Videolaryngoscopes and pre-hospital intubation

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The article by Lewis et al. [1] comparing the use of the Airtraq (Prodol Meditec S.A., Vizcaya, Spain), Pentax Airway Scope (Airway Scope S100; Pentax, Tokyo, Japan) and Macintosh laryngoscopes in simulated pre-hospital airway scenarios makes a valuable contribution to the evidence available regarding the performance of equipment for out-of-hospital airway management. However, we believe that their conclusion that ‘the Airway Scope is the more effective device to use in the pre-hospital environment’ is not convincingly proven.

The study was performed using manikins and Lewis et al. make the point that the level of resemblance to clinical practice is uncertain. Other authors go further, arguing that intubation is not reliably simulated by manikins due to the use of rigid plastic, lack of collapsible soft tissues, absence of secretions and the fact that many manikins have anatomically incorrect epiglottic and laryngeal structures [2, 3]. We accept that to evaluate the laryngoscopes in patients with difficult airways or in unfavourable positions would be an almost impossible undertaking, but having decided to use manikins, the authors should have also studied the most common causes for difficulties with pre-hospital intubation. A study by Helm et al. [4] concluded that the main reasons for failed intubation in a pre-hospital setting were the presence of blood, vomit, sputum, debris or excessive saliva in the oropharynx. In Helm et al.’s study, these causes comprised 49.5% of difficulties compared with 25.5% of difficulties ascribed to the patient’s position or anatomical causes. The optical design of videolaryngoscopes makes them particularly susceptible to degradation of the image by blood, mucus or vomit in the airway.

In common with many other studies, Lewis et al. have chosen to begin timing the intubation from the point at which the laryngoscope is placed between the teeth. This makes the study biased against the Macintosh laryngoscope and is an inaccurate representation of clinical practice. We believe that a more realistic comparison would be to include the time taken to prepare the laryngoscope. Opening the Airtraq packaging, switching on the laryngoscope and lubricating the tube will take at least 15 s. Loading the tracheal tube on to the Airtraq adds a further 6 s [1]. Similarly, the Airway Scope needs to be assembled and switched on. A further 9 s is needed to load the tracheal tube [1]. The Macintosh laryngoscope is ready to use in a fraction of that time.

Although we agree that videolaryngoscopes might have some advantages over the Macintosh laryngoscope in certain pre-hospital situations, we suspect that if the factors we have described are taken into account, videolaryngoscopes may not prove so promising.

No external funding and no competing interests declared. Previously posted at the Anaesthesia Correspondence website: http://www.anaesthesiacorrespondence.com.

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