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The impact of different sampling techniques on the results of breath analysis was to be assessed in this study. Alveolar, mixed expiratory and time-controlled samples were collected from ten volunteers and from eight lung cancer patients. Breath sampling was visually controlled by means of capnometry. PCO(2) and 13 VOCs were determined. Mixed expiratory sampling yielded 25% lower concentrations of CO(2) and blood-borne VOCs. Time-controlled sampling generated high variation of results. Ratios C(alv)/C(mixed) were >1.5 for CO(2), acetone and isoprene, and <1 for isopropanol, 2-butanone and hexanal. Acetonitrile, butane, dimethylsulfide, pentane, butanal, benzene and hexane showed 1.5 > C(alv)/C(mixed) > 1. The ratio C(alv)/C(mixed) of CO(2), acetone and isoprene was different in healthy volunteers and lung cancer patients. Alveolar samples showed the highest concentrations of endogenous and lowest concentration of exogenous substances. Sampling can impact results in breath analysis. Valuable information can be obtained from ratios of alveolar and mixed expired concentrations.

Patients with end-stage renal disease (ESRD) are at risk for a numerous complications. This study was intended to evaluate breath analysis for monitoring and therapy initiation under haemodialysis (HD). Exhaled alveolar air from 30 ESRD patients during 4 h thrice-weekly HD was analysed by means of HS-SPME-GC-MS. Venous blood samples were taken for determination of conventional serum parameters. Exhaled concentrations of isoprene (10-589 ppbV) were dropped at initiation of HD and increased at the end of HD. Isoprene concentration changes were similar to changes of serum LDH activities. Variation of exhaled acetone concentrations (59 to 8509 ppbV) was significantly lower in diabetic patients when compared to non-diabetics. Exhaled pentane (0.3 to 12 ppbV) increased at onset of HD and returned to baseline levels afterwards. Benzene concentrations showed typical washout characteristics. Ethanol and DMS concentrations remained constant during HD. Breath analysis can be used to recognize oxidative stress, metabolic conditions and haemolysis during HD. Hence, non-invasive breath testing could be used to monitor ESRD patients under HD and prevent them from being affected by well-known detrimental side effects of renal replacement therapy.

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