快速，准确的呼出气测量氨
Summary
Ammonia is an important physiologic metabolite relevant to various disease and wellness states. It is also a difficult molecule to measure in breath, which demands particular precautions be taken to obtain accurate results. Not all factors influencing ammonia are known, but progress can be difficult without accounting for these factors.
Abstract
This exhaled breath ammonia method uses a fast and highly sensitive spectroscopic method known as quartz enhanced photoacoustic spectroscopy (QEPAS) that uses a quantum cascade based laser. The monitor is coupled to a sampler that measures mouth pressure and carbon dioxide. The system is temperature controlled and specifically designed to address the reactivity of this compound. The sampler provides immediate feedback to the subject and the technician on the quality of the breath effort. Together with the quick response time of the monitor, this system is capable of accurately measuring exhaled breath ammonia representative of deep lung systemic levels.
Because the system is easy to use and produces real time results, it has enabled experiments to identify factors that influence measurements. For example, mouth rinse and oral pH reproducibly and significantly affect results and therefore must be controlled. Temperature and mode of breathing are other examples. As our understanding of these factors evolves, error is reduced, and clinical studies become more meaningful. This system is very reliable and individual measurements are inexpensive.
The sampler is relatively inexpensive and quite portable, but the monitor is neither. This limits options for some clinical studies and provides rational for future innovations.
Introduction
氨是蛋白质代谢1无处不在的副产品。因此，氨测量可以帮助医生评估各种疾病和健康状态2。然而，氨是很难精确测量，通过血液或呼气，因为它是非常活泼。虽然常用，血液化验有许多缺点，包括约3精度基本问题。但随着血液化验的主要问题是，他们永远只能收集幕的现实。这是重要的，因为氨的生理，就像血糖和其他许多代谢过程，是流动的和不断变化4。相比之下，呼吸分析是完全非侵入性，快速，从而容易使重复测量。因此，呼气氨测量是有吸引力的，因为它可能会解决一个严重的未满足的需要以独特的方式。
呼气收集，然而，提出了独特的顾虑。而放血天生携带JEO错误的几种不可预知的方式pardy（ 例如 ，止血带的时间，汗水污染，血细胞溶血，延误实验室测量等5），呼吸测量研究者必须与不同组新的挑战：变异呼吸，污染与口腔黏膜或细菌氨，周围空气和装置的湿度和温度的影响，等6。事实上，这是不可低估的任务中使用的实验程序，以发现未知生物实验设备连接到人类。在由于这些障碍的一部分，呼气氨尚未达到其潜力。
在此，我们提出我们的呼吸氨测量协议进行快速，准确的结果。我们的协议有实力在三个方面：显示器，接口采样，并注意人类活动的影响。该显示器是由赖斯大学的同事建立如前面所述7。 MEA的基础几种常用的是石英增强的光声光谱法（QEPAS）技术，它采用一个压电石英音叉作为声换能器。当声波通过调制激光辐射的目标痕量气体物质的吸收发生产生光声效应。使用声电池，它是声学谐振的调制频率被检测出的微量的气体。吸收波长为氨被选中，是免费的从呼吸中干扰物质的光谱干扰。人类呼出气体测量的目的，显示器的主要功能包括广泛的测量范围（从50〜十亿分之，ppb到至少5000 PPB）和速度（1秒测量的）。显示器的速度使得时间分辨率在整个呼吸周期。
该显示器被连接到专门设计的呼吸采样器。该采样器包括一个压力传感器和二氧化碳监测仪的。它显示和归档实时测量口压力和二氧化碳以及由传感器测定的氨浓度。该取样器，因此，使技术人员来评估呼吸努力的质量为呼吸是收集。这使我们能够超越，分析呼吸一氧化氮（NO铁），提出由美国胸科协会/欧洲呼吸学会的特别工作组（ATS / ERS）8的建议。对于所有的呼吸气体取样，一次性单向管式阀被用在呼气采样口口。
因为采样器提供显示器和质量控制的速度，我们可以仔细评估人类影响9。大多数受试者，例如，最初强力呼吸时指示呼吸。其他重要的影响，如口服pH和口腔冲洗液，温度的取样器，显示器和所有相关联的管道，和呼吸模式，随后的研究，并且是依据FOř下面的说明实验。
最后，也许是最显著，但必须强调的是多个经验丰富的组采用完全不同的传感器和测量程序测量呼气氨。这可能有重要的优势和有效性。一个完整的比较超出了目前的工作10,11,12的范围。
Protocol
Representative Results
Discussion
能够检测到微量的代谢产物进行实时一种非侵入性程序的好处是显而易见的。然而，呼吸研究领域一直在努力实现这一潜力。呼吸测量是一个动态的过程中容易受到很多干扰因素。我们的方法具有重要的优势：即，水稻QEPAS基氨显示器耦合到所述呼吸采样器的灵敏度和速度，使我们能够评估和确定有密切关系的精确测量呼气采集的因素。这种方法是非常可靠的：例如，一些初步的实验后，每收集?…
Divulgations
The authors have nothing to disclose.
Acknowledgements
作者承认从美国国家科学基金会（NSF）的财政支持给予EEC-0540832，题为“中红外技术用于健康和环境（MIRTHE）”
Materials
| Rice Ammonia Monitor System | N/A | N/A | Not available for commercial purchase |
| Loccioni Breath Sampler | Loccioni Humancare | N/A | Single breath version |
| Disposable Mouth Piece | WestPrime Healthcare | G011-200 | Manufacturer is AlcoQuant |
| Laptop | Lenovo | N/A | Old model no longer sold by manufacturer |
| Acid Rinse | N/A | N/A | Household acidic drink (coffee, soft drink, citrus juices, etc) |
| Base Rinse | N/A | N/A | Water mixed with a nonexact amount of sodium bicarbonate (Arm & Hammer Baking Soda) |
| Neutral Rinse | N/A | N/A | Water |
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