Efficacy of head up position versus supine position with high flow nasal oxygenation compared with conventional preoxygenation in patients undergoing exploratory laparotomy: A randomised controlled study

A total of 45 patients will be randomized and allocated into the following three groups:

 Ã˜  **Group SMO [Standard Mask Oxygenation] (n=15):**Patient to be preoxygenated via an anatomical face mask at10L/min.

Ø  **Group HFNO [High Flow Nasal Oxygen] (n=15):**Patient to be preoxygenated via High Flow Nasal Oxygen at 50L/min with mouth closed with a FiO2 of 1(100%).

 Ã˜  Group HFNO HU[**High Flow Nasal Oxygen Head Up] (n=15):**Patient to be preoxygenated at 25degree head up via high flow nasal oxygen at 50 L/min with mouth closed with a Fio2 of 1(100%)

 All patients will be distributed randomly into the above three groups and written informed consent will be taken from them. Arterial blood gas analysis (ABGA) will be done before the start of preoxygenation. This ABGA will be taken as standard and reference. Patients from each group will be preoxygenated with SMO, HFNO in supine position and HFNO with 25degree head up position for 5 minutes and ABGA will be performed 5 minutes after preoxygenation.

Patients in the HFNO group and HFNO HU group will be asked to keep their mouths closed to ensure better efficacy of the HFNO. After preoxygenation, rapid sequence induction (RSI) will ensue and endotracheal intubation will be performed while keeping the HFNO canula in nostrils during intubation in the HFNO AND HFNO HU group. Another ABGA will be done 1 minute after intubation.

The patient’s hemodynamics will be monitored for the entire duration of surgery and standard general anaesthesia protocol will be followed.

 Preoxygenation in 25degrees head position has been shown to improve oxygenation than standard preoxygenation; HFNO offers an effective alternative to standard preoxygenation. However, on an extensive search of literature we did not find any study where the effect of head up position using HFNO has been studied for exploratory laparotomy patients. Therefore, this study is designed to compare the efficacy of head up position using HFNO vs supine position as a preoxygenation technique when compared to standard face mask oxygenation by assessment of the arterial partial pressure (PaO2) at defined set time points following the preoxygenation in patients of exploratory laparotomy.The primary objective of this study is to compare the change in PaO2 after 5 mins of preoxygenation with HFNO with 25 degrees head up position versus HFNO in supine and conventional preoxygenation using a face mask.