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Daily millions of patients around the world receive intravenous infusion therapy, a number of times assisted by a smart infusion pump. Smart infusion pumps offer well-regulated drug delivery over an extended period of time and are of incredible help for hospital staff. However, there is a downside when it comes to dependable failure detection.
Present day infusion pumps lack the technology to straightaway measure the flow rate of the drug inside the tubing which causes two key problems: First, there are failures that remain undetected and, second, over-sensitive pumps produce a high number of false alarms. Alarm fatigue and infusion pump medication errors were named as number one and two by the ECRI Institute on its list of top 10 health technology hazards for 2014.
Common failures during infusion therapy include air-in-line, occlusion, free flow, cross-flow in multi-infusion settings and infiltration or extravasation. While all of the above failure modes are very well-established to hospital staff, current infusion pumps can at best only spot the first three. Sensirion’s liquid flow sensing technology enables smart infusion pumps to detect not only these failures, but also cross-flow, reverse flow, and even infiltration errors in a reliable manner.
Sensirion’s Sensor Technology
Sensirion’s sensor technology for medical devices is based on over 10 years of experience in measuring extremely low flow rates using advanced CMOSens® components that integrate MEMS and CMOS portions on one monolithic silicon chip. By incorporating this miniature flow sensor chip into a range of packages, Sensirion has effectively optimized diagnostics, automation and semiconductor industry processes globally. The same proven technology can be used in infusion applications and medical devices to improve 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 small amount of heat into the bypassing liquid. The shape of this “heat cloud” is observed 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 reliably and continually measure the low flow rates which are common for medical applications. Every sensor is completely calibrated and delivers a linearized, digital output to guarantee maximum accuracy. CMOSens® technology is extremely scalable and allows sensor solutions to be technically as well as economically viable. The sensor chip is packaged into a plastic housing which features all electrical, mechanical, and fluidic connections needed to easily combine it into for example an infusion set.
Combined into an infusion set, Sensirion’s disposable liquid flow sensor communicates the flow rate inside the tubing in real-time allowing an unparalleled reliability and safety for infusion therapies. Occlusion for instance can be detected within a few seconds by sensing a decrease in the flow rate even in ultra-low flow ranges.
There is no need to wait for 45 minutes before an alarm is activated by an infusion pump. Drops in main infusions because of cross-flow errors from secondary lines can be detected swiftly so that corrections can be done without influencing patient therapy. The sensor also features bubble detection to detect air inside the infusion tubing. Sensirion’s liquid flow sensor is quick, precise, and smart. Moreover, it is sufficiently sensitive to detect the smallest variations in the flow rate. For example, it is so sensitive that it can detect the systematic 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 (see Figure 1).
Detecting the heartbeat on the flow rate is a direct sign of an intact connection of the infusion cannula to the vein of the patient; on the contrary, absence of the pulsation specifies an interrupted connection. Probable causes may include for example, 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 offers a unique probability of detecting infiltration rapidly and preventing detrimental 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 (see Figure 2). With infiltration, the IV fluid is a so-called non-vesicant agent causing irritations, while extravasation describes the efflux of vesicant agents that can damage the tissue.
Potent drugs, used in chemotherapy for instance, are such vesicant agents. The damage can extend to involve tendons, nerves, and joints and can last for months after the preliminary incident. If treatment is delayed, skin grafting, surgical debridement, and even amputation may be the unnecessary consequences. Possibly severe consequences reinforce the need to include disposable liquid flow sensors for improved safety and reliability in infusion therapy.
The frequency of complications caused by extravasation is not easy to define clearly, differing heavily between different hospitals and tending to be basically underreported. However, the estimated incidence rate published in literature is between 0.1% and 6% for patients undergoing chemotherapy. Extravasation not only causes harm to patients but also imposes heavy costs on the healthcare system, while both of them could be avoided. The costs following an extravasation injury can be huge including prolonged therapy, a longer hospital stay as well as legal costs.
Figure 2. Illustration of infiltration. (Source: Sensirion)
Cause of Extravasation
The leakage of IV fluid into the nearby tissue can be caused by numerous reasons including damage to the vein’s backside during catheter insertion. However, one of the most usual reasons is the puncture of the vein wall by mechanical friction of the catheter needle.
This is usually preceded by an occlusion. With a traditional 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 sometimes almost an hour later. Detecting the occlusion rapidly and reliably and thus stopping the infusion pump can prevent the rupture of the vein and the ensuing 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 intrinsic 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 allow for a regulated drug delivery on a much wider scale than today.
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Failures that remain totally undetected today can be detected or even prevented. This will result in increased patient safety and well-being, a lessened workload and less stress for hospital staff, and overall savings in the healthcare system.
This information has been sourced, reviewed and adapted from materials provided by Sensirion Inc.
For more information on this source, please visit Sensirion Inc.