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How is it that a breathalyzer can measure the alcohol content in someone's blood, hours after they had their last drink, based on their breath alone?
体内酒精检测仪到底是怎样单凭人们的呼吸，就能检测饮酒几小时后的血液里的酒精含量？
Exhaled breath contains trace amounts of hundreds, even thousands, of volatile organic compounds: small molecules lightweight enough to travel easily as gases.
呼出的气息里包含着成百上千的挥发性有机化合物：这些质量极轻的小分子，被呼吸带了出来。
One of these is ethanol, which we consume in alcoholic drinks.
其中包含着我们从酒精饮料中摄取的乙醇。
It travels through the bloodstream to tiny air sacs in the lungs, passing into exhaled air at a concentration 2,000 times lower, on average, than in the blood.
它随着血流被输送到肺部的微小气囊中，然后再被呼出，这时乙醇的平均浓度是血液中的1/2000。
When someone breathes into a breathalyzer, the ethanol in their breath passes into a reaction chamber.
当一个人向检测仪呼气时，呼吸中的乙醇进入到一个反应器中。
There, it's converted to another molecule, called acetic acid, in a special type of reactor that produces an electric current during the reaction.
在那里，它被转化成了另一种分子，那就是醋酸，在这个特别的反应器里，一股电流在反应中产生了。
The strength of the current indicates the amount of ethanol in the sample of air, and by extension in the blood.
电流的强度反映了气息中乙醇的浓度，然后通过估算可得出血液里的乙醇浓度。
In addition to the volatile organic compounds like ethanol we consume in food and drink, the biochemical processes of our cells produce many others.
除了我们从饮食中摄取的像乙醇这样的挥发性有机化合物，人体细胞的生化反应还产生许多其他的物质。
And when something disrupts those processes, like a disease, the collection of volatile organic compounds in the breath may change, too.
当这些反应受到干扰时，比如疾病，呼吸中包含的挥发性有机化合物可能也会改变。
So could we detect disease by analyzing a person's breath, without using more invasive diagnostic tools like biopsies, blood draws, and radiation?
因此，我们是否可以通过分析人体的呼吸来检测疾病，从而避免使用更具侵入性的诊断工具，例如活组织切片、抽血和放射扫描呢？
In theory, yes, but testing for disease is a lot more complicated than testing for alcohol.
理论上来说，行得通，但是检测疾病可比检测酒精浓度复杂多了。
To identify diseases, researchers need to look at a set of tens of compounds in the breath.
为了识别病症，研究人员需要检测数十种呼吸中所含的化合物。
A given disease may cause some of these compounds to increase or decrease in concentration, while others may not change
某种特定疾病可能导致某些化合物数量上的增加或减少，同时并不影响其他化合物，
the profile is likely to be different for every disease, and could even vary for different stages of the same disease.
而不同疾病造成的这类数量影响也各有区别，甚至同一种疾病的各个阶段也会产生不同影响。
For example, cancers are among the most researched candidates for diagnosis through breath analysis.
比如，癌症是运用呼吸分析的诊断方法最广泛的疾病之一。
One of the biochemical changes many tumors cause is a large increase in an energy-generating process called glycolysis.
肿瘤会造成众多生化反应改变，其中之一，是一种能量产出反应的大幅增加，被称为“糖酵解”。
Known as the Warburg Effect, this increase in glycolysis results in an increase of metabolites like lactate
也称“瓦氏效应”，糖酵解的增加导致代谢物增加，比如产生大量乳酸，
which in turn can affect a whole cascade of metabolic processes and ultimately result in altered breath composition,
这反过来影响了一系列的新陈代谢反应，最终改变了呼吸中的化合物组成，
possibly including an increased concentration of volatile compounds such as dimethyl sulfide.
某些挥发性化合物可能会大量聚集，例如二甲基硫醚。
But the Warburg Effect is just one potential indicator of cancerous activity, and doesn't reveal anything about the particular type of cancer.
但是瓦氏效应仅仅是癌性活动的一个可能性指标，并且不能揭示癌症的具体种类。
Many more indicators are needed to make a diagnosis. To find these subtle differences,
想要确诊，还需要获得许多其他的指标。为了明确这些细微差别，
researchers compare the breath of healthy people with the breath of people who suffer from a particular disease using profiles based on hundreds of breath samples.
研究人员向健康者的呼吸样本与罹患某种特定疾病的人的呼吸样本进行数百次的比对。
This complex analysis requires a fundamentally different, more versatile type of sensor from the alcohol breathalyzer. There are a few being developed.
完成这一复杂的分析过程所需的探测器，比酒精测定仪更加全能。人们正在研发一些这样的机器。
Some discriminate between individual compounds by observing how the compounds move through a set of electric fields.
有的通过观察化合物们经过一系列电场的路径，辨别出不同的化合物。
Others use an array of resistors made of different materials that each change their resistance when exposed to a certain mix of volatile organic compounds.
有的利用一组由不同材料制成的电阻器，通过观测每种电阻器在接触挥发性有机化合物的混合物时，其阻力发生的变化，来进行辨别。
There are other challenges too. These substances are present at incredibly low concentrations
这一过程困难重重。这些化合物的浓度极低，
typically just parts per billion, much lower than ethanol concentrations in the breath.
通常只有十亿分之一，这可比呼吸中乙醇的浓度低多了。
Compounds' levels may be affected by factors other than disease, including age, gender, nutrition, and lifestyle.
化合物的数量水平同时还受到其他因素的影响包括年龄、性别、营养状况和生活方式。
Finally, there's the issue of distinguishing which compounds in the sample were produced in the patient's body and which were inhaled from the environment shortly before the test.
最后，要在取得样本后，快速分辨其中有哪些化合物来自于患者体内，哪些来源于外界，也颇具挑战。
Because of these challenges, breath analysis isn't quite ready yet.
基于这些困难与挑战，利用呼吸分析疾病的技术还很不成熟。
But preliminary clinical trials on lung, colon, and other cancers have had encouraging results.
即便如此，基于肺癌、结肠癌以及其他癌症的临床试验方兴未艾。
One day, catching cancer early might be as easy as breathing in and out.
总有一天，探测出早期癌变会变得如同呼吸一般轻而易举。
