The interrater reliability of inferior vena cava ultrasonography performed by intensive care fellows

Abstract

Background and aim: Inferior vena cava (IVC) measurements by ultrasonography (USG) is a repeatable and noninvasive tool but it is sonographer dependent and requires experience. The aim of this study is to investigate the interrater reliability of IVC-USG measurements performed by intensive care fellows. Methods: After training, four first-year intensive care fellows and an experienced ultrasonography trainer performed IVC USG within 5 minutes of each other without the fellows knowing the clinical history, the fluid balance and the previous IVC USG measurements of the patients. The minimum IVC diameter (IVC-min) and the maximum diameter (IVC-max) were measured using both M-mode and B mode. IVC collapsibility index (IVC CI) and the IVC distensibility index (IVC-DI) were calculated. The interrater reliability of the measurements was analyzed using intraclass correlation coefficients (ICC) with 95% confidence intervals (CI). Results: One hundred and seven IVC-USG measurements were conducted on 29 ICU patients. The trainer measured the median (minimum-maximum) IVC-min as 1.20(0.63-2.60) cm, IVC max as 1.76(0.95- 3.09) cm, and calculated IVC-CI as 0.23(0.05-0.68), and IVC-DI 0.30 (0.05-2.10) with B mode. The same measurements with M mode were as 1.34 (0.46-2.53) cm, 1.75 (1.07-3.08) cm, 0.19 (0.09-0.66), and 0.23 (0.10-1.95) respectively. All measurements of all of the fellows showed significant moderate-good correlations with the trainer’s measurements and each other (ICC > 0.6-0.8, p<0.001). One fellow’s parameters of B mode and M mode IVC collapsibility and distensibility index showed weak correlation to the trainer’s and other fellows’ parameters. Most correlations between fellows’ calculated parameters were also moderate (ICC >504- 777, p<0.001). Conclusion: The interrater reliability of IVC diameters, IVC collapsibility and IVC distensibility measurements performed by intensive care fellows is moderate.