This Correspondence accompanies the following article: Biro P. Performance of tracheal intubation with the SensaScope in severe difficult airway: authors’ reply. Eur J Anaesthesiol 2012; 29:56–57. Editor, In a recently published prospective randomised manikin study, Ludwig et al.1 found that in a simulated severely difficult airway, the SensaScope performed as well as in normal anatomy, whereas tracheal intubation with a direct laryngoscope proved to be impossible. This is the first study to evaluate intubation performance of the SensaScope in simulated normal and difficult airways, and their findings have a potential implication for the management of severely difficult airways. However, there are several possible limitations that can interfere with interpretation of the results of this study. First, in the severely difficult intubation scenario, a Cormack–Lehane grade 4 laryngeal view was simulated by the inflation of the manikin's tongue base with 40 ml of air. Also, intubation performance of the SensaScope was compared with that of a Macintosh laryngoscope as the control device. For this severe airway difficulty, however, tracheal intubation with a direct laryngoscope may not be a sensible choice in clinical practice. Furthermore, when direct laryngoscopy cannot expose any epiglottic structure, for example Cormack–Lehane grade 4 laryngeal view, blind tracheal intubation will also be very difficult or even impossible.2 In this case, flexible fibreoptic intubation is often considered as a ‘gold standard’ method of difficult airway management.3 The SensaScope was designed to combine the benefits of both rigid and flexible fibreoptic scopes in a single device,1,4 but the relative efficacy of the SensaScope in comparison to other fibreoptic devices, such as the fibreoptic bronchoscope, Bonfils intubation fibrescope, Shikani Seeing Optical Stylet and StyletScope,5 have not really been determined. Thus, we believe that when evaluating the intubation performance of the SensaScope in a difficult airway scenario, the rational control device should be a flexible or rigid fibreoptic scope, rather than a direct laryngoscope. Second, this is a manikin study and the difficult intubation scenario simulated in this study cannot represent all clinical situations. Actually, the cause of difficult intubation in this manikin study is a reduced oropharyngeal space. In real patients, difficult intubation often has multiple causes, such as reduced head and neck mobility, limited mouth opening, reduced mandibular space, obesity and poor dentition.6 A recognised problem with manikin studies is that the times required to perform airway interventions are generally quicker than in patients.7 By four modern manikins in several domains of airway management, Mihai et al.8 have demonstrated that tracheal intubation could not reliably be simulated by manikins. Also, a manikin lacks two major problems for any kind of fibreoptic scopes: secretions in the airway and fogging of the scope by the humidity of the breath. Currently, even the best manikin model cannot reproduce these difficulties. It has been reported that obscure vision by secretions and fogging was a cause of the difficult intubation with the SensaScope in patients with an anticipated difficult airway.9 Therefore, before the results of the study by Mihai et al. are extrapolated to clinical practice, clinical accumulation and randomised trials of the intubation performance of SensaScope vs. other promising flexible and rigid fibreoptic scopes in patients with difficult airways are needed.8 Finally, and as acknowledged in the original trial,1 one of the authors was involved in design and development of the SensaScope. This raises the possibility of an albeit unintended bias in favour of the performance of the tested study device. Acknowledgement None of the authors has received any financial support.
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