Malpositioning of supraglottic airway devices: preventive and corrective strategies

Airway management is one of the cornerstones for modern anaesthesia and is vital for all patients undergoing general anaesthesia. Supraglottic airway devices (SADs) are increasingly used for managing airways. The World Health Organization estimates that worldwide, ∼250 million patients undergo general anaesthesia for major surgery on an annual basis.1Weiser TG Regenbogen SE Thompson KD et al.An estimation of the global volume of surgery; a modelling strategy based on available data.Lancet. 2008; 372: 139-144Abstract Full Text Full Text PDF PubMed Scopus (1693) Google Scholar If we translate the figures of the 4th National Audit Project of the Royal College of Anaesthetists and Difficult Airway Society (NAP4) in the UK, where almost 60% of the patients receive SADs during anaesthesia, we can assume that annually, ∼150 million such devices are used worldwide.2Fourth National Audit Project of the Royal College of Anaesthetists and Difficult Airway Society. Major complications of airway management in the United Kingdom. Report and Findings. March 2011. ISBN 978-1-9000936-03-3. London: Royal College of Anaesthetists. Available from http://www.rcoa.ac.uk/nap4/ accessed 10 November 2015.Google Scholar 3Woodall NM Cook TM National census of airway management techniques used for anaesthesia in the UK: first phase of the 4th National Audit Project at the Royal College of Anaesthetists.Br J Anaesth. 2011; 106: 266-271Abstract Full Text Full Text PDF PubMed Scopus (115) Google Scholar Manufacturers continue to invest in research in designing these devices to prevent aspiration, resulting in first-generation (ventilation channel only) and second-generation (separation of ventilatory and gastric access channels) SADs, with several other modifications and characteristics designed to improve their functionality and safety.4Cook TM Kelly FE Time to abandon the ‘vintage’ laryngeal mask airway and adopt second-generation supraglottic airway devices as first choice.Br J Anaesth. 2015; 115: 497-499Abstract Full Text Full Text PDF PubMed Scopus (92) Google Scholar, 5Van Zundert T Improvements towards safer extraglottic airway devices. University of Maastricht, The Netherlands2015Google Scholar, 6Van Zundert TCRV Brimacombe JR Ferson DZ Bacon DR Wilkinson DJ Archie Brain: celebrating 30 years of development in laryngeal mask airways.Anaesthesia. 2012; 67: 1375-1385Crossref PubMed Scopus (45) Google Scholar Anaesthetists consider the SAD to be a device that is easy to insert and that can be used for ever-increasing indications during various types of general surgery, obstetrics, and gynaecology. They also advocate its use in other areas, including the following: during cardiopulmonary resuscitation, in the department of emergency medicine, in the intensive care unit, in the prehospital setting, and as an important step in the difficult airway algorithm.7Apfelbaum JL Hagberg CA Caplan RA Connis RT Nickinovich DG Practice guidelines for management of the difficult airway. An updated report by the American Society of Anesthesiologists's Task Force on Management of the Difficult Airway.Anesthesiology. 2013; 118: 251-270Crossref PubMed Scopus (1420) Google Scholar, 8Mushambi MC Kinsella SM Popat M et al.Obstetric Anaesthetists’ Association and Difficult Airway Society guidelines for the management of difficult and failed tracheal intubation in obstetrics.Anaesthesia. 2015; 70: 1286-1306Crossref PubMed Scopus (307) Google Scholar, 9Frerk C Mitchell VS McNarry AF et al.Difficult Airway Society intubation guidelines working group. Difficult Airway Society 2015 guidelines for management of unanticipated difficult intubation in adults.Br J Anaesth. 2015; 115: 827-848Abstract Full Text Full Text PDF PubMed Scopus (1139) Google Scholar Manufacturers hardly put efforts into verification of the correct placement or positioning of the device in situ after insertion. Contrary to the insertion of a tracheal tube, which is guided to the trachea under (in)direct vision of a (video)laryngoscope, the insertion of a SAD is virtually a ‘blind’ technique, whereby one relies on the practitioner's skills to insert the device correctly into the hypopharynx. Routine verifications include auscultation of the lungs and gastric area, capnogram, oxygen saturation, airway pressure, oropharyngeal leak pressure, and the gold standard to evaluate its position using a fibreoptic scope, which is typically inserted through the tube of the airway device. However, the use of a fibreoptic scope only helps in diagnosis of malpositioning but does not allow the ability to change an incorrectly positioned SAD. Supraglottic airway devices are generally forgiving devices because even suboptimally positioned SADs still can provide adequate ventilation for the patients during short procedures. However, malpositioning of the device can result in severe leaks and even obstruction of the airway, with potentially negative outcomes for the patient. Although the incidence of complications (e.g. airway trauma, obstruction, regurgitation, gastric distension with mechanical ventilation) is likely to be higher with an incorrectly placed SAD, clinical airway obstruction can result from other causes, such as laryngospasm and transient closure of the glottis. Computed tomography scans (Fig. 1a) have revealed that the epiglottis is posteriorly deflected against the posterior pharyngeal wall in most (80%) patients.10Shorten GD Opie NJ Graziotti P Morris I Khangure M Assessment of upper airway anatomy in awake sedated and anaesthetized patients using magnetic resonance imaging.Anaesth Intensive Care. 1994; 22: 165-169PubMed Google Scholar Imaging studies have also shown that malpositioning of SADs occurs in 50–80% of patients.11Brimacombe JR Laryngeal Mask Anesthesia – Principles and Practice. 2nd Edn. Saunders, Philadelphia2005: 97-99Google Scholar, 12Van Zundert A van Zundert T Brimacombe J Downfolding of the epiglottis during intubation.Anesth Analg. 2010; 110: 1246-1247Crossref PubMed Scopus (9) Google Scholar, 13Aoyama K Takenaka I Sata T Shigematsu A The triple airway maoeuvre for insertion of the laryngeal mask airway in paralyzed patients.Can J Anaesth. 1995; 42: 110-116Crossref Scopus (42) Google Scholar Fibreoptic evaluation reveals that 50% of the time, the tip of the epiglottis may lie within the bowl of the device.14Joshi S Sciacca RR Solanki DR Young WL Mathru MM A prospective evaluation of clinical tests for placement of laryngeal mask airways.Anesthesiology. 1998; 89: 1141-1146Crossref PubMed Scopus (80) Google Scholar 15Payne J The use of the fibreoptic laryngoscope to confirm the position of the laryngeal mask.Anaesthesia. 1989; 44: 865Crossref PubMed Scopus (93) Google Scholar Figure 1 shows several positions of SAD sitting in a manikin and in patients. Ideally, the correct size of the device should be inserted into the hypopharynx, with the distal tip of the SAD in the oesophagus, whereby the tip of the epiglottis is aligned with the proximal part of the (adequately inflated cuffed) mask (Fig. 1b and f). As such, the epiglottis rests on the outer side of the cuff, whereby the tube opening of the SAD opposes the entrance to the trachea. If a cuffed SAD is used, it should be inflated with enough air to produce an adequate seal that allows both spontaneous and artificial ventilation, avoiding both hyperventilation (whereby the SAD risks being dislocated from its position) and hypoventilation (which increases the risks for aspiration; Table 1). Similar risks exist when an inappropriate size of the device is used. Non-cuffed SADs may also result in a leak attributable to lack of adequate alignment and seal between device and the epiglottis (Fig. 1g).Table 1Flow chart that provides: steps to result in an adequately positioned SAD; trouble-shooting options [verify SAD position with (video)laryngoscope]; causes of a malpositioned SAD; and treatment options. SAD, supraglottic airway deviceAdequately positioned SADs produce a good seal and no leak (ideal situation)Malpositioned SADs produce a leak and airway obstruction (unwanted situation)Five requirements of an ideally positioned SAD: (i)Tip of distal cuff in oesophagus(ii)Epiglottis resting on outside of SAD cuff(iii)Tip of epiglottis aligned with proximal cuff of SAD(iv)Cuff of SAD adequately inflated to produce seal(v)Avoidance of cuff folding (silicone is better than polyvinyl chloride)Five causes of a malpositioned SAD: (i)Tip of distal cuff of SAD folding over/backward(ii)Tip of distal cuff of SAD between vocal cords(iii)Epiglottis in bowl of SAD without downfolding(iv)Epiglottis in bowl of SAD with downfolding(v)Epiglottis folding doubleTrouble-shooting options:Intracuff pressure a maximum of 60 cm H2O at induction and maintenanceAvoid: •Cuff hyperinflation (dislocation of SAD)•Cuff hypoinflation (risk for aspiration)•Use of a too deep/too small SAD•Use of a too superficial/too large SADTreatment options: •Jaw thrust to open oropharyngeal space (increase distance between epiglottis and posterior wall of oropharynx)•Use of a railroading technique with the help of a bougie or orogastric tube•Magill forceps Open table in a new tab Inappropriately sitting devices may result from use of an inappropriately small size, hypoinflation of the cuff, or too deep insertion of the device (Fig. 1c and h) or, conversely, a larger size device, hyperinflation of the cuff, or too superficial insertion of the device (Fig. 1d and i). The factors above can all result in misalignment of the opening of the tube of the SAD and the tracheal orifice, and subsequently, a leak or even malobstruction may ensue. Fairly often, the epiglottis is located in the bowl of the SAD (Fig. 1d). This does not necessarily cause airway obstruction (Fig. 1j). In the worst-case scenario, downfolding of the epiglottis (Fig. 1e) may result in a leak or obstruct adequate ventilation altogether, indicated by a very low oropharyngeal leak pressure and the absence of a normal capnogram trace, the presence of high airway pressure, and the inability to ventilate the patient. Anaesthetists will then try to readjust the device or take it out altogether and replace it with either another SAD or use a tracheal tube instead. Different positions of SADs in situ pictures were captured with videolaryngoscopy (Fig. 1), and five common malpositions of the SAD were found, as follows: (i) the tip of the distal cuff folding over backwards (Fig. 1l); (ii) the tip of the distal cuff positioned between the vocal cords (Fig. 1m); (iii) positioning of the epiglottis in the SAD bowl without downfolding of the epiglottis (Fig. 1j); (iv) downfolding of the epiglottis in the bowl of the SAD (Fig. 1n); and (v) epiglottis folding double (Fig. 1o), creating an airway leak. The material used in the production of the SAD cuff is important, because polyvinyl chloride-based cuffs tend to create foldings in the proximal part of the SAD (Fig. 1k), with a potential leak as a result, even if the cuff is adequately inflated (maximal intracuff pressure of 60 cm H2O). Medical-grade silicone-based cuffs seem not to have this disadvantage when adequately inflated (Fig. 1f and i). Strategies to readjust any malpositioning of the SAD can be obtained if one uses a (video)laryngoscope, which allows visual confirmation of an adequately positioned epiglottis and airway device. Dr Archie Brain, in his very first publication on the LMA-Classic in the BJA, advised that any malfunctioning airway should be checked with a laryngoscope.16Brain AIJ The laryngeal mask'a new concept in airway management.Br J Anaesth. 1983; 55: 801-805Abstract Full Text PDF PubMed Scopus (775) Google Scholar The use of jaw thrust during insertion of the SAD may help in creating more room in the oropharynx, thereby increasing the distance between the epiglottis and the posterior wall of the oropharynx.13Aoyama K Takenaka I Sata T Shigematsu A The triple airway maoeuvre for insertion of the laryngeal mask airway in paralyzed patients.Can J Anaesth. 1995; 42: 110-116Crossref Scopus (42) Google Scholar Other techniques include a railroading technique with the help of a bougie, orogastric tube , or Magill forceps. The proposed flow chart (Table 1) may help anaesthetists in checking the position of the epiglottis and the SAD in situ and allows manoeuvres to be made to adjust any malpositioning. Selection of the correct SAD, the right size, and all efforts to prevent aspiration are all secondary to the correct positioning of the device in situ. The epiglottis clearly plays an important role in the correct positioning of any SAD. As downfolding of the epiglottis can occur with any of existing SADs, less than optimal positioning may cause problems in creating a patent airway. Our primary role is to create a safe and effective patent airway. Only by seeing what we do and confirming an adequate position of the device in situ can we be satisfied and go on to the next step of anaesthesia. Manufacturers are advised to concentrate on providing optimal viewing tools to help us in this effort. All authors approved the final manuscript and attest to the integrity of the original data and the analysis reported in this manuscript. The hospital receives a wide range of airway devices and videolaryngoscopes for research purposes. No additional funding was received by any of the authors from any manufacturer. No external funding was obtained for this manuscript. Departmental funds.