To determine the feasibility and safety of using I-gel supra-glottic airway device for low-flow anesthesia for laparoscopic surgery

All patientswould undergo a pre-anesthetic evaluation comprising of history, generalphysical and systemic examinations. All efforts will be focused on theidentification of any comorbid diseases and their optimization before surgery.Preoperative investigations would be appropriately performed to guide andoptimize perioperative management. All patients shall be kept fasting for atleast 6 hours. Patients will be allocated to two groups of 25patients each by random computer draw. Group A - Securing airway with I-gel supraglotticairway device. Group B - Securing airway with endotracheal tube(ETT). All patients will be administered general anesthesiafor the procedure. A Drager Fabius Plus Anesthesia Machine will be used in allcases with a co-axial closed circuit breathing system. A standardized protocolfor induction and maintenance of anesthesia will be followed which wouldcomprise of intravenous fentanyl (1-2mcg/kg) followed by propofol (1.5-2mg/kg)for induction. Airway will be secured by an appropriate size oral ETT or I-gelfollowing administration of a non-depolarizing muscle relaxant. The head end ofthe patient will be covered with drapes to facilitate blinding of theinvestigator. Anesthesia will be maintained with desflurane in oxygen andnitrous oxide titrated to maintain FiO2 of 0.5 at all times. A non-depolarizingmuscle relaxant will be administered for maintenance of neuromuscular blockadeduring the surgical procedure. Standard volume control ventilation settingswill be used in both groups with tidal volume of 8ml/kg, to maintain minuteventilation of 100ml/kg and end-tidal carbon dioxide (EtCO2) between30-40 mm Hg. Initially high fresh gas flows (FGF) of 6 l/min willbe used to achieve desired expired concentration of anesthetic gases and then FGFreduced to 1000 ml/min. The time of initiation of a FGF of 1000ml/min will beconsidered as Time 0. FGF will then be reduced by 100 ml/min till the finalgoal of 400 ml/min total FGF is achieved, which will be recorded as a state ofno clinical leak in the breathing system. The FGF will not be reduced below theabove limit. The FGF will not be reduced in case of collapse of bellows,ventilation alarms or desaturation. An independent observer, unaware of theairway device used, will record all observations. The parameters will bemonitored and recorded every minute along with reduction of flows till 400 ml/minand thereafter every 15 min till 2 hours after which the study will beterminated. The following parameters will be recorded:

1. Heart rate
2. Blood pressure
3. Oxygen saturation
4. End tidal Carbon dioxide
5. Peak Airway pressure
6. Loss of tidal volume (Set tidal volume - Delivered tidal volume)
7. Total Flow delivered
8. Changes in above parameters with change in position from supine to Trendelenberg or reverse Trendelenberg.

Efficiencyof placing naso/oro-gastric tube will be noted along with gastric distension atthe beginning and end of surgery. At the end of the procedure, neuromuscularblockade will be reversed and post extubation patient will be shifted to PACUfor observation. Patients will be followed up in PACU and 24 hoursafter surgery in wards to note complaints of sore throat (constant pain, independentof swallowing, dysphagia, pain with swallowing), sore jaw, dysphonia, numbnessof tongue or oropharynx, blocked or painful ears, reduced hearing or neck pain.

Statistical Power: Thepower of the study was calculated based on the study by Uppal et al1comparing I-gel with ETT using pressure controlled ventilation. Toestimate the sample size a mean difference of 0.25 was considered to getclinically significant results between the two groups. The standard deviationvalue used was 0.05. Using a power of 80% and a significance value of 0.05 fora two-sample t-test comparing two groups a total of 24 patients per group wouldbe needed.