A fibreoptic bronchoscope is used for both diagnostic and therapeutic purposes. In anesthesia, it is used to aid intubation especially during anticipated difficult airway situations. Hypoxemia during the process of fibreoptic bronchoscopic intubation is common. This can induce anxiety and hinder the performance of the procedure which in a difficult airway situation can be very cumbersome. Transient apnoea during fibreoptic bronchoscopy either produced due to the drugs or as a reflex due to irritation of the airway can also complicate the situation.

There are different ways of oxygen supplementation.  Traditionally this supplementation is by means of low-flow oxygen nasal cannula (LFNC) which can effectively provide only up to 4 to 6 liters per minute of supplemental oxygen. Often these flows are not enough and in more than 45% of patients desaturation has been noted. High flow nasal oxygenation is new system which is capable of delivering up to 100% humidified and heated oxygen at flow rates of upto 60 liters per minute, and a humidifier that saturates the gas mixture to a temperature of 31 to 37 C. A high-flow nasal cannula accomplishes a reduction of nasopharyngeal airway resistance, leading to improved ventilation and oxygenation through the application of a positive pressure environment. Hypoxemic events are reduced by other different proposed mechanisms (washout of dead space, intrinsic PEEP etc) which low flows can not do.

This prospective randomised study tries to assess whether high flow nasal oxygen reduce episodes of desaturation during fibrescope guided intubations when compared with standard low flow (6L/min) co-oxygenation in adult patients. It will also compare the lowest oxygen saturations  reached during intubation and the arterial partial pressures of oxygen and carbon dioxide at the confirmation of intubation. The total number of episodes of hypoxemic events (fall of SpO2 >10% from baseline) would also be noted and compared.