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The effect of flow rate on the level of volatile organic compounds (voc) in exhaled breath

: Holz, Olaf; Gaida, Arne; Schuchardt, Sven; Langejuergen, Jens; Zimmermann, Stefan; Hohlfeld, Jens Michael

American Journal of Respiratory and Critical Care Medicine 189 (2014), Art. A4254
ISSN: 1073-449X
ISSN: 0003-0805
ISSN: 1535-4970
American Thoracic Society (ATS International Conference) <2014, San Diego/Calif.>
Fraunhofer ITEM ()

Introduction: A pronounced flow-dependence of a volatile breath component indicates an origin from central airways. There is data showing that ethanol concentrations (Bikov BMC Pulm Med 2013) and fragments of isoprene (Thekedar JBR 2010) in exhaled breath increase with lower flow rates. In both studies breath samples were collected in bags and analyzed by PTR-MS. It was the aim of this study to test the effect of exhalation flow on volatile organic compounts using a different sampling strategy that avoids using bags.
Methods: Five healthy volunteer subjects were asked to inhale air through an A2 carbon filter and to exhale into a stainless steel tube sampling reservoir for a total of 8 minutes. During the first 3 min no sample was collected and acutely accumulated environmental VOCs were washed out of the lung. Then during the next 5 min of breathing, 3 L of breath were continuously drawn from the reservoir onto each of 3 TENAX TA tubes. Two samples in random order were collected from each subject. Subjects exhaled against a small resistor to close the nasal velum and were asked to maintain an exhalation pressure of 3 or 6 mbar by visual control. Both the low and the high flow rate sample were collected within 45 min. After thermal-desorption the VOCs were analyzed by GC/MS. VOCs were identified using the most likely compound suggested by the NIST library (Rev.2011b).
Results: We analyzed the effect on flow rate for 29 low abundant VOCs that could be found in the spectra of all 5 volunteer subjects. The median variation coefficient (VK) for the 3 Tenax tubes of the low or high flow rate collection was 13.7 % and 15.7%. The median VK for the comparison between the 2 flow rates was 14.9 %. None of the compounds showed a significant difference between flow rates.
Conclusion: For the low abundant VOC analyzed in these 5 healthy volunteer subjects we did not find a significant effect of exhalation flow rate suggesting that these compounds are more likely derived from the alveolar region of the lung. The data also suggests that flow rate will not need to be strictly controlled. This will make the collection of breath samples easier, especially for subjects with impaired lung function.