Infrared flashing light through the cricothyroid membrane as guidance to awake intubation with a flexible bronchoscope: A randomised cross-over study.

Background: In case of distorted airway anatomy, awake intubation with a flexible bronchoscope can be extremely difficult or even impossible. To facilitate this demanding procedure, an infrared flashing light source can be placed on the patient's neck superficial to the cricothyroid membrane. The light travels through the skin and tissue to the trachea, from where it can be registered by the advancing bronchoscope in the pharynx and seen as flashing white light on the monitor. We hypothesised that the application of this technique would allow more proximal and easier identification of the correct pathway to the trachea in patients with severe airway pathology.
Methods: As part of awake intubation, patients underwent insertion of a flexible video bronchoscope via the mouth into the trachea. The procedure was performed twice, in random order in each patient, with and without the aid of the transcutaneous flashing infrared light. All insertions were video recorded to determine at which anatomical landmark within the airway the correct pathway was identified. The videos are accessible via this link: https://airwaymanagement.dk/infrared_comparative. The predefined landmarks were in successive order: oral cavity, oro-pharynx, tip of epiglottis, arytenoid cartilages, false cords, vocal cords and trachea, as well as the spaces between them.
Results: Twenty-two patients had a total of 44 awake insertions with the flexible bronchoscope. The median anatomical level, at which correct identification of the trachea was obtained on the monitor, was, past the epiglottis, with the conventional technique, and at the level of the oropharynx, when using the infrared flashing light (p = .005). The time until the flashing light or the vocal cords were seen was 21 (22) S, mean (SD), and 48 (62) S, during the insertion with and without infrared flashing light activated, respectively (p = .005). Endoscopists rated it easier (p = .001) to recognise the entrance to the trachea in the infrared-group.
Conclusion: During awake intubation of patients with airway pathology, the application of trans-cricothyroid infrared flashing light to guide the insertion of a flexible bronchoscope significantly facilitated the recognition of the pathway into the trachea and the correct advancement of the flexible endoscope.
Registration of Clinical Trial: NCT03930550.
(© 2023 The Authors. Acta Anaesthesiologica Scandinavica published by John Wiley & Sons Ltd on behalf of Acta Anaesthesiologica Scandinavica Foundation.)