The position of the inferior vena cava-right atrium junction on simple radiography: implication for optimal veno-venous extracorporeal membrane oxygenation cannula tip position.

Background: Extracorporeal membrane oxygenation (ECMO) is increasingly used. For effective oxygenation, position of cannula tip is important. The objective of this study is to identify the position of the inferior vena cava-right atrium junction (IRJ) using the vertebral body unit (VBU) and carina. This may be useful if applied to the assessment of ECMO cannula tip positions.

Method: A total of 182 patients who underwent chest computed tomography (CT) and supine chest radiography (CXR) between January 2017 and July 2018 were included, who had not previously received ECMO support. The position of the IRJ was evaluated using VBU and the efficacy of the VBU for locating the IRJ with the carina was analyzed.

Result: The mean distance (SD) from carina to IRJ was 79.2 (9.6) mm on chest CT. The mean distance in VBUs (SD) at the level of the carina was 22.3 (1.5) mm on chest CT and 23.3 (2.1) mm on CXR. The mean IRJ position was 3.6 VBUs below the carina on CT and 3.4 VBUs below on CXR with 95% limits of agreement between -0.05 and 0.5.

Conclusions: The mean position of the IRJ was estimated to be 3.4 VBUs below the carina on supine CXR. This may be useful if applied to the assessment of ECMO cannula tip positions.