How Does an IV Pump Work? Peristaltic, Piston, and Elastomeric Mechanisms

We’ve all noticed those bedside medical devices connected to patients’ circulatory systems through tubes and syringes to deliver fluids and medication.

IV pumps, or infusion pumps as they are also called, are common medical equipment in hospitals, ambulatory medical services, nursing homes, and, sometimes, even in family residents for home-based medical care.

While we know they are life-saving medical equipment, we may not always understand their working principles, often wondering, how does an infusion pump work?

The answer may be complex for anyone without much knowledge of medicine and physics.

In this article, however, I’ll simplify the working of an infusion pump in a way that sounds as simple as ABC.

Before we get there, a quick definition of IV pumps will help you understand their working principles better. So, let’s start there!

I’ve alluded to the physical appearance of an IV pump in the introduction. But, going by its function, an IV pump is a medical device used by doctors and nurses to deliver medication and nutritional or hydration fluids into a patient's cardiovascular or circulatory system in a safe and controlled manner.

Because they are of different types, infusion pumps deliver the medication and fluids in large or small doses and at programmed speeds or pressure.

While that might sound simple, there’s a complex mechanism behind the delivery of therapy drugs and fluids into a patient’s body using an IV pump, which I’ll explain in the rest of the article.

To do that, though, it’s important to know the main components of an IV pump, which are the parts that determine how it works.

Infusion pumps have external and internal components that work together to realize the fluid or drug delivery process into the patient’s cardiovascular system.

The main parts of an infusion pump include:

Most Infusion pumps used with inpatients today are electrically powered. These electric IV pumps function by the peristaltic or piston mechanism (not the syringe pumps).

However, healthcare facilities also use mechanically powered elastomeric pumps, especially in outpatient settings. These mechanically powered IV pumps use pressure from an elastomeric balloon without relying on a power source.

The main difference in the working of electric and mechanical IV pumps is in how they move fluid from the reservoir to the patient. Let’s discuss how each of the three IV pump mechanisms works

A piston mechanism IV pump works similarly to automobile filling systems. The pumps have reciprocal pistons or plungers that move back and forth from the pump cylinders.

The piston movement into the cylinder sends the fluid from the reservoir into the chamber. The piston movement from the cylinder propels the fluid or medication into the patient’s system in the programmed amount and pressure.

Piston-mechanism infusion pumps have designated IV tubing with a cartridge that has a plunger. Compared to their peristaltic counterparts, they are a better choice for fragile IV liquids like blood.

Peristaltic infusion pumps have a wave-like contraction mechanism similar to how muscles contract to move food in the digestive system. This movement explains the name peristaltic.

The mechanism uses a set of rollers to create positive displacement pressure that compresses the IV pump tubing and moves the fluid through the tube to the chamber. As the rollers squeeze the tube, they create a vacuum that moves the fluid from the pump and out into the patient’s system.

Like their piston-mechanism counterparts, peristaltic IV pumps are super accurate. However, the pressure movement makes them a less preferred option for delicate fluids like blood.

It is the same reason a study found piston-based injectors to have higher and steady flow rates than peristaltic injectors during computed tomography (CT) scans.

As mentioned, elastomeric pumps utilize pressure from a ballon to efficiently control drug or fluid flow rate during drug delivery. These are single-use IV pumps mostly used in delivering analgesics and local anesthesia.

The pressure from the elastomeric balloon replaces the battery or electrical plug-in power used with the piston and peristaltic IV pumps.

To deliver the drug to the patient, the elastomeric balloon contracts continuously to create pressure and move the drug from the balloon.

A flow restrictor (capillary) in the infusion line controls the drug flow rate using the pressure difference between the outlet and inlet points. The drug flow rate is faster when the capillary is shorter or wider and lower when it is longer or narrower.

While elastomeric pumps are easy to use, easily portable, don’t rely on a source of power, and have fewer technical issues than their electric counterparts, their accuracy level is lower, with common drug residual issues after infusion.

Research recommends strict adherence to manufacturer instructions, continuous monitoring during infusion, and using elastomeric pumps with clear volume gradation to ensure patient safety.

This article explores the infusion pump and how it works.

Electrical IV pumps work by the peristaltic or piston mechanism to move fluids from a reservoir and deliver them to the patient’s circulatory system.

 Mechanical elastomeric pumps use pressure from a balloon to deliver drugs to patients through a flow-controlling capillary.

Electric pump mechanisms are more accurate than mechanical ones.

Between peristaltic and piston pumps, peristaltic pumps are less suitable for delicate IV fluids like blood because of the high pressure in their compressing mechanism. Piston-mechanism pumps are better, in this case, because they have a steady flow rate.