Addressing challenges in using breath chemical analysis in smartphone-based health diagnostics

Abstract

Volatile organic compounds (VOCs) emitted by the human body (via e.g. breath, skin, urine, or saliva) offer unique and noninvasive insight into physiological and medical status of an individual. The analysis of this volatile chemical signature emerges as a promising and powerful approach for detecting and tracking infections, cancer development, metabolic disorders, progression of therapeutic intervention, as well as, individual's exposure to environmental pollutants and/or toxins. The rationale behind this approach is that the observed chemical pattern is unique and disease specific, thereby, can be distinguished from patterns related to other physiological states (both normal and abnormal). Amongst different physiological fluids breath holds in this context a distinguished status as it is readily and noninvasively obtainable and relatively non-complex. Moreover, its volatile and semi volatile constituents have already been demonstrated to provide valuable information on various disease processes occurring in the human body. A number of sophisticated analytical techniques e.g. Gas Chromatography-Mass Spectrometry (GC-MS), GC-MS/MS, High Performance Liquid Chromatography-Mass Spectrometry (HPLC-MS), Selective Reagent Ionization-Time of Flight-Mass Spectrometry (SRI-TOF-MS), Ion Mobility Spectrometer (IMS) have been involved to recognize and define the disease-specific chemical fingerprints. Integrating chemical sensors or more sophisticated chemical instrumentation with mobile phones will lead to a number of potential personalized health applications. However a number of challenges exist that need to be addressed; disease specific gases and/or VOCs in breath must be credible, repeatable and unambiguous. This is perhaps one of the biggest challenge due to a number of reasons such as potentialdependence of the type and concentrations of VOCs on various parameters (e.g. individuality, gender, geographic area). In this context, the characteristic VOCs in breath related to renal failure are presented and discussed in this work. Another challenge is the degree of the chemical instrument/sensor miniaturization and how this can affect performance of analytical methods. There is also the challenge of developing faster, user friendly, cost/effective applications for mobile phones.