|The influence of breath-holding on the concentration of volatile organic compounds in the exhaled breath was investigated. Alveolar sampling was done by capnometry, and the analysis was performed using SPME, GC, and MS. The isoprene concentrations increased, as expected, while the
Acetone concentrations decreased with time of breath-holding, which is possibly due to condensation in lower bronchial walls. It was found that a normalization of the measured concentrations is necessary to minimize the influence of inspired concentrations and to account for the wide range of individual variations.