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Studies examine the effectiveness, safety, and feasibility of out-of-hospital endotracheal intubation

Emergency endotracheal intubation (ETI) is a procedure that involves placing a tube into the windpipe (trachea) to maintain an open airway in patients who are unconscious or unable to breathe on their own. Out-of-hospital rescuers often require multiple attempts to accomplish ETI. Three attempts are probably reasonable to optimize the chances for ETI success according to a new study by Henry E. Wang, M.D., M.P.H., and Donald M. Yealy, M.D., of the University of Pittsburgh School of Medicine. A second study by the researchers indicates that out-of-hospital ETI remains prominent in paramedic care and is beneficial to some patients, but it has not clearly improved survival or reduced morbidity from critical illness or injury when studied more broadly. Both studies, which were supported by the Agency for Healthcare Research and Quality (HS13628), are summarized here.

Wang, H.E., and Yealy, D.M. (2006, April). "How many attempts are required to accomplish out-of-hospital endotracheal intubation?" Academic Emergency Medicine 13(4), pp. 372-377.

Out-of-hospital rescuers often require three or more attempts to accomplish ETI. Multiple attempts are associated with complications such as airway trauma, abnormally slow heart rate (<60 beats per minute), low blood oxygen levels (hypoxemia), and cardiac arrest. Yet a protocol limit of three ETI attempts for out-of-hospital rescuers offers a reasonable opportunity to accomplish ETI, while minimizing the hazards of more attempts, concludes this study.

Researchers found that for all ETIs performed on 1,941 patients, more than 30 percent of patients underwent 2 or more ETI attempts, and some patients underwent as many as 6 ETI attempts. However, cumulative ETI success rates in all groups did not approach overall success rates until at least the third ETI attempt. Cumulative ETI success among different clinical groups for the first three attempts ranged from 44 percent to nearly 70 percent. This trend is most worrisome in patients with non-arrest rapid-sequence intubation, in which first-pass ETI success is a priority due to the absence of spontaneous airway reflexes, note the researchers.

In their study, ETI was performed by a range of emergency medical services (EMS) agencies in different practice settings and clinical scenarios. Their findings were based on analysis of prospective, multicenter data from 42 EMS agencies over an 18 month period. Out-of-hospital rescuers (paramedics, nurses, and physicians) completed structured data forms describing clinical methods, course, and outcomes. An ETI attempt was defined as an insertion of the laryngoscope blade into the trachea, not the effort to pass the endotracheal tube.

Wang, H.E., and Yealy, D.M. (2006, June). "Out-of-hospital endotracheal intubation: Where are we?" Annals of Emergency Medicine 47(6), pp. 532-541.

Despite its prominent use in paramedic care and benefit to some patients, out-of-hospital ETI has not improved survival or reduced morbidity from critical illness or injury when studied more broadly. A review of studies on this topic has identified equivocal or unfavorable clinical effects of out-of-hospital ETI on patient outcome, as well as adverse events and errors. For instance, one study of 1,953 ETIs found tube misplacement in 3.1 percent of intubations, 4 or more ETI attempts in 3.2 percent of intubations, and failed ETI efforts in 18.5 percent of intubations.

Studies have also revealed that ETIs may affect other aspects of care. For example, after successful out-of-hospital ETI, rescuers commonly perform ventilation manually using only tactile feedback. Consequently, out-of-hospital ETI may result in unintended hyperventilation, which may be deleterious in certain conditions. Out-of-hospital ETI may also affect the execution of other important resuscitation interventions such as chest compressions, electrical therapy, intravenous access, or the administration of drugs.

Finally, several studies have underscored the challenges of providing and maintaining procedural skill in out-of-hospital ETI. Paramedics often receive relatively limited training and clinical experience. Overall, the studies reviewed highlight the limited understanding of out-of-hospital ETI and the need for new strategies to improve airway support in the out-of-hospital setting.

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