The RAD-57 pulse CO-oximeter is a lightweight device allowing non-invasive measurement of blood carboxyhemoglobin. Previous studies comparing RAD-57 measurements (SpCO) to standard laboratory blood gas analysis (COHb) have reported contradictory results.

the RAD-57 pulse CO-oximeter could be useful as a first-line screening test for acute CO poisoning, enabling rapid detection and management of patients with suspected CO poisoning in the prehospital emergency setting This study assesses the diagnostic value of pulse CO-oximetry, comparing SpCO to standard laboratory blood measurement for prehospital management of patients with suspected carbon monoxide (CO) poisoning.

Transcutaneous SpCO will be obtained using the RAD-57 simultaneously with blood sampling for laboratory blood gas analysis, at the time of prehospital management by emergency medical services. The diagnostic performance of SpCO for the screening of CO poisoning will be determined using ROC curve analysis, and Blood COHb levels >5% and 10% as the reference standard for CO poisonning for non-smokers and smokers respectively. Correlation between SpCO and COHb will be assessed using Bland and Altman's method.

Inclusion criteria:

• Patient aged 18 years or older
• Patient managed by prehospital emergency medical services.
• Patient with a suspected CO exposure presenting or not with clinical signs of CO poisoning

Exclusion criteria:

• Patient for whom venous blood sampling cannot be obtained prehospitally
• Patient for whom SpCo measurement cannot be performed prehospitally (cardiac arrest, peripheral vasoconstriction)