Posted in | Medical Sensor

New Liquid Bandage Measures Oxygen Levels in Transplanted Tissues

Scientists from Massachusetts General Hospital (MGH) and surgeons from Beth Israel Deaconess Medical Center (BIDMC) have conducted the first human clinical trial to confirm the accuracy and practicality of an oxygen-sensing liquid bandage that quantifies the amount of oxygen in transplanted tissues.

Published in the Science Advances journal, the clinical trial compared the performance of an innovative, paint-on bandage developed with phosphorescent materials to a wired tissue oximeter called ViOptix device—the present standard for tracking tissue oxygenation—in the female population who undergo breast reconstruction surgery following cancer.

Our trial showed that the transparent liquid bandage detected tissue oxygenation as well as the gold standard of an oximeter, which uses old technology, is uncomfortable for the patient, obstructs visual inspection of the tissue, and can give false readings based on lighting conditions and the patient’s movements.

Conor L. Evans, PhD, Study Senior Author and a Principal Investigator, Wellman Center for Photomedicine, Massachusetts General Hospital

Evans continued, “The standalone bandage is a major advancement from a wired oximeter that restricts a patient’s movements and is complicated to use.”

The researchers accepted the task of designing an improved tissue oxygenation sensor after a request from the Department of Defense that was looking for ways to minimize the failure rates of skin grafts and tissue transplant surgeries in injured soldiers.

The Military Medical Photonics Program supported the development of the technology underlying the liquid bandage. During the clinical trial, the researchers tested the bandage used in breast reconstruction—a standard type of free-flap transplant procedure in which the skin, arteries, blood vessels, and fat are harvested from the abdomen of the patient and then the vessels and tissues are microsurgically reattached to the patient’s chest.

Up to 5% of free-flap surgeries can fail, typically within 48 hours after surgery, if blood flow to the transplanted tissue is interrupted or inadequate, which is a devastating outcome.

Samuel J. Lin, MD, MBA, Study Senior Author and Plastic and Reconstructive Surgeon, Beth Israel Deaconess Medical Center

By tracking the amount of oxygen that reaches the transplanted tissue, plastic surgeons can rapidly identify a vascular issue and take measures to save the transplant.

The clinical trial, conducted from March to September 2017, included five women undergoing breast reconstruction surgery. The oxygen-sensing liquid bandage was painted on an area of 1 x 1 cm on seven transplanted flaps (in two women, both breasts were reconstructed). In addition, a wired tissue oximeter was positioned on each transplanted flap, and tissue oxygenation was tracked for a period of 48 hours following surgery.

The liquid bandage quantifies the concentration of oxygen that reaches the tissue itself, whereas the ViOptix device reads the concentration of oxygen saturation in the blood using near-infrared spectroscopy—a less direct quantification of critical blood flow to the tissue transplant.

In the latest research work, a clinician-researcher used a digital camera with custom filters to take pictures of the liquid bandage after the surgery. The flash from the digital camera activated the phosphorescent material in the liquid bandage, which subsequently glowed red to green colors based on the concentration of oxygen existing in the tissue.

Evans and collaborators have since designed a battery-powered sensor head for the novel bandage that avoids the requirement for the camera and renders the bandage self-contained. The prototype research work was published in the Biomedical Optics Express journal.

In all the seven transplanted flaps, the bandage measured the rate of change in tissue oxygenation and this value corresponded with the wired oximeter, with all the seven flaps demonstrated to be effective.

At present, the team is designing a clinical trial to analyze the ability of the bandage to detect a flap that is failing because of the absence of oxygen.

The ability to have a wireless oxygen monitoring device for blood flow is potentially a gamechanger.

Samuel J. Lin, MD, MBA, Study Senior Author and Plastic and Reconstructive Surgeon, Beth Israel Deaconess Medical Center

Clinical uses for an oxygen-sensing liquid bandage may include tracking wound healing, skin grafts for burns, tissue transplants for trauma, chronic ischemia (reduced blood flow) and limbs affected by peripheral artery disease.

The technology might also detect important tissue changes in patients with heart disease and other chronic medical conditions, providing an early warning signal that disease is progressing. And there are likely other clinical uses we haven’t yet considered,” Lin concluded.

Evans is a primary investigator from the Wellman Center for Photomedicine at MGH and is also an associate professor at Harvard Medical School (HMS). Lin is program director of the BIDMC/HMS Plastic Surgery Residency Program and associate professor of Surgery at HMS.

Haley Marks, PhD, was a research fellow at the Wellman Center for Photomedicine at MGH; Alexandra Bucknor, MD, was a research fellow at BIDMC; and Emmanuel Roussakis, PhD, is a research fellow in Dermatology at MGH.

Journal Reference:

Marks, H., et al. (2020) A paintable phosphorescent bandage for postoperative tissue oxygen assessment in DIEP flap reconstruction. Science Advances. doi.org/10.1126/sciadv.abd1061.

Source: https://www.massgeneral.org/

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