• 
• 

Three Part Question

In [patients who require field intubation] does [the use of a carbon dioxide indicator] reduce [the number of unrecognized misplaced intubations]?

Clinical Scenario

An 83-year-old restrained female passenger involved in a head-on collision is brought to the ED via helicopter. The ED evaluation reveals an unidentified esophageal intubation. On questioning the helicopter paramedic crew, it is found that a carbon dioxide indicator was not used in the field.

Search Strategy

Medline via OVID interface: 1966 to May 2011.
EMBASE 1980 to May 2011
Limit to HUMAN and English (paramedic.mp OR prehospital.mp OR out-of-hospital.mp) AND (exp Carbon Dioxide OR end-tidal.mp OR exp Capnography OR carbon dioxide.mp OR capnogr$.mp) AND (exp intubation OR intubation.mp OR intubat$.mp OR rapid sequence.mp).

Search Outcome

One thousand three hundred eleven papers were found of which five studies were deemed directly relevant to the three-part question. Two further papers were deemed supportive of the question but were not clinical trials.

Relevant Paper(s)

Author, date and country	Patient group	Study type (level of evidence)	Outcomes	Key results	Study Weaknesses
Katz SH, 2001, USA	108 out of hospital intubations	Prospective observational study	ETCO2 and auscultation on arrival to ED Laryngoscopy performed at the discretion of ED physician	Oesophageal intubation associated with absence of ETCO2 in 94% of cases Hypopharyngeal intubation resulted in lack of ETCO2 in 44.4% of cases 17.3% in cardiac arrest showed no ETCO2 trace despite confirmation of ETT position with direct laryngoscopy	Did not compare the different modes of confirmation Laryngoscopy at the discretion of the physician Four clinically suspected misplaced ETTs removed in ED without enrolment
Jones et al, 2004, USA	208 out-of-hospital oro- and nasopharyngeal intubations Excluded patients with alternative airway	Prospective observational study	Confirmation of ETT with direct visualisation by laryngoscopy, colorimetric ETCO2 oesophageal detector device and physical examination	12 misplaced ETT (5.8%, 95% CI 2.6% to 8.9%): 9 (7.8%) in the group where the verification device was not used and 3 (3.2%) in the verification group. No difference was found in the use of a verification device (p=0.233)	Rapid sequence induction not used Potential Hawthorne effect Experience of paramedics not taken into account
Grmec et al, 2004, Slovenia	81 patients with polytrauma/severe head injury undergoing field intubation	Prospective observational study	Compared auscultation to capnometry/capnography for correct ETT placement Final determination by second direct visualisation of ETT with laryngoscope	Initial capnometry Sensitivity 100% and specificity 100% PPV 100%, NPV 100% Capnography after six breaths Sensitivity 100% and specificity 100% PPV 100%, NPV 100% Auscultation Sensitivity 94% and specificity 66% PPV 94%, NPV 6%	Small numbers
Silvestri et al, 2005, USA	153 patients intubated out of hospital by EMS and admitted to ED Patients requiring airway adjuncts or a surgical airway were excluded	Prospective observational study	Association between ETCO2 monitoring and misplace ETT tubes	Missed misplaced ETT with ETCO2 monitoring 0% (95% CI 0% to 4%) Misplaced intubations without carbon dioxide monitoring 23% (95% CI 13.4% to 36%) Odds for unrecognised ETT misplacement higher in the non-monitored group OR 28.6 (95% CI 4.0 to 122.0)	Included both capnographic and colorimetric devices Intubation experience as potential confounding variable
Timmerman et al, 2007, Germany	149 patients requiring out-of-hospital emergency intubation and air transport	Prospective observational study	ETT placement by emergency physician and subsequently checked by study physician by a combination of examination, direct visualisation ETCO2 and oesophageal detection device	Right main branchus intubation in 16 cases (10.7%) Oesophageal intubation in 10 cases (6.7%). All oesophageal intubations corrected but 7 patients died within 24 h	Most of the study operators were trained anaesthetists Potential reporting bias Lack of reporting for confounders

Comment(s)

The use of end-tidal carbon dioxide monitoring is vitally important when available to facilitate the intubating physician in determining the position of the endotracheal tube. In-hospital practice dictates the use of such monitoring a standard of care, and this should be extended to situations where intubation is deemed necessary in the prehospital environment. Its use in this situation is affirmed in the above papers, as well as in recent reviews of prehospital advanced airway management by Helm and Braun.

Clinical Bottom Line

The routine use of end-tidal carbon dioxide monitoring for prehospital intubations should be standard of care. In combination with physical examination, it should eliminate the possibility of incorrectly placed endotracheal tubes.

References

1. Katz SH, Falk JL. Misplaced endotracheal tubes by paramedics in an urban emergency medical services system Ann Emerg Med 2001;37:32–7.
2. Jones JH, Murphy MP, Dickson RL, et al. Emergency physician-verified out-of-hospital intubation: miss rates by paramedics Acad Emerg Med 2004;11:707–9.
3. Grmec S, Mally S. Prehospital determination of tracheal tube placement in severe head injury Emerg Med J 2004;21:518–20.
4. Silvestri S, Ralls GA, Krauss B, et al. The effectiveness of out-of-hospital use of continuous end-tidal carbon dioxide monitoring on the rate of unrecognized misplaced intubation within a regional emergency medical services system Ann Emerg Med 2005;45:497–503.
5. Timmermann A, Russo SG, Eich C, et al. The out-of-hospital esophageal and endobronchial intubations performed by emergency physicians. Anesth Analg 2007;104:619–23.
6. Braun P, Wenzel V, Paal P. Anesthesia in prehospital emergencies and in the emergency department. Curr Opin Anaesthesiol 2010;23:500–6.
7. Helm M, Fischer S. The role of capnography in pre-hospital ventilation for trauma patients. Int J Nurs Pract 2005;12:124–30.