Human exhaled breath analysis

md_a

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"The exhaled breath is being used to diagnose inflammatory lung disease, since so many of the mediators of inflammation are volatile, but systemic diseases such as cancer and arthritis, and relatively minor stress can be detected by changes in the chemicals found in the breath. Polyunsaturated fats and their breakdown products-- aldehydes, prostaglandins, isoprostanes, hydrocarbons, and free radicals--and carbon monoxide, nitric oxide, nitrite, and hydrogen peroxide are increased in the breath by most stresses."

Ray Peat `Leakiness, aging, and cancer`

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Human exhaled breath analysis

Exhaled breath constitutes more than 3,500 components, the bulk of which are volatile organic compounds in miniature quantities. Many of these characterize the functioning of the organism as a whole (systemic biomarkers), but some are related to processes taking place in the respiratory system and the airways in particular (lung biomarkers). Assessment of lung biomarkers has proven useful in airway inflammatory diseases. It involves direct measurement of gases such as nitric oxide and inflammatory indicators in exhaled breath condensate such as oxidative stress markers (eg, hydrogen peroxide and isoprostanes), nitric oxide derivatives (eg, nitrate and nitrates), arachidonic acid metabolites (eg, prostanoids, leukotrienes, and epoxides), adenosine, and cytokines. Integral approaches have also been suggested, such as exhaled breath temperature measurement and devices of the “electronic nose” type, which enable the capture of approaches have also been suggested, such as exhaled breath temperature measurement exhaled molecular fingerprints (breath prints). Technical factors related to standardization of the different techniques need to be resolved to reach the stage of routine applicability.

Human exhaled breath analysis

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Human exhaled breath mostly contains, nitrogen (78.04%), oxygen [16%], carbon dioxide [4%-5%], hydrogen [5%],8 inert gases [0.9%]9 and water vapor. Other than that, it contains inorganics VOCs viz. nitric oxide (10–50 ppb),10 nitrous oxide (1–20 ppb),10 ammonia (0.5–2 ppm),11 carbon monoxide (0–6 ppm),9 hydrogen sulphide (0–1.3 ppm)12 etc. and organic VOCs such as acetone (0.3–1 ppm),13 ethanol, isoprene (∼105 ppb),14 ethane (0–10 ppb), methane (2–10 ppm), pentane[0–10 ppb]10 etc. The air that is inhaled goes into the alveoli in the lungs where the metabolic excretable products diffuse into the inhaled air and then it is rejected in the form of exhaled air. Therefore, the exhaled air must carry the fingerprint of the metabolic process going on endogenously. Hence it is a rich source for disease diagnosis and health monitoring. As such the principle of breath analysis is thus simple. However, it is fraught with challenges that makes it complex. Firstly, a healthy human being exhales around 500 ml of breath out of which 150 ml is dead space air which comes from the upper air tract; this does not exchange VOC/gas with the blood and therefore acts as a diluent only.15,16 Secondly, many of the exhaled breath VOCs/gases are partially or fully of exogenous in origin17,18 and depends on ambient air concentration, duration of exposure, solubility and partition co-efficient, mass and fat content of the individual etc. Thirdly, non-volatile components such as isoprostanes, peroxynitrite etc, present as aerosol in breath can be measured only from breath condensate.19 Fourthly, oral hygiene is a problem for many people. Finally, it is very difficult to detect a particular VOC with very low concentration (ppm/ppb) among thousand others. In addition, age, gender, food habit and pregnancy in case of women affects the breath composition.20–24 Furthermore, there are no standards for breath collection techniques. In spite of all these challenges breath analysis is much easier than blood testing and therefore has attracted the attention of researchers in recent times.

Diseases and Disorders Indicated by Important Biomarkers

The most important biomarkers of diseases in human body are ammonia, acetone, isoprene, nitic oxide, hydrogen sulphide, methane, ethane and pentane. In this section we will discuss the metabolic pathways of removal of these biomarkers and also will delineate in short, the diseases indicated by those when excreted in less or excess amount through the exhaled breath.

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