Ž . Sensors and Actuators B 70 2000 19–24 www.elsevier.nlrlocatersensorb An electronic nose system to diagnose illness Julian W. Gardner ) , Hyun Woo Shin, Evor L. Hines Sensors Research Laboratory, School of Engineering, UniÕersity of Warwick, Gibbet Hill Road, CoÕentry CV4 7AL, UK Received 29 September 1999; accepted 4 May 2000 Abstract Ž . Recently, medical diagnostics has emerged to be a promising application area for electronic noses e-nose . In this paper, we review work carried out at Warwick University on the use of an e-nose to diagnose illness. Specifically, we have applied an e-nose to the identification of pathogens from cultures and diagnosing illness from breath samples. These initial results suggest that an e-nose will be able to assist in the diagnosis of diseases in the near future. q 2000 Elsevier Science B.V. All rights reserved. Keywords: Electronic nose; Medical diagnostics; Neural network 1. Introduction Ž . Electronic noses e-noses have been used to analyse the complex odorous headspace of food and drink — mainly employing metal oxide or conducting polymer resistive gas sensors as shown in Table 1. The table summarises some of the reported applications of e-noses Ž . research and commercial pertaining to the food industry which are listed from seafood, such as oysters and squid, through to cheeses, such as cheddar. The applications usually involve the grading of the odor in terms of the type Ž . of foodstuff or its quality e.g., freshness . Thus an e-nose may help assure the quality of both processed and raw foodstuffs. Monitoring the spoilage of foodstuffs is closely related to the monitoring of the growth of bacteria in a certain medium. In other words, an e-nose may be able to recog- nise characteristic smells from diseases and bacteria cells because cell metabolism is the biological oxidation of Ž . organic compounds, such as glucose CH O , to yield 6 12 6 ATP and secondary metabolites as shown in Fig. 1. There is now great interest in the clinical application of an e-nose; that is in the ability of an e-nose to diagnose illness. It is well known that certain diseases are associated with characteristic smells, for example, diabetes produces ) Corresponding author. Tel.: q 44-24-76523695; fax: q 44-24- 76418922. Ž . E-mail address: j.w.gardner@warwick.ac.uk J.W. Gardner . the sweet smell of acetone on the breath and stomach ailments are often associated with halitosis. Other diseases, like cancers associated with the lungs, liver and intestine can also produce characteristic odors. Some reported clini- cal applications of e-noses are listed in Table 2. We now describe work carried out at Warwick Univer- sity on the use of an e-nose for three medical applications: Ž. i the identification of pathogens that cause infectious Ž. disease of the upper respiratory tract and ears; ii the classification of cyanobacteria, Microcystis aeruginosa, in water that may produce toxins that are poisonous to cattle Ž . and people; iii diagnosing the presence of sub-clinical or clinical ketosis from the breath of dairy cows. We believe that these three examples demonstrate that there is a role for the future employment of e-nose instrument within the field of medical diagnostics. 2. Experimental Measurement systems were designed for each of the three applications. Fig. 2 shows the design of a fully automated e-nose system to sample the headspace of the pathogen and record the data. Air is passed over the pathogen sample and passed into a specially adapted e-nose. Ž . The e-nose is based on a Fox 2,000 Alpha MOS SA and comprises odor sensor arrays. At this stage, we used only Ž . six commercial MOS gas sensors Alpha MOS in the e-nose. 0925-4005r00r$ - see front matter q 2000 Elsevier Science B.V. All rights reserved. Ž . PII: S0925-4005 00 00548-7