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From the Department of Anesthesiology, Toronto Western Hospital, University of Toronto, Ontario, Canada.
Address correspondence to David T. Wong, MD, Department of Anesthesia, Toronto Western Hospital, 399 Bathurst St, Toronto, ON, M5T 2S8. Address e-mail to david.wong{at}uhn.on.ca.
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Abstract |
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 Top Abstract IntroductionMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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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 
2 analyses.
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.
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Introduction |
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TopAbstractIntroductionMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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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 (4–9). 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.
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METHODS |
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TopAbstractIntroductionMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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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 2 analysis (4).
Insertion Techniques
Both the indicator-guided set and the wire-guided set were supplied as preassembled kits. The packages were opened and the components were assembled in ready-to-insert condition by the investigators before each insertion attempt by the participants.
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.
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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 1–2 cm. The needle was removed. The cricothyroidotomy tube was then slid over the dilator into the tracheal lumen and the dilator removed.
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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.
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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
The primary end point was insertion time. A sample size of 58 was calculated to detect a 15% difference in insertion times between wire-guided and indicator-guided attempts based on an expected mean time of 40 s with an 
error of 0.05 and 80% power (4). The sample size was increased by 10% to compensate for potential withdrawals and incompletions.
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 
45 vs <45 yr, years in practice >5 vs 
5 yr, grade resident versus fellows and staff, and cricothyroidotomy experience present versus absent, using an unpaired t-test. Categorical data including success rates were compared using 2 analysis. Success rates of the two devices were compared for participants age 45 vs <45 yr, years in practice >5 vs 5 yr, grade resident versus fellows and staff, and cricothyroidotomy experience present versus absent, using 2 analyses. Fisher's exact test was used if the value was <5 in any of the cells in the contingency table. A P value of <0.05 was considered statistically significant, except t-tests with Bonferroni correction (P = 0.05/number of comparisons in the set).
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RESULTS |
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TopAbstractIntroductionMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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Insertion Times
Over the five attempts, insertion times were 32.6 ± 14.9 s and 42.3 ± 12.5 s for the indicator-guided and wire-guided techniques, respectively (repeated measures ANOVA, P < 0.001). The insertion times for each of the five attempts were faster with the indicator-guided device than with the wire-guided device (Fig. 5, all P < 0.005). Insertion times for the indicator-guided device were faster than for the wire-guided device regardless of the order in which the techniques were performed. There were no differences in insertion times of either device when the participants were categorized according to age, training status, years of practice, or experience with cricothyroidotomy.
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Success Rate
Successful insertions occurred in 304 of 320 (95%) and 298 of 320 (93.1%) attempts with the indicator-guided and wire-guided devices, respectively. There were no differences in success rates between the two devices for the five attempts. The success rates over the five attempts were 90.6%, 93.8%, 95.3%, 98.4%, 96.9% for the indicator-guided devices and 90.6%, 93.8%, 92.1%, 90.6%, 98.4% for the wire-guided devices (nonsignificant). The order in which the techniques were performed did not influence the success rate. There were no differences in success rates with either device when the participants were categorized according to age, training status, or experience with cricothyroidotomy, Participants with more than 5 yr of anesthetic experience were more likely to be successful with the wire-guided technique compared to those with <5 yr experience (94% vs 87%, P = 0.03). This difference was not observed with the indicator-guided device.
Complications
Malpositioning was the main reason for failure using the indicator-guided device (n = 13, 4.1%). Two participants inserted the indicator needle into the posterior tracheal wall, and the cricothyroidotomy tube was twice inserted anterior to the trachea. In the remaining nine cases, the needle was placed below the cricothyroid membrane or through the thyroid cartilage. With the wire-guided device, the main reason for unsuccessful insertions was malpositioning of the device (n = 12, 3.8%) because of the needle placement below the cricothyroid membrane or through the thyroid cartilage. Placement into the posterior tracheal wall or anterior to the trachea did not occur. Kinking of the wire or the inability to thread the wire accounted for 10 (3.1%) failures. The overall number of failed attempts because of malpositioning between the two techniques was not statistically significant, whereas the rate of misplacement anterior or posterior to the trachea was higher with the indicator-guided device (4 of 320 vs 0 of 320, P = 0.12).
Repeated Attempts Effect
Insertion times plateaued by the fourth attempt (no difference between second, third, and fourth attempts by analysis of variance) (4) for the indicator-guided device and by the fifth attempt (no difference between third, fourth, and fifth attempts by analysis of variance) for the wire-guided device (Fig. 5). The success rate, assessed by 3 x 2 2 analysis, plateaued by the third attempt for both devices.
Device Assessment
The ease of insertion of the wire-guided set was judged to be good or excellent by 68.8% of the participants, compared with 65.6% for the indicator-guided device (not significant). Two participants (3.1%) judged the ease of insertion of the wire-guided set to be poor or very poor when compared with 6.3% for the indicator-guided device (not significant). The wire-guided set was considered to be intuitive or very intuitive to use by 76.6% of participants, compared with 56.3% for the indicator-guided device (P = 0.02), whereas 6.3% judged the intuitiveness of the wire-guided set to be poor or very poor, compared with 17.2% for the indicator-guided device (not significant).
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.
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DISCUSSION |
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TopAbstractIntroductionMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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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
The success rate with the indicator-guided device was similar to that with the wire-guided device (95% vs 93.1%). All attempts were completed in less than 120 s.
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 (7–9). Again, no comparable data are available for the indicator-guided Portex Cricothyroidotomy Kit.
Complications
The rate of complications and tube misplacements in our study (6.9% for the wire-guided set, 4.1% for the indicator-guided set) was similar to that in previous studies. Malpositioning of the device was the most common error for both devices. Misplacement into paratracheal tissues is a concern particularly with blind stab devices (10). The indicator-guided device was designed to reduce this complication. In our study, paratracheal misplacement occurred in 4 of 320 insertions with the indicator-guided device when compared with none with the wire-guided device. Although the difference was not statistically significant, this complication must be regarded as very serious and may have major clinical consequences. Fikkers et al. reported a misplacement rate of 5% (1 of 20 attempts) with a tube-over-needle device, whereas Vadodaria et al. saw no misplacement in 10 attempts (5,6). The potential of the indicator-guided device for paratracheal misplacement, damage to surrounding tissues, and tracheal perforation remains a concern.
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
For proficiency in manual skills, demonstrations of the procedure and repeated practice have both been shown to be important (11,12). In our study, insertion times reached a plateau after the fifth attempt for the wire-guided device and after the fourth attempt for the indicator-guided device, suggesting that both insertion techniques can be learned and applied relatively quickly in a mannequin. Wong et al. showed that repeated performance of cricothyroidotomies on mannequins leads to improvement of times and success rates. By the fifth attempt, a plateau effect was observed (4). In contrast, Schaumann et al. failed to show any improvement in insertion times over five attempts for both wire-guided and surgical cricothyroidotomy in cadavers. Our study suggests that for training purposes, five cricothyroidotomy attempts are sufficient to enable practitioners to perform the technique expediently and successfully in models.
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
In our study, the wire-guided technique was judged to be more intuitive and the majority of participants would choose the wire-guided technique in an emergency; yet results show subjects inserted the devices faster with the indicator-guided device. The explanation may be that the wire-guided set is used in the same way as the Seldinger technique for vascular cannulation, which may be advantageous for anesthesiologists and other practitioners familiar with the technique. This may be very relevant in the highly stressful real-life cannot intubate–cannot ventilate situation, where familiarity with and confidence in the device used may well outweigh the advantage of a slightly faster insertion time. Age, status, or experience were not shown to influence the choice of preferred device.
Limitations
First, a mannequin study cannot simulate real-life circumstances. Cricothyroidotomies are usually emergency procedures. They have to be performed rapidly in a high-pressure situation. Anatomical difficulties and problems such as bleeding, edema, or patient movement cannot be considered. The potential for complications during insertion may be underestimated, and late complications cannot be assessed. Training mannequins have normal airways. Nevertheless, familiarity with the equipment and the technique is an essential prerequisite for success in an emergency (13), and a mannequin offers training opportunities.
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.
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CONCLUSIONS |
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TopAbstractIntroductionMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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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.
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Footnotes |
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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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REFERENCES |
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TopAbstractIntroductionMETHODSRESULTSDISCUSSIONCONCLUSIONSREFERENCES |
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This article has been cited by other articles:
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  B. Patel and C. Frerk Large-bore cricothyroidotomy devices CEACCP, October 1, 2008; 8(5): 157 - 160. [Full Text] [PDF]
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 J. Jenvrin, D. Pean, N. Libert, T. Leclerc, S. De Rudnicki, D. A. Braude, and S. McLaughlin Cricothyroidotomy. N. Engl. J. Med., September 4, 2008; 359(10): 1073 - 1074. [Full Text] [PDF]
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 Seldinger Cricothyrotomy Kit Preferred to New Tube-over-Needle Device Journal Watch Emergency Medicine, July 27, 2007; 2007(727): 2 - 2. [Full Text]
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