Transillumination-assisted endotracheal intubation with the Bonfils Fiberscope

Editor, The Bonfils Fiberscope (Karl Storz Endoscopy; Tuttlingen, Germany) has a semi-rigid optical stylet with an outer diameter of 5.0 mm, a fixed anterior tip curvature of 40°and a 1.2 mm working channel [1]. Successful intubation using the Bonfils Fiberscope in patients with predicted or known difficult airways, either awake or under general anaesthesia, has been confirmed [2–4]. Like other fibreoptic laryngoscopes, however, the Bonfils Fiberscope is susceptible to problems inherent to endoscopes such as fogging of the lens or interference with secretions and blood. In adults who did not receive an anticholinergic drug, the incidence of obscured vision by secretions in the airway is 30% (18/60) [1]. In children with presumed normal airways, moreover, the incidence of failed intubations with the Bonfils Fiberscope on the first attempt because of secretions contaminating the optic aperture is up to 27.3%, even though airway suction is perrformed [5]. Also, pretreatment with atropine does not influence the failure rate or time to intubation significantly. This may be an important problem that hinders the Bonfils Fiberscope in becoming an effective device for managing difficult airways, especially when the paediatric device without a suctioning channel and with the small optic aperture is used or when heavy secretions are present in the airway. The Bonfils device really combines the benefits of a lightwand and a fibrescope. The purpose of this letter is to describe a new technique of intubation with the Bonfils Fiberscope under the guidance of transillumination of the soft tissues of the anterior neck. This technique is similar to the method of inserting a lightwand. After anaesthetic induction, the jaw is lifted upwards. The Bonfils device loaded with an endotracheal tube (ETT) is inserted in the midline and slowly advanced in the airway until a central, clear and bright transillumination is seen on the cricothyroid membrane, which suggests that the scope tip is positioned at the glottis [6]. At this time, the operator carefully holds the device in place and determines whether the scope tip has been correctly positioned at the glottis through the eyepiece. If a bright red glow is seen off the midline, the scope tip may lie in the lateral aspect of the larynx. In this circumstance, the Bonfils Fiberscope should be slightly withdrawn and repositioned towards the midline. When a dimmer and diffuse glow in the midline indicates unintentional oesophageal placement, the Bonfils Fiberscope should be slowly withdrawn from the oesophageal inlet with gentle anterior traction until the light suddenly intensifies with posterior displacement of the larynx. After the correct position of the scope is confirmed, an assistant helps to release the ETT from the tube adapter and advances it into the trachea along the scope. After local ethics committee approval and written informed consent, we compared this transillumination technique with the midline approach by Halligan and Charters [1] in 80 adult patients with normal airways who were randomly assigned to the two groups after anaesthetic induction. The results showed that intubation on the first attempt was successful in 40 and 37 patients, respectively, when the transillumination and midline approach techniques were used (P > 0.05 between groups). In the midline approach group, three failed intubations on the first attempt were because of the vision being obscured by secretions contaminating the optic aperture. The intubation time, namely the period from the initiation of the Bonfils device insertion to restarting of ventilation through the ETT, was 21.5 ± 5.3 s (with a range of 16–38 s) in the transillumination technique group and 42.7 ± 16.5 s (with a range of 29–76 s) in the midline approach group (P < 0.01 between groups). After intubation, the average verbal analogue scale scores (0–10, in which 0 was described as very easy and 10 as impossible) that the operator used to rate the ease of the procedures was 1.0 ± 0.9 (range 0–3) in the transillumination technique group and 2.2 ± 1.5 (range 0–6) in the midline approach group (P < 0.01 between groups). According to our experience, under the guidance of transillumination, the tip of the Bonfils device may be easily positioned at the glottis. Even if there is slightly or moderately obscured vision by secretions in the airway, reconfirmation of the scope position using the fibreoptic view through the eyepiece does not present any problems. Now we also use this technique when the intubation is performed with other rigid fibreoptic stylets such as the Shikani Optical stylet, the Levitan first pass success stylet and others. Just as for lightwand-guided intubation, however, this technique is not appropriate when the neck anatomy precludes transillumination, for example in grossly obese patients or in patients with severely limited neck extension or neck scarring.