Application of the electronic nose allows differentiation between ill and healthy patients based on holistic analysis of the volatile fraction of different biological samples, including exhaled air. Recently medicine has witnessed an increasing interest in cheap, non-invasive and simple diagnostic tests [1,4�C13,15�C18,20�C22,24,25,27,28,37], and for this reason many researchers look for solutions utilizing new diagnostic tools based exclusively on human breath analysis. Volatile organic compounds (VOCs) present in exhaled air may contain information on the internal biochemistry of the human body, which may be useful in terms of identification and description of many diseases. The literature provides information [14,38�C40] on applications of the electronic nose technique to diagnosis of chronic obstructive pulmonary disease (COPD), which employed a commercial model Cyranose 320 nose.

These investigations confirmed that due to its advantages the technique could be useful and effective as far as breath analysis and differentiation between ill and healthy patients are concerned. COPD is a syndrome revealed as a progressive restriction of air flow through the respiratory system due to malfunction of the lower respiratory system and destruction of the lung parenchyma. The most frequent cause of COPD is exposure to tobacco smoke and to all types of irritant chemical substances during a lifetime [14]. COPD is an incurable disease and treatment is only symptomatic. All treatment activities are aimed at slowing the progression of the disease.

This disease can divided into four stages: in the first stage a chronic cough is the predominant symptom, while the second stage is characterized by dyspnoea on exercise. The third stage is deemed a serious one, with escalated dyspnoea and decreased breathing endurance, and finally, in the fourth stage dyspnoea at rest and respiratory distress occur. The main causes of death of patients suffering from COPD are malfunction of the cardiovascular system, lung cancer and respiratory distress. The aforementioned facts illustrate how important early identification of COPD is, so patients’ life comfort can be improved as well as disease progress inhibited (disease retardation). Statistical data show the scale of the problem. For instance, in the United States of America COPD is the fourth on the list of death causes due to diseases.

This paper presents model studies on mixtures of reference substances based on the volatile organic compounds that are components of human breath. Some of these compounds, Drug_discovery namely N,N-dimethyl-formamide and N,N-dimethylacetamide, were mentioned in the literature as potential COPD markers [5,41,42]. A 6-sensor electronic nose prototype was utilized in the investigations. The set of sensors comprised cheap semiconductor sensors manufactured by Figaro Co.