Ying Li

Respiratory detection plays a significant role in the assessment of human health status and in aiding the diagnosis of diseases. This requires the development of fast, economical and non-invasive detection technologies. This research employed tunable diode laser absorption spectroscopy (TDLAS) to analyze exhaled methane (CH ₄ ) levels in patients with gastrointestinal diseases. The system achieving a minimum detection limit (MDL) of 42.12 ppbv, and an accuracy of 8.04 ppbv. A total of 451 samples of exhaled CH ₄ concentration from gastrointestinal surgery patients were detected, and several gastrointestinal diseases with high average CH ₄ concentration were screened out. Support vector machine (SVM) algorithms were used to investigate the relationship between CH ₄ levels and specific gastrointestinal diseases. The study achieved a classification accuracy, recall, and precision rate of 100% for ileus, ascending colon cancer (COAD), and cancers with liver metastasis. Meantime, the rate of CH ₄ positivity for patients undergone postoperative chemotherapy was observed to be significantly lower than patients with active cancer. However, the presence of CH ₄ was not significantly associated with gastrointestinal stromal tumors of the stomach (GIST), stomach cancer (SC), or rectal cancer (READ), indicating the need for a multifaceted diagnostic approach incorporating additional gas markers. In conclusion, CH ₄ analysis holds promise as a novel non-invasive diagnostic tool for gastrointestinal diseases, with significant potential for clinical application.