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.

This study aims to investigate whether apnoeic oxygenation with Optiflow Switch during tracheal intubation of the critically ill may prevent severe hypoxaemic events. Critically ill patients requiring intubation in the intensive care unit will be preoxygenated with tight facemask/NIV and Optiflow Switch or only tight facemask/ NIV.

During a period of 6-12 months with an aim to include a minimum of 50 patients, patients will be preoxygenated according to routine practice, 100% oxygen via a tight-fitting mask or NIV. During the following 6-12 months, we will change the clinical routine to adding HFNO with Optiflow Switch. During this time, patients, without contraindications will be pre and perioxygenated with HFNO, Optiflow Switch 40-70 L/min, 100 % O2, in combination with a tight facemask or NIV.

Before preoxygenation, the need for and methods for oxygen delivery is noted. Baseline patient characteristics (age, BMI, comorbidities, smoking history, airway related data) and the reason for intensive care admission and intubation will be registered. Scores for physiological compromise and length of intensive care prior to intubation will be noted.

In both groups, the duration of preoxygenation and drugs for anaesthesia induction are chosen by the intensive care physician responsible. Blood gas analysis for arterial oxygen and carbon dioxide partial pressure will be analysed before and after intubation. Before, during and after intubation, vital parameters will be registered.

Intubation-related data and immediate complications such as arterial hypotension, severe cardiac arrhythmia, cardiac arrest, death, oesophageal intubation, regurgitation, or a need for a surgical airway will be noted. Later complications such as ventilator-associated pneumonia and mortality at day 28 as well as duration of mechanical ventilation, length of stay in ICU will be registered.

Patients with contraindications against HFNO and if the responsible anaesthetist is not comfortable using HFNO will be preoxygenated with a traditional facemask or NIV and included in the study group of traditional preoxygenation.

Data will also be collected from the intensive care patient chart regarding all intubations during the study period in order to find patients not included in the study.

Inclusion Criteria:

• Adult, ≥18 years old
• Intensive care patients that require tracheal intubation for any indication

Exclusion Criteria:

• Patients with skull or facial injuries where the application of nasal cannula is to be avoided, decided by the intensivist.
• Pregnancy
• Total nasal obstruction
• Deemed not suitable for any other reason than the aforementioned

All adult critically ill patients requiring intubation in the intensive care unit at Karolinska University Hospital Solna, Sweden will be included.