The case for a 3rd generation supraglottic airway device facilitating direct vision placement

Journal of Clinical Monitoring and Computing https://doi.org/10.1007/s10877-020-00537-4 EDITORIAL The case for a 3rd generation supraglottic airway device facilitating direct vision placement André A. J. Van Zundert1 · Chandra M. Kumar2 · Tom C. R. V. Van Zundert3 · Stephen P. Gatt4 · Jaideep J. Pandit5 Received: 11 May 2020 / Accepted: 25 May 2020 © Springer Nature B.V. 2020 Abstract Although 1st and 2nd generation supraglottic airway devices (SADs) have many desirable features, they are nevertheless inserted in a similar ‘blind’ way as their 1st generation predecessors. Clinicians mostly still rely entirely on subjective indirect assessments to estimate correct placement which supposedly ensures a tight seal. Malpositioning and potential airway compromise occurs in more than half of placements. Vision-guided insertion can improve placement. In this article we propose the development of a 3rd generation supraglottic airway device, equipped with cameras and fiberoptic illumination, to visualise insertion of the device, enable immediate manoeuvres to optimise SAD position, verify whether correct 1st and 2nd seals are achieved and check whether size selected is appropriate. We do not provide technical details of such a ‘3rd generation’ device, but rather present a theoretical analysis of its desirable properties, which are essential to overcome the remaining limitations of current 1st and 2nd generation devices. We also recommend that this further milestone improvement, i.e. ability to place the SAD accurately under direct vision, be eligible for the moniker ‘3rd generation’. Blind insertion of SADs should become the exception and we anticipate, as in other domains such as central venous cannulation and nerve block insertions, vision-guided placement becoming the gold standard. Keywords Anaesthesia · Supraglottic airway device · Complications · Positioning · COVID-19 * Tom C. R. V. Van Zundert André A. J. Van Zundert Chandra M. Kumar Stephen P. Gatt Jaideep J. Pandit 1 Department of Anaesthesia and Perioperative Medicine, Royal Brisbane & Women’s Hospital, The University of Queensland, Brisbane, QLD, Australia 2 Department of Anaesthesia, Khoo Teck Puat Hospital, Singapore, Singapore 3 Department of Anaesthesia, Onze-Lieve-Vrouw Hospital, Aalst, Belgium 4 Department of Anaesthesiology and Intensive Care, Udayana University, Bali, Indonesia & University of New South Wales, Kensington, NSW, Australia 5 Nuffield Department of Anaesthetics, Oxford University Hospital NHS Foundation Trust, Oxford, UK 1 Introduction There is no firm consensus about how supraglottic airway devices (SADs) should be classified. One such classification, by Cook, designates a ‘1st generation’ (e.g. LMA-Classic) incorporating a single breathing channel’ and a ‘2nd generation incorporating separate breathing and gastric channels’, as well as other design modifications mostly based around the dual channel model. These two ‘generations’ are widely accepted but the 3rd generation remains undefined [1–3]. In this article, we make the case for a ‘3rd generation’ SAD, which would have the added facility of ‘correct placement under direct vision’. We conceptualize that this facility would be possible by incorporating cameras and fibreoptic illumination, but we do not wish to predefine any technical parameters. Our assertions are based on a theoretical notion, to make an intellectual case and thereby aim at encouraging future innovation. This proposed 3rd generation, hopefully, will attract the attention of product developers, researchers, clinicians and manufacturers into investigating actual needs of anaesthetists and other clinicians rather than concentrating on ‘me too’ copy-cat replicas of existing devices. 13 Vol.:(0123456789) Journal of Clinical Monitoring and Computing 2 Ever‑increasing indications of effective usage of SADs Roughly two decades after Brain’s revolutionary introduction of the ‘vintage’ LMA-Classic [4], and more than six decades after the filing patent of its precursor (i.e. Leech’s Pharyngeal Bulb Gasway) [5], Brain successfully launched the first prototype 2nd generation SADs, the ‘LMA-ProSeal’ [6], incorporating an airway tube with improved glottic seal and gastric drain tube channel for gastric decompression. Since then, SADs have become popular and highly effective devices in airway management [7]. The 2nd generation SAD is currently recommended over LMA-Classic or so called ‘1st generation tube-only airway device’ [8–12]. The success of 2nd generation SADs is based on a set of near-ideal attributes as promulgated by Brimacombe [13] including a higher rate of successful first attempt placement with smoother insertion. There are two seals; one by the proximal cuff around the glottis, a second by the distal cuff sitting compactly into the oesophagus, resulting in higher oropharyngeal seal pressure compared with some precursor ‘ventilation tube-only’ SADs. The gastric tube channel allows passage of a gastric tube to vent gastric fluids whilst offering better protection from aspiration of regurgitated gastric contents. A bite block is incorporated to prevent obstruction of the airway, especially during emergence from anaesthesia. Finally, there is the option to intubate the trachea with the help of a flexible optical bronchoscope. Beyond ‘securing the airway’, the applications of SADs have now widened to include use in the obese, other highrisk and specific populations in obstetric and paediatric anaesthesia and as an option using the SAD as a conduit to place a tracheal tube (TT), with or without fibreoptic assistance (e.g. LMA-Fastrach) [14]. Conversely, for some surgeries, the ‘Bailey manoeuvre’ can be used to exchange the TT at a deep plane of anaesthesia for an SAD, to facilitate smoother emergence, diminish cardiovascular stress responses, decrease respiratory complications and minimise coughing or straining [15–18]. The SAD is now recommended in resuscitation guidelines, especially as the primary airway device for airway management by nonanaesthesiologists [19]. SADs have established a foothold as rescue airway devices in ‘Plan B’ of difficult airway guidelines [8, 20–24]. Indeed, once the SAD is placed along this limb of the resuscitation ‘tree’ to rescue a failed intubation, removing it is to be regarded as a serious risk [21]. Special features of the 2nd generation SADs have well known advantages but they are also associated with hazards and required further modifications. Mask aperture 13 bars (characteristic of 1st generation SADs) and epiglottiselevating bars (i.e. LMA-Fastrach) [25] became superfluous [26] and the newer SADs have no mask aperture bars [26]. Furthermore, SADs with ‘floppy’ distal cuffs can more easily fold over causing obstruction and the cuff was replaced by a reinforced tip [27, 28]. Original 2nd generation SADs had a very soft airway shaft crushable by teethclenching during emergence [29] and this led to incorporation of (...truncated)