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

Abstract

Background Current near-infrared spectroscopy (NIRS)-based systems for continuous flap monitoring are highly sensitive for detecting malperfusion. However, the clinical utility and user experience are limited by the wired connection between the sensor and bedside console. This wire leads to instability of the flap–sensor interface and may cause false alarms. Methods We present a novel wearable wireless NIRS sensor for continuous fasciocutaneous free flap monitoring. This waterproof silicone-encapsulated Bluetooth-enabled device contains two light-emitting diodes and two photodetectors in addition to a battery sufficient for 5 days of uninterrupted function. This novel device was compared with a ViOptix T.Ox monitor in a porcine rectus abdominus myocutaneous flap model of arterial and venous occlusions. Results Devices were tested in four flaps using three animals. Both devices produced very similar tissue oxygen saturation (StO2) tracings throughout the vascular clamping events, with obvious and parallel changes occurring on arterial clamping, arterial release, venous clamping, and venous release. Small interdevice variations in absolute StO2 value readings and magnitude of change were observed. The normalized cross-correlation at zero lag describing correspondence between the novel NIRS and T.Ox devices was >0.99 in each trial. Conclusion The wireless NIRS flap monitor is capable of detecting StO2 changes resultant from arterial vascular occlusive events. In this porcine flap model, the functionality of this novel sensor closely mirrored that of the T.Ox wired platform. This device is waterproof, highly adhesive, skin conforming, and has sufficient battery life to function for 5 days. Clinical testing is necessary to determine if this wireless functionality translates into fewer false-positive alarms and a better user experience.

Attached compared with unattached surface probes for monitoring flap perfusion in microvascular head and neck reconstruction: a feasibility study

“…Attached surface probes have been developed for the O2C analysis system because of their advantages, such as limited interference from changes in probe pressure and the location of the measurement area, and they provide the basis for continuous flap perfusion monitoring over 24 h a day 14 – 16 . Nevertheless, flap failure due to damage to the flap microvasculature, infection and bleeding due to probe fixation sutures, and technical errors due to probe detachment or disconnection are the potential disadvantages of attached surface probes 17 . Therefore, in the present study, attached surface probes were compared with unattached surface probes in terms of technical feasibility, patient safety, and perfusion measurement values 6 , 11 , 12 , 18 .…”

“…A lighter, smaller, and, as a result, attachable surface probe that measures flap perfusion at a 3 mm tissue depth has recently been developed, with the potential advantages of no changes in probe contact pressure or measurement location over the postoperative monitoring period, both of which may affect flap perfusion measurement 14 – 16 . Nevertheless, damages to the microvasculature of the flap, infection and bleeding due to attachment sutures, or technical errors due to probe detachment or disconnection are potential disadvantages 17 .…”

Flap perfusion monitoring with an attached surface probe in microvascular reconstruction of the oral cavity

“…In general, the study demonstrated that flap perfusion monitoring with attached surface probes for the O2C analysis system was comparable to flap perfusion monitoring with unattached surface probes in terms of technical feasibility and patient safety, as no event of probe detachment or disconnection and no infections or bleeding due to the attachment structures were observed as potential disadvantages of the attached surface probes [ 26 ].…”

Recent Advances and Design Strategies Towards Wearable Near-Infrared Spectroscopy

“…Wu et al [62] constructed a non-invasive, self-contained Bluetooth-enabled wireless NIRS probe using red (740nm) and NIR (860nm) LEDs. With two PDs forming source-detector distances at 5 and 10 mm, the device is encapsulated in a skin-safe silicone elastomer with attachment to nonplanar skin tissue facilitated by a thin medical silicone tape (Fig.…”