When an enteral feeding is completed, a small amount of formula is may remain in the downstream tubing of the delivery set. This undelivered formula is often referred to as residual volume. Understanding why residual volume occurs, and how to compensate for it is important to ensure proper caloric intake.
An example feeding of 500 mL of formula is shown above:
1. 500 mL of formula is poured into the bag set and the feeding tube is primed. Priming the tube ensures that air is not present in the tubing, and that the formula is ready to be delivered. The pump is then programmed to deliver a dose of 500 mL.
2. The pump delivers the formula, emptying the bag. As the bag is emptied, air enters into the tubing. Once sufficient air passes the sensor, the pump determines that the bag is empty, sounds an alarm, and stops delivery of formula.
3. Because the bag and upstream tubing are empty, the pump will not deliver the formula remaining in the downstream tubing – which was part of the original 500 mL dose to be delivered. This is the residual volume.
See the infographic below to learn more about residual volume, how to determine what the residual volume is with Infinity feeding pumps, and how to compensate for this residual volume when programming a feeding.