Breath sampling methodology

The theoretical principles discussed above lead to two choices for collecting breath samples Should a mixed-exhaled air or an end-exhaled air sample be collected  

End-exhaled air is beeoming the standard for breath monitoring. Of the 36 chemicals with established BEIs, end-exhaled air is reeommended for 6, while earlier BEIs recommending mixed-exhaled air have been withdrawn. Beyond the regulatory arena, however, mixed-exhaled air eontinues to be used with satisfaetory results. 

Methodologieally, the differenee between these two types of samples is the control over which portion of the breath is collected. Many techniques make use of the Haldane-Prestley tube to collect the last portion of the expiration. Earlier work used the simultaneous monitoring of COj or temperature in the exhaled breath to identify the moment (CO2 or temperature reaching a maximum) when air from the anatomical dead space has been purged and alveolar air can be sampled. 

A variety of sampling techniques has been tried for measuring organic vapors in exhaled air. Table 15.2.1.1 shows a classification of these techniques. The main distinction is between direct reading instruments and transportable samples that require analysis in the laboratory. The former group covers the widest range, from simple detector tubes to High Resolution Mass Spectrometry. 

SAMPLE COLLECTION A.l END-EXHALED AIR Use of Haldane-Prestley tube 23, 25, 26, 28,29, 31 

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The other category of breath sampling methodology involves sample collection in the field with subsequent analysis in the laboratory. There are two groups of devices in this category ... 

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