“Comparison of the Effects of Different PositiveEnd Expiratory Pressure on RespiratoryParameters during Prone Positioning underGeneral Anaesthesia†– A RandomizedControlled Trial.

After obtaining the scientific committee and ethical committee clearance, informed consent written in their own language will be obtained from all the patients Included in the study. Study will be done on patients who are posted for elective surgery for spine fixation under prone positioning in SRM MEDICAL COLLEGE HOSPITAL AND RESEARCH CENTER, KATANKULLATHUR. Study will be   performed as a prospective randomized single-blinded control studyin patients undergoing elective Spine instrumentation surgeries in prone position under general anaesthesia.. Patients will be randomized into three groups by computer generated random numbers and kept in a sealed, opaque envelope.

Group A: No PEEP

Group B: PEEP of 5.

Group C: PEEP of 10.

General anaesthesia will be standardized in all the groups. The patients will be premedicated with alprazolam on the night and two hours before surgery. The patients will be monitored with pulse oxymeter, NIBP, ECG and capnography. Glycopyraollate 0.2mg + Ondansetron 4mg IV will be administered. Morphine 0.15mg/kg will be used as the intraoperative analgesic. Propofol 2 mg/kg is the induction agent and vecuronium 0.1mg/kg is used for intubation. Anaesthesia will be maintained with O2: air with sevoflurane. Patient will be ventilated with Pressure Controlled Ventilation (PCV) to achieve a tidal volume of 7 ml/kg. Respiratory rate will be  kept at 12/min. ETCO2 between 36 and 40. The amount of PEEP will be kept according to the group allotted. Three different timelines will be used to monitor the arterial po2, Peak pressure, plateau pressure and mean pressure, dynamic compliance: before induction (T1), 30 min after prone positioning (T2), and arterial po2 will be seen 30 mins after  extubation. Arterial line will be inserted after shifting the patient to OT. ABG will be taken at the three time lines to look for pH, PO2, and PCO2. The Peak pressure, plateau pressure and mean pressure, dynamic compliance will be measured every 15 min intraoperatively. The haemodynamic parameters like HR and MAP will also be measured every 15 min intraoperatively. The total intraoperative blood loss will be calculated at the end of surgery in all three groups. If MAP reduces by more than 20% from baseline, it will be considered as hypotension. Hypotension will be treated initially with crystalloids and ephedrine in increments of 6mg if necessary.