After approval from the Board of studies and JNMCH institutional ethical committee (D.No 349 on 19.06.2021), this prospective randomized study was conducted at a tertiary care hospital over a period of 2 years according to the principles of the Declaration of Helsinki, 2013. The study was registered at Clinical Trial Registry of India (CTRI/2022/10/04634, on 11/10/2022). Based on previous studies [4,11], we choose time of insertion as the primary criteria for calculating our sample size at 80% power and 95% confidence level; which came as 42 in each group to detect a mean difference of 15%. We recruited 90 patients for the study to overcome the dropouts as shown in consort chart (Figure 2) after obtaining written informed consent for participation in the study and use of the patient data for research and educational purposes.

Ninety patients of ASA grade I and II patients of either sex, aged 20-70years, weighing 40-70kg, of all MP (Mallampatti) grades, undergoing operative procedures under general anaesthesia were included in the study. Patients who had any pathology of the oral cavity that may obstruct the insertion of device, mouth opening less than 2.5cm, potentially full stomach patients (trauma, morbid obesity, history of gastric regurgitation and heart burn, full term pregnancy), patient with disrupted upper airway, facial or upper airway trauma, burns following caustic ingestion, patients with stiff lungs, those at risk of oesophageal reflux (hiatus hernia), had bleeding disorder or those who were unable to provide informed consent, were not included in the study.

Patients were randomly divided into 2 groups using simple randomisation by chit in a box method [5] (each of which had either of the two letters, A or B, written and one of these was opened by the assistant after induction of anaesthesia):

• Group A (PLMA or Control group) [n =45] underwent LMA ProSeal™ insertion.
• Group B (BLMA or Study group) [n =45] underwent LMA BlockBuster™ insertion.

The study was single-blinded as the patient was unaware of the group being assigned to him and allocation concealment was done using Sequentially Numbered, Opaque, Sealed Envelopes (SNOSE).

Insertion learning curve was achieved by performing 15 insertions on manikin and 10 insertions on patients, using each of the devices prior to start of study.

A detailed Pre-Anaesthetic Check-up (PAC) including history, clinical examination and routine investigations were carried out in all patients to ensure that they met the inclusion criteria and were eligible for our study. The demographic data such as age, weight, height, BMI (Body Mass Index), Mallampati Grading (MP Grade), etc were noted.

Patients were kept nil per oral (NPO) for 8 hours prior to surgery. After arrival in the OT, an 18G/20G peripheral intravenous catheter was secured and standard multichannel monitor was connected. Uniform premedication was done as per our institutional protocol, with Inj. Midazolam 0.03 mg/kg, Inj Dexamethasone 0.1 mg/kg and Inj Fentanyl 2.0 mcg/kg of body weight. After pre-oxygenation with 100% oxygen for 3 min, the patient was induced with Inj. Propofol 2.0 mg/kg and titrated to achieve an end point. After adequate muscle relaxation with Inj. Succinylcholine 1.5 mg/kg, device insertion was carried out depending on the group to which the patient was assigned. The appropriate size of SAD was selected according to body weight as per the manufacturers' guidelines. Soon after the insertion, the cuff of SAD was inflated with air and connected to the breathing circuit. Successful placement of SAD was confirmed by the ability to achieve tidal volume of at least 7-8 ml/kg with a square wave Capnogram. Adequate ventilation was defined by easy bag ventilation, bilateral equal air entry, absence of audible air leak around the cuff, adequate chest rises, airway pressure of Peak pressure<30mmH₂O, Oxygen saturation>90% and end tidal CO2 of 35-45 mmHg. Outcome measures were noted.

The primary outcome measure was the time taken for insertion which was defined from the time when the device crossed the incisors in first attempt till adequate ventilation was established as confirmed by adequate chest expansion and normal square wave capnogram [4].

All the attempts in which the supraglottic airway device crossed the incisor was considered as an attempt and recorded as secondary outcome measure. A maximum of two attempts were taken after which if adequate ventilation with chest expansion and a square wave form capnogram could not be achieved, it was declared as ‘failure to device insertion’, but the patient was included in the study and some other device or technique was used to secure the airway of that patient.

The ease of insertion was assessed using a subjective scale of 1-3 [6] (Grade: Easy - Insertion within pharynx in single attempt with no resistance, Grade 2: Difficult - Resistance to insertion felt or more than 1 attempt required, Grade 3: Impossible - Inability to place the device)

Airway sealing pressure or Oropharyngeal Leak Pressure (OLP) was measured for both the devices by closing the expiratory valve of the circle system at a fixed gas flow rate of 3 L/min (to a maximum of 40cmH2O). A gradual rise of airway pressure shown in the ventilator monitor with a sudden fall which corresponded with the audible noise lateral to the thyroid cartilage was recorded as OLP [3,7].

The position placement of the device was graded by Brimacombe score [8], that has been introduced for grading of glottic view which signifies the ease of intubation through the SAD, using fibreoptic scope through the airway tube distal to the mask opening (Figure 3). The view is scored as follows: 4-only cords seen; 3-cords plus posterior epiglottis seen; 2-cords plus anterior epiglottis seen; 1-cords not seen, but function adequate; 0-failure to function where cords not seen through the fibreoptic scope.

Haemodynamic changes (pulse rate, MABP- Mean Arterial Blood Pressure, SpO2) were noted before and after (immediately, 1min & 5min) device insertion. Surgery was allowed to commence only after the collection of the last haemodynamic data at 5 minutes post-insertion. After the surgery, the residual neuromuscular paralysis was reversed and postoperative complications were noted. Blood staining on the device was recorded as presence or absence of blood on the supraglottic airway device. Sore throat was analysed after removal of the device and defined as pain, scratchiness or irritation of throat assessed by 4-point scale: (1: No sore throat, 2: mild- complains of sore throat only on inquiry, 3:  moderate- complaints of sore throat without inquiry, 4: severe- sore throat with soreness and associated with throat pain). Post-op Nausea Vomiting was assessed presence or absence of forceful expulsion of contents of the stomach out through the mouth. All the parameters were recorded by a single observer all throughout the study, who was not a part of the study.

Categorical variables (sex, MP Grading, type of surgery, number of attempts, ease of insertion, Brimacombe score, etc) are presented in the form of number and percentage (%). Quantitative data (age, weight, height, BMI, time of insertion, OLP, etc.) are presented as the means (SD and median with 25th and 75th percentiles (interquartile range). Normality of data was checked by using Kolmogorov-Smirnov test. The cases in which the data was not normal, non-parametric tests were used. Non parametric categorical data like gender, number of attempts, post operative complications were analysed using the Chi square test. Non parametric ordinal categorical data like mallampati grade, ease of intubation was analysed by Mann-Whitney test. Parametric data like age, weight, time taken and haemodynamic changes were analysed using the Paired and Unpaired t-test as per data. Data entry was done in MS Excel spreadsheet 365 version 2211. All the tests were performed using computer program SPSS version 25.0. A p < 0.05 at 95% confidence interval was considered statistically significant.