Intubation in the intensive care unit is a standard procedure with a high risk of adverse events such as hypoxaemia and cardiovascular instability. However, it is demonstrated that HFNO (High Flow Nasal Oxygen) for pre and perioxygenation is feasible and, in many situations, prolongs the safe apnoeic period after anaesthesia induction. Previous data of the use of HFNO during intubation of the critically ill is conflicting. With the new device Optiflow Switch, which allow its combination with NIV or tight facemask with perioxygenation, we aim to evaluate whether this could reduce intubation-related hypoxaemia and other adverse events. The general purpose of this project is to compare the addition of Optiflow Switch for pre- and perioxygenation to traditional preoxygenation using a tight-fitting mask or NIV during intubation in adult intensive care patients in a prospective before-and-after study design.