Abstract
Analysis of volatile organic compounds (VOCs) in exhaled breath offers diagnostic potential in research and clinical medicine. Mass spectrometry of expiratory air allows VOC measurements in a concentration range from parts per trillion to parts per million. For the reduction of dilution-related measurement errors due to dead space admixture, the precise identification of the end-expiratory phase of expiration is essential. We used a combination of two integrated MS systems consisting of a conventional MS capable of fast CO2 tracing controlling a second, highly sensitive MS for the measurement of VOCs based on ion–molecule-reaction-MS (IMR-MS). This study intended to test the applicability of a software-based method of CO2-controlled alveolar breath-gas sampling in 12 ventilated patients using acetaldehyde, acetone, ethanol and isoprene as target VOCs (IMR-MS compound integration time 500 ms, cycle time 2 ms, measurement time 120 min). CO2-controlled versus mixed inspiratory/expiratory results are as follows: acetaldehyde 71* (61–133) versus 63 (47–87); acetone 544* (208–1174) versus 504 (152–950); ethanol 133 (99–166) versus 123 (108–185); isoprene 118* (69–253) versus 58 (44–112) (values in ppbv as medians with 25–75%; *p < 0.05 versus mixed inspiratory/expiratory values). The applied software-based CO2-controlled sampling method of expiratory air resulted in significant higher concentrations of acetaldehyde, acetone and isoprene.
Published Version
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