Comparison of the Baska â mask with the single-use laryngeal mask airway in low-risk female patients undergoing ambulatory surgery

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1 Original Article doi: /anae Comparison of the Baska â mask with the single-use laryngeal mask airway in low-risk female patients undergoing ambulatory surgery V. Alexiev, 1 A. Ochana, 2 D. Abdelrahman, 3 J. Coyne, 3 J. G. McDonnell, 4 D. P. O Toole, 4 P. Neligan 4 and J. G. Laffey 5 1 Clinical Lecturer and Clinical Tutor, 2 Specialist Registrar, 3 Registrar, 4 Consultant and Senior Clinical Lecturer, Department of Anaesthesia, Galway University Hospitals and National University of Ireland, Galway, Ireland 5 Professor, Department of Anesthesia, St Michael s Hospital and University of Toronto, Toronto, Ontario, Canada Summary We compared the Baska â mask with the single-use classic laryngeal mask airway (clma) in 150 females at low risk for difficult tracheal intubation in a randomised, controlled clinical trial. We found that median (IQR [range]) seal pressure was significantly higher with the Baska mask compared with the clma (40 (34 40 [16 40]) vs 22 (18 25 [14 40]) cmh 2 O, respectively, p < 0.001), indicating a better seal. In contrast, the first time success rate for insertion of the Baska mask was lower than that seen with the clma (52/71 (73%) vs 77/99 (98%), respectively, p < 0.001). There were no differences in overall device insertion success rates (78/79 (99%) vs 68/71 (96%), respectively, p = 0.54). The Baska mask proved more difficult to insert, requiring more insertion attempts, taking longer to insert and had higher median (IQR [range]) insertion difficulty scores (1.6 ( [ ]) vs 0.5 ( [ ]), respectively, p < 0.001). There was also an increased rate of minor blood staining of the Baska mask after removal, but there were no differences in other complication rates, such as laryngospasm, or in the severity of throat discomfort. In conclusion, in clinical situations where the seal with the glottic aperture takes priority over ease of insertion, the Baska mask may provide a useful alternative to the clma.... Correspondence to: J. G. Laffey laffeyj@smh.ca Accepted: 1 June 2013 The Baska â mask (Logikal Health Products PTY Ltd., Morisset, NSW, Australia) is a novel supraglottic airway device with a non-inflatable cuff, an oesophageal drainage inlet and side channels to facilitate aspiration of gastric contents, and an integrated bite-block [1]. The Baska mask comes in four sizes, ranging from paediatric to adult [2]. We have recently reported an initial case series using the Baska mask [1]. We found an overall device insertion success rate of > 96%, although the success rates for the first insertion attempt was lower at 77%. The device appeared relatively easy to insert, provided a high-quality seal with the glottic aperture and the incidence of throat discomfort appeared low. However, the utility of the Baska mask has not been demonstrated to date in a comparative trial [3]. Consequently, the purpose of this study was to compare the utility of the Baska mask with the single-use classic laryngeal mask airway (clma) (Integral Medical Products, Zhejiang, China) in female patients at The Association of Anaesthetists of Great Britain and Ireland

2 Alexiev et al. Baska mask vs LMA in females Anaesthesia 2013, 68, low risk for difficult tracheal intubation undergoing ambulatory surgery. We hypothesised that the Baska mask would: (a) have a better seal with the glottic aperture, as reflected by a greater seal pressure compared with the clma device; and (b) have a first time insertion success rate that was not inferior to that seen with the single-use clma device. Methods After obtaining approval from the Galway University Hospitals Research Ethics Committee and written informed patient consent, we recruited 150 women of ASA physical status 1 3, years of age, who were deemed on pre-operative assessment by their primary anaesthetist to be at low risk for gastric aspiration. Other inclusion criteria included BMI 35 kg.m 2 and non-urgent surgery of planned duration < 4 h. Exclusion criteria included patient refusal or inability to give informed consent, patients with neck pathology, previous or anticipated problems with the upper airway or the upper gastrointerstinal tract, live pregnancy and patients at increased risk of gastric aspiration. All patients received a standardised general anaesthetic [4, 5]. Standard monitoring, including ECG, blood pressure, pulse oximetry, end-tidal carbon dioxide and volatile anaesthetic levels, was used [6]. Before induction of anaesthesia, patients were given fentanyl or remifentanil (1 1.5 l.kg 1 ) intravenously. Propofol (2 4 mg.kg 1 ) was titrated to induce anaesthesia following which all patients underwent manual ventilation with sevoflurane ( %) or desflurane ( %) in oxygen. The depth of anaesthesia was increased via additional propofol increments where necessary to produce sufficient jaw relaxation to permit insertion of the supraglottic airway. All device insertions were performed by one of four investigators (VA, AO, JMcD and JC). Each had received training in insertion of the Baska mask and had performed > 30 insertions, and > 100 prior insertions of the clma. A maximum of three attempts at Baska or clma mask placement were permitted per patient. The size of the Baska mask and clma was chosen based on the patients ideal body weight, based on the manufacturers instructions for each device (size 3 for patients < 50 kg, size 4 for patients kg and size 5 for patients > 70 kg) [2]. If the device did not function effectively, the following manipulations were performed in sequence: the depth of insertion was increased; the device was rotated, the device was withdrawn slightly. If these manoeuvres were unsuccessful in achieving an effective airway, the device was removed. If the problem was predominantly due to a large leak, a device one size larger was re-inserted. If the device size was deemed too large, a smaller sized device was inserted. If insertion failed after three attempts, the alternative supraglottic airway was inserted. If this failed, tracheal intubation was performed. Thereafter, in all patients, the lungs were mechanically ventilated until spontaneous ventilation supervened. Anaesthesia was maintained with sevoflurane or desflurane in a mixture of oxygen and air or N 2 O. In patients in whom the clma was placed, the cuff pressure was checked using a hand-held pressure gauge (Tyco Healthcare, Hampshire, UK), and adjusted if necessary to keep cuff pressure < 60 cmh 2 O [7]. Further management was left to the discretion of the anaesthetist providing care for the patient. All data were collected by an unblinded observer. There were two primary outcomes, reflecting our two hypotheses, namely the seal pressure created by the supraglottic device, and the rates of first time successful placement of the supraglottic device. A seal pressure test was performed as previously described [8, 9]. Briefly, while the patient was apnoeic, and following confirmation of adequate ventilation, the adjustable pressure limit valve was set at 70 cmh 2 O, the fresh gas flow was set at 6 l.min 1, and the airway pressure was measured on the breathing system pressure gauge. Leak pressure was defined as the plateau airway pressure that was achieved. In patients in whom the airway pressure reached 40 cmh 2 O, the leak test was interrupted and a value of 40 cmh 2 O was recorded. Secondary outcomes included the duration of a device insertion attempt, which was defined as the time from the moment the device was taken up by the operator until satisfactory ventilation (bilateral chest expansion and end-tidal CO 2 with plateau) was achieved or the device was removed [10, 11]. Successful placement was defined as the presence of bilateral chest expansion, a satisfactory end-tidal CO 2 tracing with plateau and an estimated leak fraction of less 2013 The Association of Anaesthetists of Great Britain and Ireland 1027

3 Alexiev et al. Baska mask vs LMA in females than a third of the inspired tidal volume [12, 13]. We recorded the number and duration of device insertion attempts, a 10-point visual analogue difficulty scale, and the need for device manipulations to optimise positioning. We monitored the patients for the following complications: arterial oxygen desaturation; lip damage; blood staining on mask removal; and laryngospasm [10, 11]. We evaluated the incidence and severity of throat pain, dysphagia, dysphonia and heartburn at arrival and discharge from the recovery unit and on the first and third postoperative day using a 10-point verbal rating scale (VRS). In addition, we followed up patients regarding incidence and severity of nausea and vomiting during the operative day and on the first postoperative day. We carried out two separate sample size calculations, one for each of our hypotheses. To test the first hypothesis, we considered that a seal pressure with the Baska mask of 20% greater than that of the clma would be a clinically important difference. In previous studies [8, 9, 12, 13], the clma has demonstrated leak pressures of ~20 cmh 2 O, with SD 10 cmh 2 O. With a type-1 error of 0.05 and a power of 80%, we calculated that the sample size required would be 50 in each group, or 100 in total, based on a parallel group study design. We further hypothesised that the Baska mask would have a first insertion attempt success rate that is not inferior to the single-use clma. We defined inferior for the purposes of this study as a success rate of 15% lower than that seen with the clma. The first time success rate with clma has been reported to be as high as 97% [14]. With a type-1 error of 0.05 and a power of 80%, we calculated that a sample size of 121 would be required in each group, or 242 in total, based on a parallel group study design. Given these differing sample size calculations, and to minimise the potential for data loss, we aimed to enrol 125 patients per group, for a total of 250 patients. We decided a priori to perform an interim analysis once 150 patients had been recruited, with the aim of stopping the study following at the interim analysis if the second primary hypothesis was disproven with a p value < Data for continuous variables (e.g. duration of insertion attempts and leak pressure) were analysed using the t-test or the rank-sum test depending on data distribution. Data were analysed on an intention-to-treat basis. Categorical data were analysed with rank-sum test or chi-squared testing as appropriate. The a level for all analyses was set at p < Results The study was stopped after 150 patients were recruited as the stopping criteria were fulfilled (Fig. 1). There were no between-group differences with regard to patients characteristics or data regarding airway assessment in the patients enrolled in the study (Table 1). The majority of patients were undergoing ambulatory gynaecological surgery, with the remainder undergoing breast surgery or other minor procedures. The seal pressure achieved with the Baska mask was significantly greater than with the clma, indicating a better seal with the glottic aperture (Fig. 2). These values are not affected by obstruction at the glottis as the inspiratory volumes and peak pressures were similar between the groups (Table 2). In contrast, the first time success rate for the insertion of the Baska mask was significantly lower than that for the clma: 52/71 (73%) vs 77/79 (98%), respectively, p < (Fig. 3). Of interest, the overall success rates were not significantly different, with three failures with the Baska mask compared with one with the clma (Fig. 3). The Baska mask proved more difficult to insert compared with the clma. The duration of the first mask insertion attempt (Fig. 4), the number of insertion attempts required (Fig. 3), the number of additional optimisation manoeuvres (Table 2) and the difficulty of device use score (Fig. 5) were all significantly higher with the Baska compared with the clma. More patients required additional increments of propofol to permit insertion of the Baska compared with the clma (38% vs 14%, respectively, p < 0.001), resulting in a significantly greater overall propofol requirement with the Baska (Table 1). Furthermore, a greater number of patients required additional manoeuvres to position the Baska mask correctly compared with the clma (65% vs 4%, respectively, p < 0.001). There were no haemodynamic differences between the groups pre- or post-insertion of the masks (data not shown). There was a greater incidence of minor blood staining on the Baska mask after removal (Table 2). However, there were no differences in the The Association of Anaesthetists of Great Britain and Ireland

4 Alexiev et al. Baska mask vs LMA in females Anaesthesia 2013, 68, Consort Flowchart Assessed for eligibility (n = 173) Patients excluded (n = 23) Not meeting inclusion criteria (n = 8) Enrollment Randomised (n = 150) Refused to participate (n = 4) Other reasons (n = 11) - Surgery cancelled (n = 3) - Change of Surgical procedure (n = 5) - Investigators unavailable (n = 3) Group - Baska Group - clma Allocated to intervention Received allocated intervention Did not receive allocated intervention (n = 0) Allocation Allocated to intervention (n = 79) Received allocated intervention (n = 79) Did not receive allocated intervention (n = 0) Lost to follow-up (n = 0) Discontinued intervention (n = 3) Reason: 3 device insertion failures; clma substituted Follow-Up Lost to follow-up (n = 0) Discontinued intervention (n = 1) Reason: 1 device insertion failure; Baska substituted Analysed Excluded from analysis (n = 0) Analysis Analysed (n = 79) Excluded from analysis (n = 0) Figure 1 Consort diagram for study. incidence of laryngospasm (Table 2), or in the severity of throat pain, dysphagia or dysphonia on emergence, at discharge from the recovery unit and on postoperative days 1 and 3 (data not shown). Discussion Our main result is that the Baska mask provides a better seal with the glottis aperture compared with the clma. However, the Baska mask proved to be more difficult to insert than the clma device, with lower first time insertion success rates, longer insertion times and higher user-rated device difficulty scores, in this population of low-risk females undergoing ambulatory surgery. There was also an increased rate of minor blood staining of the Baska mask after removal at the end of the surgery. There were no differences in other complication rates, such as laryngospasm, or in the severity of throat pain, dysphagia, dysphonia or heartburn on emergence or up to three days postoperatively with the Baska mask compared with the clma. Our findings regarding the insertion success rates for the Baska mask in this randomised controlled clinical trial compare well with those reported in our preliminary observational study [1]. We found a first time insertion success rate of 77% (95% CI 58 90%) in the earlier report, similar to the success rate of 73% (95% CI 61 83%) in the current study. The overall success rates for the Baska mask of 97% (95% CI %) in the previous report compare well the overall success rate of 96% (95% CI 88 99%) in this study. These findings confirm the suggestion made in an editorial that accompanied our previous paper that the utility of observational studies in providing good estimates depends upon their sample size [3] The Association of Anaesthetists of Great Britain and Ireland 1029

5 Alexiev et al. Baska mask vs LMA in females Table 1 Patients characteristics and anaesthesia data. Values are mean (SD), median (IQR [range]) or number (proportion). Baska clma (n = 79) Age; years 46.9 (12.7) 45.1 (13.7) Body mass index; kg.m (4.5) 25.7 (4.0) ASA classification 1 (1 2 [1 3]) 1 (1 2 [1 3]) Airway measurements Thyromental distance; cm 7.9 (1.4) 8.2 (1.4) Inter-incisor distance; cm 4.7 (1) 4.6 (1) Mallampatti classification 1 49 (69%) 44 (56%) 2 22 (31%) 31 (39%) (5%) Summary score 1 (1 2 [1 2]) 1 (1 2 [1 3]) Type of surgery Gynaecologic non-laparoscopic 29 (41%) 35 (44%) Gynaecologic laparoscopic 21 (30%) 16 (20%) Breast 19 (27%) 23 (29%) Other 2 (3%) 5 (6%) Anaesthesia Fentanyl dose; l.kg ( [ ]) 1.4 ( [ ]) Induction propofol dose; mg.kg ( [ ]) 2.8 ( [ ]) Total propofol administered; mg.kg ( [ ]) 2.9 ( [ ]) End-tidal volatile; MAC equivalents 2.4 ( [ ]) 1.8 ( [ ]) Duration of procedure; min Anaesthesia 34 (19 50 [8 183]) 34 (22 55 [11 142]) Surgery 28 (15 45 [6 164]) 28 (18 45 [6 134]) Controlled ventilation 32 (18 48 [7 152]) 30 (18 49 [7 137]) We confirm some of the difficulties described with insertion of the Baska mask in our earlier report [1]. These include the fact that very precise positioning of the cuff orifice against the glottis is necessary to ensure optimal ventilation. Adjustment of the depth of insertion of the mask may be required to minimise leaks. However, when correctly positioned, the seal is superior to that achieved with the clma, and this is clearly evidenced by the consistently higher seal pressures with the Baska mask compared with the clma. This is a potential advantage in situations where there is some concern that leakage of gastric contents may occur, such as during laparoscopy, but that contention remains to be tested in separate studies. A second issue is the fact that the optimal approach to sizing the Baska mask remains unclear. We used the manufacturer-recommended approach to size the mask based on patients weight. Most of the patients in whom the initial insertion attempt was not successful required a different usually larger sized Baska mask to be inserted. It is reassuring that the overall success rates for both masks were not different, Figure 2 Seal pressures achieved with the Baska mask and clma. The bottom and top of the box are the first and third quartiles, the band inside the box is the median value, the whiskers represent the 10th percentile and the 90th percentile, and the black dots represent outliers. For the Baska mask, the median and the 3rd quartile are superimposed. p < with mask insertion attempt proving ultimately unsuccessful in one patient who received a clma and three patients who received a Baska mask The Association of Anaesthetists of Great Britain and Ireland

6 Alexiev et al. Baska mask vs LMA in females Anaesthesia 2013, 68, Table 2 Data regarding insertion of the supraglottic airway. Data are number (proportion), median (IQR [range]) or mean (SD). Baska clma (n = 79) p values Success rate on first insertion attempt 52 (73%) 77 (98%) < Overall success rate 68 (96%) 78 (99%) 0.54 Number of insertion attempts 1 52 (73%) 77 (98%) (21%) 1 (1%) 3 4 (6%) 1 (1%) Summary data 1 (1 2 [1 3]) 1 (1 1 [1 3]) Number of additional manoeuvres 0 25 (35%) 76 (96%) < (39%) 2 (2.5%) 2 9 (13%) (13%) 1 (1.5%) Summary data 1 ( [0 3]) 0 (0 0 [0 3]) Size of mask inserted successfully (8%) 4 34 (50%) 70 (89%) 5 34 (50%) 2 (3%) Ventilatory variables Peak airway pressure; cm H 2 O 15.9 (4.1) 14.7 (3.2) 0.04 Inspiratory volume; ml 448 (31) 454 (38) 0.27 Leak volume; ml 19 (17) 16 (13) 0.25 Arterial oxygen saturation during attempt; % Lowest value 99.1 (0.8) 99.0 (0.7) 0.63 Number of patients with SaO 2 < 95% 0 0 Need to reposition mask intraoperatively 2 (3%) 1 (1%) 0.52 Laryngospasm on emergence from anaesthesia 1 (1%) 3 (4%) 0.79 Bloodstaining on mask at removal 13 (18%) 5 (6%) This study has some limitations. The investigators who inserted the masks had more experience with using the clma. However, all had received prior training with the Baska mask, and all had inserted at least 30 Baska masks before the study, which we have previously shown to be necessary to achieve an initial level of competence with the device [1]. The study was restricted to adult females to reduce variability, particularly with regard to the size of the Baska mask required. The study was not double blinded, so investigator bias, particularly with regard to the user-reported difficulty scores, was possible. We stopped the study early, following a planned interim analysis, as it was clear that the first time success rates with the Baska were significantly lower, and the seal pressures significantly higher, compared with the clma. In conclusion, the Baska mask provides a better seal with the glottic aperture, but is more difficult to insert than the clma in this population. There may be different clinical situations when either seal pressure Figure 3 Proportion of patients who required 1 insertion attempt ( ), 2 insertion attempts ( ) 3 insertion attempts ( ) and who did not have a successful mask placement ( ) with the Baska mask and the clma. The first time success rate was significantly greater (p < 0.001) with the clma compared with the Baska mask, but the overall success rates were similar with both masks The Association of Anaesthetists of Great Britain and Ireland 1031

7 Alexiev et al. Baska mask vs LMA in females study. All other resources came from departmental funds. Competing interests No other funding or competing interests declared. Figure 4 Duration of insertion attempts for the Baska mask and the clma. The bottom and top of the box are the first and third quartiles, and the band inside the box is the median value, the whiskers represent the 10th percentile and the 90th percentile, and the black dots represent outliers. p < Figure 5 User-rated difficulty score for the Baska mask and clma. The bottom and top of the box are the first and third quartiles, and the band inside the box is the median value, the whiskers represent the 10th percentile and the 90th percentile, and the black dots represent outliers. p < or first time insertion success is the more important, and this information helps practitioners to use the device most appropriate for the scenario. Acknowledgements The Baska masks were provided free of charge by Pro- Act Medical, UK. Neither the inventor nor the supplier of the Baska mask had contributed input to the design, execution or interpretation of the findings of this References 1. Alexiev V, Salim A, Kevin LG, Laffey JG. An observational study of the Baska â mask: a novel supraglottic airway. Anaesthesia 2012; 67: Baska â Mask Instructions for use. attachments/docmp0710rev4.pdf (accessed 16/12/2011). 3. Pandit JJ. If it hasn t failed, does it work? On the worst we can expect from observational trial results, with reference to airway management devices. Anaesthesia 2012; 67: Maharaj CH, Costello JF, Harte BH, Laffey JG. Evaluation of the Airtraq and Macintosh laryngoscopes in patients at increased risk for difficult tracheal intubation. Anaesthesia 2008; 63: Maharaj CH, O Croinin D, Curley G, Harte BH, Laffey JG. A comparison of tracheal intubation using the Airtraq or the Macintosh laryngoscope in routine airway management: a randomised, controlled clinical trial. Anaesthesia 2006; 61: McElwain J, Malik MA, Harte BH, Flynn NH, Laffey JG. Determination of the optimal stylet strategy for the C-MAC videolaryngoscope. Anaesthesia 2010; 65: Keller C, Puhringer F, Brimacombe JR. Influence of cuff volume on oropharyngeal leak pressure and fibreoptic position with the laryngeal mask airway. British Journal of Anaesthesia 1998; 81: Shin WJ, Cheong YS, Yang HS, Nishiyama T. The supraglottic airway I-gel in comparison with ProSeal laryngeal mask airway and classic laryngeal mask airway in anaesthetized patients. European Journal of Anaesthesiology 2010; 27: Uppal V, Gangaiah S, Fletcher G, Kinsella J. Randomized crossover comparison between the i-gel and the LMA-Unique in anaesthetized, paralysed adults. British Journal of Anaesthesia 2009; 103: Malik MA, Maharaj CH, Harte BH, Laffey JG. Comparison of Macintosh, Truview EVO2, Glidescope, and Airwayscope laryngoscope use in patients with cervical spine immobilization. British Journal of Anaesthesia 2008; 101: Malik MA, Subramaniam R, Churasia S, Maharaj CH, Harte BH, Laffey JG. Tracheal intubation in patients with cervical spine immobilization: a comparison of the Airwayscope, LMA CTrach, and the Macintosh laryngoscopes. British Journal of Anaesthesia 2009; 102: Francksen H, Renner J, Hanss R, Scholz J, Doerges V, Bein B. A comparison of the i-gel with the LMA-Unique in non-paralysed anaesthetised adult patients. Anaesthesia 2009; 64: Janakiraman C, Chethan DB, Wilkes AR, Stacey MR, Goodwin N. A randomised crossover trial comparing the i-gel supraglottic airway and classic laryngeal mask airway. Anaesthesia 2009; 64: Brimacombe JR, Brimacombe JC, Berry AM, et al. A comparison of the laryngeal mask airway and cuffed oropharyngeal airway in anesthetized adult patients. Anesthesia and Analgesia 1998; 87: The Association of Anaesthetists of Great Britain and Ireland