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Effectiveness of the Baska mask versus the i-gel device in adult patients under general anesthesia: a systematic review protocol

Han, Qiaoyu; Sun, Liang; Liang, Hansheng; Feng, Yi

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doi: 10.11124/JBIES-20-00045
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As the gold standard method for manipulating airway during general anesthesia, endotracheal intubation requires training and practice, and carries a high risk of laryngopharyngeal problems. Supraglottic airway devices (SADs), first introduced in 1981,1 have emerged as widely used tools for airway management in patients undergoing various surgical procedures under general anesthesia and in emergency medicine,2 providing an alternative to endotracheal intubation.

Several lines of evidence suggest that the use of SADs has skyrocketed in the past decade because of its various advantages over endotracheal tube, including noninvasiveness, easiness to insert, rapidity, stable hemodynamics, low rate of postoperative complications, and reduced autonomic imbalance during insertion.3-7

However, SADs are not without complications. Common device-related complications include aspiration, trauma of the airway (from the lips to laryngeal apparatus), compression of the surrounding nerves, mucosal bruising from prolonged insertion or high cuff pressures, loss of airway on insertion, failed insertion, or displaced device.8

Thus far, SADs are broadly divided into two generations. The first-generation SADs, such as the classic laryngeal mask airway (LMA Classic, Teleflex, Ireland), only have ventilation lumen and provide a moderate pharyngeal seal (less than 20 cm H2O). These devices have several limitations that may be associated with regurgitation, pulmonary aspiration, and poor ventilation.8-10 However, the second-generation SADs provide greater pharyngeal seal pressures (around 28 cm H2O).11 They add a separate esophageal lumen for drainage of the gastric contents, thereby reducing the risk of aspiration.

Currently, the Baska mask (Baska Versatile Laryngeal Mask Pty Ltd, Sydney, Australia) and i-gel device (Intersurgical Ltd, Berkshire, United Kingdom) are the two commonly used second-generation SADs in anesthetic settings. They are both equipped with a non-inflatable cuff, gastric drainage inlet, and integrated bite-block.12,13 The non-inflatable cuff of the Baska mask, which is continuous with the central channel of the device, is molded to take the shape of the supraglottic airway. Because it does not require laryngoscopy to insert and is devoid of a cuff, the Baska mask potentially reduces the risk of oropharyngeal tissue and nerve damage caused by cuff overinflation.7,14 The cuff of the i-gel is made of medical-grade thermoplastic elastomer (styrene ethylene butadiene styrene), which provides thermal adaptation to the airway; there is no need to inflate it or adjust its pressure.14 Accordingly, the cuff of the i-gel can provide an anatomical seal with appropriate pressure. For this reason, i-gel has potential advantages including easier insertion, minimal risk of compression trauma, simplicity to manufacture, and decreased cost.15 The Baska mask has a pharyngeal drainage sump reservoir on the dorsal surface of its cuff that drains into the bilateral suction channels.13 Similarly, i-gel has an esophageal vent through which a gastric tube can be passed.15 The presence of a gastric drainage inlet may lower the risk of pulmonary aspiration of secretions or gastric contents accumulated in the supraglottic area. In addition, the integrated bite-block reduces the incidence of patients’ biting and blocking the airway.14

An ideal SAD should be easy to insert, provide appropriate airway seal pressure, and produce minimum laryngopharyngeal morbidity. The efficacy and safety of SADs are crucial to their clinical applications. To date, there is a vast array of studies comparing the clinical performance and safety of i-gel to other SADs; however, there is only limited literature comparing various parameters between the i-gel and the Baska mask, as the Bask mask is relatively new. These two SADs are being used more widely in clinical settings. Accordingly, it is necessary to compare the efficacy and safety between them. Therefore, the current study aims to compare specified parameters of clinical performance between these two SADs by performing a systematic review and meta-analysis.

A preliminary search of MEDLINE, Embase, the Cochrane Library, Web of Science, and the JBI Database of Systematic Reviews and Implementation Reports was conducted, and no current or underway systematic review protocols or review reports on the topic were identified.

The object of this review is to perform a meta-analysis and systematic review to evaluate the ease of use, effectiveness of airway management, and the incidence of perioperative complications of Baska mask compared with the i-gel device. The authors aim to provide robust evidence for airway management and highlight SAD-associated complications in clinical settings.

Review question

What are the differences between the Baska mask and the i-gel device with regard to clinical performance, such as the ease of use, effectiveness of airway management, and the incidence of perioperative complications?

Inclusion criteria


This review will consider studies that include adult surgical patients, 18 years and over, who received general anesthesia for elective surgeries. General anesthesia refers to surgical procedures maintained with general anesthetic drugs and SADs are indicated. Elective surgeries refer to non-emergency surgery.


This review will consider studies that evaluate the clinical performance of the Baska mask in adult surgical patients who received general anesthesia for elective surgery.


This review will consider studies that compared the intervention to the clinical performance of the i-gel in adult surgical patients who received general anesthesia for elective surgery.


This review will consider studies that include one or more of the following outcomes: oropharyngeal leak pressure, duration of device insertion, success rates of insertion, number of insertion attempts, ease of device and gastric tube insertion, incidence of laryngopharyngeal morbidity, and other adverse effects in the short term (within 24 hours) after surgery. The oropharyngeal leak pressure is defined as the pressure at which a leak starts, measured by the following steps: the adjustable pressure limit valve set at 40 cm to 70 cm H2O, the fresh gas flow set at 3 to 6 L/minute, and the airway pressure measured on the breathing system pressure gauge. Leak pressure is considered as the achieved plateau airway pressure when the patient was apneic. The insertion duration is measured with a chronometer, from the time the device is picked up by the operator until the first end-tidal carbon dioxide (ETCO2) waveform is obtained. The ease of device insertion is classified according to the following criteria: very easy: insertion at first attempt without any tactile resistance; easy: insertion at first attempt with tactile resistance; difficult: insertion successful at second attempt; or very difficult: insertion failed at second attempt.16 The ease of gastric tube insertion is evaluated using a three-point scale: 1 = easy, 2 = difficult, and 3 = impossible.17 Laryngopharyngeal morbidity includes sore throat, dysphagia, and dysphonia. Other adverse effects include cough, postoperative nausea and vomiting, and trauma to the tongue, lips, teeth, or palate.

Types of studies

Randomized control trials (RCTs) that focus on the comparison of Baska mask and i-gel in patients undergoing elective procedures will be included. This review will be limited to RCTs. Only studies available in English or English translation will be included. If appropriate studies are not available in English, the author(s) will be contacted to seek an English translation. There will be no date restriction on studies.


The proposed review will be conducted in accordance with JBI methodology for systematic reviews of effectiveness.18-20 The title for this protocol has been registered with PROSPERO (CRD42020168774).

Search strategy

The search strategy will aim to retrieve both published and unpublished studies. An initial limited search of MEDLINE, Embase, the Cochrane Library, Web of Science,, OpenGrey, and ProQuest Dissertations and Theses was undertaken to identify articles on the topic. The text words contained in the titles and abstracts of relevant articles, and the index terms used to describe the articles were used to develop a full search strategy for MEDLINE (Ovid; see Appendix I). The search strategy, including all identified keywords and index terms, will be adapted for each included information source. The reference lists of all studies selected for critical appraisal will be screened for additional studies.

Information sources

The databases to be searched will include MEDLINE (Ovid), Embase, the Cochrane Library, and Web of Science. The trial register to be searched will be The search for unpublished studies will include OpenGrey and ProQuest Dissertations and Theses.

Study selection

Following the search, all identified citations will be collated and uploaded into EndNote, version X9.2 (Clarivate Analytics, PA, USA) and subsequent duplicates will be removed. Titles and abstracts will then be screened by two independent reviewers for assessment against the inclusion criteria for the review. Potentially relevant studies will be retrieved in full and their citation details imported into the JBI System for the Unified Management, Assessment and Review of Information (JBI SUMARI; JBI, Adelaide, Australia). The full text of selected citations will be assessed in detail according to the inclusion criteria by two independent reviewers. Reasons for exclusion of full-text studies that do not meet the inclusion criteria will be recorded and reported in the systematic review. Any disagreements that arise between the reviewers at each stage of the study selection process will be resolved through discussion or with a third reviewer. The results of the search will be reported in full in the final systematic review and presented in a Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) flow diagram.21

Assessment of methodological quality

Selected studies will be critically appraised by two independent reviewers at the study level for methodological quality in the review using the JBI standardized critical appraisal instrument for RCTs.20 Any disagreements that arise will be resolved through discussion or with a third reviewer.

All included studies, regardless of the results of their methodological quality, will undergo data extraction and synthesis (where possible). Critical appraisal results will be included in tabular and narrative formats.

Data extraction

Data will be extracted from studies included in the review by two independent reviewers using the standardized JBI data extraction tool.20,22 The data extracted will include specific details about the populations, study methods, interventions, and outcomes of significance to the review objective. These parameters include age, sex, region, American Society of Anesthesiologists classification, sample size, study design, type of surgery, type of SADs used, oropharyngeal leak pressure, duration of device insertion, success rates of insertion, number of insertion attempts, ease of device and gastric tube insertion, and incident of laryngopharyngeal morbidities and other adverse effects. Any disagreements that arise between the reviewers will be resolved through discussion or with a third reviewer. Authors of papers will be contacted to request missing or additional data, where required.

Data synthesis

Studies will, where possible, be pooled with statistical meta-analysis using JBI SUMARI. Effect sizes will be expressed as either risk ratios (for dichotomous data) or weighted (or standardized) final post-intervention mean differences (for continuous data), and their 95% confidence intervals will be calculated for analysis. Continuous data will be pooled using the inverse variance method, whereas dichotomous data will be pooled using Mantel–Haenszel. Heterogeneity will be assessed statistically using the standard chi-squared and I2 tests. (I2 = 0 to 25% represents low heterogeneity; I2 = 25% to 50% represents moderate heterogeneity; I2 = 50% to 75% represents high heterogeneity; I2 = 75% to 100% represents extreme heterogeneity). A P-value < 0.10 (Q test) or I2 > 50% will be considered to represent substantial heterogeneity across studies.23 Statistical analyses will be performed using either a random (high between-study heterogeneity) or fixed (low between-study heterogeneity) effects model.24 If possible, subgroup analysis will be conducted to assess possible effects of potential confounding factors (eg, sex, type of surgery, size of SADs, whether neuromuscular blocking drugs were used, timeframe of follow-up) on the investigated outcomes between the two groups. Where statistical pooling is not possible, the findings will be presented in narrative form including tables and figures to aid in data presentation, where appropriate.

A funnel plot will be generated to assess publication bias if there are 10 or more studies included in a meta-analysis. Statistical tests for funnel plot asymmetry (Egger test, Begg test, Harbord test) will be performed where appropriate.

Assessing certainty in the findings

The GRADE approach for grading the quality of evidence will be followed,25 and a Summary of Findings (SoF) will be created using GRADEpro (McMaster University, ON, Canada). The SoF will present the following information where appropriate: absolute risks for the treatment and control, estimates of relative risk, and a ranking of the quality of the evidence based on the risk of bias, directness, heterogeneity, precision, and risk of publication bias of the review results. The outcomes reported in the SoF will be as follows: oropharyngeal leak pressure, duration of device insertion, success rates of insertion, number of insertion attempts, ease of device and gastric tube insertion, and laryngopharyngeal morbidity.

Appendix I: Search strategy

Search conducted in MEDLINE (Ovid): 7 May 2020


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Han Qiaoyu and Sun Liang contributed equally to this work.


airway management; anesthesia, general; Baska mask; i-gel; supraglottic airway devices

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