To compare the efficacy of HFNO with bag mask ventilation for preoxygenating the obese patients posted for surgeries under general anaesthesia using ORI – A randomized controlled trial

Endotracheal intubation necessitates an anaesthetic induction that leads to loss of consciousness and neuromuscular paralysis. This process can cause hypoventilation and apnea, increasing the risk of hypoxia, especially in challenging intubation scenarios. As a result, it is essential to perform careful preoxygenation when the patient is breathing spontaneously. This step is particularly vital for managing airway control in obese patients, who are more susceptible to hypoxia during anaesthesia induction. While traditional techniques like bag-mask ventilation (BMV) have been commonly used, newer approaches such as high-flow nasal oxygen (HFNO) are becoming more popular due to their advantages in enhancing oxygenation and reducing the likelihood of desaturation.

Obesity and Anaesthesia Challenges: Obesity significantly alters respiratory physiology, leading to decreased functional residual capacity, increased oxygen consumption and impaired airway mechanics. These factors increase the likelihood of perioperative complications, particularly during periods of apnoea that occur during intubation. Effective preoxygenation is essential to enhance the safety of anaesthesia induction in this population.

Pulse oximeter provides no indication of downward trends in PaO2 until saturation begins to fall. The ORI is a novel pulse oximeter–based non dimensional index that ranges from 0 to 1 correlating PaO2 from 80 to 200 mmHg and is measured by optically detecting changes in SvO2 once SaO2 saturates to the maximum. Therefore during a crisis, having a reliable estimate of time remaining, before hypoxemia ensues, would help guide management.