It is important to provide enough oxygen to the patients who are asleep during surgery. One way to do this is by using a mask placed over the face to help them breathe. When it becomes difficult getting enough oxygen into the patient's body using the mask, it's called difficult mask ventilation. There can be different reasons for this, and having a higher BMI is one of them. Body physique is assessed by Body Mass Index (BMI). This calculation gives an indication of a person's weight relative to their height.

There is some evidence in the research literature to suggest that when the patient is positioned in a way that helps their airway, like using a device to lift their head and torso 25 degrees , it might help the process of getting enough oxygen work better. The study aims to determine if patients with high BMI can breathe better using a face mask while they are in a head elevated position compared to lying flat on their back.

Facemask ventilation is an important technique applied by anesthesiologists after induction of general anesthesia and before tracheal intubation. It is also used as a rescue maneuver in situations where a patient's consciousness is compromised affecting oxygenation. Obesity is well known to be one of the difficult predictors for facemask ventilation. In fact, the occurrence of difficult facemask ventilation is more frequent in obese patients than non obese. One of the maneuvers described to optimize the effectiveness of facemask ventilation in the general population is positioning the patient in a 25 degree head elevated position. A previous study has demonstrated improvement in facemask ventilation in obese patients with BMI from 30 to 40 kg/m2 in the head elevated position, compared to supine. However, it is not yet determined if this is applicable to patients with a BMI above 40 kg/m2. Adult obese patients with BMI of at least 40 kg/m2 will be randomized to be ventilated after induction of general anesthesia via a face mask while in one of the positions: supine or head elevated, while the volume of air that enters and exits the lungs is measured. Participants will then be changed to the second position, ventilated in the same manner and measures obtained again.

Do patients with class 3 obesity positioned in the head elevated position can be better ventilated with a face mask and positive pressure, compared to the supine position?

Inclusion Criteria:

• BMI > 40 kg/m2
• age > 18 years
• scheduled for elective surgery under general anesthesia
• have the ability to comprehend the rationale for the study and provide consent

Exclusion Criteria:

• pregnancy,
• risk of aspiration of gastric content
• patients using glucagon-like peptide(GLP)-1 agonists
• emergency cases
• upper airway disease or airway anatomical abnormalities
• presence of major cardiovascular, respiratory, or cerebral vascular disease
• if the provider anesthesiologist indicates an awake technique to secure the airway