Small but Mighty: Sensors and Pumps Ensure Patient Safety

08/01/2016

Medical technology is lost without them: pumps and sensors. They ensure the smooth operation of large devices such as dialysis machines or CT scanners. That said, even the smallest miniature versions used in implants or blood glucose meters, for instance, can pack a punch.

Image: Insulin pump hanging at a woman's hip; Copyright: panthermedia.net/photographee.eu

Insulin pumps automatically release a dose into the body. Beforehand the dose will be set by doctor and patient; © panthermedia.net/photographee.eu

Their use also increasingly contributes to patient safety. The Fraunhofer Institute for Silicate Research in Würzburg, Germany, has developed stockings with integrated 3D sensor technology to alert the wearer if the pressure on the feet is too high, thus avoiding injuries and tissue damage. Diabetics don’t perceive this pressure in the same way healthy people do. Forty very small dielectric elastomer sensors take over the function usually performed by the nerves in the feet of diabetes patient by monitoring the pressure. Patients subsequently receive a message on their smartphone or tablet, indicating whether they need to change their foot position.

The Vivago wrist care system was specifically developed for senior citizens. The wrist watch automatically sends a signal to a dedicated caregiver if the wearer falls or passes out for example. Integrated temperature and motion sensors continuously monitor muscle contractions and skin temperature. It’s essential for wearers not to be bothered by the sensors that are embedded into clothing or into wearables, so they can go about their day without any interruptions.

A sensor developed by the RWTH Aachen University is designed to detect the level of dehydration. Four electrodes that are attached to the body indicate the water content within the muscles and alert the wearer to water depletion and dehydration.

Patients manage their own medication dispensing

Generally, these technologies can also be managed by patients. The PCA pump (patient-controlled analgesia pump), often also called pain relief pump is controlled by the patient. An overdose is impossible because a locking mechanism automatically prevents further dispensation after the suggested dose has been dispensed. The electronically controlled pump injects the drug at the push of a button.

Insulin pumps have already been used for more than 25 years to treat patients with type 1 diabetes. Attached to the body, the device pumps the medication through a plastic catheter into the subcutaneous fatty tissue. Physician and patient determine the required dose beforehand; however, it still needs to be monitored since blood glucose levels can constantly change. The patient is also able to control how much insulin the pump should dispense.

Image: HeartMate III; Copyright: Thoratec

The HeartMate III is only three to five centimeters and can be minimally invasive implanted; © Thoratec

Miniaturized ventricular assist device implants are gentle on patients

Miniature pumps are also used to treat vital organs, as is the case with HeartMate III. Cardiovascular surgeons in Tübingen have been among the first doctors in Germany to implant this modern ventricular assist system which supplements the pumping function of the heart with a small centrifugal pump. "Thanks to the pump, blood can flow from the left ventricle to the aorta," explains Prof. Christian Schlensak from the University Hospital Tübingen. The device is implanted into patients who suffer from advanced heart failure, wait for a heart transplant or are not candidates for heart transplantation as well as patients who are recovering from myocardial infarction (heart attack). 85 percent of all patients who received this implant, were able to live past the first critical year.

An electrical drive outside the body and attached battery system are connected to the assist system in the body via a cable. Thanks to its compact size of approximately three by five centimeters, the HeartMate III is implanted using a minimally invasive approach and is, therefore, gentler on the patient than conventional systems. "Smaller devices don't need an extra hollow space to position the pump in the body," explains Schlensak. The system is inserted through the chest wall, making fewer incisions necessary. With previous other devices, the chest wall always had to be opened up, oftentimes causing patients severe pain. In addition, there is less blood trauma, meaning individual blood components are less strained due to the small size of the device. "Modern pumps like the HeartMate III are able to imitate the pumping ability of the heart and are adapted to its physiology." This was previously not possible with conventional pumps.

The assist system has a fully automatic control system. "However, the patient's job is to monitor the blood flow and change the batteries after approximately 15 to 20 hours," cautions Schlensak. There are also several risk factors after the device has been implanted. The blood could form clots and cause an embolism. Bleeding might also occur since the device wearers take blood thinners in all cases. Infections may occur at the body’s incision site. According to Schlensak, there are fewer complications with transplants but since there are not enough available donor organs, implants are considered the first step at this point. "We are currently working on completely inserting the system into the body without an external controller," emphasizes Schlensak. 

Devices are more accurate and more reliable than human beings

A large number of available miniature sensors and pumps is utilized for various purposes in medical technology. They offer tremendous support to physicians and patients and can contribute to patient safety by warning of dangers or by automatically administering medication. However, integrated sensors and pumps are not able to provide 100 percent protection. Regular checkups by the doctor and patient are essential. It also implies that patients are trained in using these types of medical devices. Yet these small components also make a big contribution in providing assistance to their wearers since they are far more accurate and reliable in performing their programmed tasks than humans.

Image: Lorraine Dindas; Copyright: B. Frommann

© B. Frommann

This article was written by Lorraine Dindas and translated by Elena O'Meara.
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