Dynamic Changes in Exhaled Breath Glucose by Condensate Collection During Oral Glucose Tolerance Testing in Healthy Adults

Wen Xu,1 Qingping Zhang,1 Yilian Hong,1 Zhenjun Mao2 1Department of Internal Medicine, University Campus, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, People’s Republic of China; 2Department of Chemistry, Zhejiang University, Hangzhou, Zhejiang, People’s Republic of ChinaCorrespondence: Wen Xu, Department of Internal Medicine, University Campus, The Second Affiliated Hospital of Zhejiang University School of Medicine, Hangzhou, Zhejiang, 310012, People’s Republic of China, Email zjxuwen1982@zju.edu.cnPurpose: Invasive blood glucose monitoring is associated with pain and suboptimal patient adherence, creating a need for non-invasive alternatives. In this study, we investigated the dynamic relationship between glucose levels in exhaled breath and blood during an oral glucose tolerance test (OGTT) in healthy adults, to assess the feasibility of using exhaled breath glucose as a non-invasive marker for glycemic monitoring.Methods: Twenty healthy volunteers (12 males, 8 females; mean age 23.1 ± 2.4 years) underwent a standardized OGTT test. Exhaled breath condensate (EBC) and blood samples were collected simultaneously at fasting (0h) and at 0.5h, 1h, 2h, and 3h post-glucose load. EBC glucose concentration was measured using ion chromatography. The temporal profiles of both parameters were analyzed, and the correlation between the rate of change in exhaled breath glucose and blood glucose at each time point was assessed using Pearson or Spearman correlation test.Results: Both blood glucose and exhaled breath glucose exhibited similar temporal patterns, peaking within 0.5– 1 h after glucose administration and returning to baseline by 3h. Exhaled breath glucose increased from a fasting level of 0.49 ± 0.11 ng/L to a peak of 4.07 ± 1.44 ng/L at 1h. A statistically significant positive correlation between the rate of change in exhaled breath glucose and blood glucose was observed at 1h (r = 0.84, p < 0.000), whereas the correlation at 0.5h was not significant after correction for multiple comparisons (ρ = 0.45, adjusted p = 0.196). No significant correlations were detected at 2h or 3h. The changes in exhaled breath glucose were not associated with baseline pulmonary function—as measured by forced vital capacity (p > 0.05).Conclusion: Exhaled breath glucose levels dynamically track blood glucose changes during the early postprandial phase in healthy adults, demonstrating strong concordance during periods of rapid glycemic excursion. These findings support the feasibility of EBC as a non-invasive tool for monitoring glycemic trends. Further validation in larger cohorts and diabetic patients is required to establish its clinical utility.Keywords: exhaled breath condensate, EBC, oral glucose tolerance testing, OGTT, invasive blood monitor