Fig. 1

The spectrum of breath analysis. Exhaled breath contains a vast quantity of molecules and particles, ranging in size and volatility, which can be captured using analytical techniques. Nitric oxide is a very small, volatile compound which can be detected using an online analyser which will provide an instant measurement of the concentration in exhaled breath (a). Large, non-volatile particles can be detected in exhaled breath condensate, either through liquid chromatography-mass spectrometry (b) or enzyme immunoassay (c). Volatile organic compounds (VOCs) of varying size can be detected by using various technologies including electronic noses (d) or gas-chromatography mass spectrometry (e)