BACKGROUND: As the normal functioning of the body is dependent on oxygen, low blood oxygenation is a acute problem that needs immediate attention. Measurement of blood oxygenation is therefore central to monitor patients and is usually done using light technology with a clip on the finger. Philips manufactures a measuring clip that is designed to measure oxygenation in the nasal wing instead of the finger. The advantage of this is that the nose is not affected as much as the fingers by poor blood flow in the skin, for example caused by cold. The nose is also closer to the heart and lungs than the hand, so changes in oxygenation may be detected earlier. This newer meter is an approved CE-marked product that is available for clinical use, but the next step is to investigate it systematically during and after surgery.

METHODS: The study intends to include patients undergoing planned major surgery at the surgery department at Karolinska University Hospital Huddinge. Before surgery, patients will be asked and written informed consent for participation will be obtained. Within the framework of the study, measurement with the newer measurement method on the nose is planned to be done at the same time as standard measurement on the finger is performed. The research study and oxygen saturation measurement with the nasal clamp starts when the patient enters the operating room and continues until he or she leaving the post-operative ward the day after surgery, or at the latest 24 hours after the start of the operation. Apart from the use of two body oxygenation monitors, there is no impact on the treatment and care are not affected at all. Decisions and actions based on possible changes in oxygenation will be based primarily on the traditional measurement point in the finger. After completion of the study, all anesthesia nurses and all nurses from the surgical and postoperative department in Huddinge who have worked with the Alar SpO2 (saturation) sensor during the study will be invited to participate in a semi-structured interview. All nurses who express interest in participating will receive an information sheet and consent will be signed personally with the signed personally with the interviewer before the interview starts. The investigators will collect data on staff opinions regarding the use of the Alar SpO2 sensor (such as: the differences between the Alar SpO2 sensor and the finger SpO2 sensor, the advantages and disadvantages of the Alar SpO2 sensor, advantages of using dual oximetry, and potential expansion of the work with the Alar SpO2 sensor).

Inclusion Criteria:

• Age 18 or older
• Standard of care for planned abdominal surgery foresees continuous SpO2 monitoring intra- and post-operatively
• Standard of care for planned abdominal surgery foresees arterial catheterization in order to aspirate blood for blood gas analysis
• Expected overnight stay in the peri-operative unit
• Able to speak and understand Swedish
• Willing and able to provide written informed consent

Exclusion Criteria:

• Body weight below 50 kg
• Procedures and/or conditions affecting the face or hands that might prevent placement of sensors
• Injury/wounds or physical malformation of sensor application sites (i.e. nose, fingers)
• Severe contact allergies to standard adhesives, latex or other materials found in pulse oximetry sensors (self-reported)
• Nail fungus on application site
• Refusal to remove artificial nails or nail polish
• Severe dermatitis or hyperkeratosis (e.g. ichthyosis) at sensor application site
• Raynaud's disease
• Hemoglobinopathy
• Expected post operative ward stay ≤12 hrs
• Dye injections within 48 hours
• Pregnant or lactating during the study period
• Nasal intubation
• Patient is participating in another medical device study.

This study will be conducted in surgical patients in the peri-operative unit of Karolinska University Hospital (Huddinge site), Stockholm, Sweden and will focus on patients after upper abdominal surgery.

In order to ensure a balanced distribution of men and women, at a minimum 40% of the total subject population will be male and 40% will be female.