MEDdesign

When Accuracy and Flow Don’t Add Up: The Case for New Design in Large Volume Pumps

By Susan Niemeier, MHA, BSN, RN
April 2, 2018


• Categories: 04-Product Design & Development, MEDdesign

Approximately 9 in 10 hospitalized patients receive intravenous infusion. When medications are delivered, patients assume—as do the nurses administering the infusion—that the large volume infusion pump is delivering medications accurately and at a continuous flow rate. However, all is not what it seems, and drugs may not be administered as thought, potentially placing the patient at harm.

Large volume pumps are ubiquitous throughout the hospital and deliver a wide range of fluids and medications, from simple hydration to high-risk, critical medications. The pumps are expected to infuse fluids and medications continuously at the prescribed programmed rate. In controlled laboratory conditions, the typical flow rate accuracy would be plus or minus 5%. But it can be difficult to accurately gauge pump performance and patient response in a real-world setting, where various environmental factors may dramatically affect flow rate accuracy.

We need a fundamentally new paradigm in infusion pump engineering and design to ensure the highest quality patient care and safety. This starts with adaptive pump technology. An adaptive pump system automatically compensates for external factors that impact fluid delivery and will help administer infusions as intended. The market has begun to address this problem, and there are some new technologies in development.

High-risk Medications

Accuracy and continuity are two important concepts when addressing large volume infusion pump performance. Accuracy is how closely the average flow rate from the pump correlates with the target flow rate programmed by the nurse. Flow continuity, on the other hand, is how much the flow varies from the average. For example, an infusion pump programmed to run at 75mL per hour should deliver the volume of 75 mL within 60 minutes. Using the same example, flow continuity means that the volume delivered would gradually and continuously increase over time.

Both flow accuracy and continuity are important when administering high-risk medications, especially ones with short half-lives. These medications are often administered to critically ill patients to address conditions such as blood pressure control, arrhythmias, and, in some cases, for therapeutic paralysis. While high risk medications have been around for years, most nurses are not aware of the potential clinical impact of the infusion pump used to deliver them.

One example is Pitocin, a high-alert synthetic hormone used to induce labor. Its flow accuracy is paramount for the health and safety of the mother as well as the baby. Recommendations for delivering Pitocin are to use the lowest possible dose to achieve a positive clinical effect, using a large volume pump with an accurate flow rate. A rapid delivery of the hormone could lead to the nurse misjudging the exact dosing of the hormone, and, therefore, the progression of induction, which could lead to overmedication. Too much medication can lead to prolonged and dangerous side effects, such as uterine rupture and fetal deceleration.

Another example is Norepinephrine, a drug used to treat dangerously low blood pressure and heart failure. It has a half-life of approximately three minutes and a short duration of action of approximately two minutes. Discontinuous delivery or periods of fits and starts in flow may lead to the need to bolus, or to additional clinical interventions. A large volume pump that consistently and continuously delivers the appropriate dosing, as opposed to micro bursts, could potentially lead to beneficial patient outcomes.

These examples are not isolated cases, and they demonstrate the need for better pump performance.

Adaptive Delivery

Users of large volume pumps must be cognizant of pump performance in real-world clinical conditions, as well as controlled laboratory settings. The FDA and the industry as a whole are aware of this disconnect. AAMI is working to revise infusion device test standards to more clearly convey actual pump performance under various conditions and the potential impact to the patient.

But solely focusing on more accurate disclosures still misses the mark when it comes to
nurses, who need and expect an infusion pump that delivers medications accurately and consistently under all conditions. Why hasn’t the market answered?

Enhancing pump performance in a variety of real-world clinical conditions requires a new paradigm in pump engineering. We need adaptive technology that seamlessly interacts with the main elements of the traditional gravity driven pump—pressure and resistance—to achieve continuous flow. Rather than propelling fluid with a fixed-displacement mechanism, it should directly apply pressure to push the fluid and provide a restriction to the flow through the system. While a pressure-based system will improve flow continuity, it must also address average pump output under changing external conditions.

Peristaltic large volume pumps rely on pre-determined positions or speed measures of the various pumping elements. If a motor is turning at proper speed, the system assumes that the flow output is correct. But it may not be as external factors can influence the fluid path. The impact of this is not measured nor compensated for by infusion system software.

Adaptive pump technology allows for direct measurement of volumetric changes at the point where fluid flows from the pump to the patient. Direct flow measurement allows adjustment of the pump through its control software to maintain target flow rates as external conditions change. The combination of a smooth profile and an adaptive measurement and control system ensures that the pump is delivering what the nurses intend, regardless of external factors or system dynamics.

The use of adaptive fluid delivery has the potential to not only set a new standard for pump performance, it has the potential to streamline clinician workflow, enhance patient safety and save lives.