Supine vs Prone Position and Atelectasis Assessed by Lung Ultrasound

Atelectasis frequently develops during and after general anesthesia due to factors such as anesthesia-induced diaphragmatic dysfunction, reduced functional residual capacity, altered ventilation-perfusion matching, and surgical positioning. The development of atelectasis has been associated with postoperative hypoxemia and other pulmonary complications. Lung ultrasound (LUS) has emerged as a reliable, radiation-free bedside imaging modality for the detection and monitoring of atelectasis. LUS allows assessment of lung aeration through standardized ultrasound patterns and scoring systems, enabling dynamic evaluation in the perioperative period. This is a prospective, observational cohort study designed to compare the incidence and severity of atelectasis in patients undergoing surgery in the supine position versus the prone position under general anesthesia. Adult patients undergoing elective surgical procedures will be enrolled. No experimental intervention will be applied, and all anesthetic and surgical management will follow routine clinical practice. Lung ultrasound examinations will be performed at predefined time points after induction of anesthesia and before extubation. A standardized lung ultrasound protocol and scoring system will be used to assess lung aeration loss and detect the presence of atelectasis. The primary outcome of the study is the difference in atelectasis detected by lung ultrasound between supine and prone surgical positions. The secondary outcome is the change in lung ultrasound scores over time. This study aims to clarify the effects of supine and prone positions on perioperative atelectasis and to support the clinical use of lung ultrasound as a noninvasive monitoring tool in perioperative and anesthetic practice..