Desired PaO₂ / FiO₂ Needed Calculator

Estimates FiO₂ needed to reach a desired PaO₂ target.

Inputs

Color mode links each input to the matching equation term and solving arithmetic.

Equation and Work

Primary equation:
PAO₂ support equation:
Solving steps:
FiO₂ needed
—
%
PAO₂ needed
—
mmHg
Oxygen level
—
estimate
Reference: Room air is 21% FiO₂. For COPD shortcut estimates, the text targets a low-range PaO₂ of about 50–60 mmHg and notes SpO₂ 90% corresponds roughly to PaO₂ 60 mmHg under normal conditions.

Clinical Significance

The a/A-ratio method first estimates the PAO₂ needed for a desired PaO₂, then estimates FiO₂ from the alveolar gas equation.

Use this as a bedside oxygen estimate when oxygenation response is represented by the patient’s a/A ratio. The COPD shortcut targets a low-range PaO₂.

Severe shunt may respond poorly to oxygen alone. PEEP/CPAP and clinical assessment may be needed; this calculator is an estimate.

References (APA 7th Edition)

  1. Chang, D. W. (2020). Respiratory Care Calculations (Revised 4th ed.). Jones & Bartlett Learning. Formula content adapted from the uploaded text/reference packet.