Fig. 1.

Real-time breath analysis using SESI-HRMS. a SESI-HRMS analytical platform located in a clinical setting (University Children’s Hospital Basel) dedicated for real-time breath analysis. The system features three main elements: (i) exhalation interface, which provides feedback to the participants on the exhalation maneuver; (ii) ion source, which efficiently ionizes exhaled metabolites, and (iii) high-resolution mass spectrometer. b Real-time analysis by simultaneous monitoring of CO₂, physical exhalation parameters (exhalation flow rate and exhaled volume), and relative intensities of three representative aldehydes from one experiment. 13 consecutive exhalations within 20 min for one subject are shown (see ESM Fig. S4 for zoomed-in view of the first exhalation).