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← Could a breathalyzer detect cancer? - Julian Burschka

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Showing Revision 1 created 01/03/2020 by lauren mcalpine .

  1. How is it that a breathalyzer can measure
    the alcohol content in someone’s blood,
  2. hours after they had their last drink,
    based on their breath alone?
  3. Exhaled breath contains trace amounts
    of hundreds, even thousands,

  4. of volatile organic compounds:
  5. small molecules lightweight enough
    to travel easily as gases.
  6. One of these is ethanol,
    which we consume in alcoholic drinks.
  7. It travels through the bloodstream
    to tiny air sacs in the lungs,
  8. passing into exhaled air
    at a concentration 2,000 times lower,
  9. on average, than in the blood.
  10. When someone breathes
    into a breathalyzer,

  11. the ethanol in their breath
    passes into a reaction chamber.
  12. There, it’s converted to another molecule,
    called acetic acid,
  13. in a special type of reactor that produces
    an electric current during the reaction.
  14. The strength of the current
    indicates the amount of ethanol
  15. in the sample of air,
    and by extension in the blood.
  16. In addition to the volatile
    organic compounds like ethanol

  17. we consume in food and drink,
  18. the biochemical processes of our cells
    produce many others.
  19. And when something disrupts
    those processes, like a disease,
  20. the collection of volatile
    organic compounds in the breath
  21. may change, too.
  22. So could we detect disease
    by analyzing a person’s breath,
  23. without using more invasive
    diagnostic tools
  24. like biopsies, blood draws, and radiation?
  25. In theory, yes,

  26. but testing for disease is a lot more
    complicated than testing for alcohol.
  27. To identify diseases,
  28. researchers need to look at a set
    of tens of compounds in the breath.
  29. A given disease may cause
    some of these compounds
  30. to increase or decrease in concentration,
    while others may not change—
  31. the profile is likely to be different
    for every disease,
  32. and could even vary for different stages
    of the same disease.
  33. For example, cancers are among
    the most researched candidates

  34. for diagnosis through breath analysis.
  35. One of the biochemical changes
    many tumors cause
  36. is a large increase
    in an energy-generating process
  37. called glycolysis.
  38. Known as the Warburg Effect,
  39. this increase in glycolysis results
    in an increase of metabolites like lactate
  40. which in turn can affect a whole cascade
    of metabolic processes
  41. and ultimately result
    in altered breath composition,
  42. possibly including an increased
    concentration of volatile compounds
  43. such as dimethyl sulfide.
  44. But the Warburg Effect is just one
    potential indicator of cancerous activity,
  45. and doesn’t reveal anything
    about the particular type of cancer.
  46. Many more indicators are needed
    to make a diagnosis.
  47. To find these subtle differences,

  48. researchers compare the breath
    of healthy people
  49. with the breath of people
    who suffer from a particular disease
  50. using profiles based on hundreds
    of breath samples.
  51. This complex analysis
    requires a fundamentally different,
  52. more versatile type of sensor
    from the alcohol breathalyzer.
  53. There are a few being developed.
  54. Some discriminate
    between individual compounds
  55. by observing how the compounds move
    through a set of electric fields.
  56. Others use an array of resistors
    made of different materials
  57. that each change their resistance
    when exposed to a certain mix
  58. of volatile organic compounds.
  59. There are other challenges too.

  60. These substances are present
    at incredibly low concentrations—
  61. typically just parts per billion,
  62. much lower than ethanol concentrations
    in the breath.
  63. Compounds’ levels may be affected
    by factors other than disease,
  64. including age, gender, nutrition,
    and lifestyle.
  65. Finally, there’s the issue
  66. of distinguishing which compounds
    in the sample
  67. were produced in the patient’s body
  68. and which were inhaled
    from the environment
  69. shortly before the test.
  70. Because of these challenges,
    breath analysis isn’t quite ready yet.

  71. But preliminary clinical trials
    on lung, colon,
  72. and other cancers
    have had encouraging results.
  73. One day, catching cancer early
    might be as easy as breathing in and out.