In Reply

I thank Dr. Kelly and Professor Cook for their comments to my editorial¹  on emergency cricothyrotomy. I stated in my editorial¹  that “because it is difficult to carry out randomized controlled studies in patients, we still do not know which method is the most reliable.” In the absence of randomized controlled studies, we need to decide the most effective method of emergency cricothyrotomy, based on nonrandomized clinical studies or simulation studies. As Dr. Kelly and Professor Cook correctly point out, nonrandomized clinical studies or simulation studies have limitations, and thus we should carefully assess the evidence level of each study.

In my editorial,¹  I described that “there is growing evidence that percutaneous cricothyrotomy using a narrow-bore cannula—once advocated for use for its simplicity—may frequently be ineffective.” This statement was drawn not only from the study by Heymans et al.²  but also from several other studies. For example, a recent systematic review indicated that transtracheal jet ventilation via a narrow-bore cannula may frequently fail and may be associated with life-threatening complications.³  I referred to the report of the Fourth National Audit Project⁴ —although this is not a randomized study and thus the reasons for lower success rates of cannula cricothyrotomy may be multifactorial—I believe that the report provides a high evidence level. In fact, Professor Cook himself states in his previous article that “the Fourth National Audit Project … concluded that needle or cannula cricothyroidotomy performed by anaesthetists had a particularly low success rate.”⁵ 

I described in my editorial¹  that “the problem that we are facing now is that we do not know which model is effective for simulation training for emergency cricothyrotomy.” Nevertheless, a cadaver (in particular, a cadaver with lifelike conditions [Thiel embalming technique])⁶  and a manikin or animal model of an obese neck or neck with burn⁷  is likely to be a more suitable than a conventional manikin model, and thus studies using these models would be regarded as providing higher evidence. In the study by Heymans et al.,²  participants were students, who may not be good representatives of experienced clinicians, but the simulation model (cadavers with Thiel embalming technique) can be regarded as the best representative of patients. Similar results were obtained by a recent study,⁸  in which more experienced medical staff (senior anesthesiologists) performed the task in a less suitable model of porcine laryngopharynx. Together with these studies, studies in general have indicated that surgical cricothyrotomy is more reliable than cannula cricothyrotomy. I believe that this is why Professor Cook stated in a previous article that “[t]he Difficult Airway Society 2015 guidelines⁹  make a case for a standardized approach to front of neck airway with scalpel cricothyroidotomy because it is judged most likely to be the fastest and most reliable method of securing the airway,” and that “scalpel cricothyroidotomy should be learned and regularly rehearsed by all anaesthetists.”⁵  Therefore, I believe that the view of Dr. Kelly and Professor Cook is the same as mine.

As Dr. Kelly and Professor Cook point out, we need to establish an appropriate simulation training program using a suitable model and setting to reduce the incidence of necessitating emergency cricothyrotomy and to increase confidence in performing this task in a rare occurrence of the “cannot intubate, cannot oxygenate” situation.