 All the lumens of the line are aspirated (to ensure that they are all positioned inside the vein) and flushed with either saline or heparin.A chest X-ray may be performed afterwards to confirm that the line is positioned inside the superior vena cava and no pneumothorax was caused inadvertently.On anteroposterior X-rays, a catheter tip between 55 and 29 mm below the level of the carina is regarded as acceptable placement.