Use of the endotracheal tube introducer as an adjunct for oral tracheal intubation in the prehospital setting☆☆☆★★★

Introduction 

Recent research has shown that intubation can be safely and successfully performed in most patients in the field.1 A question that has not been adequately answered is which alternative airway adjuncts should be available to prehospital personnel if initial airway management fails or a difficult airway is encountered. Approximately 4% of operating room and up to 5.3% of ED intubations have been reported as difficult.1, 2, 3, 4

Varying intubation success rates have been reported in the prehospital setting.1, 6, 7, 8 Prehospital intubators encounter a higher rate of difficult airways compared with operating room or ED intubators. This finding is not surprising, given the challenging and unpredictable conditions faced by prehospital personnel. As prehospital personnel integrate intubation, especially rapid sequence intubation (RSI), into their management protocols, easy and reliable airway adjuncts should be readily available.

The gum elastic bougie (GEB) is a widely accepted airway adjunct primarily used among European anesthesiologists and emergency physicians for difficult airways.3, 9 Use among U.S. anesthesiologists and emergency physicians is still limited, however.10 A commercially available plastic version of the GEB, the Flex Guide endotracheal tube introducer (ETTI) (GreenField Medical Sourcing Inc., Northborough, MA), is now available. While the GEB and the ETTI are slowly making their way into EDs throughout the United States, their use has not been studied in the prehospital literature.

In this study, we performed a prospective, randomized study to compare the use of the ETTI versus standard orotracheal intubation (SOTI) in a prehospital air medical setting.

Methods 

Study protocol 

All patients requiring intubation who were 12 and older and intubated with an ETT ≥ 6.0 mm were entered into this study. The nonintubating nurse or paramedic collected the data. All intubators had been with both services longer than 5 years, had previous experience with intubating patients, and had annual intubation training in our animal laboratory. The average number of intubations performed by nurses or paramedics is 5 per year. All paramedics and nurses had a 2-hour training program on the Cormack and Lehane classification,11 shown in Figure 1, and the study method.

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Fig. 1. Laryngeal View Classification. Grading based on laryngoscopy is as follows: Grade 1: most of glottis is visible. Grade 2: only the posterior portion of the glottis is visible. Grade 3: no portion of the glottis is visible, but epiglottis is visible. This intubation is often difficult using standard techniques. Grade 4: the epiglottis cannot be seen on laryngoscopy, and intubation is very difficult without special methods or equipment. Cormack RS, Lehane J. Difficult intubation in obstetrics, Anethesia 1984;39:1105-2001. Reprinted with permission.

All participants were assessed on their ability to assign the correct laryngeal view using the Cormack and Lehane classification and passed the screening assessment during the training course. The paramedics and nurses had used the ETTI to intubate in our annual animal laboratory training program.

Patients were randomized to either ETTI or SOTI on an even/odd day regimen. Data recorded included initial approach used, success using initial approach, number of intubation attempts required and technique used (RSI versus other), successful intubating technique, laryngeal view encountered using the Cormack and Lehane classification,11 complications and total intubation time (defined as insertion of initial laryngoscope until intubation). All intubations were confirmed with esophageal detection device (EDD) and end-tidal CO2. Complications recorded included esophageal intubations, inability to intubate, and induced emesis. If the first intubation attempt was not successful, the clinician could alter the approach to either ETTI or SOTI, but intention-to-treat principles were applied.

Ninety-four percent of the patients were intubated by the air medical flight teams.

Results 

A total of 51 patients were entered into the study during a 10-month period; 20 patients were randomized to the ETTI group and 31 to SOTI. Patients enrolled in the study account for 85% of all possible intubations during the study period. Patients not enrolled in this study were either neonate or pediatric patients younger than 12 years old. Four patients (2 from each randomization group) were excluded from the study because of incomplete data.

Figure 2 describes the laryngeal view encountered, with 41 of 51 (80%) being either grade I or grade II.

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Fig. 2. Comparison of ETTI and SOTI in laryngeal view encountered using the Cormack and Lehane Grading System. Grade 1 is easiest; grade 3 and 4 are partially or completely obstructed views of the glottis. Y-axis represents absolute numbers, and X-axis is laryngeal grade encountered. Cormack RS, Lehane J. Difficult intubation in obstetrics. Anethesia 1984;39:1105-2001. Reprinted with permission.

Grade III (N = 6) first-attempt success rate was a 100% (2/2) for the ETTI versus 75% (3/4) for the OTI. Grade IV (N = 4) resulted in 2 of 2 successful intubations in ETTI group versus 0 of 2 for SOTI. Statistical analysis could not be performed because of the small numbers.

Complications included 1 esophageal intubation for the ETTI and 2 esophageal intubations for SOTI. All esophageal intubations were immediately detected using the EDD and removed before ventilation occurred. One patient in the ETTI group was not successfully intubated as a result of massive facial injuries and required placement of a Combitube for airway management. This patient was included as part of the ETTI group.

Discussion 

The GEB airway adjunct originally was introduced by Sir Robert Macintosh in 1949.12 While readily accepted by European anesthesiologists and emergency physicians, Rosenblatt10 reported that the GEB was not available at all to 52% of U.S. anesthesiologists and was readily available on a stat basis only to 30% of practicing U.S. anesthesiologists. No survey has been done in U.S. EDs and prehospital programs regarding its availability and use.

To the best of our knowledge, no prospective randomized study has been done on the use of the GEB or ETTI in the prehospital setting. Moscotti et al1 recently published an article involving 3 difficult airway cases for which the ETTI was invaluable. They recommend the ETTI as a nonsurgical adjunct in difficult ED intubations. McGill and colleagues13 recently published an abstract of their study comparing the GEB and standard airway intubation in the ED setting. Their study, which looked at 269 patients over an 8-month period, found that the overall success rate was higher with the GEB (83%) compared with the standard orotracheal approach (73%). They also found that successful intubation time was greater for the GEB only when grade I views were encountered. The GEB was the most frequent successful alternative for failed first intubations and the most successful airway adjunct for failed difficult intubations with a success rate of 77%.

Using evidence-based principles, Pitt and Woolard14 found 4 randomized controlled trials, 1 intervention, 1 case report, and 1 discussion article that evaluated the GEB or ETTI. Although none of these studies were performed in the prehospital setting, they recommend that paramedics be trained in the GEB. These 7 studies found an extremely low risk with using the GEB/ETTI and that it clearly benefited difficult intubations in which a partial or nonexistent view of the laryngeal inlet existed. Le et al15 found in a recent study that paramedics quickly and easily intubated adult mannequins that mimicked difficult airways with the ETTI.

We believe our study is the first randomized, controlled study investigating the use of the ETTI in the prehospital setting. We showed that the ETTI can be safely integrated into a ground and air service with little or no airway complications. Our data indicate that intubation with the ETTI does not take significantly more time than SOTI. Although our numbers are small for statistical analysis, it is important to note that the ETTI approach was 100% successful in intubating difficult grade 3 and 4 laryngeal views.

The GEB and ETTI have been extensively studied with similar or better results than ours in both the emergency medicine and anesthesia literature.1, 9, 16, 17, 18, 19 Because our numbers are small, we advocate further studies to validate our findings in the prehospital setting. It is reasonable to assume that the GEB or ETTI could be at least as useful in the field as in the ED or operating room.

Although rare, complications have been reported with the GEB/ETTI.20 The GEB should be used with caution in patients who have tracheal, pharyngeal, or esophageal cancer because it may cause perforations.

Limitations and future questions 

This study has several limitations, the most obvious of which is the relatively small study numbers, especially grade 3 and 4 laryngeal classifications. Therefore, we believe this should be viewed as a pilot study.

A second limitation is that prehospital clinicians assigned the laryngeal classification without independent observer observation. While the Cormack and Lehane classification is straightforward, it is possible that under- or overreporting of laryngeal views did occur.

A third limitation is the effect of new equipment. When new equipment is added to programs, some clinicians resist the change. Although we trained all study participants to use the ETTI in a controlled animal laboratory setting, some clinicians may have prematurely aborted using the ETTI early on in the study for SOTI because of unfamiliarity with the ETTI. This early abandonment would have led to a lower initial success rate for the ETTI than the SOTI.

Future prospective studies are needed with larger subject enrollment to validate our findings. Research also should investigate whether the GEB or ETTI should be used as a primary airway adjunct for all prehospital intubations or as a secondary adjunct to be used only when a difficult airway is encountered.

Conclusion 

The ETTI appears to be a safe airway adjunct that should be considered for use among prehospital personnel, especially air medical flight crews. Our study indicates the ETTI may be helpful, especially in difficult airway management, although the numbers of grade 3 and 4 laryngeal views are very small. The time required to intubate will not be increased by the ETTI.