Breath diagnostics using laser spectroscopy

In the previous two sections the effects of drug-or laser-mediated reactions on cancer cells were discussed. The redox reactions in PDT, leading to 

The primary constituents of exhaled human breath are the two main constituents of air, i.e. N2 and O2, and H2O taken up from within the lungs and in the respirationpathway (we see water condensation if we breathe at a cold surface). The major metabohte in breath, at about 4 per cent of volume, is CO2. In addition, exhaled breath contains numerous trace gases of endogenous nature, i.e. molecules that can be linked to metabolism processes some of these are summarized in Table 30.1. 

Besides the compounds listed, quite a few others have been identified however, many of those can be, or are, of exogenous origin. They have been either ingested or inhaled with (polluted) ambient air their presence in breath is not evidence of disease but rather an indicator of recent exposure to a particular compound, e.g. drinking alcohol or smoking cigarettes. 

Breath analysis is a particularly attractive diagnostic tool, in that it is a non-invasive way to monitor a patient s physiological status, other than urine tests 

Probably the most studied disease and metabolism markers are C2H6 and nitric monoxide (NO) examples of laser spectroscopic studies of these two are discussed below. 

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Miirtz M. 2005. Breath diagnostics using laser spectroscopy . Opt. Photon. News 16(1) 30-35. 

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