Infusion pumps gained prominence in the early 1990s as an improvement over the less precise gravity-fed system in which medicine slowly dripped from bags hung from poles. With the gravity system, nurses spent more time with patients, visually calculating medicine flow with wristwatches. Today, many nurses acknowledge that they dash into patients' rooms, quickly enter dosage levels on the infusion pump's keyboard, then rush off to help other patients. The pump snaps on to an IV line and regulates the flow of medicine entering a patient's body. The potential for dangerous free flow occurs when the pump is shut down and the IV line is detached from the machine.
Gravity can then pull all the medication through the line and into the patient.
If a nurse engages the roller clamp that is attached to the IV, there can be no free flow. In addition, later-model pumps include safety features that can stop the flow of medicine even if the clamp isn't closed.