The study aims at investigate whether the oxygen partial pressure is improved in the prone position postoperative after abdominal surgery. Included are 50 adults operated with abdominal surgery. The Intervention is turning from supine to prone position and then back to supine position while measuring whether an improvement occurs in oxygen saturation and oxygen partial pressure, or not.

Postoperative hypoxia complicates 30% - 50% of abdominal surgeries. The cause of postoperative restrictive lung function and hypoxia is unknown. Previous studies report that oxygen partial pressure decreases by an average of 2 kPa after abdominal surgery, while carbon dioxide partial pressure is unchanged and vital capacity decreases by 35%. Patients are operated and treated in the post anesthesia care unit in the supine position. The study aims at investigate whether the oxygen partial pressure is improved in the prone position postoperative after abdominal surgery or not.

Inclusion: 50 adults operated with abdominal surgery. Exclusion: Esophageal surgery, Abdominal vessel surgery. Decline participation. Intervention: turning from supine to prone position and then back to supine position again.

Primary outcome: Change in oxygen saturation and oxygen partial pressure. Secondary outcome: Change in carbondioxide partial pressure Procedures: Partial blood gas is taken before surgery. On the day of surgery or the day after: starting in supine position with continuous measurements of oxygen saturation from pulse oximetry, transcutaneous carbon-dioxide partial pressure and blood gas. Then turning to prone position and then back to supine position.

Inclusion Criteria:

• Being operated within 2 in the abdomen because of upper gastrointestinal surgery, colorectal surgery, urological surgery or emergency surgery
• Must be able to turn from supine position to prone position in the bed

Exclusion Criteria:

• Esophageal surgery, Abdominal vessel surgery.
• Decline participation.