Examination of accuracy in the assessment of gastric residual volume: a simulated, controlled study

Increased gastric content from enteral nutrition intolerance is thought to place patients at risk for pulmonary aspiration. Although considered a questionable practice, blind gastric tube aspiration is the most common approach to measure gastric content. This simulated study evaluated the accuracy of residual volume (RV) assessment via tube aspirations made from known volumes by controlling the syringe pull technique, feeding tube properties, fluid viscosity, and placement of tubes in the fluid.

This study was conducted in a metrology laboratory. Aspirates were obtained using a force measurement test system to control force of the syringe pull technique using 3 different procedures (slow 10 inches per minute [ipm], intermittent 10 ipm, and fast 40 ipm). Four different feeding tubes, 10 Fr and 18 Fr, each made of polyurethane and polyvinyl chloride, were placed in varying depths of 100 mL of either water or formula. The effect of fluid viscosity was also examined.

Overall, 108 RVs were analyzed using a force measurement test system. Actual content of RV was underestimated 19% on average and varied across tube size and viscosity. Intermittent and slow syringe pull techniques yielded greater aspirate quantities, although neither technique aspirated the full amount of volume available. The 10 Fr feeding tubes yielded larger RVs in more viscous fluid, yet the 18 Fr tubes performed better with fluids of lower viscosity.

Based on this simulation, RV assessment does not accurately reflect the total volume of the contents available and, therefore, the clinical utility of this assessment should be further investigated.