Two numbers do most of the sorting. In hypoxaemic failure without hypercapnia, start high-flow nasal oxygen, typically 50–60 L/min, FiO2 titrated to SpO2 92–96%. In hypercapnic failure, check the pH: below about 7.25, NIV is the treatment; above it, high-flow is acceptable only where you can switch to NIV quickly.
Reassess within one to two hours. For high-flow, the ROX index (SpO2/FiO2 divided by respiratory rate) below about 3.85 at 12 hours flags likely failure. Do not let a failing noninvasive trial delay intubation.
- Hypoxaemic, no hypercapnia: high-flow first.
- Hypercapnic, pH <7.25: NIV.
- Hypercapnic, pH ≥7.25: high-flow only with rapid NIV backup.
- Reassess at 1–2 hours; use the ROX index for high-flow.
- Set a clear escalation threshold.
Why it matters
Choosing the right mode early avoids both unnecessary intubation and dangerous delay.
Read the rest in the app
You have read your two free briefings this month. The app carries all 27 specialties, every morning, free — and this finding is waiting in it.
Scan to keep reading on your phone. No account needed to start.
Tomorrow morning, before your first patient
One edition a day for pulmonology, written by the desk, every claim tied to its paper. Six minutes.
Get the app — free