High flow nasal oxygen (HFNO) in the immediate postoperative period has been demonstrated to reduce the risk of postoperative pulmonary complications (PPC) after cardiothoracic surgery. In specific groups of patients such as the obese and after upper abdominal surgery the results are contradictive. However, there is lack of evidence if HFNO in the general high-risk patient after abdominal and non-cardiac thoracic surgery can reduce the prevalence of PPC, hypoxaemia and escalation of therapy. Therefore, the investigators aim to compare the use of HFNO with conventional oxygen therapy (COT) in high-risk patients after abdominal and non-cardiac thoracic surgery regarding postoperative pulmonary complications.

Inclusion Criteria:

Adults (≥18 years old) scheduled for elective abdominal (laparotomy or laparoscopy), open abdominal vascular or non-cardiac thoracic surgery under general anaesthesia with an estimated duration over 3 hours.

AND

Meeting at least two of the following criteria:

• Age > 65 years
• BMI >30
• Preoperative SpO2 <95 %
• Scheduled for lobectomy or pulmonary segment resection
• Respiratory tract infection the last month
• Preoperative anaemia (Hb <100) or severe hypoalbuminemia (<20 g/L)
• Current smoker or previous smoker with >30 packyears
• Pulmonary disease or OSAS
• Heart failure
• Clinical frailty (CFS 4)

Exclusion Criteria:

• Not suitable for postoperative HFNO, as decided by a study member or the anaesthetist in charge (such as total nasal obstruction, skull fracture, facial injuries)
• Pregnancy
• Not able to understand the study information or sign an informed consent.
• Not able to participate with the treatment postoperatively
• Planned for delayed extubation in the intensive care
• Preoperative non-invasive ventilation due to respiratory failure or a higher level of care than a regular ward