A reply

We thank Drs Sorbello and Frova for their interest in our work on introducers. It appears that they have largely misinterpreted our study on the Frova introducer. Firstly, they appear to have misunderstood the patient selection method used in our study. The Frova introducer was used in a series of cases presenting with difficulty in intubation. Consequently, it is not at all surprising that 54 patients (27%) in our study had either grade 3a, 3b or 4 view as inadequate view of larynx was one of the selection criteria. Furthermore, Sorbello and Frova appear to have failed to appreciate that the users of the Frova introducer in our study were clinicians and not the researchers. The decision whether or not to use the Frova introducer was made by clinicians faced with poor laryngeal view. In addition, they have misrepresented the number of cases requiring repeat laryngoscopy. No data was presented on the number of laryngosocopies performed. Drs Sorbello and Frova argue against the use of ‘clicks’ and ‘hold up’ signs for confirmation of the correct placement of the Frova introducer because of the possibility of the associated airway trauma. They advocate the use of the hollow nature of the Frova introducer to sample carbon dioxide or use an oesophageal detector device to confirm introducer placement. Advantages of the use of introducers include simplicity and speed of tracheal placement. The end-tidal carbon dioxide or oesophageal detector device, require additional time as they are used once the introducer is placed. The ‘clicks’ and ‘hold-up’ signs, on the other hand, are elicited during insertion of the introducer [1]. We found some evidence supporting the use of a carbon dioxide or oesophageal detection device for confirming introducer position [2, 3]. We would be interested to see any published data on the use of the end-tidal carbon dioxide and the oesophageal detector device with the Frova introducer from our colleagues in Italy. The end-tidal carbon dioxide or the oesophageal detector device were not used by any of the clinicians in our study in the management of their cases. We believe this represents standard practice in the United Kingdom when using introducers and believe that neither of the above devices are likely to be used with the Frova introducer to confirm tracheal placement. In vitro studies have demonstrated that the Frova introducer is significantly more rigid than the Eschmann introducer [4] thus there is increased risk of airway trauma. We have already urged caution if the ‘hold-up’ sign is used with the Frova introducer in patients [4, 5]. There does indeed appear to be a noteworthy incidence of significant trauma in clinical practice when single use introducers are used to aid difficult intubation [5, 6]. The Eschmann introducer, in contrast, has had, over many years an enviable safety record [7]. Ideally, any single-use introducer should not be more rigid and thus potentially more traumatic, than the Eschmann multiple-use introducer. It would seem more prudent to alter the design of single-use introducers in order to make them less likely to cause airway trauma, than to rely on methods of placement detection that are not fully evaluated and take longer to perform. Drs Sorbello and Frova advise against shaping the Frova introducer. They recommend that the Frova introducer should be advanced ‘in a linear way’. We did not design our study to look at whether shaping influences the tracheal placement rate so we could not make any firm conclusions regarding the effect of shaping on the successful placement of the Frova introducer. Tracheal placement of an introducer will depend on laryngeal position, the degree of bend of an introducer and the angle and length of the tip. As the use of tracheal tube introducers is frequently associated with no view of the larynx (26% of patients in our study), it is difficult to imagine that just advancing the Frova introducer in a straight line would result in tracheal placement. We are aware that undue bending can easily deliver the tip of the Frova introducer at right angles to the anterior tracheal wall and obstruct passage of the device into the trachea. This is likely to be because of the 60° angle that the tip makes with the body of the device. The diagrams provided by Sorbello and Frova are conjectural and do not appear to be based on observation of what happens when the Frova introducer is used in clinical practice. Recommendations on whether or not to bend any introducer should be based on manikin and clinical evaluation rather than on dogmatic untested claims. Our data have shown clear advantages for tracheal placement if the tracheal introducer is shaped before use: 83% success when shaped compared to 7% when used straight [8]. The ability of the Frova introducer to maintain the curved shape, a feature shared with the Eschmann introducer, is in our opinion an important reason for its high success rate. Consequently, it does not seem correct to suggest that not shaping the Frova introducer will let it ‘work properly’. We certainly recommend shaping the introducer if difficulty in tracheal placement is encountered. The optimal curve and pliability of the body of the ‘ideal’ introducer, angle and length of the tip of introducer remain to be established. Drs Sorbello and Frova recommend generous lubrication, preloading of the tracheal tube on the Frova introducer or removal of the tube connector in order to overcome the reported difficulties in railroading the tracheal tube. We believe this advice is unlikely to be followed in the United Kingdom. It would seem more sensible to make minor adjustments to the design of the Frova introducer if such adjustments facilitate clinical practice. We reject the claim that other devices and not the Frova introducer might have been responsible for trauma reported in our study. Sorbello and Frova fail to notice that we have indeed analysed our data with respect to airway manoeuvre. Laryngeal manipulation and repositioning were used in 38% and 58% of cases respectively and these would not cause tracheal or pulmonary trauma. The other possible causes of trauma, the stylet and the fibreoptic scope, were used in 1.5% and 0.5% of cases respectively and there was no evidence of airway trauma in any of those cases. There were six cases of blood on tracheal suction, in five of whom the ‘distal hold up’ sign was used. No other airway manoeuvre, other than laryngeal manipulation and repositioning were used in these six cases. Only one attempt was made to insert the Frova introducer in five of the six cases, two attempts in the other. Consequently, the Frova introducer is presumed to be the most likely cause of serious airway trauma reported in our paper. There are a number of single-use introducers and the Eschmann multiple-use introducer available on the market. On the basis of both manikin and laboratory evaluations the Frova introducer appears to be the best of the single-use introducers [4]. However, following careful evaluation it has previously been advocated that both the Frova and Eschmann introducers should be made available in all anaesthetic locations in the United Kingdom [4]. The advice proffered by the Association of Anaesthetists of Great Britain and Ireland, to use when possible single-use equipment, should be tempered with a degree of caution. Any single-use item of equipment that is selected should certainly be properly evaluated before use [9] and be ‘fit for purpose’. Cook’s hospital policy is, however at variance with the Association of Anaesthetists of Great Britain and Ireland advice. He has recently noted when discussing introducers that ‘the only one used in our hospital (until a replacement is proven to be of similar efficacy and safety) is the original gum elastic bougie’ [10]. The Frova introducer was brought into clinical practice in 1998 without any published evaluation of its clinical effectiveness or safety. It seems surprising that Drs Sorbello and Frova are reluctant to accept the evidence and modify the design of the device. We thank them again for their interest in our study, but they should accept that error in this case lies in the device, not in the artist.