated down from 0.6 to 0.4 as oxygenation improved." — Ventilator weaning note
- "Despite FiO2 of 1.0, the patient's PaO2/FiO2 ratio remained below 100, indicating severe ARDS." — Respiratory assessment