The study will commence after obtaining approval from the Postgraduate Research Monitoring Committee (PGMRC), Institute Ethics Committee (IEC) and Clinical Trials Registry-India (CTRI) registration.

Informed and written consent will be obtained from all patients after the preoperative assessment. A baseline pre-induction gastric ultrasonography will be performed by the investigating anesthesiologist on the day of the surgery. The cross-sectional area of the gastric antrum will be measured by the free tracing method and a mean value of three readings will be noted. In the operating room, standard ASA monitors will be attached, and all patients will be pre-oxygenated with 100% oxygen with a fresh gas flow of 6L/minute with a 25-degree head-end elevation. The patients will be induced with Fentanyl (2 µg/kg), titrated dose of Propofol and atracurium (0.5 mg/kg)/vecuronium (0.1 mg/kg). Once the patient is induced, and check ventilation is confirmed, an appropriate size oropharyngeal airway (Guedel) will be inserted, and the facemask will be held against the patient’s face using a 2-handed technique. The patients according to the randomization will be ventilated as follows by the attending anaesthesiologist:

Group A- Manual Facemask ventilation: The Adjustable Pressure Limiting valve (APL) will be kept at 20 cm H₂O and adjusted to achieve a tidal volume target of 8 ml/kg (IBW- Ideal Body Weight) with a pressure limit of 30 cm H₂O. The respiratory rate will be maintained at 12-15/min titrated to achieve EtCO₂ of 35-40 mmHg.

Group B-Pressure controlled ventilation: A pressure-controlled ventilation will be initiated with an initial inspiratory pressure of 15cm of H₂O_, respiratory rate of 12/min and PEEP of 5 cm of H₂O. The inspiratory pressure will be adjusted up and down by 2 cm of H₂O to achieve a target tidal volume of 8 ml/kg (IBW) with a maximum pressure limit of 30 cm of H₂O. 

 In both groups, ventilation will be continued for 3 minutes. Simultaneously, the investigating anaesthesiologist will observe the occurrence of the comet-tail artefact by real-time gastric antral ultrasonography. The peak airway pressure, at the time of appearance of the comet tail artefact will be noted. The ventilating anaesthesiologist will be unaware of the ultrasound findings. After three minutes the airway will be secured with an endotracheal tube and will be secured after confirming the position. The investigating anaesthesiologist will repeat the gastric antral ultrasonography in the same site as marked and observe for the CSA. (An average of 3 recordings will be noted). Subsquent anaesthetic management will be left at the discretion of the concerned anaesthesiologist.