Ultrasound assessment of gastric volume in severely obese individuals: a validation study

BACKGROUND: Point-of-care gastric ultrasound is an emerging tool to assess gastric content and volume at the bedside. The examination includes both a qualitative and a quantitative component. The aim of this study was to evaluate the performance of an existing model for predicting gastric volume in severely obese subjects (BMI >35 kg m^-2). METHODS: This observer-blinded experimental study compared the gastric volume predicted based on a sonographically measured cross-sectional area of the gastric antrum with the gastric volume measured by suctioning under gastroscopic guidance in a cohort of severely obese subjects. Volumes between 0 and 400 ml, in 100 ml increments, were studied. Allocation was randomized, and all study observations were blinded to group allocation. The correlation and the level of agreement between predicted and observed volumes were studied. RESULTS: Data from 38 subjects suggested that the gastric volume predicted by sonographic assessment correlated strongly with that measured by gastric suctioning (concordance correlation coefficient of 0.82 and Pearson's correlation coefficient of 0.86). In addition, Bland-Altman analysis suggested a high level of agreement between the calculated and suctioned volumes, with a mean difference of 35 ml, and 95% limits of agreement similar (within 30%) to those observed in the non-obese population. CONCLUSIONS: Our results suggest that the existing mathematical model to determine gastric fluid volume based on sonographic assessment performs well in severely obese individuals.