FEATURE MEDICAL & PHARMACEUTICAL
system that collects information about oesophageal performance in greater detail than conventional manometry. To build its tactile array sensors, PPS
arranges the electrodes as orthogonal, overlapping strips. A distinct capacitor is formed at each point where the electrodes overlap. By selectively scanning a single row and column, the capacitance at that location, and thus the localised pressure, is measured. With this approach, a PPS tactile
array can feature up to 8,192 integrated sensing elements while measuring pressures as low as 0.01 psi.
ARTERIAL LINE LOCATORS According to Dr Son, another promising application for capacitive tactile sensors is arterial line placement - a common, but difficult, procedure performed in a clinical setting. An arterial line is a thin catheter
inserted into an artery. It is most commonly used in intensive care medicine and anaesthesia to monitor blood pressure continuously and to obtain samples for blood gas analysis. This type of intra-arterial measurement is much more accurate than noninvasive alternatives. Arterial lines are typically inserted
by respiratory therapists, physicians, phlebotomists, anaesthesiologist assistants and nurse anaesthetists. The catheter is usually inserted into the radial artery in the wrist, but can also be inserted in other arteries in the body. Arterial line insertion is considered
safe, with a rate of major complications below 1%. However, insertion of an arterial catheter is an invasive procedure and complications can occur. Locating the artery can prove difficult,
even for trained clinicians. The mean diameter of the radial artery is only about 2.3mm in adults and a weak pulse can make it even more difficult. To insert the arterial line, the clinician typically uses the left hand to detect
“This new technology can measure pressure in a different way from traditional methods. It will revolutionise how easily people can take blood pressure. It is really exciting right now, not just to be a sensor provider but to actually develop these applications”
and feel for the pulsating artery, then inserts the needle and extracts a blood sample using the right hand. To hit the artery, the clinician may
need to insert the needle multiple times, which can be painful and uncomfortable to the patient. Because the artery is innervated, the patient sometimes jumps when the needle is inserted, which can lead to needle-stick injuries. This is relatively common and can be a transmission path for blood-borne infections such as Hepatitis and Human Immunodeficiency Virus (HIV). In fact, an accidental needle-stick of
a physician in the UK ultimately became the stimulus for a grant from the Scottish government to seek a safer, more reliable method of inserting arterial catheters. PPS UK, in partnership with the University of Strathclyde, set out to develop a device to simplify arterial localisation and make it safer. For this particular project, the goal was
to design a low-cost, portable sensing system capable of locating an artery accurately to within 0.5mm. The device needed to enable a one-shot procedure by relatively untrained staff that was significantly safer than existing methods. The device utilises PPS tactile sensor arrays in a conformable material that is worn over the clinician’s index and middle fingers. The sensor identifies the location of the pulse, and indicates the location using LEDs and a needle guide to facilitate needle insertion. The device also protects the clinician’s fingers against needle-stick injuries. Not only does this new device provide
a more effective means to perform artery punctures, but it offers an ideal solution for eliminating needle-stick injuries.
BLOOD PRESSURE AND CONSUMABLE WEARABLES Today, the holy grail of blood pressure monitoring is for consumer wearables such as smartwatches and fitness bands. Currently, most are limited to measuring heart rate, but many companies are already developing next generation devices with wristbands capable of taking blood pressure, pulse and other key arterial measurements. For example, Seoul-based Kairos
Watches has developed several products designed to deliver high tech elements such as text messages, push alerts, and apps to those that otherwise still want to own and wear a traditional high end Swiss analogue watch. The options include a transparent display that fits over the lens of an analogue watch, as well as a Bluetooth-enabled wristband with integrated display and touch sensors, called the T-Band. More advanced models of the T-band include features such as a 9-axis gyroscope, accelerometer, compass, optical sensor and a Galvanic Skin Sensor that detects skin temperature and sweat. The company is currently working
with PPS to integrate capacitive tactile pressure sensors into the slim form factor of the T-band for daily monitoring of pulse and blood pressure.
Using capacitive tactile sensors, blood pressure can be measured using sophisticated arrays that map the pressure above the artery
20 DECEMBER/JANUARY 2017 | INSTRUMENTATION
REVOLUTIONISING BLOOD PRESSURE MONITORING PPS is excited to see capacitive tactile pressure sensing technology enable a new wave of healthcare products based on non-invasive arterial pressure measurement. Dr Son concludes: “This new technology can measure pressure in a different way from traditional methods. It will revolutionise how easily people can take blood pressure. It is really exciting right now, not just to be a sensor provider, but to actually develop these applications.”
Pressure Profile Systems
www.pressureprofile.com
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