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NOVEL ENDOSCOPIC IN-VIVO REAL-TIME MUCOSAL OXYGEN SATURATION MEASUREMENTS OF THE GASTROINTESTINAL TRACT: DEFINING NORMAL VALUES FOR UPPER AND LOWER ENDOSCOPIES

Date
May 18, 2024

Introduction: A novel endoscopic system integrates a spectrophotometer, allowing real-time evaluation of tissue oxygen saturation (StO2) during routine endoscopy by illuminating the mucosa with select wavelengths of visible light and detecting reflected light. As oxyhemoglobin and deoxyhemoglobin have different light absorption properties, mucosal oxygen saturation can be measured. Our study aims to use this new technology to evaluate normal StO2 levels in the gastrointestinal tract.
Methods: Consecutive patients who underwent standard-of-care white light endoscopy (WLE) by a single endoscopist with the Fujifilm ELUXEO Vision endoscope between June and October 2023 were included in the study. Endoscopic images with a superimposed StO2 heatmap were taken at standardized anatomical landmarks: distal esophagus, gastric fundus, gastric antrum, and duodenal bulb for upper endoscopies; cecum, transverse colon, and sigmoid colon for colonoscopies (Figure). A circular Region of Interest (ROI) was drawn on each picture with standardized methodology, avoiding hypersaturated zones, shadowing, WLE glare, stools, and blood. Proprietary software was used to extract the average StO2 within each ROI. Paired t-tests were performed to evaluate the difference in StO2 levels between anatomical regions. As the StO2 values were not normally distributed, bootstrapping with 2000 iterations was used to obtain means and 95% confidence intervals.
Results: 67 patients (mean age 66.3 years, 64.2% females) were included. 79 procedures (53 EGDs, 26 colonoscopies) were performed, with 12 patients undergoing both upper and lower GI endoscopy. Only StO2 readings associated with endoscopically or biopsy-proven normal tissues were analyzed. Mean StO2 was 31.7% (95% Confidence Interval: 26.0-37.5) in the distal esophagus, 92.6% (89.4-95.4) in the fundus, 88.1% (82.7-92.8) in the antrum, and 78.5% (72.7-84.2) in the duodenal bulb (Table). Paired t-tests showed statistically significant differences between distal esophagus and fundus, antrum, and duodenal bulb (all p-values<0.001), between duodenal bulb and fundus (p=0.001) and antrum (p=0.02), but no significant difference between fundus and antrum (p=0.12). Mean StO2 was 84.5% (77.4-90.6) in the cecum, 70.1% (62.9-76.8) in the transverse colon, and 57.9% (49.7-66.6) in the sigmoid colon. All p-values were <0.05 (Table). No differences were seen for sex, race, and age (p>0.05).
Conclusion: In this study we report normal ranges of mucosal oxygenation of the GI tract, highlighting significant regional differences, with the lowest StO2 levels in the esophagus and in the sigmoid colon. These differences are likely explained by relative variations in arteriovenous circulation. Deviations from these values may represent pathological states and may have implications on clinical endpoints such as symptoms, surgical outcomes, and future therapies.
Figure. Typical heatmap appearance of different anatomical regions

Figure. Typical heatmap appearance of different anatomical regions

Table. Normal range of StO<sub>2</sub> in different regions and comparison with paired t-tests

Table. Normal range of StO2 in different regions and comparison with paired t-tests


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