National Research Council-Institute for Biomedical Technologies (CNR-ITB), Via Fratelli Cervi 93, 20090 Segrate (MI), Italy.
J Breath Res. 2011 Mar;5(1):016002. doi: 10.1088/1752-7155/5/1/016002. Epub 2011 Jan 11.
A series of fatty acids among other compounds have recently been detected in breath in real time by secondary electrospray ionization mass spectrometry (SESI-MS) (Martínez-Lozano P and Fernández de la Mora J 2008 Anal. Chem. 80 8210). Our main aim in this work was to (1) quantify their abundance in breath calibrating the system with standard vapors and (2) extend the study to a control group for several days, both under fasting conditions and after sucrose intake. For the quantitative study, we fed our system with controlled amounts (∼140-1440 ppt) of fatty acid vapors (i.e. propanoic, butanoic, pentanoic and hexanoic acids). As a result, we found sensitivities ranging between 1 and 2.2 cps/ppt. Estimated concentrations of these particular acids in the breath of a fasting subject were in the order of 100 ppt. These values were in reasonable agreement with those expected from reported typical plasma concentrations and Henry constants. A second set of experiments on three fasting individuals before and after ingesting 15 g of sucrose showed that the concentration of propionic and butanoic acids increased rapidly in breath for two subjects. This response was attributed to bacterial activity in mouth and pharynx. In contrast, a third subject showed no response to the administration of sucrose. In addition, we performed a survey among six fasting subjects comparing nasal and mouth exhalations during 11 days, 4 months apart. The signal intensity was comparable for mouth and nose breath. This observation, in conjunction with the quantitative study, suggests that these compounds are mostly systemic when measured under fasting conditions. We finally used the NIST MS search algorithm to evaluate the possibility of recognizing a breathing subject based on his/her breath signature. The global recognition score was 63% (41 out of 65), while the probability by chance alone was 6 × 10(-17). This indicates that (i) there are statistically recognizable differences in individual breath patterns and (ii) the breath pattern for a given subject is relatively stable in time. This is consistent with previous NMR-based studies indicating the existence of stable individual metabolic phenotypes.
一系列脂肪酸和其他化合物最近通过二次电喷雾电离质谱（SESI-MS）实时检测到呼气中（Martínez-Lozano P 和 Fernández de la Mora J 2008 Anal. Chem. 80 8210）。我们的主要目的是（1）通过用标准蒸气标定系统来定量它们在呼气中的丰度，（2）在禁食条件下和摄入蔗糖后，将研究扩展到对照组几天。在定量研究中，我们用受控量（约 140-1440 ppt）的脂肪酸蒸气（即丙酸、丁酸、戊酸和己酸）喂我们的系统。结果，我们发现灵敏度在 1 到 2.2 cps/ppt 之间。在禁食受试者呼气中这些特定酸的估计浓度为 100 ppt 左右。这些值与从报道的典型血浆浓度和亨利常数中预期的值相当一致。在摄入 15 克蔗糖之前和之后对三个禁食个体进行的第二组实验表明，两名受试者的呼气中丙酸和丁酸的浓度迅速增加。这种反应归因于口腔和咽中的细菌活性。相比之下，第三个受试者对蔗糖的给药没有反应。此外，我们在 6 名禁食受试者中进行了一项调查，比较了相隔 4 个月的 11 天中鼻呼吸和口呼吸。口呼吸和鼻呼吸的信号强度相当。这一观察结果，结合定量研究，表明在禁食条件下测量时，这些化合物主要是全身性的。最后，我们使用 NIST MS 搜索算法来评估基于呼吸特征识别呼吸主体的可能性。总的识别分数为 63%（41 个中的 65 个），而仅凭机会的概率为 6×10(-17)。这表明：（i）个体呼吸模式存在可统计识别的差异，（ii）给定个体的呼吸模式随时间相对稳定。这与之前基于 NMR 的研究一致，表明存在稳定的个体代谢表型。
