This tool estimates what a patient's blood oxygen level will be at typical cabin altitude, used to assess whether someone with lung disease is safe to fly.
The equation predicts PaO₂ at a simulated cabin altitude of about 8,000 ft (atmospheric pressure ≈ 565 mmHg).
Supplemental oxygen generally not needed.
Borderline — consider a hypoxic challenge test.
In-flight oxygen usually recommended.
In-flight oxygen recommended.
Given: sea-level PaO₂ 75 mmHg, FEV₁ 50% predicted.
33.9819.3A pressurized cabin sits around 8,000 ft equivalent, lowering inspired oxygen pressure.
Commercial cabins are pressurized to roughly 8,000 ft equivalent, not sea level, so the inspired oxygen pressure drops. Healthy lungs tolerate it easily, but someone with borderline oxygenation can become hypoxemic in flight.
A common threshold is an estimated in-flight PaO₂ below about 50–55 mmHg, which suggests supplemental oxygen should be arranged. Borderline results often prompt a formal hypoxic challenge test.
The patient breathes a reduced-oxygen gas mixture (about 15% oxygen) that simulates cabin altitude while PaO₂ or SpO₂ is measured — the most reliable pre-flight assessment when the estimate is borderline.
Pre-flight fitness assessment in COPD, interstitial lung disease, and other chronic respiratory conditions where resting oxygenation is already reduced.