None listed
Conditions
Brief summary
We will investigate the occurrence of incorrect positioning in four commonly used supraglottic airway devices in anaesthesia using both blind and videolaryngoscopic techniques, including examination of the importance of such information to anaesthetists. The proposed pilot study is in preparation for a larger investigation. It is anticipated that it will provide a rich perspective on the occurrence of incorrectly positioned supraglottic airway devices which may potentially cause complications including patient pain and discomfort. Valuable insights and information will guide future research to improve clinical anaesthesia practice. Supraglottic airway devices (SADs) are the most commonly selected airway management device for general anaesthesia, and have a prominent role in the difficult airway algorithm of American Society of Anesthesiology. Although generally effective, the oropharyngeal airway seal in these devices is not airtight and there is the possibility of subsequent failure due to the added effects of inappropriate size, insertion technique, dislodgement following malpositioning and impact on anatomical structures. Imaging studies of SADs have revealed that a variety of malpositioning occurs in up to 70% of all ‘blind’ insertions, with the epiglottis posteriorly deflected. This results in partial epiglottic downfolding in the bowl of the airway device (70-80%) producing air leaks, airway obstruction, trauma (oedema, ischemia), and sore throat. Ideally, the SAD tube opening opposes the glottic opening and the entrance to the trachea, allowing for spontaneous breathing and mechanical ventilation. 1st generation SADs are simple airway devices with a single airway tube connected to a bowl and cuff with low oropharyngeal leak pressures (<20 cm H20). 2nd generation SADs have specifically designed features to reduce the risk of aspiration. Assessment of malpositioning provides a baseline to improve placement and better understand positioning for cuffed and uncuffed devices . Oropharyngeal leak pressure is a function of the cuff pressure of airway devices with inflatable cuffs, and determination of this pressure is defined as the airway pressure at which leakage is first detected as escaped air. This pressure indicates when the airway device is patent and positioned correctly. This primary end point has been previously used in clinical and fiberoptic assessments of SADs. The SADs LMA Classic 'Registered Trademark', LMA Supreme 'Registered Trademark' and igel 'Registered Trademark' have been evaluated alone or in pairwise comparisons but differing study designs make it difficult for comparison of results. The LMA Protector 'Registered Trademark' has not been clinically assessed. The aims of the study are to provide information about malpositioning indicated by the oropharyngeal leak pressure (OPLP) in the four different SADs,
Interventions
The following interventions placed by the consultant anaesthetist, the supraglottic airway devices the LMA-Supreme 'Registered Trademark', LMA-Protector 'Registered Trademark' and i-gel 'Registered Trademark' devices inserted with blind or video-guided methods will be sequentially allocated to each study participant for use as airway management during anaesthesia. Blind or video-guided insertion will be at the clinical discretion of the treating anaesthetist based on skills and preference. Maxim
The following interventions placed by the consultant anaesthetist, the supraglottic airway devices the LMA-Supreme 'Registered Trademark', LMA-Protector 'Registered Trademark' and i-gel 'Registered Trademark' devices inserted with blind or video-guided methods will be sequentially allocated to each study participant for use as airway management during anaesthesia. Blind or video-guided insertion will be at the clinical discretion of the treating anaesthetist based on skills and preference. Maximum of three attempts will be allowed for each intervention insertion, at which time standard care device is used. Anatomical details will be recorded during insertion for each device using both the blind and video-guided insertion methods. Postoperative incidence of sore throat, dysphagia and dysphonia will also be assessed. Characteristics of each of these supraglottic airway devices (SADs), also termed laryngeal mask airways (LMAs), are as follows: The LMA-Supreme 'Registered Trademark' (The Laryngeal Mask Company, Le Rocher, Victoria, Mahe,Seychelles) combines features of earlier devices, such as the LMA-ProSeal 'Registered Trademark' (high oropharyngeal seal cuff, gastric access and bite block – to facilitate ventilation, airway protection and airway obstruction, respectively), the LMA-Fastrach 'Registered Trademark' (fixed curve tube and guiding handle – to facilitate insertion and fixation) and the LMA-Unique 'Registered Trademark' (single use – prevention of disease transmission). Furthermore, the LMA-Supreme 'Registered Trademark' incorporates additional features: the anatomically shaped airway tube incorporates a drain tube within its lumen to separate the ventilation and digestive tracts; an elongated cuff at the distal drainage orifice and a 10 degree slant to fit better in the oesophageal tube; an oval-shaped tube to match better the shape of the mouth and to reduce rotation in the pharynx; a strengthened inner cuff to prevent airway obstruction from infolding; and epiglottic fins to prevent airway obstruction from epiglottic downfolding. The LMA-Protector 'Registered Trademark' (Teleflex Medical, Athlone, Westmead, Ireland) is a later single-use CE-marked and TGA (Therapeutic Goods Administration, Australia) approved laryngeal mask that has similar features to the LMA-Supreme 'Registered Trademark', but has similarities to the LMA-Classic 'Registered Trademark' and LMA-ProSeal 'Registered Trademark', as this device is made entirely from medical-grade silicone. This makes it more flexible and potentially less traumatic than the rigid LMA-Supreme 'Registered Trademark' which is made of polyvinyl chloride. The LMA-Protector 'Registered Trademark' provides access to, and functional separation of the ventilation and digestive tracts. The anatomically shaped airway tube is elliptical in cross-section and ends distally at the laryngeal mask, with the cuff is designed to conform to the contours of the hypopharynx. The LMA-Protector 'Registered Trademark' contains two drainage channels, which emerge as separate ports proximally and enter a chamber, located behind the cuff bowl, which is a new feature. The chamber communicates distally with the upper oesophageal sphincter. Removal of gastric fluid through the upper oesophageal sphincter can be realized by attaching a suction tube to the male suction port or by insertion of a gastric tube through the female drainage port to the stomach. The i-gel 'Registered Trademark' is an innovative second generation SAD, designed to create a non-inflatable, anatomical seal of the pharyngeal, laryngeal and perilaryngeal structures while avoiding compression trauma. The shape, softness and contours accurately mirror the perilaryngeal anatomy, requiring no cuff inflation.
Sponsors
Royal Brisbane and Womens Hospital
Study design
Allocation
Non-randomised trial
Intervention model
Parallel
Primary purpose
Treatment
Masking
Open (masking not used)
Eligibility
Sex/Gender
All
Age
18 Years to No maximum
Healthy volunteers
No
Inclusion criteria
Patients aged > 18 years; Planned general anaesthesia; ASA (American Society of Anesthesiologists) Score 1-3; Informed written consent.
Exclusion criteria
Requiring endotracheal intubation with a high risk of aspiration; Pregnancy; Surgery requiring non-supine positioning; Head and neck surgery; Potentially difficult airway.
Outcome results
None listed