Exhaled breath condensate based breath analyser: Real-time thermofluidic standardisation of hydrogen peroxide for longitudinal COPD monitoring: a pilot investigation.

Chronic obstructive pulmonary disease (COPD) remains a leading cause of morbidity and mortality worldwide, yet current monitoring strategies based on clinic spirometry and symptom reporting often fail to detect early exacerbations. Exhaled breath condensate (EBC) offers a non-invasive alternative; however, substantial variability in biomarker concentrations has limited its clinical translation. This study aimed to quantify longitudinal variability of EBC hydrogen peroxide (H2O2) in healthy volunteers and COPD participants and to determine whether real-time correction for physiological sampling conditions could improve measurement consistency. We developed a handheld EBC collection device integrating temperature and inspiratory flow sensors with an on-the-fly correction algorithm to compensate for temperature- and flow-dependent heat and mass transfer effects. In artificial breath experiments, the algorithm reduced measurement variability from 20% to 7%. In a three-month longitudinal pilot study, 15 COPD participants and 15 healthy volunteers were assessed at monthly intervals (three visits per subject). H2O2 concentrations were significantly higher in COPD participants than in healthy controls (p < 0.001), and this difference was preserved after standardisation. After standardisation, month-to-month variation in healthy volunteers was no longer statistically significant. Electrochemical detection using a Prussian blue-based sensor showed good agreement with a fluorometric reference method, with 94.8% of measurements within the 95% limits of agreement, a mean bias of 0.112 μM, and a standard deviation of 0.41 μM. Most participants rated the device as easy and comfortable to use. These findings support the technical feasibility of portable, standardised EBC H2O2 measurement. This approach warrants further evaluation in COPD studies.