Michael A. Rothfuss

Comparative analysis of compressive sensing approaches for recovery of missing samples in implantable wireless Doppler device

An implantable wireless Doppler device used in microsurgical free flap surgeries can suffer from lost data points. To recover the lost samples, the authors considered the approaches based on a recently proposed compressive sensing. In this paper, they performed a comparative analysis of several different approaches by using synthetic and real signals obtained during blood flow monitoring in four pigs. They considered three different bases functions: Fourier bases, discrete prolate spheroidal sequences and modulated discrete prolate spheroidal sequences, respectively. To avoid the computational burden, they considered the approaches based on the l 1 minimisation for all the three bases. To understand the trade-off between the computational complexity and the accuracy, they also used a recovery process based on a matching pursuit and modulated discrete prolate spheroidal sequences bases. For both the synthetic and the real signals, the matching approach with modulated discrete prolate spheroidal sequences provided the most accurate results. Future studies should focus on the optimisation of the modulated discrete prolate spheroidal sequences in order to further decrease the computational complexity and increase the accuracy.

Assessing interactions among multiple physiological systems during walking outside a laboratory

Gait function is traditionally assessed using well-lit, unobstructed walkways with minimal distractions. In patients with subclinical physiological abnormalities, these conditions may not provide enough stress on their ability to adapt to walking. The introduction of challenging walking conditions in gait can induce responses in physiological systems in addition to the locomotor system. There is a need for a device that is capable of monitoring multiple physiological systems in various walking conditions. To address this need, an Android-based gait-monitoring device was developed that enabled the recording of a patients physiological systems during walking. The gait-monitoring device was tested during self-regulated overground walking sessions of fifteen healthy subjects that included 6 females and 9 males aged 18-35 years. The gait-monitoring device measures the patients stride interval, acceleration, electrocardiogram, skin conductance and respiratory rate. The data is stored on an Android phone and is analyzed offline through the extraction of features in the time, frequency and time-frequency domains. The analysis of the data depicted multisystem physiological interactions during overground walking in healthy subjects. These interactions included locomotion-electrodermal, locomotion-respiratory and cardiolocomotion couplings. The current results depicting strong interactions between the locomotion system and the other considered systems (i.e., electrodermal, respiratory and cardiovascular systems) warrant further investigation into multisystem interactions during walking, particularly in challenging walking conditions with older adults.

The Development of a Wireless Implantable Blood Flow Monitor.

Summary: Microvascular anastomotic failure remains an uncommon but devastating problem. Although the implantable Doppler probe is helpful in flap monitoring, the devices are cumbersome, easily dislodged, and plagued by false-positive results. The authors have developed an implantable wireless Doppler monitor prototype from off-the-shelf components and tested it in a swine model. The wireless probe successfully distinguished between femoral vein flow, occlusion, and reflow, and wirelessly reported the different signals reliably. This is the first description of a wireless implantable blood flow sensor for flap monitoring. Future iterations will incorporate an integrated microchip-based Doppler system that will decrease the size to 1 mm2, small enough to fit onto an anastomotic coupler.

Innovation and Translation Efforts in Wireless Medical Connectivity, Telemedicine and eMedicine: A Story from the RFID Center of Excellence at the University of Pittsburgh

Translational research has recently been rediscovered as one of the basic tenants of engineering. Although many people have numerous ideas of how to accomplish this successfully, the fundamental method is to provide an innovative and creative environment. The University of Pittsburgh has been accomplishing this goal though a variety of methodologies. The contents of this paper are exemplary of what can be achieved though the interaction of students, staff, faculty and, in one example, high school teachers. While the projects completed within the groups involved in this paper have spanned other areas, the focus of this paper is on the biomedical devices, that is, towards improving and maintaining health in a variety of areas. The spirit of the translational research is discovery, invention, intellectual property protection, and the creation of value through the spinning off of companies while providing better health care and creating jobs. All but one of these projects involve wireless radio frequency (RF) energy for delivery. The remaining device can be wirelessly connected for data collection.

A System for Simple Real-Time Anastomotic Failure Detection and Wireless Blood Flow Monitoring in the Lower Limbs

Current totally implantable wireless blood flow monitors are large and cannot operate alongside nearby monitors. To alleviate the problems with the current monitors, we developed a system to monitor blood flow wirelessly, with a simple and easily interpretable real-time output. To the best of our knowledge, the implanted electronics are the smallest in reported literature, which reduces bio-burden. Calibration was performed across realistic physiological flow ranges using a syringe pump. The devices sensors connected directly to the bilateral femoral veins of swine. For each 1 min, blood flow was monitored, then, an occlusion was introduced, and then, the occlusion was removed to resume flow. Each vein of four pigs was monitored four times, totaling 32 data collections. The implant measured 1.70 cm3 without battery/encapsulation. Across its calibrated range, including equipment tolerances, the relative error is less than ±5% above 8 mL/min and between -0.8% and +1.2% at its largest calibrated flow rate, which to the best of our knowledge is the lowest reported in the literature across the measured calibration range. The average standard deviation of the flow waveform amplitude was three times greater than that of no-flow. Establishing the relative amplitude for the flow and no-flow waveforms was found necessary, particularly for noise modulated Doppler signals. Its size and accuracy, compared with other microcontroller-equipped totally implantable monitors, make it a good candidate for future tether-free free flap monitoring studies.Current totally implantable wireless blood flow monitors are large and cannot operate alongside nearby monitors. To alleviate the problems with the current monitors, we developed a system to monitor blood flow wirelessly, with a simple and easily interpretable real-time output. To the best of our knowledge, the implanted electronics are the smallest in reported literature, which reduces bio-burden. Calibration was performed across realistic physiological flow ranges using a syringe pump. The device’s sensors connected directly to the bilateral femoral veins of swine. For each 1 min, blood flow was monitored, then, an occlusion was introduced, and then, the occlusion was removed to resume flow. Each vein of four pigs was monitored four times, totaling 32 data collections. The implant measured 1.70 cm3 without battery/encapsulation. Across its calibrated range, including equipment tolerances, the relative error is less than ±5% above 8 mL/min and between −0.8% and +1.2% at its largest calibrated flow rate, which to the best of our knowledge is the lowest reported in the literature across the measured calibration range. The average standard deviation of the flow waveform amplitude was three times greater than that of no-flow. Establishing the relative amplitude for the flow and no-flow waveforms was found necessary, particularly for noise modulated Doppler signals. Its size and accuracy, compared with other microcontroller-equipped totally implantable monitors, make it a good candidate for future tether-free free flap monitoring studies.

Impact of ISO 18000 Series RF Signals on CRMDS: A Unified Approach

Abstract Radio Frequency Identification technology in recent times is finding several application in the health care industry. With the increase in integration of RFID in daily hospital routines, there is a growing concern about its impact on infirmary equipment and implantable devices. Several organizations have published results on this issue developing individual test procedures but few have tried to generalize the testing procedures. This article is a sincere attempt to understand the science that is unexplored and unreasoned behind the raw results provided; to unify the data sources and present a direction for future research in this branch of engineering. RF sources conforming to ISO 18000 series and impact on Cardiac Rhythmic Medical Devices are presented as an embodiment to summarize the results of testing completed at the RFID Center of Excellence, University of Pittsburgh. The discussion and results presented in this article can be interpolated and extrapolated to the RF communication and Active Implantable Medical Devices.

Abstract 109: venous flow monitoring using an entirely implanted, wireless Doppler sensor.

PurPose: Successful salvage of the threatened free flap is dependent upon prompt diagnosis of vascular occlusion and timely restoration of blood flow. Many monitoring systems can be used to augment clinical exam, but all suffer from drawbacks. The implantable venous Doppler offers rapid diagnosis of vascular compromise, but has a cumbersome transcutaneous wire and is reported to have high false positive rates largely due to inadvertent internal probe dislodgement. A wireless device would avoid these problems. This study describes the implementation of an entirely implanted Doppler sensor with wireless transmission of flow data in a pig femoral vein model.

Automatic Patency Discrimination in the Pig Bilateral Femoral Veins for Biomedical Implants

Free flap surgeries require hourly monitoring to detect vascular compromise. If not caught promptly, the flap can be lost. Monitoring free flaps using the gold standard requires experienced operators to interpret blood flow signatures, which are often difficult to distinguish from background noise. Previously reported hardware-only automatic patency classification showed a high sensitivity, specificity, and a low false-positive rate, but it was demonstrated using bulky discrete electronics and a syringe pump to generate the expected flow rates. In this paper, we investigate automatic hardware-only patency classification on blood flow data collected from the bilateral femoral veins during flow and occluded states using SPICE simulations in an IBM 130-nm CMOS process with a 1-V supply voltage and a 200-ms window length. Experimental results show a very high sensitivity (99.45%), specificity (99.93%), and very low false-positive rate (0.07275%) at just 8.715

System and method for real time asset location and tracking

\mu \text{A}

Automatic Early-Onset Free Flap Failure Detection for Implantable Biomedical Devices

. This paper shows that automatic hardware-only patency classification is effective for monitoring patency on real pig blood flow data. The demonstrated classifier’s performance makes it suitable for integration as part of a wirelessly-powered biomedical patency monitor.