Comparison of tracheal intubation through intubating laryngeal mask airway and Airtraq? laryngoscope in different non-conventional positions
We read with interest the recent article of Grosomanidis et al.1, who compared applicability and efficacy of the tracheal intubation using an intubating laryngeal mask airway (ILMA) or an Airtraq? laryngoscope (Airtraq) in four non-conventional positions in a manikin study. Their findings that success rates of tracheal intubation using both techniques in an acceptable time period (up to 120 s) are up to 100% appear very encouraging, but there are some aspects of this study that require discussion.
First, this study showed significantly different intubation times with ILMA and Airtraq in the Lat and Fac positions. However, comparing the Airtraq intubation time with the ILMA intubation time is not an entirely appropriate comparison, because the ILMA intubation time includes the times needed for insertion of ILMA, confirmation of ventilation through ILMA, blind advancement of the endotracheal tube (ETT) through ILMA and finally confirmation of ventilation through the ETT. Actually, the ventilatory capacity of ILMA is arguably equally important to its effectiveness as an intubation conduit during airway resuscitation.2
Moreover, final goal of airway management in the prehospital emergency setting is maintenance of oxygenation, rather than performing tracheal intubation. The patients with difficult airways can desaturate during laryngoscopy and intubation, but the ILMA is an effective ventilatory device with a high success rates.3 If tracheal intubation is not successful, the presence of an effective airway can evidently be lifesaving.
Second, the study was performed using manikins. However, clinical applicability and efficacy of the results from a manikin study are highly dependent on the overall realism of the simulated setting. One can argue that tracheal intubation is not reliably simulated by manikins due to the use of rigid plastic, lack of collapsible soft tissues, and the fact that many manikins have anatomically incorrect epiglottic and laryngeal structures.4 Also, anatomic structures of the manikin's airway does not accurately reflect changes of the human airway associated with different positions. Indeed, evaluation of the intubation techniques in patients with difficult airways or in non-conventional positions indeed is an almost impossible undertaking. However, the manikin study should have included the most common causes for difficult airway management in the prehospital sitting. Other than the non-conventional positions, in an actual prehospital emergency situation, tracheal intubation is often performed in patients with limited head and neck movement or/and limited mouth opening, even in presence of blood, vomit, sputum, debris or excessive saliva in the oropharynx.5 In addition, in this study, the manikin was also placed on a table with a suitable height for intubation procedure, rather than on the ground. Thus, the overall level that this study simulated real clinical practice was uncertain.
Recently, a prospective, randomized control trial6 demonstrated that when the Airtraq was used as first-line device for prehospital tracheal intubation (n=106), success rate was only 47%. Also, reasons for failed Airtraq intubation were related to the fiberoptic characteristic of this device (i.e., impaired sight due to blood and vomitus, n=11) or to assumed handling problems (i.e., cuff damage, tube misplacement, or inappropriate visualization of the glottis, n=24). For this reason, Trimmel et al.6 recommend that for the operators without significant clinical experience, the Airtraq should not be used as a primary airway device in the prehospital setting. Even experienced airway providers should be aware that predominant manikin training does not qualify for successful Airtraq use in emergency situations. We agree with their view that further clinical studies are necessary in order to validate these preliminary data in manikins.
Third, an important issue not discussed by the authors is the challenge of obtaining proficiency while at the same time controlling cost. The manufacturer recommends two to four uses before use in a patient with a difficult intubation. As in all techniques for intubation, there is a learning curve. Each Airtraq costs approximately $80 and cannot be reused. This may pose a large expense to train an entire department.6 In addition, Maharaj et al.7 observed a substantial decline in both direct laryngoscopy and Airtraq skills over time and emphasized the need for continued reinforcement of these complex skills. If at least 50 Airtraq intubations in patients per year are considered as the minimum number needed to achieve and maintain skills, implementation of this device becomes expensive. In contrast, maintaining airway management skills with the ILMA is associated less costs because it can be reused.
Four, other than same success rates of tracheal intubation (100%) with both techniques, and a longer intubation time with ILMA than with Airtraq in the Lat position, other results obtained in the four positions were really better with ILMA than with Airtraq. Based on the results of this study, we believe it would be more appropriate to conclude that both ILMA and Airtraq can be used for securing airways when direct laryngoscopy is impossible due to the patient's position in a prehospital sitting. However, ILMA may be more effective and safer device because of less numbers of attempts for successful intubation, low risk of airway injury, and less difficulty of intubation procedure. In an unanticipated difficult airway management algorithm in the prehospital emergency setting, the ILMA has been recommended as a rescue airway device after failed intubation with direct laryngoscopy.8
Fifth, when an ILMA is used as a rescue airway device in the prehospital setting, we recommend to use the ILMA CTrach? with the integrated fibreoptic channels and a detachable liquid crystal display viewer, rather than the ILMA Fastrach?. The clinical trial has demonstrated that compared with the ILMA Fastrach?, the ILMA CTrach? can enable a higher first- attempt success rate of tracheal intubation because of its ability to view the glottis, optimize placement of device and observe the process of tracheal intubation through the devices.9 Also, data from the clinical study of Nickel et al3 suggest that the ILMA CTrach? is a suitable device for emergency airway management in the prehospital setting as it provides ventilation and facilitates intubation with a very high success rate.
1. Grosomanidis V, Amaniti E, Pourzitaki C, et al. Comparison between intubation through ILMA and Airtraq, in different non-conventional patient positions: a manikin study. Emerg Med J 2011 doi:10.1136/emj.2010.100933.
2. Goldman A, Rosenblatt W. The LMA CTrach? in Airway Resuscitation: Six case reports. Anaesthesia 2006; 61:975-7.
3. Nickel EA, Timmermann A, Roessler M, et al. Out-of-hospital airway management with the LMA CTrach--a prospective evaluation. Resuscitation 2008; 79:212-8.
4. Rai MR, Popat MT. Evaluation of airway equipment: man or manikin? Anaesthesia 2011; 66: 1-3.
5. Helm M, Hossfeld B, Sch?fer S, et al. Factors influencing emergency intubation in the pre-hospital setting-a multicentre study in the German Helicopter Emergency Medical Service. Br J Anaesth 2006; 96: 67-71.
6. Trimmel H, Kreutziger J, Fertsak G, et al. Use of the Airtraq laryngoscope for emergency intubation in the prehospital setting: A randomized control trial. Crit Care Med 2011?39: In press. DOI: 10.1097/CCM.0b013e318206b69b.
7. Maharaj CH, Costello J, Higgins BD, et al. Retention of tracheal intubation skills by novice personnel: A comparison of the Airtraq and Macintosh laryngoscopes. Anaesthesia 2007; 62:272-278.
8. Combes X, Jabre P, Margenet A, et al. Unanticipated difficult airway management in the prehospital emergency setting: prospective validation of an algorithm. Anesthesiology 2011; 114:105-10.
9. Liu EH, Goy RW, Lim Y, et al. Success of tracheal intubation with intubating laryngeal mask airways: A randomized trial of the LMA Fastrach and LMA CTrach. Anesthesiology 2008; 108:621-6.
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