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BACKGROUND: Percutaneous cricothyroidotomy may be a life-saving procedure in cannot intubatecannot ventilate situations. In this study we compared the insertion times of a new indicator-guided cricothyroidotomy device and a wire-guided device in mannequins.
METHODS: This study was a crossover trial comparing the insertion times and success rates of an indicator-guided tube-over-needle device and a wire-guided cricothyroidotomy device in a mannequin. After an audiovisual training session, 64 anesthesiologists performed five cricothyroidotomies with each of the two devices. Successful insertion was defined as insertion of a device into the correct anatomic location. The insertion times and success rates between the two techniques for the five attempts were compared using repeated measures ANOVA, paired t-test, and RESULTS: Insertion times were faster (32.6 ± 14.9 s vs 42.3 ± 12.5 s, P < 0.001) while success rates were similar (95% vs 93.1%) with the indicator-guided device when compared with the wire-guided device. For both devices, performance improved with repeated attempts. Four insertion attempts (1.3%) were positioned anterior or posterior to the trachea lumen with the indicator-guided device compared to none with the wire-guided device (P = 0.12) Subjectively, more participants chose to use the wire-guided than the indicator-guided device (59% vs 31%, P < 0.001) in a clinical emergency situation. CONCLUSION: In a mannequin model, cricothyroidotomy insertion times were faster for the indicator-guided technique than for the wire-guided technique, but success rates were similar. Subjectively, more participants chose to use the wire-guided device in a clinical emergency situation.
Cricothyroidotomy, establishing an airway in patients when intubation and ventilation by other means have failed, is a potentially life-saving procedure. It is an essential component of difficult airway algorithms and may become necessary in prehospital settings, emergency departments, or operating rooms (13). Yet emergency cricothyroidotomy is rarely performed in clinical practice. Many providers therefore have little or no practical experience, and may not have received training in models. Although a number of different devices have been designed to enhance the speed and precision of establishing an emergency airway via cricothyroidotomy, there is no consensus in the literature as to which technique or device is superior or preferred by clinicians (49). The devices currently in use can be broadly divided into Seldinger technique (wire-guided) and tube-over-needle devices. The latter have no means of indicating correct placement in the trachea. A new percutaneous device (Portex Cricothyroidotomy Kit, PCKTM, Smiths Medical International, Hythe, Kent, UK) using a tube-over-needle design, has recently become available. With this device, correct tracheal placement of the locator needle is facilitated by a red flag indicator in the needle hub. We conducted a study comparing insertion times and success rates of the indicator-guided and a wire-guided technique in mannequins. The training effect of repeated performance with each device was also evaluated. In addition, the participants were asked to assess both devices using a questionnaire.
The study was approved by the institutional Research Ethics Board. A randomized crossover trial was conducted with informed and consenting volunteers. The participants were anesthesiologists of all grades. Their age, training grade, years of practice, and previous cricothyroidotomy experience (patient or model) were recorded. Participants were randomized by blinded number allocation to one of two groups to determine the order in which the two techniques would be performed. Participants allocated to the indicator-guided group performed the indicator-guided technique first, followed by the wire-guided technique, while those in the wire-guided group started with the wire-guided technique, followed by the indicator-guided technique. Each participant was shown a 2.5-min video demonstrating the technique to be performed first. After allowing time for questions, each participant performed the first technique to which they were randomized. Upon completion, participants were shown the demonstration video of the other technique and then performed that technique. Participants performed cricothyroidotomy using each device five times in succession on a standard cricothyroidotomy mannequin (Nasco Cricothyrotomy Simulator LF 1081IU, Nasco, Fort Atkinson, WI) with an anatomically correct airway. The laryngeal inserts and skin used in this model were changed for each participant and each device. The number of attempts was derived from a previous study in which participants achieved a 96% success rate and the cricothyroidotomy insertion times reached a plateau by the fifth attempt on a mannequin model (4). The primary outcome variable, insertion time, was measured from palpation of the skin to ventilation via the cricothyroidotomy tube. The mannequin was inspected for correct positioning after each attempt. All attempts were supervised and the data collected by one or two investigators.
Successful insertion was defined as insertion of the device in the anatomically correct position. Cricothyroidotomy time was considered to have plateaued when there were no significant changes in cricothyroidotomy insertion time in three consecutive attempts by analysis of variance (4). Cricothyroidotomy success rate was considered to have plateaued when there were no significant changes in success rates in three consecutive attempts by 3 x 2
Insertion Techniques The Portex indicator-guided cricothyroidotomy kit® (PCK, Smiths Medical International, Hythe, Kent, UK) uses a novel technique to insert and position the cricothyroidotomy tube within the trachea. It was packaged as a preassembled set in which a locator spring-loaded needle was nested in a dilator over which a 6-mm ID cuffed cricothyroidotomy tube was snugly fitted (Fig. 1). The tube had a 15-mm connector. The kit also included a scalpel and a 10-mL syringe.
After a vertical skin incision with the scalpel, a locator spring-loaded needle that indicated tissue contact with a red flag (Fig. 2) was inserted perpendicular to the skin into the trachea. Once the tracheal lumen was reached and tissue contact was lost, the indicator flag in the needle hub disappeared (Fig. 3). The device was then advanced further until the red flag reappeared, indicating contact with the posterior tracheal wall. At this point, the device was angled caudally until the red flag was down, and advanced another 12 cm. The needle was removed. The cricothyroidotomy tube was then slid over the dilator into the tracheal lumen and the dilator removed.
The Melker wire-guided cricothyroidotomy set (Cook, Bloomington, IN) is also a preassembled kit that includes a scalpel, a-6 mL syringe, an 18-guage catheter introducer needle and an 18-guage catheter, a 0.038-in. guidewire and a tapered dilator nested in a 5-mm ID cuffed curved tube (Fig. 4). For our study, the introducer needle was used.
After a vertical skin incision with the scalpel, insertion was performed using a typical Seldinger technique. During advancement of the introducer needle through the cricothyroid membrane caudally at a 45 ° angle to the frontal plane, the attached syringe was continuously aspirated. Aspiration of air confirmed needle placement in the tracheal lumen. The syringe was removed and the guidewire was inserted through the needle into the trachea, and advanced approximately 15 cm. After removal of the needle, the dilator and cricothyroidotomy tube were inserted, followed by removal of the wire and the dilator. After completion of the 10 attempts, participants were asked to assess both devices using a questionnaire (Appendix). On a 5-point scale ranging from very poor to excellent, participants rated the ease of insertion, intuitiveness of technique, and their confidence level using each device. They were also asked to state which of the two devices they would use in an emergency and whether they felt practicing cricothyroidotomies in mannequins was useful for their clinical practice.
Statistical Analysis
Data were analyzed using SPSS statistical software (SPSS Inc., version 10.0 for Windows, Chicago, IL). Continuous variables were expressed as mean ± sd. Overall, the insertion times between the two devices over the five attempts were compared using repeated measures analysis of variance (ANOVA). If there was a significant difference in insertion times between the two devices by repeated measures ANOVA, then insertion times between the two devices at each of the five attempts were compared using the paired t-tests with Bonferroni correction. Insertion times of the two devices were compared for participants age
Sixty-four participants performed 640 cricothyroidotomies, 320 with each device. All participants completed the study. There was no significant difference between subjects randomized to perform the indicated-guided or wire-guided technique first in terms of age, status, and years of anesthetic experience or prior experience with cricothyroidotomies (Table 1).
Insertion Times
Success Rate
Complications
Repeated Attempts Effect
Device Assessment Three-quarters (75%) of participants felt confident or very confident about using the wire-guided set in a clinical emergency, compared with 56.3% with the indicator-guided device (P = 0.03). In a clinical emergency, 59.4% selected the usage of the wire-guided set, whereas 31.3% opted for the indicator-guided device (P < 0.001). Five participants (7.8%) would use neither of the two devices. All participants considered training in a mannequin useful for their clinical practice.
Insertion Times The main finding of this study was that the indicator-guided technique can be performed faster than the wire-guided technique in a mannequin. The insertion times for the indicator-guided set were faster overall and in each of the five attempts when compared with the wire-guided attempts. The difference may have been due to the fact that insertion of a wire-guided device involves several pieces of equipment and several discrete steps that limit the maximum achievable speed. Threading of the wire was frequently the most time-consuming step. The insertion of the indicator-guided set involved only one piece of equipment and fewer steps. Although the difference in insertion time is statistically significant, the clinical relevance of this finding is unclear. Insertion times reported in previous studies vary. Vadodaria et al. compared cricothyroidotomy devices in a mannequin and found faster insertion times with the wire-guided set compared to the tube-over-needle set (38 s vs 51 s) (5). Notably, no training was provided, and the familiarity of participants with the Seldinger technique was possibly an important factor. The study involved fewer participants (n = 10) than our study and evaluated only one attempt per device. Fikkers et al. found insertion times of 150 s with a wire-guided device and 48 s with a "blind stab" tube-over-needle device (Quicktrach II) on a pig larynx; but this included preparation time (6). In studies on human cadavers, Eisenburger et al. found insertion times of 100 s with a wire-guided device for first-time performance, whereas Schaumann et al. found insertion times of 108 s for repeated attempts (7,8). In another study on cadavers, Chan et al. showed an insertion time of 73 s for the wire-guided technique and 75 s for open surgical technique (9). To our knowledge, no data have been published on the indicator-guided Portex Cricothyroidotomy Kit, so no direct comparison can be made. However, an insertion time of 33 s for this device used in our study is faster than previously reported times for tube-over-needle devices (5,6).
Success Rates Success rates in previous studies were variable. Fikkers et al. found that 85% of attempts with a Seldinger technique on a pig larynx were placed correctly within the 240 s time limit, compared with 95% with a tube-over-needle device (Quicktrach II) (6). Vadodaria et al. found a 100% success rate for both a wire-guided set (Melker) and the tube-over-needle set (Quicktrach) in a simulator (5). The time limit used in that study was 300 s. Studies in cadavers resulted in success rates ranging from 60% to 93% with wire-guided devices and from 70% to 87% with surgical cricothyroidotomy (79). Again, no comparable data are available for the indicator-guided Portex Cricothyroidotomy Kit.
Complications The main technical problem with the wire-guided set was kinking of the wire and consequent failure to thread the wire (3.1%). This problem has been previously noticed with these devices. Schaumann et al. and Eisenburger et al. reported incidences of 7% and 25%, respectively (7,8).
Repeated Attempts Effects Previous cricothyroidotomy experience did not lead to improved times or success rates, indicating that sporadic performance of the technique may not be sufficient. Success rates with the wire-guided set were higher in the subgroup of participants with longer (>5 yr) anesthetic experience, possibly because of a higher degree of familiarity with the Seldinger technique.
Device Assessment
Limitations Second, although we have demonstrated improvement in performance of cricothyroidotomy with repeated attempts in a single setting, we did not assess skill retention. A follow-up study testing the ability to perform the procedure with both devices after a time interval (e.g., 6 or 12 mo) without retraining may be valuable. Third, in our study, subjects received training before performing both techniques. In contrast, a real-life emergency scenario allows physicians no time to familiarize themselves with either the device or the technique used. Therefore, our findings may not be directly extrapolated to clinical situations. Fourth, as a large proportion of participants had experience with cricothyroidotomies with wire-guided devices, the study may disadvantage the indicator-guided device. However, the insertion times were faster with the indicator-guided technique compared to the wire-guided technique. Furthermore, we found that the insertion times were similar with both devices for participants with and without prior cricothyroidotomy experience. Last, only two commercially available cricothyroidotomy devices were tested in our study. Our results may not be generalized to other tube-over-needle cricothyroidotomy devices.
Cricothyroidotomy insertion times are faster for the indicator-guided technique than for the wire-guided technique, but success rates are similar. Paratracheal misplacement, potentially a serious complication, occurred in 1.3% of the insertions with the indicator-guided technique, but did not occur with the wire-guided technique (P = 0.12). Insertion times reached a plateau after the fourth attempt with the indicator-guided device and after the fifth attempt with the wire-guided device. Training efforts using five cricothyroidotomy attempts therefore seem reasonable. Participants found the wire-guided device more intuitive and preferred using it compared to the indicator-guided device.
Accepted for publication March 9, 2007. Supported by The Department of Anesthesia, Toronto Western Hospital, University of Toronto, and in part by Smiths Medical Canada Ltd. Reprints will not be available from the author.
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