Effectiveness of Two Different Body Positions During Facemask Ventilation in Obese Patients

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?