Exhaled breath analysis by electronic nose in respiratory diseases

Abstract

Breath analysis via electronic nose is a technique oriented around volatile organic compound (VOC) profiling in exhaled breath for diagnostic and prognostic purposes. This approach, when supported by methodologies for VOC identification, has been often referred to as metabolomics or breathomics. Although breath analysis may have a substantial impact on clinical practice, as it may allow early diagnosis and large-scale screening strategies while being noninvasive and inexpensive, some technical and methodological limitations must be solved, together with crucial interpretative issues. By integrating a review of the currently available literature with more speculative arguments about the potential interpretation and application of VOC analysis, the authors aim to provide an overview of the main relevant aspects of this promising field of research.

Aging Airways: between Normal and Disease. A Multidimensional Diagnostic Approach by Combining Clinical, Functional, and Imaging Data

“…It can focus on selected exhaled gases, which can be determined through different analytical methods, such as high-performance liquid chromatography (HPLC) or mass spectrophotometry. Alternatively, a comprehensive non-qualitative picture of exhaled gases can be obtained by using the electronic nose, the so-called “e-nose” [46]. The ensuing breath pattern may be viewed as a sort of metabolic marker, reflecting non-respiratory diseases that impact the overall metabolism, e.g.…”

Techniques and Issues in Breath and Clinical Sample Headspace Analysis for Disease Diagnosis

“…Other gas sensor techniques may also be used in direct analysis of breath or headspace, but these tend to be non-specific. This includes various types of so-called electronic nose, which use an array of sensors of various types [35,[86][87][88][89][90][91][92][93]. Originally, electronic noses contained between 10 and 40 sensors, but newer technology means that a very high number of sensors can be included in a small array.…”

“…Examples of infections causing a change in VOC profile are tuberculosis [33], mycobacteria infection [31], infections causing ventilator associated pneumonia [34], respiratory disease [35]. Gastrointestinal disease may be due to a change in the gut flora, or some pathology of the gut or a combination of both, and these have been shown to give distinct VOC profiles from headspace of urine or faeces as well as breath [36][37][38][39][40] [41].…”

“…Summary of exhaled breath sampling techniques giving their main advantages andTechniquesThere is a very wide range of techniques for the analysis for individual VOCs or VOC profiles from a sample. These range from sophisticated and expensive techniques that can analyse samples of breath or headspace directly in real time, such as selected ion flow tube mass spectrometry (SIFT-MS)[65][66][67][68][69][70][71][72][73][74][75][76][77][78][79][80] or proton transfer mass spectrometry (PTR-MS)[67,[81][82][83][84][85], to techniques which do not identify or analyse individual components but look at patterns, for example gas sensor arrays (electronic nose)[35,[86][87][88][89][90][91][92][93]. If compound identification is required, it is essential to use a mass spectrometric technique, and preferably one that is coupled with a separation technique to avoid complicated spectra, for example gaschromatography-mass spectrometry.…”

Breath‐print analysis by e‐nose may refine risk stratification for adverse outcomes in cirrhotic patients

“…Breath analysis for medical purposes is an ancient approach, which has been validated in more recent years by the use of novel technologies able to characterize the spectrum of volatile organic compounds (VOCs) in the exhaled breath. 23 While analytical techniques, such as gas chromatography with mass spectrometry (GC-MS), ion mobility spectrometry (IMS) and proton transfer reaction time of flight mass spectrometry (PTR-MS), allow the recognition of specific molecular compounds and, hence, are more suitable for pathophysiological research, gas sensor array (commonly dubbed e-nose) technology provides a sort of fingerprint of exhaled breath (breath-print, BP) that can be subjected to pattern recognition algorithms. 24,25 Like human olfaction, this is extremely effective but does not allow the identification of the responsible VOCs, as it does not measure individual molecules or their concentrations.…”