How is it that a breathalyzer can measure the alcohol content in someone's blood,
為什麼酒測器可以單單根據一個人的呼氣，
hours after they had their last drink, based on their breath alone? 在他喝完酒的幾小時後，還能測量出血液中的酒精濃度？
在他喝完酒的幾小時後，還能測量出血液中的酒精濃度？
Exhaled breath contains trace amounts of hundreds, even thousands,
在呼出的氣體中，含量達到可追蹤標準的揮發性有機化合物
of volatile organic compounds: small molecules lightweight enough to travel easily as gases.
就有數百種甚至數千種：它們是小型分子，輕到能以氣體的方式輕鬆移動。
One of these is ethanol, which we consume in alcoholic drinks.
其中一種是乙醇，我們會從酒精性飲料喝到它。
It travels through the bloodstream to tiny air sacs in the lungs,
它會通過血流，到達肺中的小氣囊，
passing into exhaled air at a concentration 2,000 times lower, on average, than in the blood.
進入到呼出的氣體當中，此時的濃度比在血液中時平均要低兩千倍。
When someone breathes into a breathalyzer, the ethanol in their breath passes into a reaction chamber.
當一個人對著酒測器呼氣，呼吸中的乙醇就會進入一個反應室中。
There, it's converted to another molecule, called acetic acid,
在那裡，乙醇會被轉換成另一種分子，叫做乙酸，
in a special type of reactor that produces an electric current during the reaction.
在特殊的反應裝置中，反應過程會產生出電流。
The strength of the current indicates the amount of ethanol in the sample of air,
電流的強度表示呼吸氣體樣本中的乙醇量，
and by extension in the blood.
由此算出血液中的量。
In addition to the volatile organic compounds like ethanol we consume in food and drink,
除了我們從食物和飲料中取得的揮發性有機化合物，比如乙醇，
the biochemical processes of our cells produce many others.
我們細胞的生化過程也會產生許多其他揮發性有機物。
And when something disrupts those processes, like a disease,
當那些過程被比如疾病給打斷，
the collection of volatile organic compounds in the breath may change, too.
從呼吸中收集到的揮發性有機化合物也有可能改變。
So could we detect disease by analyzing a person's breath,
所以，我們能不能透過分析呼吸來偵測一個人的疾病，
without using more invasive diagnostic tools like biopsies, blood draws, and radiation?
而不用更侵入性的診斷工具如切片檢查法、抽血和放射線？
In theory, yes, but testing for disease is a lot more complicated than testing for alcohol.
理論上可行，但檢測疾病比檢測酒精複雜許多。
To identify diseases, researchers need to look at a set of tens of compounds in the breath.
要辨識出疾病，研究者需要檢視呼吸中數十種化合物。
A given disease may cause some of these compounds to increase or decrease in concentration,
某種疾病可能會造成當中某些化合物濃度增加或減少，
while others may not change, the profile is likely to be different for every disease,
其他的則沒改變。每一種疾病的特徵都不同，
and could even vary for different stages of the same disease.
就連同一種疾病，在不同階段呈現的狀況也不同。
For example, cancers are among the most researched candidates for diagnosis through breath analysis.
比如，最常被研究的呼吸分析診斷候選疾病之一是癌症。
One of the biochemical changes many tumors cause is a large increase in an energy-generating process called glycolysis.
許多腫瘤會造成的其中一種生化改變就是醣酵解大量增加，它是一種產生能量的過程。
Known as the Warburg Effect,
這就是所謂的瓦氏效應，
this increase in glycolysis results in an increase of metabolites like lactate,
醣酵解的增加會導致代謝物如乳酸鹽的增加，
which in turn can affect a whole cascade of metabolic processes,
它們就有可能會再影響整個一連串的代謝過程，
and ultimately result in altered breath composition,
最後，會造成呼吸中的成分改變，
possibly including an increased concentration of volatile compounds such as dimethyl sulfide.
可能包括揮發性有機化學物如二甲硫醚的濃度增加。
But the Warburg Effect is just one potential indicator of cancerous activity,
但瓦氏效應只是癌症活動的一種可能指標，
and doesn't reveal anything about the particular type of cancer.
且它沒有任何信息能指出是哪一種癌症。
Many more indicators are needed to make a diagnosis.
還需要更多指標才能做出診斷。
To find these subtle differences, researchers compare the breath of healthy people with the breath of people,
為了找出這些微小的差異，研究者比較健康受試者的呼吸和
who suffer from a particular disease using profiles based on hundreds of breath samples.
特定疾病病人有什麼不同，比較的基礎是數百件呼吸樣本的特徵。
This complex analysis requires a fundamentally different, more versatile type of sensor from the alcohol breathalyzer.
這種複雜分析所需要的感測器必須要有更多功能，與酒測器有很大不同。
There are a few being developed.
目前有幾種在開發中。
Some discriminate between individual compounds,
有些裝置區別不同化合物的方式
by observing how the compounds move through a set of electric fields.
是觀察化合物如何在一組電場中移動。
Others use an array of resistors made of different materials that each change their resistance,
有些裝置則是用不同材料製成的電阻器，每個都會在
when exposed to a certain mix of volatile organic compounds.
接觸到揮發性有機化合物的某種混合時改變其電阻。
There are other challenges too.
還有其他的困難。
These substances are present at incredibly low concentrations,
這些物質出現的濃度非常低，
typically just parts per billion, much lower than ethanol concentrations in the breath.
通常都是用分率來計算，比呼吸中的乙醇濃度還要低很多。
Compounds' levels may be affected by factors other than disease, including age, gender, nutrition, and lifestyle.
化合物的量可能會受到疾病以外的其他因子影響，包括年齡、性別、營養，以及生活方式。
Finally, there's the issue of distinguishing which compounds in the sample were produced in the patient's body,
最後，還有一個問題：如何區別出樣本中的哪些化合物是在病人體內產生的，
and which were inhaled from the environment shortly before the test.
哪些是在檢測前沒多久從環境中吸入的。
Because of these challenges, breath analysis isn't quite ready yet.
因為有這些困難，呼吸分析還沒有成熟。
But preliminary clinical trials on lung, colon,
但針對肺、結腸，
and other cancers have had encouraging results.
及其他癌症的初步臨床試驗顯現出十分讓人振奮的結果。
One day, catching cancer early might be as easy as breathing in and out.
也許有一天，單靠吸氣吐氣就可以發現癌症了。