The goal of this clinical trial is to compare the effects of nasopharyngeal and oropharyngeal airway on gastric insufflation in patients undergoing general anesthesia and expected difficult mask ventilation. The main questions it aims to answer are:

• Is there a difference between the presence of gastric insufflation in the use of nasopharyngeal and oropharyngeal airways?
• Is there a difference between the antral area sizes measured before and after ventilation After general anesthesia induction, nasopharyngeal or oropharyngeal airway will be placed in participants and real-time ultrasonographic gastric antral area imaging will be performed during mask ventilation. Researchers will compare the effects of nasopharyngeal and oropharyngeal airway use on gastric insufflation.

Patients who are expected to have difficult mask ventilation and receive general anesthesia will be included in the study. After preoperative gastric antral area measurements of the patients by ultrasonography, preoxygenation will be applied and anesthesia induction will be performed. Real-time gastric ultrasonography will be performed during pressure-controlled mask ventilation for 2 minutes after nasopharyngeal or oropharyngeal airway insertion, and then antral area measurement will be repeated. After the trachea was intubated, the antral area measurement was once again performed. At the 30th, 60th, 90th and 120th seconds of ventilation, patients' SpO2, EtO2, EtCO2, peak airway pressure, tidal volume, leak volumes and hemodynamic changes will be recorded.

Inclusion Criteria:

• Patients receiving general anesthesia
• ASA score I-II-III
• At least 3 criteria out of 5 difficult mask criteria defined by Langeron et al.

Exclusion Criteria:

• Patients who did not give informed consent
• Risk of aspiration
• Respiratory disease
• Facial, oropharyngeal or nasopharyngeal pathology
• Pregnancy