Definition of the tip-to-carina (TC) distance: Each horizontal line perpendicular to the carina and central venous catheter (CVC) tip was drawn on the simple chest X-ray image. The vertical distance of the two horizontal lines was measured and defined as the TC distance. The position in the carina is defined as zero, and positioning of the CVC tip above (–) or below (+) the carina is recorded. RA, right atrium; SVC, superior vena cava.