Review Article. Summary. Introduction. D. K. Baidya, 1 Chandralekha, 2 V. Darlong, 3 R. Pandey, 3 S. Maitra 4 and P. Khanna 5

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1 Review Article doi: /anae Comparative efficacy and safety of the Ambu â AuraOnce TM laryngeal mask airway during general anaesthesia in adults: a systematic review and meta-analysis D. K. Baidya, 1 Chandralekha, 2 V. Darlong, 3 R. Pandey, 3 S. Maitra 4 and P. Khanna 5 1 Assistant Professor, 2 Professor and Head, 3 Additional Professor, 4 Senior Resident, Department of Anaesthesia and Intensive Care, All India Institute of Medical Sciences, New Delhi, India 5 Assistant Professor, Department of Anaesthesiology, Post-Graduate Institute of Medical Education and Research, Chandigarh, India Summary Previous comparisons between the Ambu â AuraOnce TM and other laryngeal mask airways have revealed different results across various clinical studies. We aimed to perform a systematic review with meta-analysis on the efficacy and safety of the AuraOnce compared with other laryngeal mask airways for airway maintenance in adults undergoing general anaesthesia. Our search of PubMed, PubMed Central, Scopus and the Central Register of Clinical Trials of the Cochrane Collaboration yielded nine randomised controlled trials eligible for inclusion. Comparator laryngeal mask airways were the LMA Unique TM (four trials), the LMA Classic â (five trials) and the Portex â Soft Seal â (three trials). The AuraOnce provided an oropharyngeal leak pressure higher than the LMA Unique (304 participants, mean (95% CI) difference 3.1 ( ) cmh 2 O, p < ) and equivalent to the LMA Classic. The Soft Seal provided a higher leak pressure than the AuraOnce (229 participants, mean (95% CI) difference 3.5 ( ) cmh 2 O, p = 0.03). Insertion was significantly faster with the AuraOnce than the LMA Unique (304 participants, mean (95% CI) difference 5.4 ( ) s, p = 0.001) and Soft Seal (229 participants, mean (95% CI) difference 9.5 ( ) s, p = 0.004), but similar to the LMA Classic. The first-insertion success rate of the AuraOnce was equivalent to the LMA Unique, LMA Classic and Soft Seal. We found a higher likelihood of bloodstaining on the cuff with the Soft Seal and a higher incidence of sore throat with the LMA Classic. We conclude that the AuraOnce is an effective alternative to the LMA Classic and LMA Unique, and easier to insert than all three other devices studied.... Correspondence to: S. Maitra souvikmaitra@live.com Accepted: 18 March 2014 Introduction Since the invention of the original laryngeal mask airway (LMA) by Dr. Archie Brain in 1983, many modifications have been introduced into clinical anaesthesia practice [1]. Recent growing concern about Creutzfeldt Jakob disease and other communicable diseases, and the cost of cleaning and sterilisation of re-usable devices, have popularised the use of disposable, singleuse airway devices [2 4]. The Ambu â AuraOnce TM Laryngeal Mask (Ambu A S, Ballerup, Denmark) is a disposable device for airway maintenance during anaesthesia. It is constructed from a single-piece polyvinyl chloride mould. It incorporates a 90 pre-formed curvature, designed to approximate airway anatomy, 2014 The Association of Anaesthetists of Great Britain and Ireland 1023

2 Baidya Ambu â AuraOnce TM and other LMAs: a meta-analysis and lacks the aperture bars of the LMA Unique TM (Intavent Orthofix, Ltd, Maidenhead, UK) or LMA Classic â (Laryngeal Mask Company, Henley-on- Thames, UK). The cuff of the AuraOnce is thin and contoured to fit the hypopharynx so that, when properly positioned, the distal tip of the cuff sits in the upper oesophageal sphincter and the proximal end rests at the base of the tongue [5]. A number of prospective clinical studies have compared the AuraOnce with the LMA Classic and also with other single-use devices e.g. the LMA Unique and Portex â Soft Seal â (Smiths Portex, Ltd, Hythe, UK). Results from these comparative clinical studies are inconsistent. One way of exploring and resolving such conflicting results is to perform a systematic review, with or without metaanalysis; this also allows more precise estimates of the effects of an intervention than those derived from the individual studies included within it. We thus aimed to perform a systematic review to establish the relative safety and efficacy of the AuraOnce in comparison with other commonly used types of LMA. Methods We searched for prospectively conducted, randomised controlled trials comparing the AuraOnce with any other LMA. Three authors (DKB, PK and VD) independently searched PubMed, Scopus and CENTRAL (the Cochrane Collaboration s Register of Clinical Trials) for eligible controlled trials published between January 2000 and 18th August 2013 using the following search words: Ambu laryngeal mask airway, laryngeal mask airway Ambu, Ambu LMA, LMA Ambu and Ambu Aura Once. The search was updated on 15th January We did not impose any language restriction in the search strategy; details of the strategy are given in Appendix 1. We also searched the reference lists from identified studies to find further potentially eligible trials. We included only published prospective human controlled trials comparing the AuraOnce with any other LMAs in adults undergoing general anaesthesia (Fig. 1). Three authors (DKB, SM and RP) independently extracted all data from the eligible trials. The following data were collected from each study: n = 33 ar cles iden fied from PubMed n = 19 ar cles iden fied through SCOPUS n = 13 ar cles iden fied through CENTRAL n = 35 ar cles a er duplicates removed (Duplicates removed automa cally by Endnote X n = 35 ar cles screened by tle and abstract n = 16 of full-text ar cles assessed for eligibility n = 9 studies included in qualita ve synthesis n = 19 irrelevant ar cles excluded (Observa onal studies/not related to LMA A mbu/case reports/correspondence) n = 1 ar cle excluded,as studied children n = 1 ar cle excluded because it compared LMA Ambu with i-gel n = 5 ar cle excluded because of nonhuman trial n = 9 studies included in quan ta ve synthesis (meta-analysis) Figure 1 Study selection flow diagram. n = 5 trial compared LMA Ambu vs LMA Classic n = 4 trial compared LMA Ambu vs LMA Unique n = 3 trial compared LMA Ambu with Portex So Seal The Association of Anaesthetists of Great Britain and Ireland

3 Baidya Ambu â AuraOnce TM and other LMAs: a meta-analysis Anaesthesia 2014, 69, name of the first author; year of publication; total number of patients studied; oropharyngeal leak pressure (including method and timing of measurement); first-insertion success rate for each type of device; time to insert the device; and any reported complications (including sore throat, dysphagia, dysphonia, laryngospasm and blood on the device). We did not collect data on the fibreoptic bronchoscopic view of the glottis through the device, as this is a poor predictor of the quality of ventilation through it mask [6]. Initially, all data were tabulated in a Microsoft Excel TM spreadsheet. We neither asked the author(s) nor contacted the manufacturer(s) for any unpublished data. The quality of eligible trials was assessed using the risk of bias tool within Review Manager v software (Review Manager (RevMan) v.5.2. Copenhagen: The Nordic Cochrane Centre, The Cochrane Collaboration, 2012) by two authors working independently (CL and PK). We assessed: random sequence generation; allocation concealment; blinding; incomplete data; and selective outcome reporting; based on the reporting of the trials, each aspect was graded yes, no, or unclear, which reflected a high risk of bias, low risk of bias and unclear risk of bias, respectively. The primary outcome of the meta-analysis was oropharyngeal leak pressure. The secondary outcomes were: success rate on first insertion attempt; time to insert the device and complications (sore throat, dysphagia, dysphonia, laryngospasm, blood on the device or any other complication). If data were reported as median with range and/or IQR, the mean value was estimated using the median and the low and high end of the range for samples smaller than 25; for samples > 25, the median itself was used. The standard deviation was estimated from the median and the extremes of the range for samples smaller than 15, as range/4 for samples from 15 to 70, and as range/6 for samples more than 70. If only an IQR was available, standard deviation was estimated as IQR/1.35 [7]. We calculated the following: (i) the odds ratio (OR) for each dichotomous outcome at individual study level; (ii) the pooled OR using the Mantel Haenszel method; (iii) the mean difference for each continuous outcome at individual study level and (iv) the pooled mean difference using the inverse variance method. All statistical variables were calculated with 95% confidence intervals (95% CI). The Q-test was used to analyse heterogeneity of trials. When I 2 > 50%, the heterogeneity was considered significant, and the Mantel Haenszel or inverse variance random effects model was used; otherwise, the fixed-effects model was used. We planned to assess publication bias using a funnel plot. Where a pooled analysis was not possible (for instance, for complications), we performed a qualitative synthesis of the reported data. Pooled statistical analyses were performed by SM. Results The initial electronic database searches yielded 65 possible articles, of which 35 remained for consideration after removal of duplicate citations. We manually searched all these articles for potentially eligible trials. We did not find any trials comparing the AuraOnce with the Proseal TM, Supreme TM or LMA flexible TM.We included published prospective human clinical trials where the AuraOnce was compared with the LMA Classic, LMA Unique and Soft Seal. A total of nine articles included one of these comparisons; however, one article was excluded as the study was conducted in children [8]. A flow diagram of study selection is shown in Fig. 1. Five clinical studies [6, 9 12] compared the AuraOnce with the LMA Classic; three studies [13 15] compared the AuraOnce, LMA Unique and Soft Seal; and a further study [16] compared the AuraOnce with the LMA Unique. Our risk of bias assessments are shown in Fig. 2. All the studies included here were randomised and allocation concealment was maintained, but, for obvious technical reasons, all are prone to performance and detection bias. However, in all studies, a blinded observer assessed postoperative outcome. The characteristics of individual studies are given in Table 1. AuraOnce vs LMA Classic Five prospective clinical trials [6, 9 12] compared the AuraOnce with LMA Classic. However, only four of them reported oropharyngeal leak pressure. Only one trial used a neuromuscular blocking agent during the induction of anaesthesia and the device insertion. A pooled analysis of these studies showed a comparable leak pressure between the two devices (245 partici The Association of Anaesthetists of Great Britain and Ireland 1025

4 Baidya Ambu â AuraOnce TM and other LMAs: a meta-analysis [10] did not report time to insert laryngeal mask airway ; rather, they reported ease of insertion, which was also similar in both types of device. Figure 3 depicts the pooled analysis of these comparisons. Reported complications were infrequent, but the incidence of sore throat was significantly lower with the AuraOnce (OR (95% CI) 0.35 ( ), p = 0.02). Figure 2 Risk of bias assessments of the studies. pants, mean (95% CI) difference 0.6 ( 2.5 to 3.7) cmh 2 O, p = 0.56). Sudhir [10], in their crossover study, primarily compared the ease of insertion of the two devices and did not measure the oropharyngeal leak pressure. They mentioned that the pressure required to provide a good seal over 50 insertions was lower with the AuraOnce on 34 insertions, lower with the LMA Classic on 14 insertions and the same for both devices on two insertions. The pressure in the cuff required to achieve a good seal was lower for the AuraOnce than for the LMA Classic (median 18 cmh 2 O vs 27 cmh 2 O, respectively). First-insertion success rate was similar for both devices (463 participants, OR (95% CI) 1.5 ( ); p = 0.18) and time to insert the device was also found to be similar (363 participants, mean (95% CI) difference 0.3 ( 1.5 to 2.0) s, p = 0.77). However, Sudhir AuraOnce vs LMA Unique Four clinical trials [13 16] compared the AuraOnce and the LMA Unique in adults. A pooled analysis from these four trials showed that the AuraOnce provided a higher oropharyngeal leak pressure (304 participants, mean (95% CI) difference 3.1 ( ) cmh 2 O, p < ]. First-insertion success rate was similar between the two devices (304 participants, OR (95% CI) 1.10 ( ), p = 0.75). The time to insert the device was also significantly less with the AuraOnce than the LMA Unique (304 participants, mean (95% CI) difference 5.4 ( ) s, p = 0.001). None of the studies included here used a neuromuscular blocking agent during induction of anaesthesia and all of them followed the standard recommendations for LMA insertion. A pooled analysis of these outcomes is shown in Fig. 4. The reported complications (bloodstaining on the device, dysphagia, sore throat and dysphonia) were uncommon in both groups. Bloodstaining on the device was similar with either type of device (159 participants, OR (95% CI) 1.21 ( ), p = 0.64). The incidence of sore throat was also not different between the two devices (158 participants, OR (95% CI) 0.64 ( ), p = 0.40). (Strydom and Le Roux [15] did not report the actual incidence of sore throat; rather, they reported a severity scoring of sore throat, which was equivalent in either type of device.) AuraOnce vs Soft Seal Three clinical trials [13 15] compared the AuraOnce with the Soft Seal for safety and efficacy. None of the studies used a neuromuscular blocking agent during mask insertion. Pooled analysis showed that the Soft Seal provided a significantly higher oropharyngeal leak pressure than the AuraOnce (229 participants, mean (95% CI) difference 3.5 ( ) cmh 2 O, p = 0.03) The Association of Anaesthetists of Great Britain and Ireland

5 Baidya Ambu â AuraOnce TM and other LMAs: a meta-analysis Anaesthesia 2014, 69, Table 1 Participants, interventions and outcomes studied in the included trials. Study Participants Intervention(s) Outcome(s) Sources of bias Shariffuddin (2008) Gernoth (2006) Sudhir (2007) Ng (2007) Suzanna (2011) Francksen (2007) Lopez (2008) Strydom (2008) Williams (2012) 40 ASA 1 2 patients, aged surgery in supine/ lithotomy position 60 adult patients ambulatory surgery 50 adult patients surgery under GA 105 ASA 1 2 female patients undergoing minor gynaecological surgery 118 ASA 1 2 patients surgery under GA 120 ASA 1 3 patients undergoing minor elective obstetric surgery 200 ASA 1 3 patients ambulatory surgery 115 ASA 1 3 patients surgery 82 ASA 1 4 patients undergoing plastic, urological, orthopaedic or breast surgery Randomised, crossover study comparing AuraOnce with LMA Classic in paralysed anaesthetised patients Prospective randomised study comparing AuraOnce with LMA Classic Randomised, crossover study comparing AuraOnce with LMA Classic; no neuromuscular blockade used Prospective, randomised, single-blind trial comparing AuraOnce and LMA Classic; no neuromuscular blockade used Prospective, randomised controlled trial comparing AuraOnce with LMA Classic in paralysed patients Prospective randomised trial comparing AuraOnce, LMA Unique TM and Soft Seal â in non-paralysed patients Prospective randomised trial comparing AuraOnce, LMA Unique, Soft Seal and Solus Prospective randomised trial comparing efficacy of AuraOnce, Soft Seal, Cobra PLA, LMA Unique and LMA Classic Prospective single-blind randomised controlled trial comparing AuraOnce with LMA Unique in spontaneously breathing patients GA, general anaesthesia; LMA, laryngeal mask airway. Oropharyngeal leak pressure (primary outcome), insertion attempts, insertion time, number of manipulations needed, quality of ventilation, fibreoptic scoring of glottis Leak pressure, insertion time, insertion attempts and complications (bloodstaining, difficulty in swallowing) First-insertion success rate, ease of insertion, cuff volume and pressure required to achieve a good seal, incidence of adverse airway events and presence of blood on the device on removal Insertion time, ease of insertion, leak pressure, first-insertion success, haemodynamic changes on insertion and complications Insertion time, insertion attempt and complications Insertion time, insertion success rate, leak pressure at different cuff volumes, ease of insertion, haemodynamic changes during insertion and complications Time and number of attempts needed for insertion, quality of ventilation, airway sealing pressure at 60 cmh 2 O cuff pressure and complications Ease of insertion, insertion attempt, insertion time, leak pressure, cuff volume, pressure to achieve adequate seal and complications Insertion time, first-insertion success rate, leak pressure, fibreoptic bronchoscopic view of glottis and complications Anaesthesiologists were more experienced with LMA Classic LMA inserted after cervical immobilisation with an extrication collar Cuff volume variable, so actual leak pressure could not be ascertained Unblinded study Cuffs of the LMAs were inflated with a fixed volume of air, rather than adjusting them to a pre-defined cuff pressure All insertions were performed by novice operators with different degrees of experience Data were collected by unblinded investigators, and neither pre-defined sample size nor power was achieved 2014 The Association of Anaesthetists of Great Britain and Ireland 1027

6 Baidya Ambu â AuraOnce TM and other LMAs: a meta-analysis Figure 3 Forest plot for comparison of the AuraOnce with LMA Classic for (top) mean difference in leak pressure, cmh 2 O; (middle) odds ratio of first-insertion success rate and (bottom) mean difference in time to insert, s. First-insertion success rate was similar in the two groups (229 participants, OR (95% CI) 1.53 ( ), p = 0.20). Insertion was significantly faster with the AuraOnce than the Soft Seal (229 participants, mean (95% CI) difference 9.5 ( ) s, p = 0.004). The analyses are shown in Fig. 5. The incidence of sore throat was similar with both devices (177 participants OR (95% CI) 0.38 ( ), p = 0.14), but bloodstaining on the device was significantly less with the AuraOnce (229 participants, OR (95% CI) 0.35 ( ), p = 0.007). Strydom and Le Roux [15] did not report the incidence of hoarseness, dysphagia and dyspnoea; however, the reported severity of these complications in their study was similar. Similarly, the incidences of these complications were also reported to be equal by Francksen [13].) Discussion The principal finding of our meta-analysis is that the AuraOnce provides an oropharyngeal leak pressure higher than with the LMA Unique and equivalent to that of the LMA Classic. However, the Soft Seal provided even better leak pressure than the AuraOnce. We have also found that device insertion is significantly faster with the AuraOnce than with the LMA Unique and Soft Seal and similar to the LMA Classic. First-insertion success rates for the AuraOnce are equivalent to those of all of the other three devices. All reported complications were infrequent, and we found no evidence of a difference between the AuraOnce and the other three devices except for a higher incidence of sore throat with the LMA Classic and more frequent bloodstaining on the device with the Soft Seal The Association of Anaesthetists of Great Britain and Ireland

7 Baidya Ambu â AuraOnce TM and other LMAs: a meta-analysis Anaesthesia 2014, 69, Figure 4 Forest plot for comparison of the AuraOnce with LMA Unique for (top) mean difference in leak pressure, cmh 2 O; (middle) odds ratio of first-insertion success rate and (bottom) mean difference in time to insert, s. The oropharyngeal leak pressure of the laryngeal mask airway LMA reflects the degree of airway protection, the feasibility of positive pressure ventilation and the likelihood of successful supraglottic airway placement. It is the most commonly used measure for quantifying the seal around supraglottic airway devices [17]. It is also regarded as the most important marker of the safety of such devices [18]. Thus, we may conclude that the AuraOnce may be at least as effective as the LMA Unique and the LMA Classic. The deeper bowl and broader tube of the Soft Seal may improve the seal, due to a tighter fit in the posterior upper pharynx, as mentioned by Lopez [14]. The AuraOnce has been used during both spontaneous ventilation and controlled ventilation. Insertion is faster with the AuraOnce than the LMA Unique and Soft Seal, which may make it particularly effective in emergency situations such as failure to intubate and ventilate. We did not find any statistical difference with the LMA Classic in terms of insertion time. However, as different authors reported the time to insert the devices in different ways, there may be some doubt about the validity of trying to combine different studies within this outcome. We did not assess ease of insertion in this review, but insertion time may be considered a possible surrogate for ease of insertion. There are reports [6, 11] in which the authors mentioned that the AuraOnce is easier to insert. The different materials of manufacture may be responsible for this ease of insertion, as well as the difference in shape between the two laryngeal devices [10]. The pre-formed airway tube and 90 angulation between the cuff and the tube may explain ease of insertion. Lopez [14] suggested that the bulkier airway tube and cuff of the Soft Seal may be responsible for its slower insertion; however, these 2014 The Association of Anaesthetists of Great Britain and Ireland 1029

8 Baidya Ambu â AuraOnce TM and other LMAs: a meta-analysis Figure 5 Forest plot for comparison of the AuraOnce with Soft Seal for (top) mean difference in leak pressure, cmh 2 O; (middle) odds ratio of first-insertion success rate and (bottom) mean difference in time to insert, s. may be precisely the features of the Soft Seal that allow its higher leak pressure also. The faster insertion of the AuraOnce may make it an attractive choice in situations where rapid airway control is desirable; it may also be easier to insert when the patient s neck is immobilised [9]. Lastly, it should be remembered that success of LMA insertion may also depend upon the technique; Choo found that the first-insertion success rate of the LMA Flexible TM was higher when it was inserted with the laryngoscope as a guide [19]. Hagberg [5] evaluated the efficacy of the AuraOnce in different head positions and found no difference in ventilatory efficacy. However, none of the studies included here evaluated the AuraOnce in any patient position other than supine. So, at this moment, it is not possible comment on its comparative efficacy in other patient positions. Although a single prospective multicentre study [5] in 2005 concluded that the AuraOnce is associated with a lower incidence of postoperative sore throat, dysphagia and dysphonia, our review does not support this notion. However, that study was not a randomised controlled trial and no direct comparison was made. The rationale of selecting the AuraOnce in this systematic review is that it is a single-use device and may be easier to insert because of its unique design. The clinical importance of our findings is that we can at least use the AuraOnce where we might use the LMA Classic or the LMA Unique as an airway management device. A difference of leak pressure of about 3 cmh 2 O may not be significant in a patient who is not obese, with normal respiratory compliance, but may become more relevant when the devices are used for emergency airway rescue in patients at risk of regurgitation and aspiration. The most important limitation of our meta-analysis is the inclusion of a relatively small number of trials. Further, some of the included trials reported a The Association of Anaesthetists of Great Britain and Ireland

9 Baidya Ambu â AuraOnce TM and other LMAs: a meta-analysis Anaesthesia 2014, 69, wide range of standard deviation, which may raise questions about the quality of the data. Oropharyngeal leak pressure, which is one of the most important outcomes here, can vary according to the methods of measurement (e.g. palpable vs audible leak) [20]. The use of a neuromuscular blocker may also change oropharyngeal leak pressure, but the small number of trials using these agents precluded the possibility of a subgroup analysis. Time to insert the device and firstinsertion success rate are always operator-dependent; hence, the possibility of biases always exists. The Aura- Once is a relatively new product, so the anaesthesiologists may have been less experienced with it than with other devices. For obvious technical reasons, all the trials are prone to performance bias. We neither asked the authors for unpublished data nor searched for ongoing trials; publication of such trials in the near future may alter these findings. All the trials included here were primarily aimed at the efficacy of the device; the incidence of complications is generally low, so a comparison of complications is of limited utility. Lastly, all the trials studied patients with normal, or at least apparently normal, airways; it is thus not possible to comment directly on their efficacy in difficult airways. Nevertheless, we conclude that the AuraOnce is similarly effective as the LMA Unique and LMA Classic and may be easier to insert than the other two devices. The Soft Seal may provide a higher leak pressure, but is more difficult to insert. Competing interests No external funding or competing interests declared. References 1. van Zundert TC, Brimacombe JR, Ferson DZ, Bacon DR, Wilkinson DJ. Archie Brain: celebrating 30 years of development in laryngeal mask airways. Anaesthesia 2012; 67: Antloga K, Meszaros J, Malchesky PS, McDonnell GE. Prion disease and medical devices. ASAIO Journal 2000; 46: S Clery G, Brimacombe J, Stone T, Keller C, Curtis S. Routine cleaning and autoclaving does not remove protein deposits from reusable laryngeal mask devices. Anesthesia and Analgesia 2003; 97: Bell SF, Morris NG, Rao A, Wilkes AR, Goodwin N. A randomised crossover trial comparing a single-use polyvinyl chloride laryngeal mask airway with a single-use silicone laryngeal mask airway. Anaesthesia 2012; 67: Hagberg CA, Jensen FS, Genzwuerker HV, A multicenter study of the Ambu laryngeal mask in nonparalyzed, anesthetized patients. Anesthesia and Analgesia 2005; 101: Shariffuddin II, Wang CY. Randomised crossover comparison of the Ambu AuraOnce laryngeal mask with the LMA Classic laryngeal mask airway in paralysed anaesthetised patients. Anaesthesia 2008; 63: Hozo SP, Djulbegovic B, Hozo I. Estimating the mean and variance from the median, range, and the size of a sample. BMC Medical Research Methodology 2005; 5: Baker PA, Brunette KE, Byrnes CA, Thompson JM. A prospective randomized trial comparing supraglottic airways for flexible bronchoscopy in children. Pediatric Anesthesia 2010; 20: Gernoth C, Jandewerth O, Contzen M, Hinkelbein J, Genzw urker H. Comparison of two different laryngeal mask models for airway management in patients with immobilization of the cervical spine. Der Anaesthesist 2006; 55: Sudhir G, Redfern D, Hall JE, Wilkes AR, Cann C. A comparison of the disposable Ambu AuraOnce Laryngeal Mask with the reusable LMA Classic laryngeal mask airway. Anaesthesia 2007; 62: Ng SY, Teoh WHL, Lim Y, Cheong VG. Comparison of the AMBU â Laryngeal Mask and the LMA Classic in anesthetized, spontaneously breathing patients. Anaesthesia and Intensive Care 2007; 35: Suzanna AB, Liu CY, Rozaidi SW, Ooi JS. Comparison between LMA-Classic and AMBU Aura Once laryngeal mask airway in patients general anaesthesia with positive pressure ventilation. Medical Journal of Malaysia 2011; 66: Francksen H, Bein B, Cavus E, Comparison of LMA Unique, Ambu laryngeal mask and Soft Seal laryngeal mask during routine surgical procedures. European Journal of Anaesthesiology 2007; 24: Lopez AM, Valero R, Bovaira P, Pons M, Sala-Blanch X, Anglada T. A clinical evaluation of four disposable laryngeal masks in adult patients. Journal of Clinical Anesthesia 2008; 20: Strydom CS, Le Roux PJ. A clinical comparison of disposable airway devices. Southern African Journal of Anaesthesia and Analgesia 2008; 14: Williams DL, Zeng JM, Alexander KD, Andrews DT. Randomised comparison of the AMBU AuraOnce laryngeal mask and the LMA Unique laryngeal mask Airway in spontaneously breathing adults. Anesthesiology Research and Practice 2012; 2012: Keller C, Brimacombe JR, Keller K, Morris R. Comparison of four methods for assessing airway sealing pressure with the laryngeal mask airway in adult patients. British Journal of Anaesthesia 1999; 82: Bele~na JM, Nu~nez M, Anta D, Comparison of Laryngeal Mask Airway Supreme and Laryngeal Mask Airway Proseal with respect to oropharyngeal leak pressure during laparoscopic cholecystectomy: a randomised controlled trial. European Journal of Anaesthesiology 2013; 30: Choo CY, Koay CK, Yoong CS. A randomised controlled trial comparing two insertion techniques for the Laryngeal Mask Airway Flexible TM in patients undergoing dental surgery. Anaesthesia 2012; 67: Maitra S, Khanna P, Baidya DK. Comparison of LMA Supreme and LMA Pro-Seal for controlled ventilation during general anaesthesia in adult patients: a meta-analysis. European Journal of Anaesthesiology 2014; 31: The Association of Anaesthetists of Great Britain and Ireland 1031

10 Baidya Ambu â AuraOnce TM and other LMAs: a meta-analysis Appendix 1 Search string Ambu[All Fields] AND ( laryngeal masks [MeSH Terms] OR ( laryngeal [All Fields] AND masks [All Fields]) OR laryngeal masks [All Fields] OR ( laryngeal [All Fields] AND mask [All Fields] AND airway [All Fields]) OR laryngeal mask airway [All Fields]) ambu[all Fields] AND lma[all Fields] Ambu[All Fields] AND AuraOnce[All Fields] The Association of Anaesthetists of Great Britain and Ireland