Breath Research Institute, Austrian Academy of Sciences, Rathausplatz 4, A-6850 Dornbirn, Austria.
J Theor Biol. 2010 Dec 21;267(4):626-37. doi: 10.1016/j.jtbi.2010.09.028. Epub 2010 Sep 29.
Human breath contains a myriad of endogenous volatile organic compounds (VOCs) which are reflective of ongoing metabolic or physiological processes. While research into the diagnostic potential and general medical relevance of these trace gases is conducted on a considerable scale, little focus has been given so far to a sound analysis of the quantitative relationships between breath levels and the underlying systemic concentrations. This paper is devoted to a thorough modeling study of the end-tidal breath dynamics associated with isoprene, which serves as a paradigmatic example for the class of low-soluble, blood-borne VOCs. Real-time measurements of exhaled breath under an ergometer challenge reveal characteristic changes of isoprene output in response to variations in ventilation and perfusion. Here, a valid compartmental description of these profiles is developed. By comparison with experimental data it is inferred that the major part of breath isoprene variability during exercise conditions can be attributed to an increased fractional perfusion of potential storage and production sites, leading to higher levels of mixed venous blood concentrations at the onset of physical activity. In this context, various lines of supportive evidence for an extrahepatic tissue source of isoprene are presented. Our model is a first step towards new guidelines for the breath gas analysis of isoprene and is expected to aid further investigations regarding the exhalation, storage, transport and biotransformation processes associated with this important compound.
人体呼吸中包含着无数内源性挥发性有机化合物（VOCs），这些化合物反映了正在进行的代谢或生理过程。虽然对这些痕量气体的诊断潜力和一般医学相关性的研究已经进行了相当规模的研究，但迄今为止，人们对呼吸水平与潜在系统性浓度之间的定量关系进行了全面分析。本文致力于对异戊二烯相关的呼出气动力学进行深入的建模研究，异戊二烯是低溶解度、血液源性 VOC 类的典型范例。在测力计挑战下对呼出呼吸进行实时测量，揭示了异戊二烯输出对通气和灌注变化的特征变化。在这里，对这些分布情况进行了有效的房室描述。通过与实验数据进行比较，可以推断出运动条件下呼吸中异戊二烯的大部分变化可以归因于潜在储存和产生部位的灌注分数增加，导致在体力活动开始时混合静脉血浓度升高。在这方面，提出了支持异戊二烯存在肝外组织来源的各种证据。我们的模型是为异戊二烯呼出气分析制定新指南的第一步，预计将有助于进一步研究与这种重要化合物相关的呼气、储存、运输和生物转化过程。
