Category: Toxicology
Keywords: Carbon Monoxide, Hyperbaric (PubMed Search)
Posted: 9/26/2025 by TJ Gregory, MD
(Updated: 9/29/2025)
Click here to contact TJ Gregory, MD
Carbon Monoxide Poisoning (COP) is a major toxicologic pathology and a common case in the Emergency Department and pre-hospital setting. History is a key component in assessment with the standard diagnostic test being blood gas analysis of Carboxyhemoglobin (COHb).
Standard pulse oximeter devices are not capable of differentiating oxyhemoglobin from carboxyhemoglobin, leading to the classic pearl that pulse ox may be falsely reassuring in COP.
In recent years, devices capable of differentiating oxyhemoglobin from COHb have been developed and are fielded in many hospitals and EMS agencies.
This meta-analysis reviews diagnostic accuracy of pulse CO-oximetry (spCO) devices in comparison to a reference standard COHb blood test. Six studies (1734 patients) were included.
This analysis found that spCO testing has a low sensitivity and high specificity.
Pooled sensitivity 0.65 (95% CI 0.44–0.81)
Pooled specificity 0.93 (95% CI 0.83–0.98)
Pooled LR+ 9.4 (95% CI 4.4 to 20.1)
Pooled LR- 0.38 (95% CI 0.24 to 0.62)
The authors conclude that the low sensitivity precludes use of spCO as an effective screening tool for COP or substitute for COHb. Conversely, we can recognize the utility of the high specificity in identifying patients who do have clinically significant toxicity. Indeed, the authors discuss potential applications for triage and transport to a hyperbaric oxygen chamber for those who are found to have elevated readings.
Technology advancement and refinement will be interesting to follow. In the meantime, don’t skip the COHb lab just because spCO measurement is reassuring.
https://pubmed.ncbi.nlm.nih.gov/38223786/
