From the Guidelines
The recommended cut-off carboxyhemoglobin (COHb) level for hyperbaric oxygen therapy (HBOT) is typically 25% or greater, though treatment may be considered at lower levels (15-25%) if the patient has significant symptoms or risk factors, as supported by the most recent and highest quality study 1.
Key Considerations for HBOT
- HBOT should be initiated for any pregnant patient with a COHb level above 15% due to increased fetal risk.
- Treatment decisions should not rely solely on COHb levels but should also consider clinical presentation, including neurological symptoms, cardiovascular instability, loss of consciousness, and metabolic acidosis.
- The timing of the COHb measurement is important as levels decrease after removal from carbon monoxide exposure, especially if supplemental oxygen has been administered.
Mechanism and Treatment of HBOT
- HBOT works by accelerating the elimination of carbon monoxide from hemoglobin (half-life reduced to 20-30 minutes compared to 4-6 hours with normal oxygen) and reducing reperfusion injury in tissues.
- Treatment typically involves 100% oxygen at 2.5-3.0 atmospheres absolute for 90-120 minutes, with possible repeated sessions for severe cases or persistent symptoms, as noted in 1.
Special Populations and Considerations
- Pediatric CO poisoning can pose special challenges, but in large series, there appear to be no marked differences in manifestations versus those reported in adult populations 1.
- Patients with significant body burns in addition to CO poisoning from a fire may be at greater risk for mortality from their burns than CO poisoning and should be managed in a specialized burn unit.
- If the CO exposure is believed to be intentional, toxicology screening should be considered to assess for toxic coingestions, and empiric treatment for cyanide poisoning may be necessary if severe metabolic acidosis is present and the source of CO was a house fire, as suggested in 1.
From the Research
Cut-off Carboxyhemoglobin Level for Hyperbaric Oxygen Treatment
- The provided studies do not specify a clear cut-off carboxyhemoglobin (COHb) level for hyperbaric oxygen treatment 2, 3, 4, 5, 6.
- According to the study by 3, treatment plans based on any specific COHgb level are not well founded.
- The study by 4 states that COHb levels do not correlate well with the clinical severity of CO poisoning.
- Hyperbaric oxygen therapy is recommended for patients with severe carbon monoxide poisoning, including those with neurologic deficits, unconsciousness, cardiac ischemia, pregnancy, and/or a very high COHb concentration 2.
- The decision to initiate hyperbaric oxygen therapy should be based on the patient's clinical presentation and severity of symptoms, rather than a specific COHb level 2, 3, 4, 5, 6.