title: [Comparison of four identical electronic noses and three measurement set-ups].
abstract: BACKGROUND
  Volatile organic compounds (VOCs) can be used as biomarkers in exhaled air. VOC profiles can be detected by an array of nanosensors of an electronic nose. These profiles can be analysed using bioinformatics. It is, however, not known whether different devices of the same model measure identically and to which extent different set-ups and the humidity of the inhaled air influence the VOC profile.
  
  
  METHODS
  Three different measuring set-ups were designed and three healthy control subjects were measured with each of them, using four devices of the same model (Cyranose 320™, Smiths Detection). The exhaled air was collected in a plastic bag. Either ambient air was used as reference (set-up Leipzig), or the reference air was humidified (100% relative humidity) (set-up Marburg and set-up Munich). In the set-up Marburg the subjects inhaled standardised medical air (Aer medicinalis Linde, AGA AB) out of a compressed air bottle through a demand valve; this air (after humidification) was also used as reference. In the set-up Leipzig the subjects inhaled VOC-filtered ambient air, in the set-up Munich unfiltered room air. The data were evaluated using either the real-time data or the changes in resistance as calculated by the device.
  
  
  RESULTS
  The results were clearly dependent on the set-up. Apparently, humidification of the reference air could reduce the variance between devices, but this result was also dependent on the evaluation method used. When comparing the three subjects, the set-ups Munich and Marburg mapped these in a similar way, whereas not only the signals but also the variance of the set-up Leipzig were larger.
  
  
  CONCLUSIONS
  Measuring VOCs with an electronic nose has not yet been standardised and the set-up significantly affects the results. As other researchers use further methods, it is currently not possible to draw generally accepted conclusions. More systematic tests are required to find the most sensitive and reliable but still feasible set-up so that comparability is improved.
authors: Klinik für Innere Medizin, Schwerpunkt Pneumologie, Philipps-Universität Marburg, Germany. koczulla@med.uni-marburg.de
authors: R
authors: R
authors: Koczulla
authors: A
authors: A
authors: Hattesohl
authors: H
authors: H
authors: Biller
authors: J
authors: J
authors: Hofbauer
authors: J
authors: J
authors: Hohlfeld
authors: C
authors: C
authors: Oeser
authors: H
authors: H
authors: Wirtz
authors: R A
authors: RA
authors: Jörres
mesh_terms: D000328:Adult; D000395:Air Pollutants, Occupational / Q000032:analysis*; D015374:Biosensing Techniques / Q000295:instrumentation*; D001944:Breath Tests / Q000295:instrumentation*; D003196:Computer Graphics; D004867:Equipment Design; D005260:Female; D006801:Humans; D006813:Humidity; D008297:Male; D008838:Microcomputers; D008875:Middle Aged; D012680:Sensitivity and Specificity; D055549:Volatile Organic Compounds / Q000032:analysis*
chemical_list: D000395:Air Pollutants, Occupational; D055549:Volatile Organic Compounds