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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?

  • Exhaled breath contains trace amounts of hundreds, even thousands,

  • of volatile organic compounds:

  • small molecules lightweight enough to travel easily as gases.

  • One of these is ethanol, which we consume in alcoholic drinks.

  • 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.

  • When someone breathes into a breathalyzer,

  • the ethanol in their breath passes into a reaction chamber.

  • There, it's converted to another molecule, called acetic acid,

  • in a special type of reactor that produces an electric current during the reaction.

  • The strength of the current indicates the amount of ethanol

  • in the sample of air, and by extension in the blood.

  • In addition to the volatile organic compounds like ethanol

  • we consume in food and drink,

  • the biochemical processes of our cells produce many others.

  • And when something disrupts those processes, like a disease,

  • the collection of volatile organic compounds in the breath

  • may change, too.

  • So could we detect disease by analyzing a person's breath,

  • without using more invasive diagnostic tools

  • like biopsies, blood draws, and radiation?

  • In theory, yes,

  • but testing for disease is a lot more complicated than testing for alcohol.

  • To identify diseases,

  • researchers need to look at a set of tens of compounds in the breath.

  • A given disease may cause some of these compounds

  • to increase or decrease in concentration, while others may not change

  • the profile is likely to be different for every disease,

  • and could even vary for different stages of the same disease.

  • For example, cancers are among the most researched candidates

  • for diagnosis through breath analysis.

  • One of the biochemical changes many tumors cause

  • is a large increase in an energy-generating process

  • called glycolysis.

  • Known as the Warburg Effect,

  • this increase in glycolysis results in an increase of metabolites like lactate

  • which in turn can affect a whole cascade of metabolic processes

  • and ultimately result in altered breath composition,

  • possibly including an increased concentration of volatile compounds

  • such as dimethyl sulfide.

  • But the Warburg Effect is just one potential indicator of cancerous activity,

  • and doesn't reveal anything about the particular type of cancer.

  • Many more indicators are needed to make a diagnosis.

  • To find these subtle differences,

  • 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.

  • This complex analysis requires a fundamentally different,

  • more versatile type of sensor from the alcohol breathalyzer.

  • There are a few being developed.

  • Some discriminate between individual compounds

  • by observing how the compounds move through a set of electric fields.

  • 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.

  • There are other challenges too.

  • These substances are present at incredibly low concentrations

  • typically just parts per billion,

  • much lower than ethanol concentrations in the breath.

  • Compounds' levels may be affected by factors other than disease,

  • including age, gender, nutrition, and lifestyle.

  • 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.

  • Because of these challenges, breath analysis isn't quite ready yet.

  • But preliminary clinical trials on lung, colon,

  • and other cancers have had encouraging results.

  • One day, catching cancer early might be as easy as breathing in and out.

How is it that a breathalyzer can measure the alcohol content in someone's blood,

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呼気検知器はがんを検知できるのか?- ジュリアン・ブルシュカ (Could a breathalyzer detect cancer? - Julian Burschka)

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    詹士緯 に公開 2021 年 01 月 14 日
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