Biomed 101: Infusion device basics

Infusion devices are used to administer analgesics,antibiotics, blood products, chemotherapy and nutrients to patients. The first ambulatory infusion pump was created in the 1950s and used for chemotherapy. By the 1970s, the market for home infusion pumps drove manufacturers to produce smaller and more cost efficient units. Multiple channel ambulatory infusion pumps were created in the early 1990s. These pumps could deliver multiple infusates to the patient, while also reducing the size and weight of the device. In response to the increasing problem of medication errors, smart pumps were introduced in the early 2000s. These pumps can store dosing guidelines in a drug library. The dosing guidelines will contain minimum and maximum dosages of various medications to prevent overdosing the patient. Today, smart pump technology has become wireless.

Infusion Terms:

Back Pressure – Back pressure refers to the resistance of the fluid and the pressure it must overcome to pass into the lumen, against its direction of flow. Fluid viscosity (“thickness” of the fluid), tubing diameter, catheter diameter, fluid height and flow rate will affect back pressure.

Bolus – A bolus is a rapidly absorbed intravenous injection of a drug.

Drip or Optical Sensor – A drip sensor is a small feedback device that is attached to the IV bag drip chamber, and is used to measure the drips using an optical sensor. It sends this information back to the controller. Most controllers and pumps no longer use sensors.

Free Flow - Free flow is an unregulated flow of IV fluids into the patient.

Infusate - Infusate is the fluid being infused into the patient over a set amount of time.

Intravenous (IV) - Within a vein.

Keep Vein Open (KVO) – KVO is an alarm that sets flow rate at approximately 5 ml/ hr when the set volume to be infused has finished. This helps prevent blood from forming at the catheter tip.

Occlusion – An occlusion is a blockage in an IV tubing.

Piggybacking – Piggybacking, also called Secondary or Secondary Rate, is a secondary volume rate that is different than the primary rate. When the primary set volume to be infused has finished on the primary, the pump switches to the secondary rate.

Rate – Rate is how fast the solution is to be infused to the patient. Rate is equal to volume over time, normally measured in ml/hr.

Volume to be infused - Volume to be infused is the volume of the IV solution to be infused into the patient, normally measured in ml.

Needleless Intravenous Tubing - Needleless IV systems are systems that administer medications through IV access devices without using needle connections. Needleless IV tubing sets were developed to prevent accidental needle-stick injuries.

In Line Filters – In line filters are fluid filters that strain the IV solution to remove particles and pathogens. Any such contaminants may complicate the IV therapy and patient recovery. Some filters are built into the primary IV tubing; others must be attached. Adding more filters will decrease fluid flow.

Three way stop cock - A three way stop cock is a tubing connector that has three tubing connections and an adjustable valve, that is used to change the fluid flow between two connectors, with the third being shut off.

Flush - To flush the line, is to let fluid flow freely through the IV tubing set to remove all air from the line before it is inserted into the patient.

Flush Valve - A flush valve is used to permit free flow of an IV solution into an IV tubing set to remove air prior to insertion into the patient or after insertion, to help force blood flowing into the IV tubing back into the vein. The valve must be manually opened by pulling the rubber stopper up.

Free Flow Protection - These devices are designed to prevent accidental free-flow conditions that may be caused by an improperly installed cassette, syringe or tubing, an open pump door, the cassette being removed from the clamp, pump failure, or having no free flow mechanism installed. Various methods are used to prevent free flow, including a tubing pinch mechanism, specialized valve tubing and electronic monitoring or alarms.

Air in-line detection - A key safety feature of an infusion pump is an air in-line detection system,which monitors for the presence of air bubbles in the fluid. If a bubble is detected, the unit will alarm and the flow will be stopped.Accuate detection of air bubbles is vital in maintaining the health and recovery of patients. Air bubbles can cause air embolisms that can lead to serious complications in blood flow to vital organs. This system uses infrared or ultrasonic technology for bubble detection. The ECRI Institute recommends that air detection system be able to detect a single bubble of air of 50 to 100 μL (this may vary with manufacturer).

Occlusion detection - Occlusion detection can sense a blockage in the IV line between the pump and the patient. If not detected, this occlusion could cause unsafe high fluid pressures to build up in the IV lines. When an occlusion is detected, the pump will shut off and go into alarm. Most occlusion detection systems use a pressure transducer to measure the back pressure of the fluid at the pump. Some pumps will permit back flow while clearing the occlusion and alarms, to prevent a large bolus of fluid being infused into the patient.

Tubing flow rate - Based on the fluid type, accuracy of fluid delivery needs and patient, various tubing sizes can be used. The most common are:

• Tubing Flow Rate: Tubing is rated for: • 20drop/ml-This is used for patients who require a very high flow rate per hour with a lower accuracy.
• 60drop/ml-This is used for patients who require a very low flow rate and a high accuracy.