Background:
Arterial cannulation can at times be difficult to perform using palpation alone to locate the best site to access the artery. Often when difficulty in arterial access is anticipated, the proceduralist will use a tool such as an ultrasound or a doppler. Both of these techniques afford the user improved ability to locate the position of the artery. The authors herein describe the development of a novel device, the Artery Mapper, that can also aid the user in more accurately locating a peripheral artery. The authors’ goal was to design and build a device that would be easier to use than the ultrasound, and less expensive so that it could be readily available in every anesthesia cart.
Methods:
The basic design consisted of a sensor with an overlying display. It was determined that a sensor that measured the pressure from arterial pulsations would be the most reliable way to find the artery. Thus a literature review was conducted on different kinds of pressure sensors such as piezoelectric crystals and polymer based sensors. Since one of the goals of this project was to keep the device inexpensive, it was determined that the cheaper, polymer based pressure sensors would be the better choice. A collaboration with the UW Center for Intelligent Materials and Systems (CIMS) was then formed, and work began shortly thereafter to build the device.
The sensor material chosen was dielectric elastomer (DE), which uses capacitance based sensing. When a pressure is applied across the sensor, a measurable capacitance change (pF) results. Many versions of this sensor were created with the goal of maximizing sensitivity, resolution, and accuracy, while not sacrificing signal to noise ratio and pixel independence, and without overburdening the support electronics.
For the overlying screen, initially electrochromic materials were investigated since they could be manufactured to have a slim, flexible profile. However, preliminary testing showed that it would be prohibitively difficult and expensive to pixelate the electrochromic material to an adequate resolution. Thus work shifted to stock LCD or oLED screens to interface with our sensor.
Results:
The current iteration of the device consists of a DE sensor array with 1mm2 pixels. The support electronics, which are mainly comprised of a capacitance to digital converter, multiplexers, and a microprocessor, have been optimized for this DE sensor. Lastly, an oLED screen sits atop the sensor. Casing to enclose the device is currently being designed to be 3D printed. Conductive polymer will be used for the casing with the hopes of creating a Faraday cage-like effect to shield the device from ambient electrical noise.
Conclusions:
In conclusion, a novel device aimed to aid in arterial cannulation and sampling has been built. Preliminary testing in the lab has shown favorable sensitivity to the radial pulses of the engineers involved in building it. A large scale clinical test to validate the device is planned, pending IRB approval.
Research reported in this abstract was supported by the WSSA Seafair Grant.
