Atelectasis means a part of the lung collapses and fills with air, making it hard to breathe. It can happen when patients get general anesthesia during surgery, especially if they are obese (which means having a high body weight for their height). This study will see if using high-flow nasal oxygen (a special way to give extra oxygen through the nose) before anesthesia can help reduce atelectasis in these patients.

• The study is for adults with a Body Mass Index (BMI) of 30 or more having surgeries that last over 2 hours.
• Participants must come for surgery under general anesthesia and agree to join the study.
• People with certain health issues or with a history of difficult airways cannot join.

Joining this study might help doctors find better ways to care for patients who have surgeries and need anesthesia. Participants will get high-flow nasal oxygen before anesthesia to see if it helps their lungs. There might be some risks, like any other medical procedure, so it's important to talk to your doctor and understand everything before joining.