Exhaled volatile organic compounds for diagnosis and monitoring of asthma

Figure 1 Differences in approach between the two techniques. While gas chromatography-mass spectrometry utilizes an analytical chemical approach, electronic-Nose operates based on pattern recognition. GC: Gas chromatography; MS: Mass spectrometry.

Figure 2 Gas chromatography-mass spectrometry. Combination of gas chromatography and mass spectrometry for the separation and identification of organic molecules, respectively: The gas serves as a medium for transporting the molecules present in the exhaled breath, which undergo absorption and desorption phenomena (Stationary Phase), passing sequentially along the transfer line. Here, the molecules are ionized and accelerated by electric fields. This allows for further separation and detection. Through data analysis, the detected molecules will appear as peaks, representing their relative abundance over the detection time. T: Temperature; TOF: Time of flight.

Figure 3 Working principle of electronic-Noses. The combination of the signal from all sensors generates the so-called “breathprint”.

Figure 4 Example of a commercially available electronic-Nose. Cyranose 320 is a small and easily portable device.