A new 'online' method to measure increased exhaled isoprene in end-stage renal failure

Background. Isoprene is the most abundant hydrocarbon present in breath, and recent reports indicate that breath concentrations increase following haemodialysis. The purpose of this study was to establish whether selected ion flow tube mass spectrometry (SIFT-MS), a newly established technique in breath analysis, may be used to quantify breath isoprene in haemodialysis patients in the clinical setting. SIFT-MS is compared and contrasted with the established gas chromatography mass spectrometric technique for this purpose. Methods. Three consecutive exhalations from 19 haemodialysis patients (12 males, seven females) undergoing a morning dialysis shift were analysed just prior to commencing treatment. Within 5 min of completing their usual dialysis regimen, using polysulphone membranes, the breath of each patient was analysed again. Additional contemporary samples were obtained from 17 normal controls. Breath isoprene was quantified using SIFT-MS, a method previously validated quantitatively using neat isoprene. Results. Successful measurements of breath isoprene were obtained for each subject within 2 min, with minimum disruption to a busy dialysis environment. The coefficient of variation of triplicate measurements of breath isoprene was < 10%. Prior to dialysis, the mean (+/- SD) breath isoprene concentration (138 +/- 63 parts per billion (ppb)) was significantly greater than for normal controls (89 +/- 36 ppb; P = 0.016). Immediately following treatment, breath isoprene increased significantly to 184 +/- 95 ppb (P = 0.023). Conclusions. SIFT-MS permits the accurate and rapid measurement of breath isoprene in haemodialysis patients in the clinical setting. The previously reported increase in breath isoprene following dialysis treatment is confirmed. SIFT-MS is the ideal analytical tool to investigate this phenomenon further.