Tetiana Protsko, Zubchuk Viktor

National Technical University of Ukraine “KPI”, Kyiv, Ukraine

Perspectives of using electronic nose in medical diagnostics

There are lot of modern methods of rapid medical diagnostics and among them electronic nose is one of the most suitable and accurate. Electronic noses have a clear potential to be a non-invasive, simple and rapid but above all accurate early diagnostic screening tool.

This review was done as part of work on developing methods for rapid diagnosis based on selective gas analyzers in the department of BMI, FBMI, NTUU “KPI”, Ukraine.

An electronic nose(e-nose) is first defined as a device which comprises of an array of chemical sensors with different selectivity, a signal-preprocessing unit and a pattern recognition system [1]. The functional scheme of the device is shown at the figure 1.

Figure 1. The functional scheme of e-nose

 

In the general case, e-nose device (Fig.1) is a set of selective sensors (D1. .. Dn), which through amplifiers (A1. .. AN), program-controlled analog multiplexer and analog-to-digital converter (ADC) connected to a computer manual for the formation of a database of measurements and accompanying information.

In a typical unit test air is sucked through the pump inlet compartment with built-in line of sensors. In the next step the sensors exhibited volatile substances pairs that make up the smell , and the odorous substances interacting on the surface and / or penetrating the volume of the active element of the sensor , forming the overall system response . During the measurement interval response touchpad analyzed and transmitted to the processor module. Then, the system serves pair flushing gas (eg, alcohol) in order to remove odorous substances from the surface and from the bulk of the active material of the sensor. Finally, in a grid of sensors is served carrier gas in order to prepare the unit for the new measuring cycle.

E-nose technical parameters directly depend on the parameters of selective sensors, so the choice of the type, number and sensitivity of sensor parameters is an important step in the design of such devices [2].

In the device, made by our department, we used amperometric sensors. Amperometric biosensors are devices that allow you to identify toxic substances at a lower level than in the case of potentiometric sensors. The principle of the amperometric biosensors is quite simple. Specified component diffuses through a semipermeable membrane into a thin layer of biological material in which the reaction to form products that are responsive electrode. Functional biosensors can be compared with sensors organisms - biosensors capable of converting the signals coming from the environment into brain electrical signals [3]. Technical characteristics of amperometric sensors used is shown in table 1.

 

Table 1. Technical characteristics of amperometric sensors

Gas

Sensor type

Min. and max. ranges of measurement, ppm

Response time

t0,9, c

Expansion, ppm

Sensitivity, mA/ppm

Ammonia

NH3, Sensor E-2

0-20, 0-5000

˂40

1

0,2±0,005

Chlorine

Cl2, Sensor E-2

0-5, 0-2500

˂40

0,05

0,05±0,001

Hydrogen sulfide

H2S, Sensor E-3

0-10, 0-1000

˂30

0,2

1±0,3

Sulfur dioxide

SO2, Sensor E-3

0-100, 0-1000

˂30

1

1,6±0,2

Nitric oxide

NO, Sensor E-3

0-20, 0-2500

˂20

1

-

Hydrogen fluoride

HF, Sensor E-2

0-10, 0-200

˂60

0,3

-

 

Electronic nose proved itself in several times heart failure diagnostics. Results showed that there are different exhaled air portraits in people with or without heart failure problems [4]. Sensing element was nitric oxide sensor.

Machado et al. used an electronic nose to identify and discriminate between 14 bronchogenic carcinoma patients and 45 healthy controls. The result demonstrated effective discrimination between samples from patients with lung cancer and those from healthy controls. In validation study, the electronic nose had 71.4% sensitivity and 91.9% specificity for detecting lung cancer, positive and negative predictive values were 66.6% and 93.4%, respectively [5].

Electronic noses can be applied to identify respiratory bacterial pathogens either in vitro or in vivo or as a potential tool for the identification of patients with COPD, asthma, and Tuberculosis. M. Bruins et al. in his study showed that the electronic nose can differentiate between tuberculosis patients and healthy controls with a sensitivity of 76.5% and specificity of 87.2% when identifying tuberculosis patients within the entire test population. The research has demonstrated a possibility of an electronic nose as a portable and fast-time-to-result device to screen search for tuberculosis cases in rural areas, which lacked highly-skilled operators or a hospital center infrastructure [6].

As for urinary tract diagnostics, approximately 80% of uncomplicated urinary tract infections (UTIs) are caused by Escherichia coli, 20% by enteric pathogens such as Enterococci, Klebsiellae, Proteus spp., coagulase (–) Staphylococci and fungal opportunistic pathogens such as Candida albicans (S. Krcmery, M. Dubrava, 1999). Electronic noses can diagnose UTIs by examining the volatile compounds produced by bacterial contaminants in urine samples. Based on this fact, Pavlou et al. employed an electronic nose consisting of 14 conducting polymer sensors to distinguish between normal urine, Escherichia coli infected, Proteus spp. and Staphylococcus spp. The study has shown the potential for early detection of microbial contaminants related to UTI using an electronic nose [7].

To summarize, electronic nose can be used in each medical field, where infection is associated with the occurrence of odors.  That’s why nowadays e-nose is one of the most flexible diagnostic methods. It can be used for respiratory infection, heart diseases, cancer and urinary tract infection detection and has a potential to make up a vital part in monitoring disease epidemiology.

 

References

1.     Handbook of Machine Olfaction. Electronic Nose Technology/ T.C. Pearce, S.S. Schiffman, H.T. Nagle, J.W. Gardner . – Weinheim: WILEY-VCH, [2003]. – 633.

2.     MDPI [Online service]: open access publishing / Chih-Heng Pan, Hung-Yi Hsieh and Kea-Tiong Tang An Analog Multilayer Perceptron Neural Network for a Portable Electronic Nose// Sensors. – 2013. – 13(1). – p. 193-207.

3.     Чвирук В.П., Линючева О.В., Кушмирук А.И. Электрохимические сенсоры нового поколения системы НТУУ «КПИ» для экологического мониторинга вооздушной среды // Збірник тез доп. п’ятої наук.-техн. Конф. «Приладобудування 2006», 25-26 квітня 2006 р. – Київ. – c. 24-25

4.     Якимчук В.С. Диагностика состояния больных с сердечно-сосудистыми заболеваниями с помощью показателей газообмена / Якимчук В.С. // Eastern-european Journal of enterprise technologies. – 2013. – №9(61) – с. 44-48.

5.     R. F. Machado, D. Laskowski, O. Deffenderfer, et al., “Detection of Lung Cancer by Sensor Array Analyses of Exhaled Breath,” American Journal of Respiratory and Critical Care Medicine, Vol. 171, No. 11, 2005, pp. 1286-1291.

6.     M. Bruins, Z. Rahimc, A. Bos, W. W. van de Sande, H. P. Endtz and A. van Belkum, “Diagnosis of Active Tuberculosis by E-Nose Analysis of Exhaled Air,” Tuberculosis, Vol. 93, No. 2, 2012, pp. 1-7.

7.     A. K. Pavlou, N. Magan, C. McNulty, J. M. Jones, D. Sharp, J. Brown and A. P. F. Turner, “Use of an Electronic Nose System for Diagnoses of Urinary Tract Infections,” Biosensors and Bioelectronics, Vol. 17, No. 10, 2002, pp. 893-899