Lung ultrasound offers a novel, reliable and radiation-free tool for diagnosing perioperative atelectasis and evaluating its severity in adult patients undergoing general anesthesia in the operating room.

Atelectases occur in up to 90% of patients undergoing general anesthesia and intubation. The aim of the present observational study was designed to further to evaluate the diagnostic performance of lung ultrasound (LUS) in detection of postoperative atelectasis in adult patients undergoing general anesthesia. Results of LUS as the experimental method will be compared to the results of computed tomography (CT) as the reference technique for the detection of atelectasis. The investigators want to confirm former findings of the appearance of perioperative atelectases and to prove that ultrasound is a valid tool for detection of atelectases.

Inclusion Criteria:

1. Aged 18 years and older;
2. American Society of Anesthesiologists (ASA) physical status within class I-III;
3. Scheduled for selective neurosurgical operation with general anesthesia;
4. Need of mechanical ventilation more than 2 hours;

Exclusion Criteria:

1. Patients decline to participate;
2. Pregnancy;
3. Previous thoracic procedures (thoracic drain, thoracotomy, thoracoscopy);
4. A history of pulmonary diseases within last two weeks with abnormal manifestation of lung CT (pulmonary parenchyma or/and interstitial lesions );
5. Pneumothorax or subcutaneous emphysema during peri-operation;
6. Patients with a body mass index (BMI) more than 30 kg/m2;
7. Emergency operation.

Patients undergoing selective neurosurgical operation in Xiangya Hospital or The Third Xiangya Hospital of Central South University