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

Abstract

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.

Intramuscular Microvascular Flow Sensing for Flap Monitoring in a Porcine Model of Arterial and Venous Occlusion

“…17 18 Additionally, these devices require a skin component for measurement. 19 Several alternative devices have been proposed, such as fully implantable ultrasound Doppler systems 26 27 and Doppler-equipped venous couplers. 28 These offer improvements on the design of the commonly-used Cook Doppler, which requires an external wire and offers no opportunities for remote monitoring.…”

A Wireless Near-Infrared Spectroscopy Device for Flap Monitoring: Proof of Concept in a Porcine Musculocutaneous Flap Model

“…This clinical problem has spurred the proposal of several potential wireless solutions. These include a totally implantable Doppler system, [19][20][21] and an implantable biodegradable arterial pressure sensor which is able to detect flow across the arterial pedicle vessel. 22,23 These innovations represent a potential improvement upon the familiar Cook-Swartz Doppler 24 which requires a wired connection between the vascular cuff and the bedside device.…”

Implantable Sensors for Post‐Surgical Monitoring of Vascular Complications

“…[1,53] Although it has been widely used and proven to be accurate, effective, and cost-efficient to reduce surgical failure rates, limitations include the limitation of patient activity that prevents long-term use, the risk of vascular injury, the potential for increased false-positive rates due to the learning curve, and the difficulty of early identification of venous occlusion. [3,32,54] However, due to the limitations of size and lifetime, there is a lack of ideal wireless implantable ultrasound sensors that have the potential to outperform traditional implantable probes for post-surgical monitoring, and the application of technologies such as wireless power transmission is expected to be a solution to the problem. [3,55] In a study, the size can be reduced to approximately 18.0 cm 3 , but it still falls short of the ideal level and has a short lifetime limited by the built-in battery.…”

“…[3,55] In a study, the size can be reduced to approximately 18.0 cm 3 , but it still falls short of the ideal level and has a short lifetime limited by the built-in battery. [54] Figure 4. A bioresorbable dynamic pressure sensor for cardiovascular postoperative care.…”