LAUSR

Objectives The tip-to-carina (TC) distance on a simple chest X-ray (CXR) has proven value in the determination of correct central venous catheter (CVC) positioning. However, previous studies have mostly focused on preventing the atrial insertion of the CVC tip, and not on appropriate positioning for accurate haemodynamic monitoring. We aimed to assess whether the TC distance could detect the passage of the CVC tip into the superior vena cava (SVC) and the right atrium (RA), and to accordingly suggest cut-off reference values for these two aspects. Design Retrospective observational cohort study. Setting Single urban tertiary level academic hospital. Participants 479 patients who underwent CXR and chest CT scan after the insertion of a CVC with a 24-hour interval during the study period. Intervention The TC distance was measured on CXR, and the position of the CVC tip was assessed on the chest CT images. The TC distance was described as a negative or positive number if the CVC tip was above or below the carina, respectively. Receiver-operating characteristics curve analyses were conducted to ascertain the TC distance to detect SVC entrance and RA insertion of CVC tip. Results The TC distance could significantly detect both SVC entrance and RA insertion (p<0.001 for both; area under curve 0.987 and 0.965, respectively), with a reference range of −6.69 to 15.61 mm. Conclusion The TC distance in CXR is a simple and precise method to confirm not only the safe placement of the CVC tip but also its optimal positioning for accurate haemodynamic monitoring.