Comparison between ultrasound and chest X-ray to confirm central venous catheter tip position.

Background: Mechanical central venous catheter (CVC) placement complications are mostly malposition or iatrogenic pneumothorax. Verification of catheter position by chest X-ray (CXR) is usually performed postoperatively.

Objectives: This prospective observational study assessed the diagnostic accuracy of peri-operative ultrasound and a 'bubble test' to detect malposition and pneumothorax.

Method: Sixty-one patients undergoing peri-operative CVC placement were included. An ultrasound protocol was used to directly visualise the CVC, perform the 'bubble test' and assess for the presence of pneumothorax. The time from agitated saline injection to visualisation of microbubbles in the right atrium was evaluated to determine the correct position of the CVC. The time required to perform the ultrasound assessment was compared to that of conducting the CXR.

Results: Chest X-ray identified 12 (19.7%) malpositions while ultrasound identified 8 (13.1%). Ultrasound showed a sensitivity of 0.85 (95% confidence interval [CI]: 0.72 to 0.93) and a specificity of 0.5 (95% CI: 0.16 to 0.84). The positive and negative predictive values were 0.92 (95% CI: 0.80 to 0.98) and 0.33 (95% CI: 0.10 to 0.65), respectively. No pneumothorax was identified on ultrasound and CXR. The median time for ultrasound assessment was significantly shorter at 4 min (interquartile range [IQR]: 3-6 min), compared to performing a CXR that required a median time of 29 min (IQR: 18-56 min) (p < 0.0001).

Conclusion: This study showed that ultrasound produced a high sensitivity and moderate specificity in detecting CVC malposition.

Contribution: Ultrasound can improve efficiency when used as a rapid bedside screening test to detect CVC malposition.