A reply

Thank you for allowing us to respond to the letter from Dr Urtubia and co-workers. We feel it is necessary to clarify some points mentioned in their letter. 1 The authors of the letter report a much lower incidence of complications in 25 patients where a Combitube was inserted with the help of a laryngoscope. We congratulate the authors on these results. However, the comparability of their results with ours is limited as our conclusion precisely refers to ‘blind insertion of the Combitube’. 2 The authors state that others have described much lower rates of complications: the first publication by Tanigawa et al. [1] describes results from a survey in nontraumatic emergency patients and evaluated three devices for securing the airway including the Combitube and the laryngeal mask airway (LMA). The second publication by Rumball et al. [2] compares several devices, also including the Combitube and the LMA. We have to point out that the scoring system for difficult intubation/insertion used in our study was subjective and served the goal of allowing a correlation when trauma was detected in a patient or a patient reported discomfort on the follow-up. With this scoring system we classified insertion conditions into excellent, good, poor and impossible. According to this classification, 84% of insertions of the Combitube and 92% of LMA insertions were graded as excellent and good. Data presented in the two studies refer to failed and successful insertion and ventilation of the tested devices. Only the percentage of successful and failed insertion is reported, without any grading. In both publications these numbers were substantially worse than in our investigation. The numbers of successful placements of the Combitube and the LMA in the two studies compared with ours are shown in the Table 2. We point out that the number of cases in our study is much smaller than in the two others, but certainly our data are not worse than those reported in the literature. Again, the goal of our study was to report on complications following the use of the Combitube, tracheal tube and LMA, and not insertion conditions. However, we do not accept that the results we reported are due to ‘inappropriate insertion technique or insufficient operator skills’. Furthermore, we had the advantage that Dr Frass is working in Vienna, and he trained us in the correct use of the device. The authors of the letter furthermore state that the rate of complications in our study is much higher than in the studies named above. In contrast to the studies named by the authors of the letter, we prospectively investigated the traumatic effects of the devices by having the patients inspected by an otolaryngologist before and after the use of the devices. Furthermore, Tanigawa et al. recognised that their study probably underestimated the incidence of complications [1]. We believe that our protocol was not biased by such difficulties and our data are valid. 3 Blind insertion vs. manufacturer recommendations: the authors of the letter refer to a review written by Dr Frass [3], who is not the manufacturer, but the inventor of this device. Although he is closely co-operating with the manufacturer, this textbook chapter is not part of the manufacturer's recommendation. The guidelines that are packed and sold with the device state that ‘the use of a laryngoscope is not necessary, although it might be helpful’ (translated from German into English by the authors). Dr Frass was aware of our protocol, and did not advise us to change the method from blind insertion to laryngoscope-guided insertion. This is understandable as it is the main feature and advantage of this device to allow blind insertion and not to require the use of a laryngoscope. Even in the textbook chapter cited by the authors of the letter [3], Dr Frass recommends the use of the laryngoscope for situations where intubation with direct laryngoscopy fails and the laryngoscope is still in place. Thus, despite the fact that we recognise the use of the laryngoscope as an interesting alternative and possible improvement of the method (although a main advantage is lost), we believe that utilising blind insertion of the Combitube in our study is the valid choice and has to be chosen when evaluated against other devices and methods. 4 The authors suggest that the pressure effects of the cuffs reported in our study could be worsened by over inflation of the cuffs with nitrous oxide. This indeed is relevant, and we regret not reporting our handling of this problem in our manuscript. It is standard procedure during every anaesthetic in our Department to monitor cuff pressure on-line. However, whereas pressure values for tracheal tubes are well known, no such values exist for LMA and Combitube. Thus, our procedure consisted of inflating the cuffs of the Combitube with the recommended volume of air and taking the (very variable) pressure value as baseline for correction of the nitrous oxide effect. With the LMA the cuff was inflated to allow an optimal sealing of the larynx and again this value was taken as baseline for correcting overinflation. This method is very simple and does not exclude that overinflation of the cuffs is responsible for some of the traumatising effects seen in our study. However, as long as no optimal values for cuff pressure for LMA and Combitube are available, we regretfully have to accept this possible bias. 5 Invalid conclusion: as described above, we believe that the participating anaesthetists were sufficiently trained to allow valid evaluation of the compared devices. Furthermore, this leads to the question of how much experience is sufficient for safe use. Can we regard a device as safe, when during a possibly long training period harm is done to patients? While we do not want to diminish the importance of the Combitube for emergency settings and recognise the need for training programmes to avoid ‘seeing the device for the first time during efforts to ventilate a failed intubation’, we believe that our conclusion is valid.

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