ETCO2 Detection via Nasal Cannula

ETCO2 pearls.

During a recent shift, my ED team investigated a simple clinical question and discovered a truth that shocked us and may change our future patient management. The discovery should have been part of my education years ago, but I must have missed that lesson.

All procedural sedations should incorporate some sort of End-Tidal CO2 monitoring. We use the device pictured, which appears similar to a standard nasal cannula but functions very differently. While a standard nasal cannula delivers oxygen into the nasal passages via the nasal prongs, the nasal prongs on the ETCO2 nasal cannula do NOT deliver ANY oxygen, they function only as CO2 detectors. AGAIN, NO OXYGEN IS DELIVERED THROUGH THE NASAL PRONGS.

CO2 is also detected by the bulb device covering the mouth, but I did not realize that the nasal prongs were only for CO2 detection. The ETCO2 nasal cannula delivers oxygen through 10 tiny pin holes on the top of the device just in front of the nasal prongs, and through 2 small holes on the underside creating a “pillow of oxygen around the nose and mouth.” So this device only blows a cloud of oxygen out in front of the patient’s face, not directly into the nose or the mouth.

Practically, while this device excels at CO2 detection, I would not consider it a significant source of oxygen delivery. So use this device with caution in patients needing end-tidal CO2 monitoring but who also require oxygen supplementation. If clinically indicated, and if the hypoxemia is not due to apnea from lack of stimulation during procedural sedation, then the ETCO2 nasal cannula can be easily augmented with a non-rebreather face mask for additional oxygenation.

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