Comparison of Volume controlled ventilation and Pressure controlled ventilation in patients undergoing gynaecological laparoscopic surgery under General Anaesthesia using I-gel: A randomized controlled trial

All patients meeting the inclusion and exclusion criteria, will undergo detailed pre-anaesthetic evaluation, written and informed consent will be taken for study. All patients will be premedicated with inj. midazolam, 0.02 mg/ kg IV in premedication room after obtaining intravenous access. In operating room, RL is started as a maintenance IV fluid, patients are connected to multi para-monitor of Avance CS20�’ Anaesthesia workstation consisting of Electrocardiography (ECG), noninvasive blood pressure (NIBP), and pulse oximeter (SpO2). After preoxygenation, anesthesia will be induced with inj.Propofol 2 mg/kg, and inj. fentanyl 2.0 mcg/kg IV. Muscle relaxation will be facilitated with inj.vecuronium 0.1 ml/kg. Post induction capnography and neuro muscular monitoring are also done. Appropriate size I gel is inserted (Size 3 for 30-60 kg and size 4 for 50 -90 kg). Successful placement of I gel is confirmed by clinical tests (square waveform in capnogram, and bilateral equal air entry). Oro-pharyngeal leak pressure will be measured in both the groups. Mechanical ventilation will be performed using the closed circuit and anaesthesia will be maintained with sevoflurane 1-2 % in Oxygen-N2O mixture (60:40) with VCV mode of ventilation with a tidal volume (TV) of 8 ml/kg, respiratory rate (RR) of 15 bpm, Positive end expiratory pressure(PEEP) of 5 cm of H2O and I: E ratio of 1:2.

Patients will be then randomly allocated into 2 groups of 25 patients each by using computer-generated random numbers available at website Research randomizer(www.randomizer.org). Allocation concealment is done using serially numbered opaque envelope (SNOSE)technique. Mechanical ventilation is further continued as per group allocation.

Group V: Mechanical ventilation continued with VCV mode without changing the settings.

Group P: Mechanical ventilation switched over to PCV mode with an initial inspiratory pressure of 15 cm of H2O, which is titrated to achieve a TV of 8 ml/kg, other settings being kept same (RR of 15 bpm, I: E of 1:2 and PEEP of 5 cm of H2O).

Later in both the groups ventilator settings are adjusted to so as to keep end tidal CO2level of 35 - 40 mm of Hg. In both the groups RR is increased/decreased by 2 breaths increments every minute so as to maintain the target ETCO2.Once it reached 20 bpm, in VCV group if required, TV is adjusted 25 ml increments every minute maximum up to 10 ml/kg, while in PCV group inspiratory pressure increased/decreased by 2 cm of H2O increments every minute so as to maintain the target ETCO2.In any patients if need arises to keep TV more than 10 ml/kg and or P peak raises more than 35 cm of H2O such patients will be excluded from the study.

In all patients, carbon dioxide pneumoperitoneum will be performed with intraabdominal pressure of 12 mm Hg.  Trendelenburg position will be set around 30 degrees. Intra operatively heart rate(HR), systolic blood pressure(SBP), diastolic blood pressure(DBP), and mean arterial blood pressure(MABP), peal inspiratory pressure(P peak), mean airway pressure (P mean), Expired tidal volume(TV), minute volume, oxygen saturation, and end-tidal carbon dioxide will be monitored at regular intervals, and data will be recorded at following point of time: 10 minutes after induction, in the supine position (baseline, or T1); after creation of pneumo-peritoneum and achieving a stable end tidal carbon dioxide (ETCO2) level of 35-40 mm of Hg for 5 minutes (T2)15 minutes after pneumoperitoneum, in the Trendelenburg position (pneumo-trend, or T3); and 10 minutes after pneumoperitoneum withdrawal, in the supine position (final, or T4). Mean operative time, pneumoperitoneum time, anaesthesia time, and complications will also be recorded. Further anaesthesia management will be carried out as per institution protocol. After the completion of surgery, the surgeons are questioned for their subjective evaluation of surgical working conditions during the laparoscopic gynecologic surgery.

 Continuous data are expressed as mean+SD and categorial data will be expressed as frequency and percentage. Data will be entered in MS excel sheet.  Appropriate statistical tests will be applied using IBM SPSS latest version. A p value less than 0.05 is considered as statistically significant.