Analysis of volatile disease markers in blood

Background: The diagnostic potential of breath analysis has been limited by a lack of knowledge on origin, distribution, and metabolism of the exhaled substances. To overcome this problem, we developed a method to assess trac e amounts of hydrocarbons (pentane and isoprene), ketones (acetone), haloge nated compounds (isoflurane), and thioethers (dimethyl sulfide) in the bloo d of humans and animals. Methods: Arterial and venous blood samples were taken from mechanically ven tilated patients. Additional blood samples were taken from selected vascula r compartments of 19 mechanically ventilated pigs. Volatile substances were concentrated by means of solid-phase microextraction (SPME), separated by gas chromatography, and identified by mass spectrometry. Results: Detection limits were 0.02-0.10 nmol/L. Venous concentrations in p igs were 0.2-1.3 nmol/L for isoprene, 0-0.3 nmol/L for pentane, and 1.2-15. 1 nmol/L for dimethyl sulfide. In pigs, substances were not equally distrib uted among vascular compartments. In humans, median arteriovenous concentra tion differences were 3.58 nmol/L for isoprene and 1.56 nmol/L for pentane. These values were comparable to pulmonary excretion rates reported in the literature. Acute respiratory distress syndrome (ARDS) patients had lower i soprene concentration differences than patients without ARDS. Conclusions: The SPME method can detect volatile substances in very low con centrations in the blood of humans and animals. Analysis of volatile substa nces in vascular compartments will enlarge the diagnostic potential of brea th analysis. (C) 2001 American Association for Clinical Chemistry.