Preoperative assessment, encompassing history taking, physical examination, laboratory investigation, and a comprehensive explanation of the study, will be conducted the day prior to surgery. Patients will be instructed to fast for 6 hours for solid foods and 2 hours for clear fluids before elective surgery.
Patients will be randomly allocated to either the Air-Q3 group (n = 45) or the Ambu AuraGain group (n = 45) using a computer-generated randomization table. After recruitment, the enrolling investigator opens the sealed opaque envelopes that concealed group allocation. Patients will be blinded to their group allocation. Patients will not receive any premedication and will be positioned supine on the operating table, head in neutral position, rested on a gel head ring. Standard monitoring including basic physiological variables, including electrocardiography, pulse oximetry, non-invasive blood pressure monitoring, and end-tidal oxygen measurement using a circle circuit ventilator (Datex Ohmeda, Aespire, Marquet), will be performed prior to anaesthesia induction.
Following establishment of intravenous access, a standard anaesthesia induction protocol will be followed, involving preoxygenation with 100% inspired oxygen for 3 minutes, intravenous administration of Fentanyl (1-2mcg/kg), and Propofol (2-3mg/kg) until loss of consciousness. Subsequently, either the Air-Q3 or Ambu AuraGain will be lubricated and prepared according to manufacturers' recommendations. The airway device will be inserted when the jaw is sufficiently relaxed. The cuff of each device will be inflated with air to a final cuff pressure of 60cmH20. The cuff pressure is measured by a handheld manometer, The airway device insertions will be performed by experienced staff anaesthesiologists with more than ten years experience with supraglottic airway management, who had performed at least 10 Air-Q3 insertions prior to trial commencement.
SAD size selection will adhere to manufacturers' recommendations based on the patient's ideal body weight. Insertion time will be recorded from facemask removal until the presence of square wave capnography tracing. The presence of square wave capnography tracing denotes successful establishment of effective ventilation. Otherwise, the device will be removed completely for another insertion attempt. Failure to insert the SAD after two attempts will be deemed a failure.
After successful insertion of the airway device, it will be secured with tape over the patient's check. A gel plug is applied to the orogastric port and a suprasternal notch test (gentle tapping over the suprasternal notch results in the gel to pulsate, confirming tip location behind the cricoid cartilage) will be done to confirm placement. A 14 French gauge gastric tube, pre lubricated with a water soluble lubricant will be inserted through the nasogastric port for both devices. The ease of insertion will be graded from 1 to 3 (1 = easy, 2 = difficult, 3 = impossible). After successful insertion of the airway device, it will be secured with tape over the patient's check. A gel plug is applied to the orogastric port and a suprasternal notch test (gentle tapping over the suprasternal notch results in the gel to pulsate, confirming tip location behind the cricoid cartilage) will be done to confirm placement. A 14 French gauge gastric tube, pre lubricated with a water soluble lubricant will be inserted through the nasogastric port for both devices. The ease of insertion will be graded from 1 to 3 (1 = easy, 2 = difficult, 3 = impossible). Confirmation of correct orogastric tube placement will be established through aspiration of gastric contents or epigastric auscultation.
Oropharyngeal leak pressure will be determined by transiently halting ventilation and closing the adjustable pressure limiting valve up to 30cmH2O with a fresh gas flow of 3L/min. The airway pressure at equilibrium or when audible air leak is heard from the throat is recorded.
Following successful SAD insertion, fibreoptic scope assessment will be conducted to evaluate LMA placement, graded based on the standardized scale by Brimacombe:
1. Vocal cords not seen
2. Vocal cords plus anterior epiglottis visible
3. Vocal cords plus posterior epiglottis visible
4. Only vocal cords visible Maintenance of general anaesthesia will be with sevoflurane with minimum alveolar concentration 1 - 2 in an oxygen-air mixture.
Postoperatively, patients will be monitored in the recovery room, with physiological variables including non-invasive blood pressure, heart rate, pulse oximetry, and respiratory rate continuously monitored. Upon full consciousness and recovery, a blinded investigator will assess for the presence of sore throat.
