Carbon Monoxide and Nonquantitative Carbon Dioxide Detection

Abstract

AbstractIntroduction: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°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; 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.