Immersion ultrasonography improves the repeatability of cephalic vein diameter measurements for inexperienced operators

OBJECTIVE: To reduce the empirical dependence of ultrasound measurement of the cephalic vein diameter, improve the repeatability of measurements for inexperienced operators, and provide a new method for inexperienced operators. METHODS: Operators without ultrasound experience used contact ultrasound and immersion ultrasound to measure the diameter of the cephalic vein. The intraobserver and interobserver repeatability of measurements obtained via the two methods were analyzed. RESULTS: The intraobserver and interobserver repeatability of the cephalic vein diameter measured via contact ultrasound by inexperienced operators were average, with intraclass correlation coefficients (ICCs) of 0.572 (95% CI: 0.239–0.759) and 0.405 (95% CI: −0.057–0.666), respectively. The intraobserver and interobserver reproducibility of the cephalic vein diameter measured by immersion ultrasound were very good, with ICCs of 0.955 (95% CI: 0.922–0.975) and 0.943 (95% CI: 0.900–0.967), respectively. In the Bland–Altman diagram of the intraobserver and interobserver agreement of the immersion ultrasound measurements of the cephalic vein diameter, 96% of the points fell within the 95% limits of agreement. CONCLUSION: Immersion ultrasonography can be used to measure the cephalic vein diameter while reducing the dependence of the results on operator experience; inexperienced operators can achieve very good repeatability.