Wearable, Wireless Deep-tissue Sensing Patch for Continuous Monitoring of Recovery from Microsurgical Tissue Transfer

Technologies that can closely monitor surgical recovery and wound healing for timely, proactive
treatments represent an essential keystone to developing next-generation personalized medicine that can further
reduce patient pain, prevent morbidity and death, and improve individual wellbeing. Microsurgical tissue transfer
entails surgical elevation of a portion of tissue (or flap) based upon its defined vascular supply in the form of a
single artery and vein. While this reconstructive strategy is well-accepted, failures do occur and almost always
result from early microvascular thrombosis. This flap-threatening event occurs in 6-14% of cases, and if
untreated flap necrosis and reconstructive failure are inevitable. The most common flap monitoring strategies is
serial physical examination and external doppler examination. However, these strartegies are limited by its
inherently subjective nature and the requirement for skilled bedside personnel to check the flap frequently. And
the intermittent assessment is subject to delay in the diagnosis of malperfusion, since clear signs of malperfusion
may take several hours to become obvious. Recent developments in wearable electronic sensors with built-in
systems on chip enable opportunities for real-time monitoring of physiological conditions of targeted tissues.
However, wearable biosensors that feature skin-interface pose a challenge: to sense physiological
parameters such as oxygenation of tissue microenvironments at depth. In the case of flap monitoring,
existing devices such as ViOptix are only able to monitor flaps which bear a cutaneous skin. This deficiency
means that muscle flaps must be monitored with indirect sensing technology through neighboring skin, which is
predisposed to delay recognition of muscle malperfusion.
This absence of direct, real-time monitoring technology for muscle-only flaps gives rise to the
fundamental and overarching unmet clinical need: to advance technological platforms for deep-tissue
monitoring. We propose a soft wearable intelligent patch (SWIP) that incorporates microneedle waveguides
to enable deep-tissue sensing of oxygenation without implantation procedures for continuous monitoring of
recovery after microsurgical tissue transfer. We aim for the proposed device to enable physiological
measurements from 4 different locations of skin to yield both local (tissue oxygenation, pulsation intensity, and
blood flow rate) and global (pulsation rate and respiration rate) physiological information continuously and
simultaneously. The sensing interface will rely on biocompatible, optical waveguides in the form of microneedles
to enable light-matter interaction at deep tissue (~ 2 cm below the skin surface). The device will be equipped
with a control module that provides a series of signal pre-processing and a Bluetooth Low Energy (BLE) interface
to advertise the data for further processing by a cloud-based computing device. We envision that the proposed
SWIP will advance diagnostic technology for reconstructive surgery and beyond, and offer real-time monitoring
to facilitate precise customization and personalization in surgical recovery and rehabilitation.