A longitudinal study of breath isoprene in healthy volunteers using selected ion flow tube mass spectrometry (SIFT-MS)

Thirty volunteers (19 males, 11 females) were recruited for a 6-month study of the volatile compounds in their exhaled breath using the selected ion flow tube mass spectrometry (SIFT-MS) analytical technique. Volunteers provided weekly breath samples between 8:45 am and 1 pm (before lunch), and the concentrations of several trace compounds were obtained. In this paper, we focus on the isoprene in alveolar breath, which was monitored by SIFT-MS using NO⁺ precursor ions. The mean isoprene level for all samples was 118 parts per billion (ppb) with a standard deviation of 68 ppb and the range of values for breath samples given is 0–474 ppb. Variability in isoprene levels was similar in most volunteers. Isoprene levels increased immediately after moderate exercise, but returned to normal within 2–3 min for those few volunteers that were investigated. Cholesterol levels analysed for only three of the subjects were not obviously correlated with isoprene concentration in breath. Differences in isoprene levels were not directly correlated to gender, age or body mass index.