Cricothyroidotomy is the final rescue maneuver in algorithms of difficult airway management.1,2 There are multiple techniques to achieve oxygenation in this manner, but few clinical studies compare different methods of cricothyroidotomy to determine the optimal approach. Studies vary in the anatomic validity and outcome measures.3 – 6 Consequently, conflicting results and recommendations have been made. Most studies have compared only a small number of techniques, limiting relevant comparisons on which to base clinical practice.7,8
We compared 4 different techniques of emergency oxygenation via the cricothyroid membrane (CTM) in a manikin. The chosen techniques represent the spectrum of devices likely to be available to anesthesiologists in clinical practice. We hypothesized that there would be a difference among the techniques in terms of time required to successfully achieve ventilation.
After standardized training, the participants (anesthesiologists) inserted 4 different cricothyroidotomy devices into the airway of the manikin on 5 occasions. The first 4 attempts were performed in the same session, and the fifth attempt was performed 1 month later to examine skill retention. These techniques are described briefly below and are detailed elsewhere.9
The airway model (BILL I, VBM Medizintechnik, Tuttlingen, Germany) is anatomic and incorporates a patent larynx with a palpable cricothyroid membrane (Fig. 1). A resuscitation bag was used to demonstrate ventilation except in the case of the use of the needle cannula in which a jet ventilator was used.
For the trocar technique (TT), the Quicktrach II device (VBM Medizintechnik) was used, which consisted of a preassembled cuffed cricothyroidotomy tube and a curved trocar with a cutting edge. The device is advanced through the skin until puncture of the airway lumen occurs. The rubber stopper is removed, and the trocar is withdrawn. The cuffed tube is advanced further into the airway lumen.
Needle cricothyroidotomy with jet ventilation (NCJ) consisted of a 13-gauge cricothyroidotomy cannula (VBM Medizintechnik) and a jet ventilator (Manujet III, VBM Medizintechnik). Tracheal placement of the cannula is confirmed by aspiration and then is connected to the jet ventilator.
The wire-guided technique (WGT) (Minitrach II, Smiths Medical, Hythe, UK) consisted of an uncuffed tube (internal diameter 4 mm), 2 dilators, a scalpel, a guidewire, and a short 17-gauge Tuohy needle. Briefly, after a transverse “stab” incision with a guarded blade, the needle is passed through the CTM, and placement is confirmed by aspiration. The wire is passed through the needle, the dilator is passed over the wire after removal of the needle, and ultimately the uncuffed tube is placed over the wire into the airway.
The blade technique (BT) consisted of a 6.0-mm cuffed endotracheal tube (Mallinckrodt®, Mallinckrodt Medical, Athlone, Ireland) with a scalpel (size 11 disposable). A 1.5- to 2.0-cm transverse incision made in the CTM is dilated with the scalpel handle. The endotracheal tube is passed through the incision into the trachea.
The primary outcome measure was time to ventilation. Clinical experience, previous attendance at an airway management course, experience in cricothyroidotomy, confidence, preferred technique, and equipment-related complications were also assessed.
Data were analyzed using SigmaStat (Version 2.0, Jandel Corp., San Rafael, CA). Continuous variables were analyzed using repeated-measures analysis of variance. Categorical data were analyzed using Fisher exact test and χ2 testing with Yates correction as appropriate. Significance was considered at P < 0.05. Categorical data are presented as numbers and percentages. Continuous variables are presented as mean with SD for parametric data or median with SEM for nonparametric data.
Twenty-one anesthesiologists participated. Twelve had <5 years' experience, and 9 had 5 to 10 years' experience.
The time taken to achieve an airway on the first attempt was longest with the WGT (Fig. 2). The rank order was WGT > TT = NCT = BT. WGT took longer than all other techniques on attempts 2, 3, 4, and 5 (P < 0.001). There were no differences among the BT, NCJ, and TT at any time. Attempts 4 and 5 did not differ with any technique. Participants who had attended an airway course performed the BT quicker on attempts 3, 4, and 5, whereas the WGT, NCJ, and TT groups did not differ. There were no differences among those with more or less than 5 years' experience.
The percentage of attempts that took ≤40 seconds differed between groups (Fig. 3). There were no successful attempts in the WGT group within this time limit. On attempt 4, all groups had more than the WGT. In groups BT and TT, success in <40 seconds increased with repetition (Fig. 3). There were no outright failures with any technique.
Participants' confidence in their ability to obtain cricothyroid access increased after participation (21 of 21 vs 16 of 21; P = 0.048). There was no difference in first preference of participants after completion: BT (38.1%), TT (33.3%), NCJ (14.3%), and WGT (14.3%). Kinking of the airway device was more common in the NCJ than the BT and TT groups (P = 0.011 and 0.038, respectively) (Table 1). Retrograde intubation did not differ among techniques (Table 1).
This study shows that the WGT was slower than all other techniques in a manikin model. Despite improvements in performance times observed with subsequent attempts, the WGT remained slower than other techniques, and successful ventilation within 40 seconds was not achieved. TT, BT, and NCT did not differ in performance time, but the frequency of successful ventilation in <40 seconds improved with the BT and TT with repetition. Our study is consistent with previous reports in which WGT took longer than simpler, limited-step surgical techniques.10 In a cadaveric model, Eisenburger et al.8 did not show a difference between WGT and BT, but only 70% of airway placements were successful in the BT group and 60% in the WGT group.
Cricothyroidotomy is a recommended core skill for all anesthesiologists.1 There is considerable international variation in approaches to difficult and failed airway management.1,2,11 – 13 Local guidelines that consider skills and experience of practitioners are encouraged. The American Society of Anesthesiologists Practice Guideline for Management of the Difficult Airway does not advocate any specific technique for invasive airway access.2 The Difficult Airway Society, based in the United Kingdom, recommends that 3 devices should be available to manage this situation: a needle cannula with a high-pressure ventilation system, a surgical cricothyroidotomy kit, and a large-bore cricothyroid cannula. A WGT is not advocated. Our study provides further support for this recommendation. Anesthesiologists can improve skills by repetition on an airway model.
Each author was involved in study design, conduct of the study, data collection, data analysis, and manuscript preparation.
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