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Development of an intraluminal photoplethysmography sensor for the assessment of bowel viability

Patel, Z (2019). Development of an intraluminal photoplethysmography sensor for the assessment of bowel viability. (Unpublished Doctoral thesis, City, University of London)

Abstract

Intestinal anastomotic complications that occur mainly due to ischaemia are a serious risk in colorectal cancer patients undergoing surgery. Surgeons continue to rely on subjective methods such as visual inspection, due to the lack of assessment tools. Continuously and quantitatively monitoring bowel viability is therefore essential to minimise postoperative complications, which are currently not being identified efficiently.

A novel intraluminal optical sensor and processing system, have been designed and developed to overcome the limitations in bowel viability assessments. Within the lumen of the colon, the sensor uses the techniques of photoplethysmography (PPG) and pulse oximetry (PO). Advanced Monte Carlo modelling was also utilised for a better understanding of the light-tissue interaction occurring within the lumen of the bowel. The sensor specifications were reinforced by in-silico evaluations of contact and non-contact geometries between the sensor and colon. Prior to clinical pilot studies, the sensor was evaluated in twenty healthy volunteers on the buccal mucosa, as a surrogate for the colon mucosa. Furthermore, in-vivo measurements were made in twenty patients prior to bowel resection surgeries.

The in-silico evaluations revealed, for the first time, the behaviour of photons within the colon. Contact and non-contact modelling have shown that photons penetrated no further than the muscularis layer, where a large detection of photons could still be achieved in a non-contact instance. These results correlated with the in-vivo study within the buccal mucosa. Non-contact distances up to 5mm were the most optimal, producing signals of high quality with a maximum signal-to-noise ratio (SNR) of 26 dB, resulting in reliable estimations of blood oxygen saturation (SpO2).

The first in-human colorectum results demonstrated the ability to continuously acquire good quality PPG signals at different depths with a SNR ranging between 30 dB and 37 dB. A multiple comparison of the colorectal SpO2 at each depth indicated no significant difference was found [ANOVA, F = 0.43, p = 0.7847 (p < 0.05)]. The intraluminal PPG sensor could be used as an assessment tool for bowel viability.

Publication Type: Thesis (Doctoral)
Subjects: Q Science > QM Human anatomy
Departments: School of Mathematics, Computer Science & Engineering
URI: https://openaccess.city.ac.uk/id/eprint/23776
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