Analysis of Expired Breath

The absorption bands of water vapor and carbon dioxide are always present in the infrared spectrum of the expired breath because both these substances strongly absorb infrared radiation. On the other hand, oxygen, nitrogen, and the inert gases do not absorb infrared radiation and therefore cannot be detected— an advantage for the methods to be discussed. 

For the qualitative analysis of most volatile compounds and gases the collection of expired breath samples is quite adequate. For quantitative analysis of breath alveolar air should be collected to minimize the variations arising from individual collection techniques. Collection techniques were described by Stewart and Erley (1965). An apparatus used to desorb vapors from silica gel (used as an alternative technique for sampling) was also described. 

Breath Analysis After Exposure to Toxic Gases or Volatile Compounds 

In healthy adults the mean concentration of acetone in the breath is 1.1 0.5 jug/liter (Stewart and Boettner, 1964). Witha 10-mor40-mgascell such concentrations are not detectable. The acetone content of diabetic breath may range from 0.1 /ig/Iiter to more than 2000 /ig/Iiter. Before the onset of significant ketonemia, the acetone content in the diabetic s breath rises to amounts detectable by infrared spectroscopy and therefore analysis of the breath gives a rapid method for determining the degree of ketosis. 

Carbon monoxide analysis in the breath by the infrared method is much faster and more sensitive than the standard carboxyhemoglobin technique. Infrared 

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