The subclavian vein (SCV) is a preferred site for placement of central venous catheter. However, pneumothorax is a major concern during subclavian venous catheterization. Lung deflation, by decreasing lung volume, may reduce the risk of pneumothorax by increasing the distance between the pleura and the SCV. The investigators evaluated the effect of lung deflation on the relative position between the pleura and the line of the imaginary needle pathway during supraclavicular and infraclavicular approach to the subclavian vein (SCV) using ultrasonography.

Inclusion Criteria:

• Pediatric patients who were scheduled for elective operation under general anesthesia
• Neonates (0 ~ 1 mo), Infants (1 mo ~ 1 yr)

Exclusion Criteria:

• Structural anomalies of the chest wall
• History of lung and chest wall operations
• Prior central venous catheterization
• Upper respiratory tract infection, or pneumonia within 2 weeks