A team of researchers from City, University of London, working with the National Bowel Research Centre, has developed a sensor that will aid during and after bowel resection surgeries for treating colorectal cancer. The team, led by Zaibaa Patel, is working on a photoplethysmography (PPG) sensor that measures physiological variables through the interaction of light with the tissue, to monitor the intestine’s wellbeing, during and after surgery. Currently, the gold standard for assessment of bowel surgery is visual inspection, which is not objective (EMBC doi: 10.1109/EMBC.2017.8037204).
The research group aims to provide a proof-of-concept for a device that will provide a continuous stream of measurements during and after bowel resection. They hope to implement this technology to help monitor the health of the large intestine, as the current method of supervision is subjective and can only be done before closing the patient. Further supervision is then limited to observing clinical signs and symptoms.
Designing the proof-of-concept
The researchers faced various challenges in designing a probe, and focused on minimizing the PPG technology to make a device suitable for use during surgery and comfortable after. The technology had to be consistent with standard functionalities of PPG sensors and safe to use inside the body. The team miniaturized the probe to have the LEDs and sensor fully contained in an area of 5.2 x 10.4 mm. To put this in perspective, a standard PPG sensor for the finger spans an area of twice that size.
To prove that the device was safe to use in soft tissue, the researchers designed an experiment to simulate the conditions in a patient intestine using a pig’s intestine. They then monitored closely the temperature inside and outside the intestine wall while the probe was in operation. The temperature of the tissue remained within a safe 37 °C.
Finally, Patel and collaborators tested the device’s performance in twelve test subjects, by placing the sensor inside the mouth and comparing the recorded signal to a signal acquired from the finger, as is traditionally done in PPG measurements. They obtained satisfactory readings that showed correlation between the signals from both locations.
Bringing the technology into the operating room
According to Cancer Research UK, colorectal cancer is the second most common cause of cancer deaths in the UK, where the only curative treatment is removing the tumour-bearing area. This involves surgeons cutting away the section of the bowel that is affected, and reattaching the two ends. A huge risk during (and after) the operation is that the bowel will not reattach properly, and the bowel content will leak into the abdomen. This is a difficult condition to diagnose within a short enough time-frame to save the patient. This latest research, therefore, aims to provide the tools to assess the patient’s bowel in real time.
