Bougie-related airway trauma: dangers of the hold-up sign*

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1 Original Article doi: /anae Bougie-related airway trauma: dangers of the hold-up sign* B. A. Marson, 1 E. Anderson, 1 A. R. Wilkes 2 and I. Hodzovic 3 1 Foundation Trainee, 2 Senior Research Fellow, 3 Senior Lecturer, Department of Anaesthetics, Intensive Care and Pain Medicine, Cardiff University, Cardiff, UK Summary The bougie is a popular tool in difficult intubations. The hold-up sign is used to confirm tracheal placement of a bougie. This study aimed to establish the potential for airway trauma when using this sign with an Eschmann reusable bougie or a Frova single-use bougie. Airways were simulated using a manikin (hold-up force) and porcine lung model (airway perforation force). Mean (SD) hold-up force (for airway lengths over the range cm) of 1.0 (0.4) and 5.2 (1.1) N were recorded with the Eschmann and Frova bougies, respectively (p < 0.001). The mean (SD) force required to produce airway perforation was 0.9 (0.2) N with the Eschmann bougie and 1.1 (0.3) N with the Frova bougie (p = 0.11). It is possible to apply a force at least five times greater than the force required to produce significant trauma with a Frova single-use bougie. We recommend that the hold-up sign should no longer be used with single-use bougies. Clinicians should be cautious when eliciting this sign using the Eschmann re-usable bougie.... Correspondence to: I. Hodzovic hodzovic@cf.ac.uk *Presented in part at the Euroanaesthesia meeting, Amsterdam 2011, The Netherlands, and the Difficult Airway Society Annual Meeting, Nottingham, UK, Accepted: 3 November 2013 Introduction National UK [1] and international [2, 3] difficult airway algorithms recommend the use of bougies in the early stages of unanticipated difficult airway management. Bougies remain a popular airway management adjunct in the UK when an intubation proves to be difficult [4, 5]. There are two main types of bougies available commercially. The Eschmann re-usable bougie (Re-usable guide bougie ; Smiths Medical International, Hythe, Kent, UK) was introduced to clinical practice in the 1980s [6]. Single-use bougies have also become available amidst concerns about prion transfer on re-usable medical equipment [7]. The Frova Intubating Introducer (Cook UK Ltd, Letchworth, UK) was brought into clinical practice in This bougie was the most frequently available single-use bougie in a 2009 national UK survey on the availability of introducers [4]. As part of the Difficult Airway Society (DAS) difficult intubation algorithm, two strategies are suggested for confirming tracheal rather than oesophageal placement of the bougie [1]. These involve feeling for clicks as the bougie touches the tracheal rings, or waiting for the hold-up sign. The hold-up sign involves advancing the bougie in a controlled manner to a maximum of 45 cm, stopping when an increase in resistance is felt when the tip of the bougie becomes lodged in the smaller airways The Association of Anaesthetists of Great Britain and Ireland 219

Marson et al. Bougie-related airway trauma The use of the hold-up sign is associated with a sensitivity of 100%, whereas the sensitivity of feeling for clicks is 90% [6].

medicine literature [1, 8]. The purpose of this study was to establish the airway trauma potential of the hold-up sign when using Eschmann re-usable and Frova single-use bougies.

2 Marson et al. Bougie-related airway trauma The use of the hold-up sign is associated with a sensitivity of 100%, whereas the sensitivity of feeling for clicks is 90% [6]. However, there is no evidence as to the safety profile of using these tests, despite the recommendation of their use in the DAS guidelines and reports of the tests used in anaesthetic and emergency medicine literature [1, 8]. The purpose of this study was to establish the airway trauma potential of the hold-up sign when using Eschmann re-usable and Frova single-use bougies. We set to determine the forces exerted in the airway when the hold-up is used to confirm tracheal placement and to test these forces on a porcine model to determine the forces required to cause significant airway trauma. Methods The study was undertaken in two parts. Firstly, we aimed to establish the maximum force that could be exerted at the tip of a bougie during tracheal placement the hold-up force (Fig. 1). This was completed by modelling the anatomy of a human airway using a manikin with variable length airways, as there is evidence that the position at which the bougie is held influences the maximum force measured at the tip [9] (Fig. 1). The second part of this study was set to find the airway perforation force the force required to produce significant airway trauma using a porcine model (Fig. 2). The hold-up force, defined as the maximum (peak) force that could be transmitted to the tip of the bougie, was established using an anatomically realistic manikin model (Laerdal Airway Intubation Trainer, Laerdal Medical Ltd, Orpington, Kent, UK). Ten samples each of the Eschmann re-usable and Frova single-use bougies were tested. Each sample was inserted into the mouth of the model and positioned in the airway. Adjustable bronchial extensions were used to produce five different simulated airway lengths (25, 30, 35, 40 and 45 cm). A force gauge (Mecmesin PFI200N; Mecmesin, Slinford, West Sussex, UK) was positioned at the end of the airway model to measure the force transmitted to the tip of the introducer (Fig. 1). Force data were collected using a custom (a) (b) Figure 1 (a) Airway manikin with bronchial extension. (b) Force transducer positioned at the end of the extended manikin s airway. (a) (b) Figure 2 (a) Force transducer located at the distal end of the tray and sliding tray. (b) Porcine airway and lungs stitched to the sliding tray using nylon surgical stitch The Association of Anaesthetists of Great Britain and Ireland

3 Marson et al. Bougie-related airway trauma Anaesthesia 2014, 69, LabVIEW programme (National Instruments, Austin, TX, USA) and the peak force measured was recorded. Each test at each length was repeated with each sample of introducer three times. The airway perforation force was defined as that required to produce airway damage using a porcine model. We used 10 fresh samples of porcine lungs attached to the upper airway obtained from a local butcher. The porcine lungs were fixed to a board positioned on a sliding tray (Fig. 2a), with a force transducer abutted to the distal end of the board (Fig. 2b). Three samples of the Eschmann and Frova bougies were studied. Each bougie was gently inserted into the airway model until it was positioned snugly in a bronchiole. Gradually increasing force was then applied until the airway was perforated. The perforation was manifested by the sudden give and appearance of the tip of the introducer in the subpleural tissue. All measurements were completed by a single operator. For the hold-up force, data were analysed using repeated measures ANOVA [10]. Introducer (Eschmann and Frova) was added as the between subjects factor and length (25, 30, 35, 40 and 45 cm) and replicate (1, 2 and 3) were added as the within subjects factors. Post-hoc tests were carried out with the Bonferroni correction to determine significant differences between the various lengths. Perforation force data were compared using paired t-tests. A p value < 0.05 was taken to indicate statistical significance. Results Peak forces measured with the Frova (range of mean values N) were more than four times greater than those measured with the Eschmann ( N) at the same lengths (Table 1). From the repeated measures ANOVA analysis, bougie, length and the interaction term bougie 9 length had significant effects on peak force (p < for all). The overall difference in peak force between the Frova and Eschmann introducers was 4.2 N. From the post-hoc tests, there were significant differences in the peak forces measured between length 25 cm and lengths 30, 35 and 40 cm and between length 45 cm and lengths 30, 35 and 40 cm. The significant effect of the interaction term indicated that there was a difference in the effect of length on the peak force measured with the two bougies. Table 1 Peak forces measured at the tip of the Eschmann and Frova introducers during hold-up at different distances, and force required to perforate porcine airway tissue. Values are mean (SD). Peak force; N Eschmann Frova p value 25 cm 1.4 (0.5) 6.3 (1.2) 30 cm 0.6 (0.1) 4.7 (0.7) 35 cm 0.7 (0.2) 4.7 (0.6) 40 cm 1.0 (0.3) 4.8 (0.6) 45 cm 1.4 (0.2) 5.7 (0.9) Mean (all distances) 1.0 (0.4) 5.2 (1.1) < Mean perforation force 0.9 (0.2) 1.1 (0.3) 0.11 The mean (SD) force required to produce airway perforation was 0.9 (0.2) N with the Eschmann bougie and 1.1 (0.3) N with the Frova bougie (p = 0.11). Discussion The results from this study demonstrate that significantly greater peak forces can be generated at the tip of the Frova single-use bougie than the Eschmann reusable bougie. When evaluating applicability of the study findings to clinical practice, a number of limitations need to be considered. Firstly, the hold-up force part of the study was conducted on a manikin where resemblance to clinical practice is uncertain [11]. Due to ethical considerations, this study would not be possible in the clinical setting. We placed the bougie within the airway when measuring the force exerted at the bougie tip (Fig. 1), which simulated closely the use of a bougie in clinical setting. Secondly, the force required to produce airway perforation may not be replicated in vivo due to different tissue elasticity and variations in anatomy of our animal model. A porcine model is, however, the closest we can get to the human airway as it has been previously validated to provide similar tissue elasticity and airway anatomy to that found in humans [12, 13]. This study was not randomised or blinded, but the order in which the bougies were tested was unlikely to have significant effect on the forces exerted at the tip in either experimental setting. Successful blinding would have required potentially altering the mechanical qualities of the bougies by masking them from the operator, 2014 The Association of Anaesthetists of Great Britain and Ireland 221

4 or would have obscured the tactile response from the bougie. For these reasons, neither was attempted. It is not known how commonly the tracheal clicks or hold-up signs are used by anaesthetists. Described over two decades ago [14], Kidd et al. [6] suggested that no intubation should be attempted in the absence of at least one of the two signs as it will almost certainly result in oesophageal intubation. As the clicks are not always present (90% sensitivity) during blind bougie placement, the anaesthetist has to rely on the hold-up sign to confirm tracheal placement (100% sensitivity) [6]. Anaesthetists reported using clicks to confirm tracheal bougie placement in 65% [5] and 81% [15] of cases when a bougie was used to aid tracheal tube placement. The incidence of use of the distal hold-up sign among anaesthetists is reported to be 13% [5] and 15% [15]. Although mostly concerned with potential airway trauma when using the Frova single-use bougie, our study suggests that the hold-up sign should no longer be used with any single-use bougie. Previous studies have shown mean forces of 0.4 and 1.1 N for the Eschmann bougie [16], and 1.2 and 3.8 N for the Frova bougie [17] for 40 and 20 cm distances held from the tip, respectively (i.e. forces exerted at the tip were lower than the forces we recorded). The differences in the experimental set-up between our study (bougie placed within a manikin s airway) (Fig. 1) and previous studies (bougie pressed against the force transducer outside the airway) may account for the differences in findings. Nonetheless, all these forces are well above the level of the force required to perforate the airway. The consensus seems to be that the increased stiffness of the single-use bougie allows greater transmission of force, and thus permits greater potential for airway trauma. We recorded the maximum forces exerted at the tip of the bougie when eliciting the hold-up sign. The forces recorded in this manikin model are not likely to be too dissimilar to the forces that may be exerted when eliciting the hold-up sign in the clinical setting, as unexpected difficulty associated with tracheal intubation is often a terrifying problem; anaesthetists using the hold-up sign are not always likely to be gentle and careful when eliciting it. The potential for harm when using the hold-up sign is great: a force of 2 N corresponds to a peak pressure of 80 kpa exerted over a Marson et al. Bougie-related airway trauma surface area of a bougie tip of 25 mm 2 (2pr 2 = 25 mm 2, for r = 2 mm). It is not surprising that the forces as small as 0.8 and 1.1 N caused airway perforation in the lung model. These concerns are reinforced with case reports of airway trauma associated with the use of single-use bougies [18 20]. We found two reports, 13 years apart, in which airway trauma has been caused by using the hold-up sign with the Eschmann bougie [21, 22]. Although the precise forces found in clinical practice at the hands of practitioners with a range of experience and expertise would be difficult to estimate, findings of this study add weight to concerns surrounding the use of singleuse bougies. Airway trauma associated with the use of hold-up sign might be minimised by: (i) gently advancing the bougie with the tip facing anteriorly during tracheal placement and feeling for clicks as the tip of the bougie is sliding over tracheal cartilages; (ii) avoiding the hold-up sign or if elicited (with Eschmann re-usable bougie only), retracting the bougie a few centimetres before railroading the tracheal tube [21]; (iii) avoiding advancement of the bougie accidentally into smaller airways by asking the assistant to hold the bougie during railroading [23]. We conclude that, based on the potential for harm we report (and until new safer single-use bougies are introduced into clinical practice), the hold-up sign should not be elicited if a single-use bougie is being used. Great caution should be exercised if attempting to elicit the hold-up sign with Eschmann re-usable bougie. Acknowledgements Bougies used in this study were donated free of charge by Cook Medical (Frova) and Smiths Medical UK (Portex Eschmann). Competing interests No external funding or competing interests declared. References 1. Henderson JJ, Popat MT, Latto IP, Pearce AC. Difficult Airway Society guidelines for management of the unanticipated difficult intubation. Anaesthesia 2004; 59: Combes X, Le Roux B, Suen P, et al. Unanticipated difficult airway in anesthetized patients: prospective validation of a management algorithm. Anesthesiology 2004; 100: The Association of Anaesthetists of Great Britain and Ireland

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How do you use a bougie as an airway adjunct for endotracheal intubation?

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