COHb Decision Tool

Carbon Monoxide (COHb) Tool

COHb interpretation, oxygen therapy, and hyperbaric O₂ criteria.

Initial COHb (%)

Arterial/Venous pH

Exposure time (h)

Pregnant

Smoker

Loss of consciousness

Neurologic deficits/confusion

Chest pain/ischemia/arrhythmia

Severe symptoms (coma, seizures)

Room air (min)

100% O₂ (NRB) (min)

HBO 2.5 ATA (min)

You can adjust half‑life assumptions based on local practice (typical ranges: RA 240–360, O₂ 60–90, HBO 20–30).

Targets used: ≤5% for non‑smokers & pregnancy; ≤10% for smokers (unless pregnant → ≤5%).

Start 100% oxygen (NRB) immediately for all suspected cases; avoid pulse‑ox alone for monitoring (reads falsely normal).
Consider Hyperbaric O₂ (HBO) if any: COHb ≥25% (≥15–20% in pregnancy), loss of consciousness, severe neurologic symptoms, ischemia/arrhythmia, or significant metabolic acidosis (e.g., pH < 7.1).
Do not delay oxygen while arranging HBO. Clinical picture outweighs a falling COHb after O₂.
Reassess symptoms and COHb after therapy; watch for delayed neurologic sequelae.