Performance of the C-MAC videolaryngoscope for emergent tracheal intubation in prehospital setting
By a preliminary prospective, multicentre, observational study, Cavus et al.1 concluded that the C-MAC videolaryngoscope was suitable for prehospital emergency intubations with complicated airway conditions. Although they may have provided valuable information, several aspects of their study should be clarified and discussed.
First, in results, the authors stated that it was possible to obtain a view of the glottis and to intubate all patients with the C-MAC (100%). In fact, five of 80 patients have a Cormack-Lehane class 3 or 4 laryngeal view without glottis, which is generally regarded as a difficult laryngoscopy.2 The authors did not comment the detailed reasons of these inadequate laryngeal views. Also, it was not clear how tracheal intubation was completed in these patients with a difficult laryngoscopy.
Second, all patients were successfully intubated, but 17 of 80 patients (21%) required two or more attempts to complete tracheal intubation. Also, maximum time to successful intubation was 300 s. The authors did not specify the causes of multiple intubation attempts and long intubation time in these patients. We speculate that these issues may be contributed to difficulty delivering the tracheal tube through the glottis under the videolaryngoscopic view because of no use of a stylet. A Macintosh laryngoscope blade design of the C-MAC can indeed reduce stylet use compared with the angulated videolaryngoscopes, but use of a stylet may be valuable in controlling the direction of passage of an EET under indirect view of steering videolaryngoscopes. By providing increased rigidity and malleability, it allows more accuracy to guide the tracheal tube into the glottis under the videolaryngoscopic view.3 In this study from prehospital emergent environment, 6 of 80 patients (7.5%) could not be intubated with the videolaryngoscopic view of the C-MAC because of difficulty to advance the tracheal tube through the glottis. In a study from controlled operating room environment, a stylet must to be used for successful intubation in 7% of the anesthetized patients when tracheal intubation is performed with the V-MAC, older model of the C-MAC.4 In contrast, in the operating room, when a styletted tracheal tube is used for tracheal intubation with the C-MAC in 17 patients with easy and difficult airways, all cases are intubated successfully on the first attempt either under direct vision or using the video view.5 Other than success rate of tracheal intubation, the intubation time is actually also an important parameter to evaluate performance of airway management device in prehospital sitting, because any prolongation of intubation time could increase a risk of hypoxia or aspiration, especially in critically ill, trauma, or already hypoxic or aspirating patients.6 Thus, it may be unacceptable in certain critical situations if the advantage of no stylet use is achieved at the expense of multiple attempts and a considerably longer time required for tracheal intubation. We recommend that when emergent intubation is performed with the C-MAC in prehospital sitting, a styletted tracheal tube be best used, especially when difficulty to delivery tracheal tube into the glottis occurs.
Third, the authors seem to overemphasize the problems by use of a stylet under the videolaryngoscopic view. Although videolaryngoscopes has been practiced for more than ten years, there have been very few reported complications and most of complications are of a minor nature. Besides use of a stylet, other possible reasons for the airway injuries are use of too large blades, or unnecessary force during insertion of the tracheal tube.7 Furthermore, it is generally believed that traumatic airway complications can be avoided by correct intubation procedures. For example, tracheal tube is inserted under direct observation, until it reaches the uvula and then the operator's attention is directed to the monitor.
Fourth, in this study, 28% of patients presented with challenging intubation conditions such as limited mouth opening or maxillofacial trauma, and 31% had a Mallampati grade 3 or 4. They may indeed make airway management complex, but do not necessarily result in difficult tracheal intubation. Actually, difficult tracheal intubation are often contributed to multiple causes, such as reduced head and neck mobility, limited mouth opening, reduced mandibular space, obesity and poor dentition.2 The design of the C-MAC blade has the unique advantage that it provides both direct and indirect glottic views, but the sharp angle of the angulated videolaryngoscopes may be advantageous in patients with anatomic variations, such as anterior larynx, micrognathia, neck immobility, or sublingual tonsillar hypertrophy, etc.7,8
Moreover, a clinical study from the emergency department showed that, of the 158 patients with good laryngeal view on direct laryngoscopy of the C-MAC, video laryngoscopy worsened the laryngeal view in 4 cases (3%).9 Thus, further clinical studies are necessary to evaluate the role of C-MAC in securing an airway for patients with difficult tracheal intubation in the prehospital setting.
Fu Shan Xue, Xu Liao, Yu-Jing Yuan, Qiang Wang, Jian-Hua Liu Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing, People's Republic of China. Correspondence to Fu Shan Xue, Department of Anesthesiology, Plastic Surgery Hospital, Chinese Academy of Medical Sciences and Peking Union Medical College, 33 Ba-Da-Chu Road, Shi-Jing-Shan District, Beijing 100144,China. Email: firstname.lastname@example.org
1. Cavus E, Callies A, Doerges V, et al. The C-MAC videolaryngoscope for prehospital emergency intubation: a prospective, multicentre, observational study. Emerg Med J 2011; 28:In Press. doi:10.1136/emj.2010.098707
2. Caplan RA, Benumof JL, Berry FA, et al. Practice guidelines for management of the difficult airway: an updated report by the American Society of Anesthesiologists Task Force on Management of the Difficult Airway. Anesthesiology 2003; 98: 1269-77.
3. Cooper RM, Pacey JA, Bishop MJ, et al. Early clinical experience with a new videolaryngoscope (GlideScope?) in 728 patients. Can J Anesth 2005; 52: 191-8.
4. van Zundert A, Maassen R, Lee R, et al. A Macintosh laryngoscope blade for videolaryngoscopy reduces stylet use in patients with normal airways. Anesth Analg 2009; 109:825-31.
5. Aziz M, Brambrink A. The Storz C-MAC video laryngoscope: description of a new device, case report, and brief case series. J Clin Anesth 2011; 23:149-52.
6. Maruyama K, Tsukamoto S, Ohno S, et al. Effect of cardiopulmonary resuscitation on intubation using a Macintosh laryngoscope, the AirWay Scope, and the gum elastic bougie: a manikin study. Resuscitation 2010; 81:1014-1018.
7. Niforopoulou P, Pantazopoulos I, Demestiha T, et al. Video- laryngoscopes in the adult airway management: a topical review of the literature. Acta Anaesthesiol Scand 2010; 54:1050-61.
8. Maassen R, Lee R, Hermans B, et al. A comparison of three videolaryngoscopes: the Macintosh laryngoscope blade reduces, but does not replace, routine stylet use for intubation in morbidly obese patients. Anesth Analg 2009; 109:1560-5.
9. Brown CA 3rd, Bair AE, Pallin DJ, et al. Improved glottic exposure with the video Macintosh laryngoscope in adult emergency department tracheal intubations. Ann Emerg Med 2010; 56:83-8.
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