title: Standardised exhaled breath collection for the measurement of exhaled volatile organic compounds by proton transfer reaction mass spectrometry.
abstract: BACKGROUND
  Exhaled breath volatile organic compound (VOC) analysis for airway disease monitoring is promising. However, contrary to nitric oxide the method for exhaled breath collection has not yet been standardized and the effects of expiratory flow and breath-hold have not been sufficiently studied. These manoeuvres may also reveal the origin of exhaled compounds.
  
  
  METHODS
  15 healthy volunteers (34 ± 7 years) participated in the study. Subjects inhaled through their nose and exhaled immediately at two different flows (5 L/min and 10 L/min) into methylated polyethylene bags. In addition, the effect of a 20 s breath-hold following inhalation to total lung capacity was studied. The samples were analyzed for ethanol and acetone levels immediately using proton-transfer-reaction mass-spectrometer (PTR-MS, Logan Research, UK).
  
  
  RESULTS
  Ethanol levels were negatively affected by expiratory flow rate (232.70 ± 33.50 ppb vs. 202.30 ± 27.28 ppb at 5 L/min and 10 L/min, respectively, p < 0.05), but remained unchanged following the breath hold (242.50 ± 34.53 vs. 237.90 ± 35.86 ppb, without and with breath hold, respectively, p = 0.11). On the contrary, acetone levels were increased following breath hold (1.50 ± 0.18 ppm) compared to the baseline levels (1.38 ± 0.15 ppm), but were not affected by expiratory flow (1.40 ± 0.14 ppm vs. 1.49 ± 0.14 ppm, 5 L/min vs. 10 L/min, respectively, p = 0.14). The diet had no significant effects on the gasses levels which showed good inter and intra session reproducibility.
  
  
  CONCLUSIONS
  Exhalation parameters such as expiratory flow and breath-hold may affect VOC levels significantly; therefore standardisation of exhaled VOC measurements is mandatory. Our preliminary results suggest a different origin in the respiratory tract for these two gasses.
authors.forename: Andras
authors.initials: A
authors.lastname: Bikov
authors.forename: Koralia
authors.initials: K
authors.lastname: Paschalaki
authors.forename: Ron
authors.initials: R
authors.lastname: Logan-Sinclair
authors.forename: Ildiko
authors.initials: I
authors.lastname: Horváth
authors.forename: Sergei A
authors.initials: SA
authors.lastname: Kharitonov
authors.forename: Peter J
authors.initials: PJ
authors.lastname: Barnes
authors.forename: Omar S
authors.initials: OS
authors.lastname: Usmani
authors.forename: Paolo
authors.initials: P
authors.lastname: Paredi
mesh_terms: D000096:Acetone / Q000378:metabolism; D000328:Adult; D001944:Breath Tests / Q000379:methods*; D000431:Ethanol / Q000378:metabolism; D045853:Exhalation / Q000502:physiology*; D005260:Female; D006801:Humans; D008297:Male; D013058:Mass Spectrometry / Q000379:methods* / Q000592:standards*; D010366:Peak Expiratory Flow Rate / Q000502:physiology; D015203:Reproducibility of Results; D012137:Respiratory System / Q000378:metabolism; D013997:Time Factors; D014109:Total Lung Capacity / Q000502:physiology; D055549:Volatile Organic Compounds / Q000378:metabolism*
chemical_list: D055549:Volatile Organic Compounds; D000096:Acetone; D000431:Ethanol