To the Editor:
We read with great interest Professor Asai’s editorial on the management of “can’t intubate, can’t oxygenate” situations1 and Heymans et al.’s2 study of cricothyrotomy in cadavers. We agree with Professor Asai that this topic is extremely difficult to study and that it is difficult to recommend a definitive best technique for front of neck airway. The importance of the topic is exemplified by a recent statement and editorial by several anesthetic and surgical bodies in the United Kingdom supporting cricothyrotomy (not tracheostomy) as the first option in “can’t intubate, can’t oxygenate”3 and a response to this by the Australian and New Zealand College of Anaesthetists (Melbourne, Australia).4
Our first concern is that Professor Asai places weight on the finding of Heymans et al.’s2 study in which medical students performed cricothyrotomy in cadavers. Without disrespecting medical students, they are not equipped with the knowledge, attitudes, or skills of those likely to be performing front of neck airway. As such it is not possible to disentangle whether the study tells us most about the model, the techniques, or the operators. Such studies are most valuable when performed on appropriate models by clinicians likely to be involved in such emergencies.
Our second concern is that Professor Asai emphasizes that cannula cricothyroidotomy was less likely to be successful than a surgical approach in the United Kingdom’s Fourth National Audit Project.5 This study was a joint project organized by the Royal College of Anaesthetists (London, United Kingdom) and the Difficult Airway Society (London, United Kingdom) and it looked at all complications of airway management in the United Kingdom in a 1-yr period. The reasons for this were multifactorial. Importantly, needle-based approaches were mostly performed by anesthetists in “end-of-algorithm” situations in which they had to abandon the upper airway and attempt the procedure in a periarrest situation—a situation familiar to the American literature too.6 Conversely, surgical approaches generally involved trained otolaryngologic surgeons performing their procedure while the anesthetist continued attempts to maintain oxygenation from above. The fact that many of these cases took up to 30 min, and in some more than 60 min, illustrates how different they were from those managed with a cannula. Importantly, the Fourth National Audit Project tells us little about how anesthetists manage performing surgical or scalpel front of neck airway techniques.
Finally, we wholeheartedly agree with Professor Asai’s statement that front of neck airway is technically more difficult in obese patients, where “the tissues overlying the larynx are thick and it is difficult to locate the cricothyroid ligament.”1,7 We note that the very patients who tend to need an emergency front of neck airway are often patients with a high body mass index5 and are concerned that this is often forgotten in manikin and model design. We believe that more emphasis should be placed on investigating which techniques work best in obese patients. In a study we performed evaluating an “obese neck manikin,” all trained anesthetists reported increased difficulty than with a standard neck manikin and 40% required a change from their planned technique to successfully establish a front of neck airway.8 Hybrid techniques such as that proposed by Heard et al.9 or described in recent U.K. guidelines10 are likely to be more appropriate. Training is usually carried out using manikins that mimic a patient with a slim neck: we advocate training for both the slim (e.g., cachectic, postradiotherapy) neck and for necks with several centimeters of subcutaneous fat. Liaison with industry is needed to improve realistic manikins to assist with the latter.
The authors declare no competing interests.