Original contributionCapnography alone is imperfect for endotracheal tube placement confirmation during emergency intubation1
Introduction
What this comes down to is hubris: sinful pride. I know that I can intubate. I know where that tube is. The problem with being wrong is it won’t hurt my pride, but it might kill somebody. [Comment on the fatal complication of missed esophageal tube placement. Cory Slovis, MD, Chairman, Vanderbilt Emergency Medicine residency. Interview CBS Evening News (John Roberts, anchor), Jan 1, 1999.]
Emergency intubation of the critically ill patient provides liberal opportunity for misfortune. Whereas successful completion may be lifesaving, failure often hastens patient death. The science and practice of emergency intubation has progressed significantly within the past decade (1). Rapid-sequence intubation (RSI) has nearly replaced intubation minus paralysis (IMP) as standard of care for both emergency trauma and medical patients 2, 3, 4. Decreased complication rates during emergency intubation can be attributed to greater acceptance of rapid-sequence techniques, intensive training of emergency physicians (EPs) within specialty training programs, improvement in failure detection, and increased training in rescue techniques. Future advances in emergency intubation now largely focus on early recognition of unanticipated esophageal intubation 5, 6, 7. Two previous prospective series totaling 530 patients showed that such unanticipated tube placement occurs in 8% of intubation attempts 4, 8.
For EPs, portable capnography has become widely available for use in tube confirmation, providing one method of recognizing improper esophageal tube placement. However, capnography has two major disadvantages for emergency use. First, it functions poorly for the portion of patients intubated for disorders that limit or terminate production of exhaled CO2 and is not recommended for primary tube confirmation in such cases (5). In some centers where intubation occurs frequently for cardiac arrest, such cases may represent a significant portion of intubations. Second, capnography requires a trial of ventilation. In previously fasted elective surgery patients, accidental esophageal intubation is usually of little consequence because these patients are adequately pre-oxygenated, denitrogenated, and have empty stomachs. In contrast, patients undergoing emergency intubation have not fasted and often cannot receive an adequate period of pre-oxygenation because of the illness at hand. A trial of esophageal ventilation in these cases may be catastrophic because of rapid hypoxia and large-volume aspiration of gastric contents 5, 6, 7, 8, 9.
Despite the marketing of capnographic devices for emergency department (ED) intubation confirmation, most previous capnography studies have focused on nonemergent populations whose illnesses are not complicated by low flow or cardiac arrest states. Accordingly, the primary objective of this study was the quantification of overall success and failure rates of capnographic confirmation in populations of emergency patients. Secondary objectives were validation of previously reported rates of unanticipated esophageal intubation in emergency populations and quantification of the portion of emergency intubations performed in patients with cardiac arrest, where capnography is expected to fail.
Section snippets
Materials and methods
For the primary trial objective, a meta-analysis of selected trials was undertaken to determine the effectiveness of end-tidal CO2 devices for detection of inadvertent esophageal tube placement in emergency populations. This analysis was designed in accordance with the Quality of Reporting of Meta-analyses statement on meta-analysis methodology (10). Trials were identified by a computerized search of the National Institutes of Health database from 1966 to 1999, hand and computerized search of
Results
For the meta-analysis, 512 trials of capnography from 1966 to 1999 were identified. Of these, 25 trials involved intubation in emergency patient populations. However, 15 of these 25 trials did not report numbers of tracheal and esophageal intubations. The remaining 10 trials (all published after 1990) met the entry criteria for the analysis 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22. Characteristics of the trials that met entry criteria are presented in Table 1.
Intubations reported from the 10
Discussion
The purpose of this analysis was to provide emergency practitioners with information to judge the effectiveness of tube placement capnography in daily clinical practice. In previous studies enrolling healthy elective surgery patients, capnography has been demonstrated to be useful for rapidly identifying unanticipated esophageal intubation. However, the emergency population is a heterogeneous one, and patients may present with healthy, compromised, or nonexistent pulmonary perfusion. Except for
Conclusion
Given the possibility of errors in confirmation when capnography is used in isolation as well as current reported rates of accidental esophageal intubation, we recommend that clinicians performing emergency intubations use multiple techniques to confirm tube placement.
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Original Contributions is coordinated by John A. Marx, MD, of Carolinas Medical Center, Charlotte, North Carolina