Expiratory flow rate and breath hold affect exhaled volatile organic compounds (VOC) in healthy subjects

Introduction: 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 been standardized and the effects of expiratory flow rate and breath hold have not been studied. These manoeuvres may also reveal the origin of exhaled compounds. Methods: 12 healthy volunteers (34±7 years) participated in the study. Subjects inhaled through their nose and exhaled immediately at two different flow rates (5 L/min and 10 L/min) into methylated polyethylene bags. In addition, the effect of 15 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). Results: Ethanol levels were negatively affected by expiratory flow rate (250±38 vs. 204±31 ppb at 5 L/min and 10 L/min, respectively, p Conclusions: Exhalation parameters such as expiratory flow rate 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. The first author is receiving an ERS Long Term Fellowship.