Exhaled breath not only contains high concentrations of carbon dioxide and water vapor, but also contains a signature of all chemicals in the blood that have at least some vapor pressure to allow their exchange from the blood into the exhaled breath through the alveoli in the lungs. Chemicals that have extremely low vapor pressures can also be transported through aerosols that are also emitted in the exhaled breath. Chemicals that are the result of metabolic processes in the body are called endogenous compounds, and their presence or unusual levels relative to other markers can indicate the presence various conditions or diseases. Chemicals that were introduced from external sources through inhalation, consumption, or dermal absorption or injection, are called exogenous compounds. Both endogenous and exogenous chemicals can be detected and quantified using a couple of different techniques, depending on what is of interest to the investigator.
Chemicals in the blood will equilibrate with inhaled air in a similar fashion to that of O and CO. Concentrations in breath can be correlated to blood concentrations, making breath analysis an ideal means for simple screening applications. e non-invasive sampling process makes breath collection inherently safe and easy allowing eld collection of samples by non-clinical personnel. e following uses for breath analysis have been demonstrated:
Monitoring Metabolic Breakdown Products for Clinical Diagnosis
Chemicals in the blood will equilibrate with inhaled air in a similar fashion to that of O and CO. Concentrations in breath can be correlated to blood concentrations, making breath analysis an ideal means for simple screening applications. The non-invasive sampling process makes breath collection inherently safe and easy allowing field collection of samples by non-clinical personnel. The following uses for breath analysis have been demonstrated: Analysis of volatile chemicals in breath can be a powerful tool for clinical diagnosis. The relative concentration of “chemical markers” in breath can be used to diagnose several diseases in their earliest and most treatable stages. Many tests are also currently performed using isotopically labeled (¹³C) fats or carbohydrates to determine whether the expected concentration of the isotopes show up in metabolites, including CO. Some of the markers and their corresponding disease or conditions are as follows:
Chemicals in the boiling point range of -80˚C to +230˚C can be collected using evacuated ultra-inert sampling bottles for remote analysis in a GCMS laboratory. Entech has disposable mouth pieces to assist in transferring the breath sample into the sampling containers. The GCMS analysis is performed using the 7200 Preconcentrator combined with the 7650 inlet systems to preconcentrate the sample while eliminating the high levels of CO2 and water vapor prior to GCMS injection.
Chemicals with boiling points from 150˚C to >400˚C are more effectively analyzed by collection of breath condensate. A small sample bottle chilled to -50˚C can collect the breath condensate in 10–20 liters of breath, improving the detection limit for these heavier and often lower concentration compounds. Analysis is done by exposure of the breath condensate to Entech’s PCME media (Porous Cartridge Micro-Extraction), with near complete transfer of the volatile and semi-volatile compounds to the cartridge, followed by thermal desorption to a GCMS for detection of literally hundreds of compounds ranging up to C30 in molecular weight. Unlike thermal desorption tubes that utilized reactive adsorbents that limit the recovery of thermally labile compounds, PCME Cartridges perform extractions using the same absorptive coating materials found inside of capillary GC columns, so all GC compatible compounds may be recovered and quantified.
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