Cricothyrotomy Technique Using Gum Elastic Bougie Is Faster Than Standard Technique: A Study of Emergency Medicine Residents and Medical Students in an Animal Lab
Presented at the Society for Academic Emergency Medicine conference, New Orleans, LA, May 2009.
Address for correspondence and reprints: Chandler Hill, MD; e-mail: firstname.lastname@example.org.
Objectives: The objective was to compare time to completion, failure rate, and subjective difficulty of a new cricothyrotomy technique to the standard technique. The new bougie-assisted cricothyrotomy technique (BACT) is similar to the rapid four-step technique (RFST), but a bougie and endotracheal tube are inserted rather than a Shiley tracheostomy tube.
Methods: This was a randomized controlled trail conducted on domestic sheep. During a 3-month period inexperienced residents or students were randomized to perform cricothyrotomy on anesthetized sheep using either the standard technique or the BACT. Operators were trained with an educational video before the procedure. Time to successful cricothyrotomy was recorded. The resident or student was then asked to rate the difficulty of the procedure on a five-point scale from 1 (very easy) to 5 (very difficult).
Results: Twenty-one residents and students were included in the study: 11 in the standard group and 10 in the BACT group. Compared to the standard technique, the BACT was significantly faster with a median time of 67 seconds (interquartile range [IQR] = 55–82) versus 149 seconds (IQR = 111–201) for the standard technique (p = 0.002). The BACT was also rated easier to perform (median = 2, IQR = 1–3) than the standard technique (median = 3, IQR = 2–4; p = 0.04). The failure rate was 1/10 for the BACT compared to 3/11 for the standard method (p = NS).
Conclusions: This study demonstrates that the BACT is faster than the standard technique and has a similar failure rate when performed by inexperienced providers on anesthetized sheep.
ACADEMIC EMERGENCY MEDICINE 2010; 17:666–669 © 2010 by the Society for Academic Emergency Medicine
Cricothyrotomy is a critical procedure in emergency airway management. While the incidence of emergency department cricothyrotomy is decreasing, it remains one of the most important skills of the emergency physician (EP).1,2 Many techniques of cricothyrotomy have been described in the literature.3–9 The accepted standard is an open technique that involves the use of a midline vertical incision, a dilator to open this incision, and the insertion of a tracheostomy tube.6,7 A simplified technique known as the rapid four-step technique (RFST) has been described and found to be faster with a higher success rate than the standard technique.8
The RFST offers the advantages of eliminating both the vertical midline incision and the use of a tracheal dilator that are recommended in the standard open surgical method. This makes the procedure faster to perform while continuing to be highly successful in cadaver models.8 In our clinical and laboratory experience with both the standard technique and the RFST, we have noted that the limiting step in this procedure is the insertion of a tracheostomy tube through the tracheal incision. This step can require significant force, and inexperienced providers often are unable to pass the tube into the trachea or create a false tract into the subcutaneous tissue. We studied a new variation of the RFST that employs a gum elastic bougie, a tool familiar to EPs, to facilitate the insertion of an endotracheal tube into the trachea. Specifically, we compared the speed, efficacy, and ease of insertion of a novel cricothyrotomy technique using a gum elastic bougie (bougie-assisted cricothyrotomy technique [BACT]) to a standard open technique.
This was a prospective, randomized comparison of two cricothyrotomy techniques conducted on anesthetized domestic sheep. The study protocol was approved by the Human Subjects Research Committee and the Institutional Animal Use and Care Committee of Hennepin County Medical Center.
Study Setting and Population
The study was conducted during the routine animal procedure training lab for Hennepin County Medical Center emergency medicine (EM) residents (PGY 1–3), and medical students on their EM rotation, from September to November 2008.
Operators were each chosen on 21 separate days over a 3-month period on a volunteer basis from students attending the training lab that day and were randomized to perform either standard cricothyrotomy (Table 1) or BACT (Table 2). Randomization was achieved by assigning each data collection sheet a computer generated random number (1 or 2), which corresponded to the procedure to be used. The data sheets were kept in opaque folders in numbered order. At the beginning of each lab session day, the next folder was removed in consecutive order by the investigator to discover the procedure to be performed. The operators were shown a short instructional video in the animal lab describing the technique to be performed. No further instruction was given. The operator was allowed time to become familiar with the equipment and ask questions about anatomical landmarks. The instructional video for the BACT, using the Sun-Med Endotracheal Introducer (Sun-Med, Largo, FL), was developed by the investigators (Video Clip S1, available as supporting information in the online version of this paper). The instructional video for the standard method was a New England Journal of Medicine (NEJM) video entitled “cricothyroidotomy” obtained from the NEJM website in the “videos in clinical medicine” series published May 2008.4 The steps of the procedures for a right handed operator are described in Figures 1 and 2. Each procedure was supervised by one of two investigators who collected the data. An investigator and a lab instructor who was either a PGY 3 EM resident or an EM faculty member supervised the training lab. Neither supervisor intervened during the study procedure unless the attempt was a failure.
| Scalpel with No. 11 blade, curved hemostat, Trousseau dilator, tracheal hook, and No. 5 Shiley tracheostomy tube|
| 1. Standing on the right side of the patient, stabilize the larynx with thumb and index finger of the left hand, and identify the cricothyroid membrane.|
| 2. Make a 2.5-cm midline incision over the cricothyroid membrane using a No. 11 blade.|
| 3. Use the curved hemostat to dissect through the subcutaneous tissue to the cricothyroid membrane.|
| 4. Use the scalpel to make an incision into the trachea.|
| 5. Extend the incision laterally in both directions.|
| 6. Insert a tracheal hook on the caudal aspect of the larynx.|
| 7. Insert a Trousseau dilator and open the membrane vertically.|
| 8. Insert a No. 5 tracheostomy tube.|
| 9. Remove the inner cannula and insert the adaptor.|
The Bougie-assisted Cricothyrotomy Technique
| Scalpel with No. 20 blade, tracheal hook, 70-cm gum elastic bougie (Sun-Med Endotracheal Introducer, Sun-Med, Largo, FL), and 6-0 endotracheal tube|
| 1. Standing on the left side of the patient, stabilize the larynx with the thumb and middle finger of your left hand, and identify the cricothyroid membrane.|
| 2. Using a No. 20 scalpel blade make a transverse stabbing incision through the skin and cricothyroid membrane.|
| 3. Place a tracheal hook at the inferior margin of the incision and pull up on the trachea.|
| 4. Insert the bougie through the incision.|
| 5. Place 6-0 endotracheal tube over the bougie and into the trachea.|
The level of training of the operator, the number of attempts, the total length of the procedure, and any complications were recorded. The operator was then asked to rate the difficulty of the technique on a five-point scale from 1 = ”very easy” to 5 = ”very hard.” The start of the procedure was marked when the operator began to palpate for the cricothyroid membrane. The end of the attempt was marked at the inflation of the cuff of either the endotracheal tube or the tracheostomy tube. Correct placement was assessed by end tidal CO2. The procedure was considered a failure if the first placement of the endotracheal tube or tracheostomy tube was not confirmed to be in the trachea. Based on previously defined standards for optimal cricothyrotomy procedure times, an attempt longer than 3 minutes was also considered a failure.10
Data were collected by the investigators. Data analysis was performed using STATA 10.0 (StataCorp, College Station, TX). Descriptive statistics were used as appropriate. The times to complete the procedure and the operator’s perceived difficulty of the technique score were compared using Wilcoxon rank sum tests. The level of training of the operators and the number of attempts made during the procedure were compared using chi-square tests. To detect a 50% difference in the length of the procedure, with a power of 90% and an alpha of 0.05, 10 subjects were required in each group.
Twenty-one individuals were included in the study: 11 in the standard group and 10 in the BACT group. The level of experience of the operators was similar in both groups. In the BACT group the operators were six medical students, three first-year residents, and one second-year resident. The standard group consisted of six medical students, three first-year residents, one second-year resident, and one third-year resident. Only one cricothyrotomy was performed by each of the 21 participants.
Compared to the standard technique, the insertion time for the BACT technique was faster (median time = 67 seconds [IQR = 55–82] vs. 149 seconds [IQR = 111–201]; p value = 0.002). The BACT was also rated easier to perform than the standard technique (median rating = 2, [IQR = 1–3] vs. median rating = 3 [IQR = 2–4], respectively; p = 0.04).
Failure to correctly place the tube occurred in 3/11 (27.3%, 95% confidence interval [CI] = 6.02% to 61%) in the standard group versus 1/10 (10.0%, 95% CI = 0.25% to 44.5%) in the BACT group (p = 0.31). In the standard method group, one operator placed the tracheostomy into the subcutaneous tissue. Two operators were unable to pass the tracheostomy tube, and a repeat incision was made and the tube was placed correctly by the lab instructor. In the BACT group, one operator was unable to pass the bougie through the incision, and a new incision was made and the procedure completed by the lab instructor.
Emergent cricothyrotomy is a procedure where time matters. Patients are critically ill and the procedure is often begun with life-threatening hypoxia already present. Many techniques for cricothyrotomy exist.5–8 The RFST was developed to eliminate the unfamiliar Trousseau dilator that is used in the standard open technique and the time-consuming midline incision.8 In previous research, the RFST has been shown to be faster than both the open surgical technique and the Seldinger technique.3,8 In our experience, the limiting step of both the RFST and the open surgical technique is the insertion of the tracheostomy tube through the incision. We developed the BACT as a combination between the RFST and the use of the bougie to overcome this limiting step. The BACT has the added benefit of eliminating the tracheostomy tube, a piece of equipment not as familiar to EPs as the endotracheal tube. In this study, the BACT took half the time to complete compared to the open surgical technique. It was subjectively easier to perform than the standard technique and had a similar failure rate. This method has been used successfully in our clinical practice and is now taught routinely in our animal lab.
The bougie is a valuable piece of equipment for EPs as a rescue device for the difficult airway. In typical use, the bougie is inserted into the trachea during difficult orotracheal intubation. The endotracheal tube is then placed over the bougie, allowing it to serve as a guide into the trachea. The addition of the bougie to cricothyrotomy offers several advantages over other techniques. The thinner bougie is easier to place through the incision made during cricothyrotomy than either the tracheostomy tube or endotracheal tube. As the bougie enters the trachea, tactile confirmation of correct placement is possible, as the curved edge of the bougie is designed to create vibrations as it passes over the tracheal rings. The bougie then serves as a guide for the endotracheal tube through the ostomy during placement. In this study, the three failures of the standard open technique involved either false passage into the soft tissue of the neck or the inability to push the tracheostomy tube through the incision. These complications are addressed by the addition of the bougie in the BACT, likely improving the speed of the procedure and trend toward fewer failures.
The technique described here does not use a midline incision. However, it is important to note that some patients, especially those with large necks, will require a midline incision to appropriately palpate the cricothyroid anatomy. While not studied here, in these select cases we recommend the use of a vertical midline incision followed by the steps of the BACT.
We have used anesthetized sheep as a model for the human airway. While sheep have similar anatomy to humans, clearly differences exist. These differences may have made it easier to perform the BACT compared to the standard method. Other studies of cricothyrotomy have used cadaver models, preserved pig larynxes, or plastic models.3,8 In comparison to these models, using live animals does more accurately simulate the complications that arise from bleeding at the incision site, one of the major sources of complication in retrospective reviews of cricothyrotomy.1,10 Using a live animal model also better simulates the sense of urgency for providing a rapid airway.
Additionally, our operators were very inexperienced. Over half in each group were medical students who may have had increased difficulty in performing the more complex standard technique. A study of more experienced physicians with significant cricothyrotomy experience may not have found such a difference in speed or success rate between the procedures. However, given the declining incidence of cricothyrotomy, it is important that any cricothyrotomy technique have high success rates by inexperienced operators.
We have studied a new technique of cricothyrotomy that uses the addition of a bougie to facilitate tracheal cannulation. This technique is faster and subjectively easier to perform than the standard method when performed by inexperienced operators undergoing procedure training on an animal simulation model. Failure rates between the two techniques were similar.