Sensor technology takes infusion pumps to the next level by making failure detection reliable, even for infiltration.
Daily millions of patients around the world receive intravenous infusion therapy, many times aided by a smart infusion pump. Smart infusion pumps offer well-controlled drug delivery over an extended period of time and are of great help to hospital staff. However, they fail to provide reliable failure detection.
Present-day infusion pumps lack the technology to measure the flow rate of the drug inside the tubing immediately, which results in two main issues: first, there are failures that remain unobserved and second, over-sensitive pumps produce a high number of false alarms. The ECRI Institute listed alarm fatigue and infusion pump medication errors as number one and two in their compilation of top 10 health technology hazards for 2014.
Common failures during infusion therapy include occlusion, free flow, air-in-line, cross-flow in multi-infusion settings, and extravasation or infiltration. While hospital staff are well aware of all of the above failure modes, present-day infusion pumps can at best only detect the first three. Liquid flow sensing technology from Sensirion allows smart infusion pumps to detect not only these failures, but also cross-flow, reverse flow, and even infiltration errors consistently.
Sensirion Sensor Technology
Sensirion’s sensor technology for medical devices is based on more than a decade of experience in measuring very low flow rates using advanced CMOSens® components that integrate CMOS and MEMS portions on one monolithic silicon chip.
By combining this miniature flow sensor chip into a range of packages, Sensirion has successfully enhanced diagnostics, semiconductor and automation sector processes worldwide. The same established technology can be applied to medical devices and infusion applications to increase patient safety and considerably support hospital staff during their day-to-day work.
The measurement technique is based on a micro-thermal principle by which a microscopic heating element adds a slight amount of heat into the bypassing liquid. The shape of this “heat cloud” is tracked by two temperature sensors and is directly related to the flow rate within the fluidic channel.
By using this principle, Sensirion’s liquid flow sensors can dependably and constantly measure the low flow rates which are common for medical applications. Every sensor is completely calibrated and offers a linearized, digital output to ensure maximum accuracy. CMOSens® technology is extremely scalable and allows sensor solutions to be both technically and economically practical.
The sensor chip is packaged into a plastic housing, which features all electrical, mechanical and fluidic connections required to smoothly incorporate it into, for example, an infusion set.
Incorporated into an infusion set, Sensirion’s disposable liquid flow sensor communicates the flow rate within the tubing in real-time enabling unparalleled safety and reliability for infusion therapies. Occlusion, for instance, can be detected within a few seconds by observing a drop in the flow rate even in ultra-low flow ranges. It no longer requires waiting for 45 minutes before an alarm is activated by an infusion pump.
Drops in primary infusions because of cross-flow errors from secondary lines can be detected rapidly, so that corrections can be made without affecting patient therapy. The sensor also has a bubble detection feature to identify air inside the infusion tubing. Sensirion’s liquid flow sensor is quick, precise and smart.
Furthermore, it is sensitive enough to detect the slightest variations in the flow rate. For example, it is so sensitive that it can identify the regular peaks in the infusion flow rate created by the oscillating back pressure of the patient’s venous pulse—the sensor can feel the patient’s heartbeat (refer Figure. 1).
Sensing the heartbeat on the flow rate is a direct sign of an intact connection of the infusion cannula to the patient’s vein, and absence of the pulsation specifies an interrupted connection. Likely causes may include disconnected, kinked or ruptured tubing, or a dislodged infusion cannula which may in turn result in infiltration.
By assessing the sensor signal, Sensirion’s sensor solution provides a unique opportunity for detecting infiltration rapidly and preventing damaging consequences to the patient.
Figure 1. Liquid flow sensor signal showing the pulsation generated by the venous pulse of the patient (Source: Sensirion AG)
Infiltration and Extravasation
Infiltration and extravasation define the leaking of IV fluid into the tissue surrounding the vein (refer Figure. 2). With infiltration, the IV fluid is a so-called non-vesicant agent that causes irritations, while extravasation describes the efflux of vesicant agents that can easily damage the tissue. For instance the potent drugs used in chemotherapy are such vesicant agents.
The damage can extend to involve tendons, nerves, and joints and can continue for months after the preliminary incident. If treatment is delayed, skin grafting, surgical debridement, and even amputation may be the unfortunate consequences. Potentially severe consequences reinforce the need to add disposable liquid flow sensors for improved reliability and safety in infusion therapy.
It is hard to clearly establish the frequency of complications caused by extravasation, differing heavily between various hospitals and tending to usually be underreported. Conversely, the projected incidence rate published in literature is between 0.1% and 6% for patients receiving chemotherapy.
Extravasation not only causes harm to patients but also imposes heavy costs on the healthcare system, both of which could be avoided. The costs following an extravasation injury can be huge including extended therapy, an extended hospital stay and legal costs.
Figure 2. Illustration of infiltration (Source: Sensirion)
Cause of Extravasation
Various reasons, including damage to the vein’s backside during catheter insertion, can cause the IV fluid to leak into the surrounding tissue. However, one of the most typical reasons is the puncture of the vein wall due to mechanical friction of the catheter needle. This is usually preceded by an occlusion.
With a standard infusion pump, the occlusion may go unnoticed until the pressure in the tubing touches a specific threshold level, activating the alarm through a pressure sensor many minutes and occasionally close to an hour later. Detecting the occlusion swiftly and reliably and consequently halting the infusion pump can prevent the vein from rupturing and the subsequent leakage.
Plenty of Benefits from Integrating a Liquid Flow Sensor
A majority of medical device manufacturers—acquainted with the art of infusion therapies—are aware of the challenges integral to the technology of smart infusion pumps. Incorporating a liquid flow sensor into infusion tube sets will take the infusion therapies a significant step forward and enable a controlled drug delivery on a much wider scale than the present.
Failures that remain completely undetected can be detected or even prevented. This will result in increased patient safety and well-being, less stress and reduced workload for hospital stafas, and also overall savings in the healthcare system.
All images sourced and provided by Sensirion
Medical devices must meet the highest standards in terms of quality and reliability. Doctors, nurses, and patients benefit daily from applications in the field of medical technology that are getting smarter by the day.
The use of proven Sensirion sensor solutions contributes to this and offers the possibility of making applications safer, more reliable, and more convenient. Our many years of experience in the field of medical technology make us the preferred experts for leading medical-technology companies.
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