Postoperative pulmonary complication (PPC) is a common complication after surgery resulting in increased morbidity, mortality and prolonged hospital stay. Post operative hypoxaemia has been reported in 10-50% of patients after surgery and in abdominal surgeries it has been reported as high as 40%. To prevent this, oxygen therapy has been a norm after surgery. Recently, high-flow nasal cannula (HFNC) has been evaluated for this indication and found to be superior to conventional oxygen therapy (COT) in cardiac and thoracic surgeries, obese patients, critically ill patients and in neonates. However, its use in specific patient subpopulation still needs to be investigated.This study is undertaken to evaluate and compare the efficacy of High Frequency Nasal Oxygenation with conventional oxygen therapy for postoperative oxygenation in patients undergoing exploratory laparotomies for prevention of postoperative pulmonary complications. 

The present RCT includes patients aged 18-65 years, scheduled for exploratory abdominal surgeries under GA with ARISCAT score ≥26 i.e., moderate to high risk.  Patients with chronic obstructive pulmonary disease or asthma causing limitations in everyday activities,  heart failure with clinical symptoms equivalent to NYHA functional classification > 2,  restrictive lung disease with > 20% reduction in total lung capacity,  BMI>40 kg/m2 or inability to comprehend oral or written information will be excluded

 After adequate reversal of neuromuscular blockade and removal of endotracheal tube, patients in both the group will be shifted to postoperative room and depending on the group allocation, they will receive either COT or HFNC. Patients in High flow nasal oxygenation (HFNO) group will receive a flow rate of 35 to 60 L/min and FiO2 will be titrated (from 45% to 100%) by the treating clinician to maintain a peripheral oxygen saturation (SpO2) of 95% or more. The COT group will receive oxygen via simple facemask with oxygen flow titrated (from 45% to 100%) by the bedside clinician to maintain a SpO2 of 95% or more. In COT group, each additional litre/min of oxygen adds an FiO2 of 0.4 for the first 3liters and FiO2 of 0.3 for every litre thereafter. Arterial blood samples will be collected after extubation at various designated time points i.e. after 2nd hr, 6th hr, 12th and 24th hr. Non-invasive blood pressure (NIBP), Heart rate (HR) will be recorded for 2 hrs.

The primary outcome is to determine PaO2/FiO2 at the end of 24th hr between the two groups and secondary outcomes are PaO2, SaO2/FiO2, PaCO2, patient satisfaction, chest X ray proven PPCs, proportion of PPCs and acute hypoxemic respiratory failure, proportion of reintubation or non-invasive ventilation (NIV) use and complications.