The aim of this study is to compare the preoperative and postoperative ultrasonographic measurements of patients undergoing in the prone position and the change in upper airway edema.

The secondary aim of the study is to investigate the relationship between OSAS risk levels determined by the STOP-BANG score in the preoperative period of the patients participating in the study, and airway ultrasound measurements and postoperative critical respiratory events in the preoperative and postoperative period.

Inclusion Criteria:1-American Society of Anesthesiologists Physical Status Classification (ASA) I-II-III-IV risk group who will undergo Percutaneous Nephrolithotomy surgery

Exclusion Criteria:

1. prone position contraindications
2. history of maxillofacial deformity, tumor or trauma,
3. difficult airway history
4. decompensated cardiac, respiratory, hepatic, renal diseases
5. cervical spine fracture
6. Patients refusal -