WHITE PAPER

The Patient Safety Benefts of the Plum™ CassetteA review and assesment of infusion therapy technologies and the clinical impact of pumping
mechanisms and administration set design
JW Beard MD, Dan Shea RN, Zehra Tilahun RN

Introduction
Today’s infusion pumps perform essential clinical functions with increasingly advanced technology and safety features.
The use of “smart pumps”—infusion pumps with drug libraries—to reduce errors during the infusion of medications
and fluids has become the industry standard,1,2 and is recommended practice by leading safety organizations.3,4,5
However, smart pumps do not eliminate all types of errors.3,4,5 There is considerable variability in smart pump userinterfaces, clinical work flows, pumping mechanisms, andadministration sets.6,7 Device user interfaces and workflows
have been an FDA focus for usability8 and have been the
There is considerable variability insubject of bench research.6 The fluid pumping mechanism
smart pump user interfaces, clinicaland administration set are also important, as they determine
how fluid is delivered to a patient as well as the accuracy andwork flows, pumping mechanisms,
consistency of the fluid delivery in various clinical settings.
and administration sets.6,7This review of infusion therapy technology demonstrates thatthe design of pumping mechanisms and administration sets
have signifcant clinical impact.

Patient safety issues linked to smart pumps
Risks and errors associated with smart pumps are described in surveys,2 complaint investigations,4 literature reviews,5,9and by public agencies.10 The potential types of smart pump errors are numerous,9,11 and certain use cases are consideredhigher risk than others.6,10 Recent publications add to the knowledge base by describing experiences and priorities offrontline clinicians and the technologies used to address smart pump errors.2,4
Two recent Institute for Safe Medication Practices (ISMP) surveys, including more than 1,000 healthcare respondents,
provide a glimpse into the prevalence of medication errors at the bedside and the types of challenges or obstacles thatusers experience with smart pumps.2 The most common types of medication errors experienced in the last 12 months by
respondents involved secondary infusions due to delays, omissions, or wrong rates. Users reported challenges with theuse of smart pumps in categories such as Drug Library Creation, Maintenance, and Engagement; Technology Limitations;and Programming Workflow. Secondary Infusions were also described as a category of challenges, including issues suchas the lack of an alert/alarm if the secondary is not running, secondary setup errors such as bag height and closed
clamps, programming the primary infusion as a secondary, and forgetting to restart the primary afer the secondary iscomplete. Challenges specifc to Alarms and Sensors included difculty managing occlusions and air-in-line alarms.

A challenge in the category of Pump Availability was described as a lack of availability of syringe pumps to deliver
medications in lower volumes due to drug shortages.
Smart pump errors and the technology solutions to address them have been studied by the ECRI Institute.4 An investigationof 100 smart pump complaints reported to ECRI demonstrated that the leading source of errors was related to incorrect
infusion concentration or parameter entries. The ECRI analysis indicates that 75% of the studied errors would be
prevented by smart pump–EHR interoperability. Of the 25% of errors not addressed by interoperability, 15% were related
to secondary infusion setup and require an infusion pump technology solution.
An additional set of infusion pump challenges with potential for error comes from administration sets and pumping
mechanisms susceptible to variation in fluid delivery accuracy by as much as 30% with changes in administration set
intake and outlet pressures.12 Pressure variability may be brought about by clinical changes such as a high-resistancevenous catheter and the height diferential between the fluid container and the pump.

Ideal attributes of infusion pump technology
With an understanding of the types of infusion pump errors and a focus on the pumping mechanism and administration
set, technology solutions can be envisioned to address errors related to primary and secondary infusions.

Primary infusions
Ideally, infusions from the primary fluid container should take place at the programmed rate without concern of variability
during care from a changing height diferential between the fluid container, pump, and patient. For example, the fluiddelivery rates should be constant regardless of positioning pumps on an IV pole, transferring a patient from the operating
room table to a bed, or the patient ambulating in their room.
The infusion alarm burden should be minimized, and management of common alarm types, such as air-in-line anddistal occlusion, would be facilitated. Ideally, air-in-line could be managed by limiting air accumulation in the fluid pathand removal of air without the need to disconnect the administration set from the patient, reducing the possibility ofcontamination. Transient distal occlusions due to changing conditions, such as a kinked catheter from a flexed elbow,
would be managed without requiring a clinician at the bedside.

Secondary infusions
The ideal pump would deliver secondary infusions without dependence on a head height diferential or the need toadminister the secondary infusion as an independent primary. Delivery of the secondary infusion would not be dependent
on a single back-check valve within the primary set to prevent secondary medication from flowing into the primarycontainer rather than to the patient. The pump would alert the nurse when the secondary infusion was obstructed by aclamp or other source. The pump would
deliver the exact programmed secondary
volume and would then switch back to the
The ideal pump would deliver secondary
primary infusion when indicated. In theinfusions without dependence on a headsetting of smart pump–EHR interoperability,
the ideal pump would be capable of assuring
height diferential or the need to administer thethat the secondary infusion is delivered andsecondary infusion as an independent primary.
accurately documented.

Pump technology overview
There are two large volume fluid pumping mechanisms on the market today: linear peristaltic and cassette based. Linear
peristaltic pumps are available from several manufacturers while all cassette-based clinical experience comes from thePlum infusion pump platform (ICU Medical Inc., San Clemente, CA, USA). As described below, several signifcant clinicalperformance diferences exist between the linear peristaltic and cassette-based system.

Deep-dive: Limitations of linear peristaltic pumping mechanisms

Linear peristaltic pumping mechanism

Most infusion pumps utilize a peristaltic pumping mechanism, which moves fluid downstream in the administration set
with the assistance of the pumping mechanism and gravity. Proper flling and emptying of the pumping segment areneeded for accurate fluid delivery.

Silicone pumping segment design may lead to air accumulation
The administration set pumping segment on a linear peristaltic pump is the length of tubing that interacts with thepumping mechanism to propel fluid distally to the patient. The pumping segment may be manufactured from silicone
which has permeability properties that may allow air to enter the set, leading to bubble formation and air-in-line alarms.
Air accumulation in the pumping segment may impact pumping accuracy as air displaces fluid from the segment, which
may lead to under delivery of fluid during a pumping cycle.

Inflow pressure afects the accuracy of fluid delivery
For proper flling of the pumping segment, a height diferential between the fluid container and pump is recommended
by manufacturers. Fluid inflow into the pumping segment may be reduced by inadequate primary fluid container headheight or falling container pressure levels with emptying, and this may reduce the volume of fluid delivery during thepumping cycle. Flow into the pumping segment may be reduced approximately 1% with each 15 mmHg of inflow pressure
reduction12 within the system. Additionally, restricted container emptying by inadequate venting or an obstructed fluid
path from flters or kinked tubing may also reduce flow.

Increases in back pressure reduce pump accuracy
High back pressures may lead to reduced emptying and backflling of the pumping chamber during the pumping cycle.
The net result of an increase in back pressure is a reduction in the delivery of fluid. Increased back pressure may arise fromseveral clinically relevant conditions such as partial tubing obstruction, high flow rates, increased fluid viscosity, smallbore tubing, small bore catheters, and long catheters such as PICC lines. Outlet pressure is expected to vary over time. andinfusion pumps may be programmed to deliver fluid until reaching a distal occlusion pressure threshold, which may lead

Back pressure increases may reduce
flow up to 3% per PSI depending onpump design, which may translate into
pump inaccuracy.

to under delivery. For example, when a distal occlusionpressure threshold is set to 11 pounds per square inch(psi), the pump will deliver fluid against a back pressureof 10 psi without alarming. Back pressure increases may
reduce flow up to 3% per PSI depending on pump design,
which may translate into pump inaccuracy.12 Additive
efects of intake and outlet pressures may create negative
flow errors of up to 30%.12

Secondary infusions may be omitted or delayed
The peristaltic pump delivers fluid through the administration set without controlling whether it is from the primaryor secondary container. The selection of a secondary infusion flow is determined by manual processes including the
setup of the required primary–secondary head height diferential, roller clamp opening, and ensuring the presence of aback-check valve in the primary line. The connection of the secondary at the primary Y-site also requires a fully opened,
low-resistance needlefree connector to ensure proper fluid flow from the secondary container. In the event of a secondary
setup error, such as a closed roller clamp, the pump may be programmed to deliver the secondary medication and thesecondary medication may be displayed on the user interface, but due to the closed clamp on the secondary line, themedication on the primary line will be infused at the secondary rate programmed by the clinician.

Secondary infusions interrupt primary infusions
When delivered properly, secondary infusions stop the delivery of the primary infusion until fluid flow from the primarycontainer resumes. While the clinical signifcance of an interrupted primary is patient specifc, frequent interruptions of anordered primary infusion may be associated with issues related to fluid balance and electrolyte homeostasis.

Administration of secondary infusions as a primary requires a dedicated flush
To bypass the risks associated with delays in secondary administration or interruptions of primary infusions, a secondary
may itself be administered as a primary. When this strategy is followed, the clinician is then required to initiate a strategy
to flush the utilized primary tubing to deliver the remainder of the secondary fluid. Delivering the secondary remaining
in the tubing is critical to avoid a potential underdose as secondary infusion containers may be 50 or 100 mL while
the primary set priming volume may be 20 mL or greater. Discarding the fluid remaining in the tubing may lead to aconsiderable portion of the prescribed dose being wasted.

Deep-dive: Advantages of the Plum cassette-based pumping mechanism
The Plum cassette-based pumping mechanism delivers primary and secondary medications diferently than a peristaltic
pumping mechanism. The technology is best understood with a description of the administration set and cassette,followed by a description of the pumping mechanism.

Structure of the Plum administration set with Plum cassette
The Plum administration set includes several components common to all administration sets. At its proximal end, theset includes a bag spike and a drip chamber. At its distal end, the set includes a male luer with a spin collar for secureattachment to a female luer. The diferentiating feature is the cassette, which is located near the middle of the set andengages with the pumping mechanism.

Bag
spike

Drip
chamberCassette

Male
luer

Structure of the Plum cassetteA schematic description of the cassette describes the flowof fluid from container to the patient.

Line fromprimary
container

The Plum cassette has a U-shaped fluid path inside
a rectangular housing. Fluid from the primary and/or
secondary lines flows into the cassette, flls the air trap,
flls the pumping chamber, and then exits the cassettethrough the infusion line which connects to the patient.
During priming, the cassette is inverted to expel air fromthe air trap and fll the pumping chamber with fluid, thenflipped to normal orientation for loading into the pump.

Port forsecondarycontainer

Technical capabilities of thecassette-based pumping mechanism
VOLUMETRIC DELIVERYPlum infusion pumps deliver a set volume of fluid with eachpumping cycle, independent of inflow pressure and backpressure. The administration set cassette incorporates
a pumping chamber with a flexible silicone diaphragmthat is compressed by a piston from the pump. When thechamber is full and the piston extends, a set volume of fluid
is pushed from the chamber into the distal administration
set. When the piston retracts, the diaphragm expands andpulls fluid from the container into the pumping chamber.
The programmed rate determines the frequency of thepiston extension and retraction pumping cycle and thus
the volume of fluid delivery.

Air trap

Line topatient

U-shaped
fluid path
Pumping
chamberCassettebody

INDEPENDENT PUMPING CONTROL OF
PRIMARY AND SECONDARY INFUSIONSThe cassette incorporates a valving mechanism thatacts as the gatekeeper for fluid to flow into the cassettefor primary and secondary infusions. When delivering asecondary infusion, the pumping mechanism selects fluid
from the secondary port and closes the flow from theprimary. When programmed for a primary infusion, thepumping mechanism selects fluid from the primary line
and closes the flow from the secondary.

PistonDiaphragm

Volumetric delivery

ALARM CAPABILITIES FOR PRIMARY AND SECONDARY INFUSIONS
Independent control of primary and secondary infusions enables infusion pump alarms to be issued for each line
independently. Alarms are confgured to detect proximal and distal occlusions throughout the infusion duration.

AIR TRAPPING AND ELIMINATIONThe cassette air trap is designed to retain up to 1 mL of
air prior to generating an alarm. Once air is present andan alarm is generated, the air can be removed throughan automated process of backpriming through thesecondary port. Backpriming is initiated by the clinician
selecting the feature through the keypad, which directs
fluid from the primary container to fll the air trap and
expel the air into a container attached to the secondaryport, such as the secondary infusion line or a syringe.

CONCURRENT FLUID DELIVERY

Air trapping and elimination

In addition to the delivery of a secondary medication,
the cassette valving mechanism enables concurrent
fluid administration. Concurrent delivery is the infusionof primary and secondary fluids at the same time atindependently determined rates. The pumping mechanism
alternates drawing fluids into the cassette from primaryand secondary containers to achieve the programmed
administration rate of each fluid. For example, the primary
infusion can be infused at 100 mL/hour while the secondary
infusion can be infused simultaneously at 50 mL/hour.
The rules of compatibility still apply as medications should
only be infused together if they are compatible.

SYRINGE OR INFUSION SET CONNECTION
The Plum cassette allows for a needlefree connector
or female luer to serve as the attachment point for thesecondary infusion. This connection point enables
attachment of administration set tubing or a syringe forcontainer and volume flexibility in infusion delivery.
Syringe or infusion set connection

The clinical impact of the Plum infusion system
Infusion rates are stable when the clinical setting changes
Volumetric delivery infuses the primary and secondary infusions at the programmed rate regardless of bag height, system
resistance, and back pressure for both secondary and primary infusions. Changes of bag heights and pump location, suchas a patient transfer from a bed to a chair, are managed without the need to reconfgure the infusion system setup. An
additional beneft of independence from head height requirements is the ability to confgure the infusion system (pump,bags, pole, etc.) to suit the clinical setting to optimize workflows in tight spaces.

Secondary infusion delivery is simplifed and sources of error eliminatedWith independent control of primaries and secondaries, secondary administration no longer requires the clinician to lower
the primary infusion bag with a hanger, maintain a head height diferential, or be dependent on a back-check valve tosafely administer the infusion. The clinician can hang the infusion bags to ft the care area and clinical scenario whether it
be on the IV pole or on a pump-based hanger.
Alarms dedicated to secondary infusions recognize obstructed secondary fluid flow, for example from a closed roller
clamp, and alert the clinician. In contrast, an occluded secondary line on a peristaltic pump will not generate an alarm andwill lead to fluid flowing from the primary infusion container at the programmed secondary rate and a delay or omissionof the secondary medication.

The 2020 ISMP Smart Pump Guidelines
recommend that clinicians "use an
automated secondary IV infusion
management system not dependenton head height diferential."

Prompt recognition of an obstructed secondary line
enables the clinician to restore flow and avoid delaysin therapy with medications that are frequently timesensitive antibiotics and electrolytes. In one study, closed
clamp errors occurred at a rate of 1.1%,13 which translates
to the potential for frequent patient impact as an individual
hospital may have hundreds of patients, each receiving
multiple secondary infusions each day.

The 2020 ISMP Smart Pump Guidelines recommend thatclinicians “use an automated secondary IV infusion management system not dependent on head height diferential andcan assure secondary flow.”3 The Plum infusion system is the only infusion pump currently used in clinical care to meetthis recommendation.

Air-in-line alarms are reduced and can be cleared without breaking the line
Air-in-line alarms interrupt infusions, can be time intensive to resolve, frequently recur, and can contribute to alarm fatigue.
Furthermore, breaking the infusion line to remove air may expose the patient to injection site contamination and possible
infection. The Plum cassette air trap captures up to 1 mL of air to reduce alarm burden, while backpriming enables air
clearance without disconnecting the line from the patient. Air issues are further reduced as the Plum administration set's
silicone diaphragm is limited to approximately the size of a dime, signifcantly less silicone surface area than alternative
peristaltic pumping segments, which reduces the opportunity for air accumulation as bubbles.
Air management was studied in a side-by-side evaluation of the Plum 360™ and a competitive pump during a bench studyof a placebo chemotherapeutic agent known for outgassing and generation of air-in-line alarms. At the study conclusion,
the Plum 360 had zero air-in-line alarms while the competitor had 21.14

Documentation and Billing Claims Submissions Are Improved with Independent Primaryand Secondary Infusion Control
With independent control of primary and secondary infusions, documentation with smart pump–EHR interoperability
is accurate. The documentation benefts of interoperability facilitate completion of an accurate medical record and may
translate to improved hospital fnancial performance. One community hospital found that interoperability was associatedwith increased infusion therapy CPT code submissions totaling an annualized $1,147,652 (USD).15
Without this independent primary and secondary control with a peristaltic pump, when a secondary infusion is not flowing,
the primary medication may be delivered and incorrectly recorded as a secondary infusion.

The primary can continue during secondary infusions
Concurrent infusion capability enables clinicians to determine whether a secondary infusion will be delivered by piggyback(secondary infuses, primary stops) or concurrently (primary and secondary infusing) and has multiple potential benefts.

Fewer primary infusion interruptions
A maintenance fluid infusion can continue at the desired rate while secondary intermittent medications are infused. Thisis especially valuable when intravenous access sites are limited and the primary infusion is critical to the patient’s fluidbalance. Repeated primary interruptions with piggybacks may impact fluid balance and complicate intake and output
calculations and balance. Beta-lactam antibiotics, such as ZOSYN®, are increasingly infused over extended periods oftime. ZOSYN may be administered over 4 hours, 3 times per day. When delivered by piggyback, ZOSYN may lead to aninterruption of the primary infusion 12 hours per day.16 Primary infusions frequently include electrolytes, thus frequently
interrupted fluid and electrolyte infusions may also afect electrolyte hemeostasis.

Time-savings with multiple infusions
Infusing a secondary concurrently can also reduce therapy times. In a bench study of Plum 360 versus a competitor, thetime required to complete a simulated chemotherapeutic regimen was reduced by concurrent infusion of premeds with
the Plum 360.14

Potential improvement in patient comfort with irritating infusions
During the infusion of irritant medications, concurrent administration may improve patient comfort by diluting the
medication with the primary infusion.17

Secondary medications can be delivered
with syringes or bags
The secondary port can be used with an administration
set or a syringe attached to the standard Plum cassette
without specialized equipment. The flexibility to infuse
medications for various container types is valuable withchanging drug preparations and in times of medication
shortage.2

Repeated primary interruptions withpiggybacks may impact fluid balanceand complicate intake and output
calculations and balance.

Conclusion
The use of smart pumps for the infusion of medications and fluids reduces many types of medication errors, but due todiferences in design, the safety benefts vary by device. A comparison of smart pump peristaltic and cassette-based fluid
pumping mechanisms demonstrates that the cassette-based infusion pumps have multiple important clinical benefts
for the delivery of primary and secondary infusions. The full safety benefts of smart pumps will be realized throughthe efective utilization of drug library sofware, interoperability with the EHR, and pumping technology that delivers
primary and secondary fluids accurately in complex clinical environments while also reducing the risk of human error bysimplifying the administration of secondary infusions.

How a cassette-based delivery system helps streamline secondary delivery
A direct connection from the secondary line to cassette reduces risk and increases efciency
Take a look at the infusion scenario below, both with and without the Plum cassette, to fnd out.

Without Plum cassetteWith Plum cassetteHang the secondary bag.
Since it does not rely on fluid
dynamics, it is not necessary
to lower the primary bag.

Hang the secondary
bag and lower the
primary bag.

Connect the secondary line
directly to the Plum cassette.

Connect the secondaryline to the primary line
above the infusion pump.

Program and start
the secondary
infusion.

Rx List

RxA
RxB

RxC
RxD

Nurse is pulled from thepatient’s room for an
emergency and leaves
without opening the clamp
on the secondary line.

The pump delivers the primary
medication at the secondary
rate. The secondary medication
is not being delivered, and no
alarm is triggered.

Program and start
the secondary infusion.

Nurse is pulled from thepatient’s room for an
emergency and leaves
without opening the clamp
on the secondary line.

Proximal
ProximalOcclusion
Occlusion

The pump alarm sounds,
alerting the nurse to thestation. The nurse clears thealarm, opens the clamp, andstarts the secondary infusion.

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Dr. JW Beard is Medical Director for ICU Medical, Inc.. Dan Shea and Zehra Tilahun were employees of ICU Medical, Inc.
as of the writing of this paper.

© 2020 ICU Medical Inc.

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