Correspondence Anaesthesia, 2005, 60, pages 198–211 . ....................................................................................................................................................................................................................
which, though not critical in themselves, were deemed ‘undesirable’. If there is indeed a link between the two, perhaps more attention should be paid to the many instances where things do not go as smoothly as they might but will apparently remain in control. This is worthy of further study. A. F. Smith D. S. Goodwin M. Mort Royal Lancaster Infirmary Lancaster LA1 4RP, UK E-mail: Andrew.Smith@ rli.mbht.nhs.uk C. Pope School of Nursing and Midwifery University of Southampton Southampton, UK
References 1 Smith AF, Goodwin D, Mort M, Pope C. Expertise in practice: an ethnographic study exploring acquisition and use of knowledge in anaesthesia. British Journal of Anaesthesia 2003; 91: 319–28. 2 Smith AF, Mort M, Goodwin D, Pope C. Making monitoring ‘work’: human– machine interaction and patient safety in anaesthesia. Anaesthesia 2003; 58: 1070–8. 3 Smith A, Goodwin D, Mort M, Pope C. Encouraging expertise in the use of monitoring. Journal of Clinical Anesthesia 2003; 15: 644. 4 Medical Devices Agency. Hazard Notice HN 9702, 1997 [www document]. http://www.smtl.co.uk/Documents/ Newsletters/Volume1-Issue1-Oct1997 [accessed 19 July 2004]. 5 Wenger E. Communities of Practice: Learning, Meaning, and Identity. Cambridge: Cambridge University Press, 2000. 6 Boe¨lle P-Y, Garnerin P, Sicard J-F, et al. Voluntary reporting system in anaesthesia: is there a link between undesirable and critical events? Quality in Health Care 2000; 9: 203–9.
A reply We greatly welcome Dr Smith and colleagues’ letter in response to our paper. It is a useful and interesting contribution to the debate. They raise three points, on which we would like to comment. 202
Firstly, what is the real incidence of violations in anaesthesia? At best, the Theory of Planned Behaviour used in our paper gives an estimate of the intention to violate. There are any numbers of ways that intention may be thwarted in practice, some of which will be associated with the safety procedures in place in well-run departments of anaesthesia. Thus, the incidence level may be very low in practice as the examination of their field notes suggests. However, our study was prompted by observations by the Medical Defence Union of closed cases. There needs to be further field research using a violations focused approach if we are to find out the nature and rate of the true incidence. Secondly, we agree with them that the term ‘violations’ may have offputting professional overtones. It is a rather aggressive term but it is one that the psychology community uses and which has established scientific definitions, which is why we used it in the paper. We agree that it may not be the most appropriate term in some circumstances. It is a definition that would include some of the variations they note. If a new terminology is to be used within anaesthesia, it should be one that does not encourage a culture in which violations are acceptable. Lastly, we find intriguing their suggestion that minor aberrations, though not critical in themselves, may be indicators of developing paths to critical incidents. It is an idea that would fit well into the sort of cascade effect in accident development demonstrated by Reason [1] and others. P. Beatty S. Beatty University of Manchester Manchester M13 9PT, UK
Reference 1 Reason J. Human Error. Cambridge: Cambridge University Press, 1990.
Difficult airway management
I read with interest the paper by Bein et al. comparing the performance of the intubating laryngeal mask airway
(ILMA) and the Bonfils intubating fibrescope in patients with difficult airways (Anaesthesia 2004; 59: 668–74). Management of the difficult airway is certainly an important aspect of anaesthetic practice, and it follows that identifying equipment that is the most effective in this situation is also important. This study, however, has limitations. In particular, the recruitment methods used were such that the devices may not actually have been assessed on any difficult airways. Patients were recruited on the basis of Mallampati score, thyromental distance, mouth opening (interincisor distance) and mobility of the atlanto-occipital joint. However, all of these predictive tests have been shown to be unreliable in predicting patients with difficult airways [1–3]. This means that many of the patients recruited may have had a normal airway and the study groups compared were likely to have been unfair. One suggestion would be that in addition to these predictive tests, each patient should have been assessed by direct laryngoscopy using a Macintosh laryngoscope in the anaesthetic room prior to using the ILMA or fibrescope, to confirm whether or not they actually had a difficult airway. In addition, patients who had a history of a previous failed intubation should not have been excluded from the study, as this is likely to have been a more reliable way than any of the predictive tests to recruit patients with anticipated difficult airways. Overall, the authors’ conclusion was to advocate the use of both the ILMA and the Bonfils intubation fibrescope in the management of anticipated difficult airways. The authors cannot therefore be criticised for unfairly suggesting one device is better than another on the basis of their study. However, the flaws in their study, particularly with regard to recruitment of patients, mean that the results cannot be used to assess reliably the efficacy of these devices in the management of the difficult airway. L. Russell James Cook University Hospital Middlesbrough, UK E-mail:
[email protected]
2005 Blackwell Publishing Ltd
Anaesthesia, 2005, 60, pages 198–211 Correspondence . ....................................................................................................................................................................................................................
References 1 Cobley M, Vaughan RS. Recognition and management of difficult airway problems. British Journal of Anaesthesia 1992; 68: 90–7. 2 Oates JDL, Oates PD, Pearsall FJ, MacLeod AD, Howie JC. Phonation affects Mallampati classification. Anaesthesia 1990; 45: 984. 3 Savva D. Prediction of difficult tracheal intubation. British Journal of Anaesthesia 1994; 73: 149–53.
A reply We thank Dr Russell for her comments. We agree that clinical predictors are far from being a ‘magic bullet’ for identifying patients with a difficult airway. This holds true, however, for virtually every test on a phenomenon with low prevalence in the population. Therefore, we did not suggest that patients in our study had a difficult laryngoscopy, but enrolled them based on a predicted difficult airway. However, given the positive predictive value of the tests used [1, 2], a considerable proportion of patients in our study were likely to have a difficult laryngoscopy, and it is hard to imagine from a statistical point of view that these patients were distributed unequally between the groups. Therefore, the patients in our study were likely to represent a population ‘at risk’. We had to exclude patients who had a history of a previous failed intubation since it was considered unethical to test a device like the Bonfils intubation fibrescope in this patient population without sound data on its feasibility. We have recently finished the study suggested by Dr Russell: using the Bonfils intubation fibrescope after failed direct laryngoscopy [3]. Interestingly, the results obtained are similar to our previous study. This suggests that either the Bonfils fibrescope performs similarly in both difficult and normal airways or that patients in the Bonfils group in the first study predominantly had a ‘true’ difficult airway. B. Bein F. Worthmann J. Scholz F. Brinkmann P. H. Tonner
2005 Blackwell Publishing Ltd
M. Steinfath V. Doerges University Hospital Schleswig-Holstein Kiel, Germany E-mail:
[email protected]
References 1 Ezri T, Warters RD, Szmuk P, et al. The incidence of class ‘zero’ airway and the impact of Mallampati score, age, sex, and body mass index on prediction of laryngoscopy grade. Anesthesia and Analgesia 2001; 93: 1073–5. 2 Schmitt H, Buchfelder M, RadespielTroger M, Fahlbusch R. Difficult intubation in acromegalic patients: incidence and predictability. Anesthesiology 2000; 93: 110–4. 3 Bein B, Yan M, Tonner PH, et al. Tracheal intubation using the Bonfils intubation fibrescope after failed direct laryngoscopy. Anaesthesia 2004; 59: 1207–9. Choice of cricothyroidotomy equipment
There is currently much interest in subglottic airway management. Studies using a human patient simulator (Vadodaria et al. Anaesthesia 2004; 59: 73–9), a model lung (Craven and Vanner, Anaesthesia 2004; 59: 595–9), guidelines from the Difficult Airway Society (Henderson et al. Anaesthesia 2004; 59: 675–94), editorial comment (Chambers, Anaesthesia 2004; 59: 631– 3), and correspondence (McGuire et al. Anaesthesia 2004; 59: 1029–30) have been published in this journal in recent months. The studies by Vadodaria et al. and Craven and Vanner used models, be they simple or complex, to mimick the living airway. For example, Craven and Vanner simulated complete upper airway obstruction by clamping the tubing of their model. From this they concluded (and extrapolated) that ‘with complete upper airway obstruction it was impossible to ventilate the lung with the Ravussin cannula’ (our italics). Authors of both studies extrapolate their findings to make judgements for equipment choice in real life, but differ in their preferred choice. In fact, these choices may not necessarily be the most
optimal in certain clinical settings, especially that of life threatening airway obstruction, the ‘can’t intubate, can’t ventilate’ scenario. Equipment must be ‘fit for purpose’. This is based on its efficacy, safety and reliability in a clinical setting and when used by an individual. These variables will define the ‘context of use’. In the context of emergency airway access in a patient at risk from impending or actual upper airway obstruction, there are important issues involving performance anxiety over time pressure, situational uncertainty and the potential for a ‘high impact outcome’. In other words, the patient can die within minutes unless the airway is promptly and safely rescued. In this setting, success rates are lower and complications higher [1]. Bearing in mind the ‘context of use’, we feel that the Ravussin system is generally the most reasonable choice for emergency airway rescue in the setting of the operating room, critical care area or emergency room, provided the equipment is available (which includes the jet ventilator) and provided the individual is ready, able and willing to act. Training for this is, of course, crucial (Chambers, Anaesthesia 2004; 59: 631–3). We readily acknowledge that each airway device has its own strengths and weaknesses. Whilst the use of all cricothyroidotomy equipment can be practised on a manikin or model, use of the Ravussin system can, additionally, be learned in an elective setting in patients needing laryngeal surgery. This is not so for the other devices. Needle cricothyroidotomy is also a common procedure for airway management using fibreoptic techniques. We emphasise that the context of use and operator skill, allied to an appropriate ‘situation awareness’ [2], is a crucial factor to be considered before conclusions based on laboratory or simulator work are applied to the real world. D. Pathak D. R. Ball Dumfries and Galloway Royal Infirmary Dumfries DG1 4AP, UK E-mail:
[email protected]
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