False-positive end-tidal CO2

Survey of the Use of Capnography in UK Intensive Care Units

Capnography is not currently part of standard monitoring in intensive care practice in the UK. In order to investigate how widely capnography is used and reasons for lack of use, we sent a survey to lead clinicians of adult intensive care units. The response rate was 61%; 45% of responding units did not have the facility to monitor carbon dioxide at all funded bedspaces. Approximately 30% of units were covered at least part of the time by doctors who did not have advanced airway skills. Reasons for not using capnography included its lack of correlation with arterial blood gases and the fact that capnography is not 100% sensitive or specific for the diagnosis of airway misplacement. Capnography should be used during intubation to confirm airway placement in the intensive care unit.

Capnography alone is imperfect for endotracheal tube placement confirmation during emergency intubation

This analysis primarily sought to determine the effectiveness of end-tidal capnography for tube placement confirmation during emergency airway management. Secondary objectives were validation of the rate of unanticipated esophageal placement during emergency intubation and quantification of the portion of intubations performed in patients with cardiac arrest where capnography is not recommended. The study was performed in two phases. For the primary objective, a meta-analysis was performed on all experimental capnography trials enrolling emergency populations. For the secondary objectives, inadvertent esophageal intubation and cardiac arrest rates were calculated from a large prospective multicenter observational study of emergency intubation cases. Data analysis included calculation of descriptive statistics, sensitivity, specificity, and confidence intervals (CI). Based on 2,192 intubations, a meta-analysis of previous capnography trials resulted in an aggregate sensitivity of 93% (95% CI 92-94%) and an aggregate specificity of 97% (CI 93-99%) for emergency tube placement confirmation. Thus, for emergency capnography use, the false-negative failure rate (tube in trachea but capnography reports esophagus) was 7% and the false-positive rate (tube in esophagus but capnography reports trachea) was 3%. This translates to potential harm for one patient in every 10 treated with capnographic confirmation alone (number needed to harm: 14 for false-negative, 33 for false-positive, and 10 for both). A further literature review demonstrated no sole method of tube placement confirmation is completely foolproof. Of 4,602 consecutive intubations reported to the National Emergency Airway Registry, 4% of emergency intubation attempts resulted in accidental esophageal intubation, and 10% occurred in nontraumatic cardiac arrest patients. During tracheal intubation of critically ill patients, it is concluded that the rate of accidental esophageal tube placement warrants continued improvement in emergency airway techniques. Misidentification of esophageal placement in the emergency setting may occur with capnography. Multiple methods of tube placement confirmation are superior to any single method because no single method has perfect accuracy.