Estimation of catheter insertion depth during ultrasound-guided subclavian venous catheterization.

BACKGROUND: Several methods have been used to predict the optimal depth of central venous catheter (CVC) tip position when using the anatomical landmark technique. In the present study, we devised a simple formula to predict CVC depth using ultrasound images and chest X-ray (CXR) in patients undergoing ultrasound-guided subclavian venous catheterization.

METHODS: Central venous catheterization via the subclavian vein was performed under ultrasound guidance. We measured five parameters to determine the distance between the needle insertion point and the CVC tip: insertion point to vein puncture point (A), insertion point to a skin point indicating a vertical position above the vein puncture point (B), insertion point to the clavicular notch (C), clavicular notch to the carina (D), and catheter tip to carina (E). Catheter insertion depth was then determined as follows: calculated catheter insertion depth = A - B + C + D; actual catheter insertion depth = (A - B + C + D) + E.

RESULTS: The calculated CVC insertion depth (mean ± SD) was 15.4 ± 1.5 cm from the needle insertion point to the carina [95 % confidence interval (CI) 15.0-15.9 cm]. Actual depth was 15.4 ± 1.5 cm (95 % CI 15.0-15.9 cm). No significant difference was observed between the calculated CVC insertion depth and the actual distance from the needle insertion point to the carina (p = 0.940).

CONCLUSIONS: The appropriate length of a CVC inserted through the subclavian vein can be estimated by a formula using ultrasound images and CXR.