Carbon monoxide and nonquantitative carbon dioxide detection.

Abstract

INTRODUCTION: The capnometric demonstration of end-tidal carbon dioxide (CO2) is a reliable method of differentiating between a correct endotracheal tube position and an accidental misplacement of the tube into the esophagus. Recently, several CO2 detectors have been introduced for monitoring end-tidal CO2 in the "out-of-hospital" setting, where quantitative capnometry with capnography is not yet available. HYPOTHESIS: These devices are not influenced by carbon monoxide (CO) present in lethal concentration. METHODS: A heated (37 degrees C) 2.3 L reservoir bag filled one-third full with water (representing the stomach in esophageal misintubation) was machine ventilated (tidal volume: 450 ml; frequency: 16/min) with the following mixtures for three minutes each: 1) 95% O2, 5% CO; 2) 45% O2, 5% CO, 50% N2O; and 3) 44% O2, 5% CO, 50% N2O, 1% halothane. The presence of end-tidal CO2 was monitored with each of the following devices: 1) MiniCAP III CO2 Detector; 2) StatCAP CO2 Detector; 3) EasyCAP CO2 Detector; 4) PediCAP CO2 Detector; and 5) Colibri CO2 Detector. RESULTS: In none of the cases was the presence of CO2 signaled by the detector. CONCLUSION: The presence of 5% CO does not interfere with infrared spectrometry detection (MiniCAP and StatCAP) or chemical detection (EasyCAP, PediCAP, and Colibri) of CO2. The devices can be used safely in patients with CO poisoning for monitoring of endotracheal tube position.